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Transport NFSv4 example This document describes the structure of NFSv4 ACLs and their role in the NFSv4 security architecture. While their role in providing a more flexible approach to file access authorization than is made available by the POSIX-derived authorization-related attributes, the potential provision of other security-related functionality is covered as well. While the goals of the description are similar to that used in previous specficaion, the approach taken is substantally different, in that a core set of functionality, derived form the the now-withdrawn POSIX draft ACLs is the conceptual base of the feature set while extensions to that functionality are made available as OPTIONAL extensions to that core. The current version of the document is intended, in large part, to result in working group discussion regarding existing NFSv4 security issues and to provide a framework for addressing these issues and obtaining working group consensus regarding necessary changes. When the resulting document is eventually published as an RFC, it will supersede the descriptions of ACL structure and semantics appearing in existing minor version specification documents such as RFCs 7530 and 8881, thereby updating RFC7530 and RFC8881.

Introduction This document describes the ACL-related features of the NFsv4 protocol, all of which are accessed through the use of a set of OPTIONAL attribuutes described in . These attributes provide:

• Additional means of specifying file access authorization constraints that are more flexible than those provided by the authorization model inherited from POSIX, based on the attributes Mode, Owner, and OwnerGroup.
• A number of security-related facilities separate from authorization that use ACLs to identify sets of actions that might be subject to vrious forms of montoring as described in .

Relationship to the Overall Security Document This document is best understood when it is read together with which dicusses, as a whole, security features provided that are not connected with ACLs, and which is a complete description in cases in which the OPTIONAL ACL-related attributes are not implemented. In many cases, the overall ecurity document will have abbreviated descriptions that serve as an introduction to material in this document and reference sections within this document. Similarly, there will be occasions where it is necessary for this document to reference general features of NFSv4 security documented in . For the most part, these two documents are indepenendent, except for the inter-document reference discussed above. However, the following execptions should be noted:

• Section 1 of , in its entirety, applies to both document, even in the absence of explicit inter-document references.
• The terminology defined in Section 4.1 of can be used in either document, without en explcit reference
• The sections dealing with Security Considerations and IANA Considerations appearing in , i.e., Sections 18 and 19 apply to the security-related changes being made in the current update as a whole, i.e. to both documents.
• Appendix A of , in describing the security-related changes made from previous specifications, includes change made in both this document and the overall security document.
• The Appendices devoted to tracking Consensus Items, i.e., Appendix A of this document and Apppendex B of , need to be considered together, even though each appendix applies only to the document in which it appears. This is because there are related consensus items in the several document whose resolution might affect one another, including some that result from consensus items affecting material now in muliple documents.

Changes to the Description of ACLs in this Document This document has the same goals as previous descriptions of ACLs in earlier specifications and earlier drafts of the security document . The most important of these is how to address the need to support multiple semantic models for ACLs,including UNIX ACLs, NFSv4 ACLs and various hybrids of the two. In this document we shift between the two approaches listed below:

• Prevuously the NFSv4 ACL model has been presented as canonical, while the inability of many servers to provide such support addressed by a pervasive laxness about descriptions of the semantics. This approach did not give clients any way to determine which ACL model was supported by a given server, sharply limiting the actual value of the additional elements added to UNIX ACLs.
• [Author Aside (Item #10Da)]: This shift, elements of which affect Large parts of this docement will be identified as Consensus Item #10D. In this document the more limited UNIX ACL Model is presented aa foundational, while the elements necessary to provide support for NFSv4 ACLs are treated as OPTIONAL to the UNIX ACL model. [Author Aside (#Item #10Ea)]: The apparatous referred to is defined in later sections of this document where it is identified as Conensus Item #10E. To allow clients to determine which elements of the more flexible model are present an additional OPTIONAL attribute Aclfeature is defined and supplemented by means of inferring the extensions availble when it is not present/

Requirements Language

Keyword Definitions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as specified in BCP 14 when, and only when, they appear in all capitals, as shown here.

Special Considerations Because this document needs to revise previous treatments of its subject, it will need to cite previous treatments of issues that now need to be dealt with in a different way.  This will take the form of quotations from documents whose treatment of the subject is being obsoleted, most often direct but sometimes indirect as well. Paragraphs headed "[Previous Treatment] or otherwise annotated as having that status, as described in Section 1 of , can be considered quotations in this context. Such treatments in quotations will involve use of these BCP14-defined terms in two noteworthy ways:

• The term may have been used inappropriately (i.e not in accord with ), as has been the case for the "RECOMMENDED" attributes, which are in fact OPTIONAL. In such cases, the surrounding text will make clear that the quoted text does not have a normative effect.
• The term may been used in accord with , although the resulting normative statement is now felt to be inappropriate. In such cases, the surrounding text will need to make clear that the text quoted is no longer to be considered normative, often by providing new text that conflicts with the quoted, previously normative, text.

ACL-based Authorization-related Attributes [Author Aside: (Items #14a, #15a... )]: The treatment of the various ACL-based attributes in the included subsections replaces the corresponding sections in earlier minor sections, in which the attribute descriptions were not consolidated in one place and were disbursed amonga number of top-level sections. Where it has been necessary to make significant changes, the annotations for those changes, including author asides and proposed text, appear here while vestigial text that is now superseded has not been brought forward. The per-object attributes acl, dacl, and sacl sacl consist of an ACL object as described in and its subsections.

Table of ACL-related Attributes

Types of ACLs The ACL allows authorization schemes outside those conforming to the POSIX approach to be specified and applied to file objects. This provides additional flexibility in a number of ways:

1. There may be multiple users or sets of users assigned different privileges to address cases in which the appropriate privilege assignments do not conform to the POSIX model in that they are different for users in the same group or different for two groups outside the owning group. ACLs support this by allowing an array of Access Control Entries, each of which specifies handling for a user or user group.
2. For partcular users or sets of users, the set of operations to be allowed might not be expressible using the three bits provided by POSIX as supplemented by special privileges for operations reserved to file owner.

NFSv4 ACLs, as described in , addresss both issues by defining, within the Access Control Entry, a large set of distinct privilege bits, modeled on those provided by Windows ACLs. ACLs based on the withdrawn POSIX ACL draft, (i.e. UNIX ACLs) make a more limited change to the POSIX authorization model and are represented by the same sorts of structures as NFSv4 ACLs, altough there are restrictions imposed by the UNIX ACL model. Although these two have some common goals, they are substantially different, in that:

• The draft POSIX ACLs addresses only the first of the motivations for extension, while the NFSv4 ACL model is intended to address both of them, by defining a large range of bits in the ACE mask, rather than the three POSIX bits.
• NFSv4 ACLs, by supporting DENY entries allow specfic privileges to be allowed for some member of a group and be denied to some particular users.
• NFSv4 ACLs provide additional security-related facilities in addition to authorization control, through the use of AUDIT and alarm ACEs.

{Author Aside (Item #61a)]: In order to justify a shift of the acl and dacl attributes back to be OPTIONAL, it is necessary to define for each file system, the type of ACL semantics provided. In so doing, we will have to mke provision for various hybrids if such implementations actually exist, while not necessarily seeking to preserve the ability to generate other such potential hybrids. [Consensus Needed, Including List (Item #61a)]: The determination of the type of ACL semantics proceeds as follows:

• If the aclsupport attribute indicates that either AUDIT or ALARM ACEs are supported, then it can be assumed that NFSv4 ACL semantics are provided.
• If the aclsupport attribute is not supported, then if the sacl attribute is supported then it also can be assumed that NFSv4 ACL semantics are provided.
• Otherwise, If the aclsupport attribute is supported then the presence of support for DENY ACEs determines whether support is NFSv4 ACL semantics is provided.
• In the case in which neiter the aclspport attribute not the SACL attribute is supported, then it can also be assumed thatsupport is NFSv4 ACL semantics is provided. As a conequence, server implementations providing support for UNIX ACLs only, need to support the aclsupport attribute.

The Acl Attribute (v4.0) This per-object attribute consists of an array of Access Control Entries which apply to operations performed on the current object, controlling authorization and monitoring of attempted operations. This attribute, as opposed to the sacl and dacl attributes, consists only of an ACE array and does not support automatic inheritance. The acl attribute is OPTIONAL and there is no requirement that a server support it. However, when the dacl attribute is supported, it is a good idea to provide support for the acl attribute as well, in order to accommodate clients that have not been upgraded to use the dacl attribute. {Consenses needed, Including List (Item #65a)]: While the original intention was to define a usable OPTIONAL attribute based on the NFSv4 ACLs defined previous specfications, it is now more appropriate to designate this under-specified attribute as experiemental although still formally OPTIONAL, until the items below have been addressed.

• The intention to support, as values of this attribute two different ACL approaches, each with its own semantics. These include both the NFSv4 ACLs based on the Windows ACL model and a subset based on the more restricted semantics provided by the withdrawn POSIX ACL document with a straightforward mapping of those into the format of NFSv4 ACLs. The association of two such different semantic models without giving the client a way to determine which semantic model is in effect.
• The potential interoperability problems are vastly expanded by the specific method by which these two models are supported. Instead of allowing servers to choose between these two approaches, e.g. by using the term "MAY", most statements regarding ACL semactics use the term "SHOULD", described in the text as "intentional", apparently assuming that the result is essentially equivalent to the use of "MAY". Even apart from the misuse of the terms defined in [RFC2119], this has the effect of replacing a single choice by allowing a large number of unco- ordinated choices, exponentially raising the number of possibly valid semantic models that clients and users have to accmmodate.
• It is not clear how far this pick-and-choose approach extends. In the case of the ace mask bits which are finer-grained than the three bits in the mode and in POSIX ACLs, there is no explicit text indicating how the coarser-grained approach would be supported by a server built to support POSIX ACLs, leaving the actual requirements uncertain.
• Although some efforts have been made to limit the damage caused by this specification uncertainty by urging clients to determine authorization decisions using ACCESS rather than by examining the ACL itself, this only addresses half of the problem and the question of what ACL to set to effect a particular authorization regime remains unaddressesd, limiting the usefulness of the ACL-related features. Although significant efforts have been made to widen the information returned by ACCESS beyond the three-bit POSIX model, ther are still cases in which it is insufficiently fine-grained. For example, adding a new file and a new sub-directory which have dfferent ACE mask bits are both represented by a single bit in ACCESS.

[Author Aside]: Although it has generally been assumed that changes to sacl and dacl attributes are to be visible in the acl and vice versa, NFSv4.1 specification do not appear to document this fact. [Consensus Item, Including List (Item #16a)]: For NFSv4.1 servers that support Both the acl attribute and one or more of the sacl and dacl attributes, changes to the ACE's need to be immediately reflected in the other supported attributes:

• The result of reading the dacl attribute MUST consist of a set of ACEs that are exactly the same as the ACEs ALLOW and DENY ACEs within the the acl attribute, in the same order.
• The result of reading the sacl attribute MUST consist of a set of ACEs that are exactly the same as the ACEs AUDIT and ALARM ACEs within the the acl attribute, in the same order.
• The result of reading the acl attribute MUST consist of a set of ACEs that are exactly the same as the union of ACEs within the sacl and dacl attributes. Two ACEs that both appear in one of the sacl or dacl attributes will appear in the same order in the acl attribute.

The Aclsupport Attribute (v4.0) A server need not support all of the ACE types described in Section 6.1. This attribute indicates which ACE types are supported for the current file system by any of the acl, sacl, or dacl attributes. The bitmask constants used to represent the abovementioned definitions within the aclsupport attribute are as follows: const ACL4_SUPPORT_ALLOW_ACL = 0x00000001; const ACL4_SUPPORT_DENY_ACL = 0x00000002; const ACL4_SUPPORT_AUDIT_ACL = 0x00000004; const ACL4_SUPPORT_ALARM_ACL = 0x00000008; [Author Aside (Item #14b)]: Even though support aclsupport is OPTIONAL, there has been no mention of the possibility of it not being supported. [Consensus Needed (Item #14b)]: If this attribute is not supported for a server or filesystem, the client is entitled to assume that, if the acl attribute is supported, support for ALLOW ACEs is present. Thus, if such a server supports the the sacl attribute, clients are not likely to use it if aclsupport is not supported by the server. [Previous Treatment (Item #61a)]: Servers that support either the ALLOW or DENY ACE type SHOULD support both ALLOW and DENY ACE types. [Author Aside, Including List: (Items #61a, #62b)]: The use of "SHOULD" in the preceding is unhelpful for the following reasons:

• While it is unclear what the intention is, it is certainly is not in accord with RFC2119 since there is no indication of potential harm or what might be valid reasons to do otherwise.
• While it might be one of "intentional" SHOULDs, that would make the paragraph meaningless since such SHHOULds are essentially equal to MAYs.
• The most likely source of divergence in the support for ALLOW and DENY ACEs is not mentioned at all.

[Consensus Needed (Item #61b)]: Servers that support either the DENY ACE type MUST support the ALLOW and ACE type as well. [Consensus Needed, Including list (#61b)]: Clients should not attempt to set an ACE unless the server claims support for that ACE type. The server MUST reject requests with NFS4ERR_ATTRNOTSUPP if any of the following apply:

• If the server receives a request to set an ACE type that is not allowed as part of the acl attribute being set.
• If the server receives a request to set an ACE, it cannot store.

Support for any of the ACL attributes is OPTIONAL. However, certain restrictions apply regarding the interaction of support for these attributes, A server that supports either of the new ACL attributes (dacl or sacl) MUST support use of the new ACL attributes to access all of the ACE types that it supports. In other words, if such a server supports ALLOW or DENY ACEs and the sacl attribute, then it MUST support the dacl attribute and any ALLOW or DENY ACE tyopes supported by the tha acl attribute MUST be supported in the dacl attribute as well. Similarly, if it supports AUDIT or ALARM ACEs and the dacl attribute, then it MUST support the sacl attribute any AUDIT or ALARM ACE types supported by the tha acl attribute MUST be supported in the dacl attribute as well.

The Aclfeature Attribute (v4.2 extension)

The Dacl Attribute (v4.1) The dacl attribute was added in NFSv4.1 in order to divide ACLs so that the authorization-related entries (i.e. ALLOW and DENY entries) were no longer combined in the same attribute as AUDIT and ALARM entries. {Consensus needed, Thru rest of Section (Item #65b)]: While the original intention was to define a usable OPTIONAL attribute based on the NFSv4 ACLs defined previous specifications, it is now more appropriate to designate this under-specified attribute as exprimental although still formally OPTIONAL until the issues discussed in are addressed Athough the issues applying to the acl attribute apply equally to the dacl attribute, given the description in earlier specifications, it may be easier to resolve them in the case of the dacl attribute for the following reasons:

• Implementaions of POSIX ACLs might not have been updated to support the sacl attriute, since doing so would add no value.
• Even if such POSIX-ACL-oriented implentations of the sacl attribute did exist, it might be easier to get agreement on regularizing the sacl attribute since, if acl were left as it is, the POSIX ACL support would still be available.

The Sacl Attribute (v4.1) The sacl attribute is like the acl attribute, but sacl allows only AUDIT and ALARM ACEs. The sacl attribute supports automatic (see ). {Consensus needed, Thru rest of Section (Item #65c)]: While the original intention was to define a usable OPTIONAL attribute based on the NFSv4 ACLs definedin previous specifications, it is now more appropriate to designate this under-specified attribute as exprimental although still formally OPTIONAL until the issues discussed in are addressed The sacl attribute was added in NFSv4.1 in order to divide ACLs so that the non-authorization-related entries (i.e. AUDIT and ALARM entries) would no longer be combinded in the same attribute with the ALLOW and DENY entries. [Author Aside, Including List (Item #61c)]: Athough the exsting discussion of ACE structure results in the same sortof lack of clarity affecting the acl and dacl attributes, it us more likely that these will resolved in the case of the sacl attribute as compared to the acl or dacl attributes, even though the problems with the existing text are essentially the same.

• There are no AUDIT or ALARM entries, in POSIX ACLs, so there would be no need accommodate existing implementations of these that embody a more POSIX-oriented semantic model. As a result, it is likely to be easier to get WG approval for changes that clearly state that the ACE mask bits are to followed strictly for the these types of ACEs.
• Since such entries have no role in compute a corresponding mode attribute, the effect of this issue for the sacl attribute is not problematic.

Structure and Function of NFSv4 Access Control Lists NFSv4 Access Control Lists consisting of multiple Access Control Elements. While originally designed to support a more flexible authorization model, these lists have multiple uses within NFSv4, with the use of each element depending on its type, as defined in .

• ACLs may be used to provide a more flexible authorization model as described in Section 8.4 of . This involves use of Access Control Entries of the ALLOW and DENY types.
• They may be used to provide the security-related services described in . This involves use of Access Control Entries of the AUDIT and ALARM types.

[Consensus Needed (Item #61d)]: Subsections of this section and of define the structure of and semantics of NFSv4 ACLs, whether they are used to represent UNIX ACLs or various extensions thereof, upto the full set of extensions provided by NFSv4 ACL semantics. Matters that relate only to extensions provided to support NFSv4 ACLs including the definition of the NFSv4.1-specific attribute Sacl, are discussed in and smmarized in Section 8.4 of .

ACL Semantics Choices [Consensus Needed, Including List (Item #61e)]: There are a range of potential authorization models that can be supported using the acl and dacl attributes:

• Full NFSv4 ACLs, with expanded semantics derived from Windows ACLs. This includes a finer-grained permissions model, the inclusion of DENY ACEs, and the use of ACLs for non-authorization functions, via the use of AUDIT and ALARM ACEs, and a number of features related to ACL inheritance.
• UNIX ACLs, based on the withdrawn POSIX ACL draft. This approach retains the three bits typical of POSIX semantics and maps them, with a number of implied restrictions, to a subset of the more expansive set of ACE mask bits defined in .
• Various hybrids of the two models, supporting some, but mot all of the extensions to UNIX ACLs introduced in earlier minor version specifications. The new Aclfeature attribute, available as an extension in NFSv4.2, allow the client to determine which extensions are implemented for a particular file system. See xref target="ACL-sem-discovery"/> for further discussion. Where this feature is not available, including NFSv4.0 and NFSv4.1, information on the extensions supported can be inferred based on the value of the Aclsupport attribute. See xref target="ACL-sem-inference"/> for details. In all of these cases the client can rely on the fact that the core features derived from UNIX ACLs are always available when the Acl or Dacl attributes are supported.

[Author Aside, Including List (Items #30a, #61e)]: Earlier specifications of the ACL feature allowed servers to provide any of these semantic models. Unfortunately, the server was not given an explicit choice and the client has no way of determing the semantics associated with the ACL and adapting accordingly. Instead the approach was to widen the range of permissible server behavior to be implemented for ACLs, so it included both sorts of ACL semantics, various hybrids unlikely to be implemented, as welll as a lot of miscellaneous variants, many probably unintende, as well.

• The keyword SHOULD was used for just about every element of ACL semantics, without proper attention to the meaning of that term as defined in . The resulting text often stated that these uses of "SHOULD" were "intentional" without explicitly providing any reason that would justify not performing the recommended action or discussion of the consquenes of doing so. The result was to effectively replace a single MAY by a lare number instances of SHOULD each treated essentilly as MAY with an exponential expansion of the number behaviors a client would have to be prepared for.
• In many cases, the use of SHOULD with the implied meaning MAY, leaves open more than two possiilities since it is not always clear what restictions apply to the case in which the recommendation is bypassed. As a result, the number of notionally valid server behaviors can expand even beyond the exponential increase discuused above.
• In the handling of the mapping of ACLs to modes, important when ACLs are supported and used, there are further sources of confusion that need to be resolved. What is almost surely the preferred method in introduced in Section 6.3.2 of without a MUST or even a SHOULD but instead says it "can be used", even though Section 6.4 of states that these methods are covered by an "intentional" SHOULD. An alternate method is introduced by stating that "Some server implementations" do, without any discussion of the effect on interoperability, although it does say that "implementations are discouraged" from doing this. Although Section 6.4 of indicates the motivation of this alternate method is to provide support for servers supporting the withdrawn POSIX draft ACLs, there is no indication of a normative connection betweeen these two choices.

Discovery of ACL Semantics The OPTIONAL attribute Aclfeature defined as an NFSv4.2 extension (see provides a way for the client to determine what extensions to the UNIX ACL model are supported on a given file system. The specific extensions that may be supported include the following:

• The support for ACE mask bits (see in addition to the three that represent the POSIX-derived privilege bits: Read, Write, and Execute, which are always supported. In addition to these coarse-grained mask bits, which are discussed in , there are flags withing the Aclfeature attribute that indicates whether the additional mask bits defined in Sections and are supported as well.
• The inclusion of support for ACE types in addition to ACE4_ACCESS_ALLOWED_ACE_TYPE is deteminabe using the Aclsupport attribute. In addition, the AclFeature attribute allows the client to determine the of ACE types that, while not supported, can be stored
• flags
• who

Inferring ACL Semantics In cases in which the Aclfeature attribute is not supported, including minor version for which it is not defined (i.e. minor versions below two), there are way to determine the extensions supported but sets of extensions are more limited and the client might require more effort to adapt in order to use the extensions while andling gor clients that are not prepared to use the extensions is dealt with trivially, since the core elements of UNIX ACL are always present. The following limitations should be noted:

Structure of Access Control Entries The attributes acl, sacl (v4.1 only) and dacl (v4.1 only) each contain an array of Access Control Entries (ACEs) that are associated with the file system object. The client can set and get these attributes while the server is responsible for using the ACL-related attributes to perform access control. The client can use the OPEN or ACCESS operations to check access without modifying or explicitly reading data or metadata. The NFS ACE structure is defined as follows: typedef uint32_t acetype4; typedef uint32_t aceflag4; typedef uint32_t acemask4; struct nfsace4 { acetype4 type; aceflag4 flag; acemask4 access_mask; utf8str_mixed who; };

ACE Type The constants used for the type field (acetype4) are as follows: const ACE4_ACCESS_ALLOWED_ACE_TYPE = 0x00000000; const ACE4_ACCESS_DENIED_ACE_TYPE = 0x00000001; const ACE4_SYSTEM_AUDIT_ACE_TYPE = 0x00000002; const ACE4_SYSTEM_ALARM_ACE_TYPE = 0x00000003; All four are permitted in the Acl attribute. For NFSv4.1 and beyond, only the ALLOWED and DENIED types are used in the Dacl attribute, and only the AUDIT and ALARM types are used in the Sacl attribute.

Value	Abbreviation	Description
ACE4_ACCESS_ALLOWED_ACE_TYPE	ALLOW	Explicitly grants the ability to perform the action specified in acemask4 to the file or directory. When all such actions to be done by a given operation are explcitly allowed, the operation is authorized and scanning of the ACL to dtermine authorization stops.
ACE4_ACCESS_DENIED_ACE_TYPE	DENY	Explicitly denies the ability to perform the action specified in acemask4 to the file or directory. When any of the actions to be done by a given operation are explcitly denied, the operation is unauthorized and scanning ofthe ACL to determine authoriztion stops.
ACE4_SYSTEM_AUDIT_ACE_TYPE	AUDIT	Log (in a system-dependent way) any attempt to perform, for the file or directory, any of the actions specified in acemask4.
ACE4_SYSTEM_ALARM_ACE_TYPE	ALARM	Generate (in a system-dependent way) an alarm upon any attempt to perform, for the file or directory, any of the actions specified in acemask4.

The "Abbreviation" column denotes how the types will be referred to throughout the rest of this document.

ACE Access Mask The bitmask constants that might be used within the access mask field of the ACE are as follows: const ACE4_READ_DATA = 0x00000001; const ACE4_LIST_DIRECTORY = 0x00000001; const ACE4_WRITE_DATA = 0x00000002; const ACE4_ADD_FILE = 0x00000002; const ACE4_APPEND_DATA = 0x00000004; const ACE4_ADD_SUBDIRECTORY = 0x00000004; const ACE4_READ_NAMED_ATTRS = 0x00000008; const ACE4_WRITE_NAMED_ATTRS = 0x00000010; const ACE4_EXECUTE = 0x00000020; const ACE4_DELETE_CHILD = 0x00000040; const ACE4_READ_ATTRIBUTES = 0x00000080; const ACE4_WRITE_ATTRIBUTES = 0x00000100; const ACE4_WRITE_RETENTION = 0x00000200; const ACE4_WRITE_RETENTION_HOLD = 0x00000400; const ACE4_DELETE = 0x00010000; const ACE4_READ_ACL = 0x00020000; const ACE4_WRITE_ACL = 0x00040000; const ACE4_WRITE_OWNER = 0x00080000; const ACE4_SYNCHRONIZE = 0x00100000; Note that some masks have coincident values, or are treated differently when used with different types of object. For example, ACE4_READ_DATA and ACE4_LIST_DIRECTORY designate the same mask bit which is treated differently depeding on whether the object is a directory or other type of object. Note that,

• The mask values ACE4_ADD_FILE, ACE4_ADD_SUBDIRECTORY, and ACE4_DELETE_CHILD are intended to be used with directory objects and are not supported when used with objects of other types.
• The mask value ACE4_APPEND_DATA is intended to be used with non-directory objects.
• The mask value used for ACE4_READ_DATA and ACE4_LIST_DIRECTORY designate the same mask bit is which treated differently depeding on whether the object is a directory or other type of object.
• The mask bit designated by ACE4_EXECUTE controls two different sets of action depending on whether the underlying object is a directory.

[Consensus Needed (Items #10Ba, #10Ca), through end of list]: These mask bit are explained in more detail in the sections mentioned below based on their relationshup to the three POSIX-derived permission bits: Read, Write, and Execute. Changes include material in multiple subsections of .

• Mask bits whose set of authorized actions corresponds to a single POSIX-drived permission bit are explained in . These mask bits are always supported although the set of authorized is smaller when other mask bits covering a smaller set of actions are supported.
• Mask bits whose set of authorized actions is a subset of those normally controlled by a single POSIX-drived permission bit are explained in . These mask bits are not always supported, but depends on ACL extensions supported by the server. For detailed guidance regarding how the client can determine which mask bits are supported, see Sections and .
• Most Mask bits whose set of authorized actions is neither identical to nor a subset of those controlled by a single POSIX-drived permission bit are explained in . This section covers mask bits for which we have found existing implementations. These mask bits are not always supported, but clients need to prepared for support actually present depending on the set of ACL extensions supported
• Mask bits defined in existing specfication but for which no corresponding imlementation has yet been found are explained in .

[Consensus Needed (Item #5a) The descriptions in the section below relevant to both authoriztion and for recognizing operations whose success or failure are to be recorded when ACL are used for the non-authorization functions described in . With regard to ACCESS whose returned bits are affected, it is not necessarily the case that the occurrence of ACCESS in these lists implies that such operations are recordable events. Revisions in handling of the masks WRITE_RETENTION and WRITE_RETENTION_HOLD. These are parts of consensus items #10.

Changes in Descriptions of Mask Bits [Author Aside, Through end of section]: The material in this section identiies changes it has been necessary to make in the description of the ACE mask bits. It is ikely that it will be removed before the successor document is published as an RFC The following items should be noted as cases in which a change related to the description of ACE mask bits. In soome cases, there will be corresponding annotations near the actual text change,nut this is not always the case. Nevertheless, there will need to be consensus regarding the following changes:

• [Author Aside (Item #3a)]: Because the following sections have been moved to be part of a general description of ACEs, not limited to authorization, the descriptions no longer refer to permissions but rather to actions. This coud be considered a purely editorial change, but, to allow for possible disagreement on the matter, it will be considered, here and in , as consensus item #3.
• [Author Aside (Item #4a)]: In a large number of places, SHOULD is used inappropriately, since there appear to be no valid reasons to allow a server to ignore what might well be a requirement. Such changes are not always noted individually below. However, they will be considered, here and in , as part of consensus item #4.
• [Author Aside (Item #5)}: In a significant number of cases the ACCESS operation had not been listed as an operation affected by the mask bit where logic suggests it needs to be. These individuall additions are not noted individually below, although there is, in each affected section, an annotation indicating that section requires consensus on this point. In all cases, they will be considered, here, in the affected sections and in , as part of consensus item #5. When ACCESS is included as an affected operation, the description identifies the returned bits that are to affected. When ACCESS is listed as affected, this is only with regard to authorization. Non-authorization uses are discussed elsewhere, as part of this consensus item.
• [Author Aside, Including entite bulleted item]: In a number of cases, there are additional changes which go beyond editorial or arguably do so. These will be marked as their own consensus items usually with an accompanying author aside but without necessarily citing the previous treatment. These include the following: [Author Aside (Item #7a)]: Revisions were necessary to clarify the relationship between READ_DATA and EXECUTE. [Author Aside (Item #8a)]: Revisions were necessary to clarify the relationship between WRITE_DATA and APPEND_DATA. These are part of consensus item #8. [Author Aside (Item #9a)]: Clarification of the handling of RENAME by ADD_FILE, ADD_SUBDIRECTORY.

Role of Sticky Bit in ACL-based Auhorization [Author Aside (Item #62a)]: Because of the need to address sticky-bit issue as part of of the ACE mask descriptions, it is appropriate to introduce the subject here. [Author Aside (Item #20bA)]: Despite the fact that NFSv4 ACLs and mode bits are separate means of authorization, it has been necessary, even if only for the purpose of providing compatibility with earlier implementations, to introduce the issue here, since reference to this mode bit are necessary to resolve issues regard directory entry deletion, as is done in . [Consensus Item, Including List (Item #62a): The full description of the role of the sticky-bit appears in Section 5.3.2 of . In evaluating and understanding the relationship between the handling of this bit when NFSv4 ACLs are used and when they are not, the following points need to be kept in mind:

• This is troublesome in that it combines data normally assigned to two different authorization models and breaks the overall architectural arrangement in which the mask bits represent the mode bits but provide a finer granularity of control.
• It might have been possible to conform to the existing architectural model if a new mask bit were created to represent the directory sticky bit. It is probably too late to do so now, even though it would be allowed, from the protocol point of view, as an NFSv4.2 extension.
• The new treatment in is more restrictive than the previous one appearing in . This raises potential compatibility issues since the new treatment, while designed to address the same issues was designed to match existing Unix handling of this bit.
• This handling initially addresses REMOVE and does not address directory sticky bit semantics with regard to RENAME. Whether it will do so is still uncertain.
• The handling of this mode bit was not documented in previous specifications. However, there is a preliminary attempt to do so in Section 5.3.2 of . The reason for doing so, is that, given the Unix orientation of the mode attribute, it is likely that servers currently implement this, even though there is no NFSv4 documentation of this semantics This treatment needs to be checked for compatibility issues and also to establish a model that we might adapt to the case of NFSv4 ACLs.
• In the long term, it would make more sense to allow the client rather than the server to have the primary role in determining the semantics for things like this. That does not seem possible right now but it is worth considering.

Uses of Core Mask Bits [Consensus Needed (Items #4b, #5a, #7a, #8a, #10Aa, #10Fa, #10Ga, #10Ha), Throughout section] ACE4_READ_DATA (for non-directory objects)

• Operation(s) affected:

  READ [Consensus Needed (Item #10Aa)]: READLINK OPEN (for read or read-write) ACCESS (ACCESS4_READ)

  Discussion:

  The action of reading the data of the file, or, in some cases, providing necessary preparation to do so. [Previous Treatment (Items #4b, #7a)]: Servers SHOULD allow a user the ability to read the data of the file when only the ACE4_EXECUTE access mask bit is allowed. [Author Aside (Item #7a)]: The treatment needs to be clarified to make it appropriate to all ACE types. [Consensus Needed (Items #4b, #7a)]: When used to handle READ or OPEN operations, the handling MUST be identical whether this bit, ACE4_EXECUTE, or both are present, as the server has no way of determining whether a file is being read for execution are not. The only occasion for different handling is in construction of a corresponding mode or in responding to the ACCESS operation.

ACE4_LIST_DIRECTORY (for directories)

• Operation(s) affected:

  READDIR ACCESS (ACCESS_READ)

  Discussion:

  The action of enumerating the contents of a directory, as opposed to searching for a particlar name.

ACE4_WRITE_DATA (for non-directory objects)

• Operation(s) affected:

  WRITE OPEN (for write or read-write) ACCESS (ACCESS_MODIFY) ACCESS (ACCESS_EXTEND)

  • Only when ACE4_EXTEND_DATA in not supported.

  ACCESS (ACCESS_DELETE)

  • Only when ACE4_DELETE in not supported.

  SETATTR of size (extension)

  • Only when ACE4_EXTEND_DATA in not supported.

  SETATTR of size (truncation)

  Discussion:

  [Author Aside (Item #8a)]: Needs to be revised to deal with issues related to the interaction of WRITE_DATA and APPEND_DATA. [Consensus Needed (Item #8a)]: The action of modifying existing data bytes within a file's current data. When ACE4_APPEND_DATA is not supported, the action of extending a file's, data (e.g. by a WRITE which extends EOF, is included as well [Consensus Needed (Item #8a)]: As there is no way for the server to decide, in processing an OPEN or ACCESS request, whether subsequent WRITEs will extend the file or not, the server will, in processing an OPEN treat masks containing only WRITE_DATA, only APPEND_DATA, or both bits, in identical fashion. The result of ACCESS will reflect the individal authorizations to write existing bytea and to extend the file. [Consensus Needed (Item #8a)]: In processing a WRITE request, the server is presumed to have the ability to determine whether the current request extends the file and whether it modifies bytes already in the file. [Consensus Needed (Item #8a)]: ACE4_WRITE_DATA is required to process a WRITE which spans pre-existing bytes in the file, whether the file is extended or not.

ACE4_WRITE_DATA (directories)

• Operation(s) affected:

  CREATE

  • Will require ACE4_ADD_FILE, ACE4_ADD_SUBDIRECTORY, when these are supported.

  LINK OPEN (which creates file in the directory) ACCESS (ACCESS4_EXTEND) REMOVE (may require ACE4_DELETE_CHIILD, when supported RENAME (on the target drectory)

  Discussion:

  Operations which modify a directory Many of these operations may controlled at a finer granularity, when the appropriate mask bits are supported.

ACE4_EXECUTE (for non-diectory objects)

• Operation(s) affected:

  READ OPEN (for read or read-write) ACCESS (ACCESS4_EXECUTE) REMOVE RENAME LINK CREATE

  Discussion:

  The action of reading a file in order to execute it. Servers MUST allow a user the ability to read the data of the file when only the ACE4_EXECUTE access mask bit is allowed. This is because there is no way to execute a file without reading the contents. Though a server may treat ACE4_EXECUTE and ACE4_READ_DATA bits identically when deciding to permit a READ or OPEN operation, it MUST still allow the two bits to be set independently in NFSv4 ACLs, and distinguish between them when replying to ACCESS operations. In particular, servers MUST NOT silently turn on one of the two bits when the other is set, as that would make it impossible for the client to correctly enforce the distinction between read and execute permissions. As an example, following a SETATTR of the following NFSv4 ACL:

  • nfsuser:ACE4_EXECUTE:ALLOW

  A subsequent GETATTR of acl attribute for that file will return:

  • nfsuser:ACE4_EXECUTE:ALLOW

  and MUST NOT return:

  • nfsuser:ACE4_EXECUTE/ACE4_READ_DATA:ALLOW

ACE4_EXECUTE (for directories)

• Operation(s) affected:

  LOOKUP ACCESS(ACCESS4_LOOKUP)

  Discussion:

  The action of traversing directory by searching for a particular named item.

Uses of Finer-grained Mask Bits Derived from Write ACE4_ADD_FILE

• Operation(s) affected:

  CREATE LINK OPEN RENAME

  Discussion:

  The action of adding a new file in a directory. The CREATE operation is affected when nfs_ftype4 is NF4LNK, NF4BLK, NF4CHR, NF4SOCK, or NF4FIFO. (NF4DIR is not included because it is covered by ACE4_ADD_SUBDIRECTORY.) OPEN is affected when used to create a regular file. LINK is always affected and RENAME is affected when a file/directory is moved betweewn directories, with ACE4_ADD_SUBDIRECTORY covering the case when a directory is renmed.

ACE4_APPEND_DATA

• Operation(s) affected:

  WRITE ACCESS OPEN SETATTR of size

  Discussion:

  [Author Aside]: Also needs to be revised to deal with issues related to the interaction of WRITE_DATA and APPEND_DATA. The action of modifying a file's data, but only starting at EOF. This allows for the specification of append-only files, by allowing ACE4_APPEND_DATA and denying ACE4_WRITE_DATA to the same user or group. [Consensus Needed (Item #8a)]: As there is no way for the server to decide, in processing an OPEN or ACCESS request, whether subsequent WRITEs will extend the file or not, the server will treat masks containing only WRITE_DATA, only APPEND_DATA or both, identically. [Consensus Needed (Item #8a)]: If the server is processing a WRITE request and the area to be written extends beyond the existing EOF of the file then the state of APPEND_DATA mask bit is consulted to determine whether the operation is permitted or whether alarm or audit activities are to be performed. If a file has an NFSv4 ACL allowing only APPEND_DATA (and not WRITE_DATA) and a WRITE request is made at an offset below EOF, the server MUST return NFS4ERR_ACCESS. [Consensus Needed (Item #8a)]: If the server is processing a WRITE request and the area to be written does not extend beyond the existing EOF of the file then the state of APPEND_DATA mask bit does not need to be consulted to determine whether the operation is permitted or whether alarm or audit activities are to be performed. In this case, only the WRITE_DATA mask bit needs to be checked to determine whether the WRITE is authorized.

ACE4_ADD_SUBDIRECTORY

• Operation(s) affected:

  CREATE RENAME

  Discussion:

  [Author Aside]: The RENAME cases need to be limited to the renaming of directories, rather than saying, "The RENAME operation is always affected." [Consensus Needed (Item #9a)]: The action of creating a subdirectory in a directory. The CREATE operation is affected when nfs_ftype4 is NF4DIR. The RENAME operation is always affected when directories are renamed and the target directory NFSv4 ACL contains the mask ACE4_ADD_SUBDIRECTORY.

ACE4_DELETE_CHILD

• Operation(s) affected:

  REMOVE RENAME

  Discussion:

  The action of deleting a file or directory within a directory. See for information on now ACE4_DELETE and ACE4_DELETE_CHILD are to interact.

ACE4_DELETE

• Operation(s) affected:

  REMOVE

  Discussion:

  The action of deleting the associated file or directory. See for information on how ACE4_DELETE and ACE4_DELETE_CHILD are to interact.

Uses of Other Additional Mask Bits The mask bits discussed in this section all authorize actions, that, in the absence of support for that bit mask bit, are not resolved by one of the three POSIX-derived permission bits. Where these bits are not supported, the authorization decision will be arrived at, in one of the ways listed below, with the specifics prsented below as part of the discussion of that particular bit.

• The authorization can be controlled by file ownershiip.
• The authorization can be controlled by some boolean combination of multiple permission bits
• The authorization can be controlled by some boolean combination file ownership

[Consensus Needed (Item #10Ba)]: The default authorization prsented here is based on the only known implementtion of the speicfied bit. Dacilties need to be discussed to allow the specific to be derived as part of mask support discovery. ACE4_WRITE_ATTRIBUTES

• Operation(s) affected:

  SETATTR of time_access_set, time_backup, time_create, time_modify_set, mimetype, hidden, system.

  Discussion:

  The action of changing the times associated with a file or directory to an arbitrary value. Also permission to change the mimetype, hidden, and system attributes. A user having ACE4_WRITE_DATA or ACE4_WRITE_ATTRIBUTES will be allowed to set the times associated with a file to the current server time.

ACE4_WRITE_ACL

• Operation(s) affected:

  SETATTR of acl and mode

  Discussion:

  The action of modifying the acl or mode attributes.

ACE4_WRITE_OWNER

• Operation(s) affected:

  SETATTR of owner and owner_group

  Discussion:

  The action of modifying the owner or owner_group attributes. On UNIX systems, this done by executing chown() and chgrp().

ACE4_SYNCHRONIZE

• Operation(s) affected:

  NONE

  Discussion:

  Permission to use the file object as a synchronization primitive for interprocess communication. This permission is not enforced or interpreted by the NFSv4.1 server on behalf of the client. Typically, the ACE4_SYNCHRONIZE permission is only meaningful on local file systems, i.e., file systems not accessed via NFSv4.1. The reason that the permission bit exists is that some operating environments, such as Windows, use ACE4_SYNCHRONIZE. For example, if a client copies a file that has ACE4_SYNCHRONIZE set from a local file system to an NFSv4.1 server, and then later copies the file from the NFSv4.1 server to a local file system, it is likely that if ACE4_SYNCHRONIZE was set in the original file, the client will want it set in the second copy. The first copy will not have the permission set unless the NFSv4.1 server has the means to set the ACE4_SYNCHRONIZE bit. The second copy will not have the permission set unless the NFSv4.1 server has the means to retrieve the ACE4_SYNCHRONIZE bit.

Possible Uses of Additional Mask Bits The mask bits discusssed in this section all have definitions in exising specificsation, but, so far, no substantive support for them has been found. ACE4_READ_NAMED_ATTRS

• Operation(s) affected:

  OPENATTR

  Discussion:

  The action of reading the named attributes of a file or of looking up the named attribute directory. OPENATTR is affected when it is not used to create a named attribute directory. This is when 1) createdir is TRUE, but a named attribute directory already exists, or 2) createdir is FALSE.

ACE4_WRITE_NAMED_ATTRS

• Operation(s) affected:

  OPENATTR

  Discussion:

  The action of writing the named attributes of a file or creating a named attribute directory. OPENATTR is affected when it is used to create a named attribute directory. This is when createdir is TRUE and no named attribute directory exists. The ability to check whether or not a named attribute directory exists depends on the ability to look it up; therefore, users also need the ACE4_READ_NAMED_ATTRS permission in order to create a named attribute directory.

ACE4_READ_ATTRIBUTES

• Operation(s) affected:

  GETATTR of file system object attributes VERIFY NVERIFY READDIR

  Discussion:

  The action of reading basic attributes (non-ACLs) of a file. On a UNIX system, such basic attributes can be thought of as the stat-level attributes. Allowing this access mask bit would mean that the entity can execute "ls -l" and stat. If a READDIR operation requests attributes, this mask need s to be be allowed for the READDIR to succeed.

ACE4_WRITE_RETENTION

• Operation(s) affected:

  SETATTR of retention_set, retentevt_set.

  Discussion:

  The action of modifying the durations for event and non-event-based retention. Also includes enabling event and non-event-based retention. [Author Aside]: The use of "MAY" here ignores the potential for harm which unexpected modification of the associated attributes might cause for security/compliance. [Previous Treatment]: A server MAY behave such that setting ACE4_WRITE_ATTRIBUTES allows ACE4_WRITE_RETENTION. [Consensus Needed (Items #10a, #11a)]: Options for coarser-grained treatment involving this mask bit need to be discussed.

ACE4_WRITE_RETENTION_HOLD

• Operation(s) affected:

  SETATTR of retention_hold.

  Discussion:

  The action of modifying the administration retention holds. [Previous Treatment]: A server MAY map ACE4_WRITE_ATTRIBUTES to ACE_WRITE_RETENTION_HOLD. [Author Aside]: The use of "MAY" here ignores the potential for harm which unexpected modification of the associated attributes might cause for security/compliance. [Consensus Needed (Items #10a, #11a)]: Options for coarser-grained treatment of this mask bit need to be discussed.

Handling of Deletion [Author Aside]: This section, exclusive of subsections contains a proposal for the revision of the ACL-based handling of requests to delete directory entries. All unannotated material within it is to be considered part of consensus item #12a. [Author Aside]: The associated previous treatment is to be found in This section describes the handling requests of that involve deletion of a directory entry. It needs to be noted that:

• Modification or transfer of a directory, as happens in RENAME is not covered.
• The deletion of the file's data is dealt with separately as this, like a truncation to length zero, requires ACE4_WRITE_DATA.

In general, the recognition of such an operation for authorization/auditing/alarm depends on either of two bits mask bits being set: ACE4_MASK_DELETE on the file being deleted and ACE4_MASK_DELETE_CHILD on the directory from which the entry is being deleted. In the case of authorization, the above applies even when one of the bits is allowed and the other is explicitly denied. [Consensus Items, Including List (#6c, #12a): When neither of the mask bits is set, the result is normally negative. That is, permission is denied and no audit or alarm event is recognized. However, in the case of authorization, the server MAY make permission dependent on the setting of MODE4_SVTX, as follows:

• If that bit not set, allow the removal if and only if ACE4_ADD_FILE is permitted.
• If that bit is set, allow the removal if and only if ACE4_ADD_FILE is permitted and the requester is the owner of the target.

Previous Handling of Deletion [Author Aside]: This section contains the former content of . All unannotated paragraphs within it are to be considered the Previous Treatment associated with consensus item #12b. [Author Aside, Including List]: Listed below are some of the reasons that I have tried to replace the existing treatment rather than address the specific issues mentioned here and in later asides.

• The fact that there is no clear message about what servers are to do and about whether behavior clients might rely rely on. This derives in turn from the use of "SHOULD" in contexts in which it is clearly not appropriate, combined with non-normative reports of what some systems do, and the statement that the approach suggested is a way of providing "something like traditional UNIX-like semantics".
• The complexity of the approach without any indication that there is a need for such complexity makes me doubtful that anything was actually implemented, especially since the text is so wishy-washy about the need for server implementation. The probability that it would be implemented so widely that clients might depend on it is even more remote.
• The fact that how audit and alarm issues are to be dealt with is not addressed at all.
• The fact that this treatment combines ACL data with mode bit information in a confused way without any consideration of the fact that the mode attribute is OPTIONAL.

Two access mask bits govern the ability to delete a directory entry: ACE4_DELETE on the object itself (the "target") and ACE4_DELETE_CHILD on the containing directory (the "parent"). Many systems also take the "sticky bit" (MODE4_SVTX) on a directory to allow unlink only to a user that owns either the target or the parent; on some such systems the decision also depends on whether the target is writable. Servers SHOULD allow unlink if either ACE4_DELETE is permitted on the target, or ACE4_DELETE_CHILD is permitted on the parent. (Note that this is true even if the parent or target explicitly denies one of these permissions.) If the ACLs in question neither explicitly ALLOW nor DENY either of the above, and if MODE4_SVTX is not set on the parent, then the server SHOULD allow the removal if and only if ACE4_ADD_FILE is permitted. In the case where MODE4_SVTX is set, the server may also require the remover to own either the parent or the target, or may require the target to be writable. This allows servers to support something close to traditional UNIX-like semantics, with ACE4_ADD_FILE taking the place of the write bit.

ACE flag bits The bitmask constants used for the flag field are as follows: const ACE4_FILE_INHERIT_ACE = 0x00000001; const ACE4_DIRECTORY_INHERIT_ACE = 0x00000002; const ACE4_NO_PROPAGATE_INHERIT_ACE = 0x00000004; const ACE4_INHERIT_ONLY_ACE = 0x00000008; const ACE4_SUCCESSFUL_ACCESS_ACE_FLAG = 0x00000010; const ACE4_FAILED_ACCESS_ACE_FLAG = 0x00000020; const ACE4_IDENTIFIER_GROUP = 0x00000040; const ACE4_INHERITED_ACE = 0x00000080; [Author Aside]: Although there are multiple distinct issues that might need to be changed, in the interest of simplifying the review, all such issues within this section will be considered part of Consensus Item #13a with a single revised treatment addressing all the issues noted. [Previous Treatment]: A server need not support any of these flags. [Author Aside]: It is hard to understand why such broad license is granted to the server, leaving the client to deal, without an explicit non-support indication, with 256 possible combinations of supported and unsupported flags. If there were specific issues with some flags that makes it reasonable for a server not to support them, then these need to be specifically noted. Also problematic is the use of the term "need not", suggesting that the server does not need any justification for choosing these flags, defined by the protocol. At least it needs to be said that the server SHOULD support the defined ACE flags. After all they were included in the protocol for a reason. [Previous Treatment]: If the server supports flags that are similar to, but not exactly the same as, these flags, the implementation may define a mapping between the protocol-defined flags and the implementation-defined flags. [Author Aside]: The above dealing how an implementation might store the bits it supports, while valid, is out-of-scope and need to be deleted. [Previous Treatment]: For example, suppose a client tries to set an ACE with ACE4_FILE_INHERIT_ACE set but not ACE4_DIRECTORY_INHERIT_ACE. If the server does not support any form of ACL inheritance, the server should reject the request with NFS4ERR_ATTRNOTSUPP. If the server supports a single "inherit ACE" flag that applies to both files and directories, the server may reject the request (i.e., requiring the client to set both the file and directory inheritance flags). The server may also accept the request and silently turn on the ACE4_DIRECTORY_INHERIT_ACE flag. ]Author Aside]: What is the possible justification for accepting a request asking you do something and then, without notice to the client, do something else. I believe there is none. Consensus Needed (Item #13a)]: Servers SHOULD support the flag bits defined above as described in . When a server which does not support all the flags bits receives a request to set an NFSv4 ACL containing an ACE with an unsupported flag bit set the server MUST reject the request with NFS4ERR_ATTRNOTSUPP. Consensus Needed (Item #13a)]: The case of servers which do not provide support for particular flag combinations is to be treated similarly. If a server supports a single "inherit ACE" flag that applies to both files and directories, receives a request set an NFSv4 ACL with ACE ACE4_FILE_INHERIT_ACE set but ACE4_DIRECTORY_INHERIT_ACE not set, it MUST reject the request with NFS4ERR_ATTRNOTSUPP.

Details Regarding ACE Flag Bits

ACE4_FILE_INHERIT_ACE

Any non-directory file in any sub-directory will get this ACE inherited.

ACE4_DIRECTORY_INHERIT_ACE

Can be placed on a directory and indicates that this ACE is to be added to each new sub-directory created. If this flag is set in an ACE in an NFSv4 ACL attribute to be set on a non-directory file system object, the operation attempting to set the ACL SHOULD fail with NFS4ERR_ATTRNOTSUPP.

ACE4_NO_PROPAGATE_INHERIT_ACE

Can be placed on a directory. This flag tells the server that inheritance of this ACE is to stop at newly created child directories.

ACE4_INHERIT_ONLY_ACE

Can be placed on a directory but does not apply to the directory; ALLOW and DENY ACEs with this bit set do not affect access to the directory, and AUDIT and ALARM ACEs with this bit set do not trigger log or alarm events. Such ACEs only take effect once they are applied (with this bit cleared) to newly created files and directories as specified by the ACE4_FILE_INHERIT_ACE and ACE4_DIRECTORY_INHERIT_ACE flags. If this flag is present on an ACE, but neither ACE4_DIRECTORY_INHERIT_ACE nor ACE4_FILE_INHERIT_ACE is present, then an operation attempting to set such an attribute SHOULD fail with NFS4ERR_ATTRNOTSUPP.

ACE4_SUCCESSFUL_ACCESS_ACE_FLAG and ACE4_FAILED_ACCESS_ACE_FLAG

The ACE4_SUCCESSFUL_ACCESS_ACE_FLAG (SUCCESS) and ACE4_FAILED_ACCESS_ACE_FLAG (FAILED) flag bits may be set only on ACE4_SYSTEM_AUDIT_ACE_TYPE (AUDIT) and ACE4_SYSTEM_ALARM_ACE_TYPE (ALARM) ACE types. If during the processing of the file's NFSv4 ACL, the server encounters an AUDIT or ALARM ACE that matches the principal attempting the OPEN, the server notes that fact, and the presence, if any, of the SUCCESS and FAILED flags encountered in the AUDIT or ALARM ACE. Once the server completes the ACL processing, it then notes if the operation succeeded or failed. If the operation succeeded, and if the SUCCESS flag was set for a matching AUDIT or ALARM ACE, then the appropriate AUDIT or ALARM event occurs. If the operation failed, and if the FAILED flag was set for the matching AUDIT or ALARM ACE, then the appropriate AUDIT or ALARM event occurs. Either or both of the SUCCESS or FAILED can be set, but if neither is set, the AUDIT or ALARM ACE is not useful. The previously described processing applies to ACCESS operations even when they return NFS4_OK. For the purposes of AUDIT and ALARM, we consider an ACCESS operation to be a "failure" if it fails to return a bit that was requested and supported.

ACE4_IDENTIFIER_GROUP

Indicates that the "who" refers to a GROUP as defined under UNIX or a GROUP ACCOUNT as defined under Windows. Clients and servers MUST ignore the ACE4_IDENTIFIER_GROUP flag on ACEs with a who value equal to one of the special identifiers outlined in .

ACE4_INHERITED_ACE

Indicates that this ACE is inherited from a parent directory. A server that supports automatic inheritance will place this flag on any ACEs inherited from the parent directory when creating a new object. Client applications will use this to perform automatic inheritance. Clients and servers MUST clear this bit in the acl attribute; it may only be used in the dacl and sacl attributes.

ACE Who The "who" field of an ACE is an identifier that specifies the principal or principals to whom the ACE applies. It may refer to a user or a group, with the flag bit ACE4_IDENTIFIER_GROUP specifying which. There are several special identifiers that need to be understood universally, rather than in the context of a particular DNS domain. [Author Aside, including list]: so far, so good, but the following problems need to be addressed:

• Lack of clarity about which special identifiers can be understood by NFSv4.
• Confusion of "authentication" and "identification".

[Previous treatment (Item #50a)]: Some of these identifiers cannot be understood when an NFS client accesses the server, but have meaning when a local process accesses the file. The ability to display and modify these permissions is permitted over NFS, even if none of the access methods on the server understands the identifiers. [Consensus Needed (Item #50a)]: These identifiers, except for OWNER@, GROUP@, EVERONE@, cannot be reliably understood when an NFS client accesses the server, but might have meaning when a local process accesses the file or when protocols other than NFSv4 are used As a result, when ACEs containing these who values are encountered, the server is free to make its own judgment as to whether any particular request will be treated as matching. [Consensus Needed (Item #50a)]: The ability to display and modify these permissions is provide for by NFSv4, even though they are not useful when processing NFSv4 requests,

Who	Description
OWNER	The owner of the file.
GROUP	The group associated with the file.
EVERYONE	[Previous treatment (Item #50a)]: The world, including the owner and owning group. [Consensus Needed (Item #50a)]: All requesters, including the owner, members of the owning group, and requests for which no user information is available.
INTERACTIVE	Accessed from an interactive terminal.
NETWORK	Accessed via the network.
DIALUP	Accessed as a dialup user to the server.
BATCH	Accessed from a batch job.
ANONYMOUS	[Consensus Needed (Item #50a)]: Accessed without any authentication of the user principal.
AUTHENTICATED	[Consensus Needed (Item #50a)]: Any authenticated user (opposite of ANONYMOUS).
SERVICE	Accessed from a system service.

To avoid conflict, these special identifiers are distinguished by an appended "@" and will appear in the form "xxxx@" (with no domain name after the "@"), for example, ANONYMOUS@. {Previous treatment (Item #51a)]: The ACE4_IDENTIFIER_GROUP flag MUST be ignored on entries with these special identifiers. When encoding entries with these special identifiers, the ACE4_IDENTIFIER_GROUP flag SHOULD be set to zero. [Author Aside]: I don't understand what might be valid reasons to ignore this or how a server would respond in the case the that it was ignored. [Consensus Needed (Item #51a)]: The ACE4_IDENTIFIER_GROUP flag MUST be ignored on entries with these special identifiers. When encoding entries with these special identifiers, the ACE4_IDENTIFIER_GROUP flag MUST be set to zero. It is important to note that "EVERYONE@" is not equivalent to the UNIX "other" entity. This is because, by definition, UNIX "other" does not include the owner or owning group of a file. "EVERYONE@" means literally everyone, including the owner or owning group.

Automatic Inheritance Features The acl attribute consists only of an array of ACEs, but the sacl and dacl attributes also include an additional flag field. struct nfsacl41 { aclflag4 na41_flag; nfsace4 na41_aces<>; }; The flag field applies to the entire sacl or dacl; three flag values are defined: const ACL4_AUTO_INHERIT = 0x00000001; const ACL4_PROTECTED = 0x00000002; const ACL4_DEFAULTED = 0x00000004; and all other bits are to be cleared. The ACE4_INHERITED_ACE flag can be set in the ACEs of the sacl or dacl (whereas it always needs to be cleared in the acl). Together these features allow a server to support automatic inheritance, which we now explain in more detail. Inheritable ACEs are normally inherited by child objects only at the time that the child objects are created; later modifications to inheritable ACEs do not result in modifications to inherited ACEs on descendants. However, the dacl and sacl provide an OPTIONAL mechanism that allows a client application to propagate changes to inheritable ACEs to an entire directory hierarchy. A server that supports this feature performs inheritance at object creation time in the normal way, and SHOULD set the ACE4_INHERITED_ACE flag on any inherited ACEs as they are added to the new object. A client application such as an ACL editor may then propagate changes to inheritable ACEs on a directory by recursively traversing that directory's descendants and modifying each NFSv4 ACL encountered to remove any ACEs with the ACE4_INHERITED_ACE flag and to replace them by the new inheritable ACEs (also with the ACE4_INHERITED_ACE flag set). It uses the existing ACE inheritance flags in the obvious way to decide which ACEs to propagate. (Note that it may encounter further inheritable ACEs when descending the directory hierarchy and that those will also need to be taken into account when propagating inheritable ACEs to further descendants.) The reach of this propagation may be limited in two ways: first, automatic inheritance is not performed from any directory ACL that has the ACL4_AUTO_INHERIT flag cleared; and second, automatic inheritance stops wherever an ACL with the ACL4_PROTECTED flag is set, preventing modification of that ACL and also (if the ACL is set on a directory) of the ACL on any of the object's descendants. This propagation is performed independently for the sacl and the dacl attributes; thus, the ACL4_AUTO_INHERIT and ACL4_PROTECTED flags may be independently set for the sacl and the dacl, and propagation of one type of acl may continue down a hierarchy even where propagation of the other acl has stopped. New objects are to be created with a dacl and a sacl that both have the ACL4_PROTECTED flag cleared and the ACL4_AUTO_INHERIT flag set to the same value as that on, respectively, the sacl or dacl of the parent object. Both the dacl and sacl attributes are Recommended, and a server MAY support one without supporting the other. A server that supports both the old acl attribute and one or both of the new dacl or sacl attributes MUST do so in such a way as to keep all three attributes consistent with each other. Thus, the ACEs reported in the acl attribute will be the union of the ACEs reported in the dacl and sacl attributes, except that the ACE4_INHERITED_ACE flag will be cleared from the ACEs in the acl. And of course a client that queries only the acl will be unable to determine the values of the sacl or dacl flag fields. When a client performs a SETATTR for the acl attribute, the server SHOULD set the ACL4_PROTECTED flag to true on both the sacl and the dacl. By using the acl attribute, as opposed to the dacl or sacl attributes, the client signals that it may not understand automatic inheritance, and thus cannot be trusted to set an ACL for which automatic inheritance would make sense. When a client application queries an NFSv4 ACL, modifies it, and sets it again, it needs to leave any ACEs marked with ACE4_INHERITED_ACE unchanged, in their original order, at the end of the NFSv4 ACL. If the application is unable to do this, it needs to set the ACL4_PROTECTED flag. This behavior is not enforced by servers, but violations of this rule may lead to unexpected results when applications perform automatic inheritance. If a server also supports the mode attribute, it SHOULD set the mode in such a way that leaves inherited ACEs unchanged, in their original order, at the end of the ACL. If it is unable to do so, it SHOULD set the ACL4_PROTECTED flag on the file's dacl. Finally, in the case where the request that creates a new file or directory does not also set permissions for that file or directory, and there are also no ACEs to inherit from the parent's directory, then the server's choice of ACL for the new object is implementation-dependent. In this case, the server SHOULD set the ACL4_DEFAULTED flag on the ACL it chooses for the new object. An application performing automatic inheritance takes the ACL4_DEFAULTED flag as a sign that the ACL is to be completely replaced by one generated using the automatic inheritance rules.

Processing Access Control Entries To determine if a request succeeds, the server processes each nfsace4 entry of type ALLOW or DENY in turn as ordered in the array. Only ACEs that have a "who" that matches the requester are considered. An ACE is considered to match a given requester if at least one of the following is true:

• The "who' designates a specific user which is the user making the request.
• The "who" specifies "OWNER@" and the user making the request is the owner of the file.
• The "who" designates a specific group and the user making the request is a member of that group.
• The "who" specifies "GROUP@" and the user making the request is a member of the group owning the file.
• The "who" specifies "EVERYONE@".
• The "who" specifies "INTERACTIVE@", "NETWORK@", "DIALUP@", "BATCH@", or "SERVICE@" and the requester, in the judgment of the server, feels that designation appropriately describes the requester.
• The "who" specifies "ANONYMOUS@" or "AUTHENTICATED@" and the requestor's authentication status matches the who, using the definitions in

Each ACE is processed until all of the bits of the requester's access have been ALLOWED. Once a bit (see below) has been ALLOWED by an ACCESS_ALLOWED_ACE, it is no longer considered in the processing of later ACEs. If an ACCESS_DENIED_ACE is encountered where the requester's access still has unALLOWED bits in common with the "access_mask" of the ACE, the request is denied. When the ACL is fully processed, if there are bits in the requester's mask that have not been ALLOWED or DENIED, access is denied. Unlike the ALLOW and DENY ACE types, the ALARM and AUDIT ACE types do not affect a requester's access, and instead are for triggering events as a result of a requester's access attempt. AUDIT and ALARM ACEs are processed only after processing ALLOW and DENY ACEs if any exist. This is necessary since the handling of AUDIT and ALARM ACEs are affected by whether the access attempt is successful. [Previous Treatment]: The NFSv4.1 ACL model is quite rich. Some server platforms may provide access-control functionality that goes beyond the UNIX-style mode attribute, but that is not as rich as the NFS ACL model. So that users can take advantage of this more limited functionality, the server may support the acl attributes by mapping between its ACL model and the NFSv4.1 ACL model. Servers must ensure that the ACL they actually store or enforce is at least as strict as the NFSv4 ACL that was set. It is tempting to accomplish this by rejecting any ACL that falls outside the small set that can be represented accurately. However, such an approach can render ACLs unusable without special client-side knowledge of the server's mapping, which defeats the purpose of having a common NFSv4 ACL protocol. Therefore, servers should accept every ACL that they can without compromising security. To help accomplish this, servers may make a special exception, in the case of unsupported permission bits, to the rule that bits not ALLOWED or DENIED by an ACL must be denied. For example, a UNIX-style server might choose to silently allow read attribute permissions even though an ACL does not explicitly allow those permissions. (An ACL that explicitly denies permission to read attributes should still be rejected.) [Author Aside]: While the NFSv4.1 provides that many might not need or use, it is the one that the working group adopted by the working group, and I have to assume that alternatives, such as the withdrawn POSIX ACL proposal were considered but not adopted. The phrase "unsupported permission bits" with no definition of the bit whose support might be dispensed with, implies that the server is free to support whatever subset of these bits it chooses. As a result, clients would not be able to rely on a functioning server implementation of this OPTIONAL attribute. If there are specific compatibility issues that make it necessary to allow non-support of specific mask bits, then these need to be limited and the client needs guidance about determining the set of unsupported mask bits. [Previous Treatment]: The situation is complicated by the fact that a server may have multiple modules that enforce ACLs. For example, the enforcement for NFSv4.1 access may be different from, but not weaker than, the enforcement for local access, and both may be different from the enforcement for access through other protocols such as SMB (Server Message Block). So it may be useful for a server to accept an ACL even if not all of its modules are able to support it. [Author Aside]: The following paragraph does not provide helpful guidance and takes no account of the need of the the client to be able to rely on the server implementing protocol-specifying semantics and giving notice in those cases in which it is unable to so [Previous Treatment]: The guiding principle with regard to NFSv4 access is that the server must not accept ACLs that appear to make access to the file more restrictive than it really is.

Combining Authorization Models

Background for Combined Authorization Model Both and contain material relating to the need, when both mode and ACL attributes are supported, to make sure that the values are appropriately co-ordinated. Despite the fact that these discussions are different, they are compatible and differ in only a small number of areas relating to the existence absence of the set-mode-masked attribute. Such co-ordination is necessary is necessary since it is expected that servers providing both sets of attributes will encounter users who have no or very limited knowledge of one and need to work effectively when other users changes that attribute. As a result, these attributes cannot each be applied independently since that would create an untenable situation in which some users who have the right to control file access would find themselves unable to do so. [Author Aside]: From this point on, all paragraphs in this section, not other annotated are to be considered part of Consensus Item #63a. The description in this section of changes to be made reflects the author's proposal to address this issue and related issues. It might have to be adjusted based on working group decisions. As a result, in this document, we will have a single treatment of this issue, in Sections through . In addition, an NFSv4.2-based extension related to attribute co-ordination will be described in . The current NFSv4.0 and NFSv4.1 descriptions of this co-ordination share an unfortunate characteristic in that they are both written to give server implementations a broad latitude in implementation choices while neglecting entirely the need for clients and users to have a reliable description of what servers are to do in this area. As a result, one of the goals of this new combined treatment will be to limit the uncertainty that the previous approach created for clients, while still taking proper account of the possibility of compatibility issues that a more tightly drawn specification might give rise to. The various ways in which these kinds of issues have been dealt with are listed below together with a description of the needed changes proposed to address each issue.

• In some cases, the term "MAY" is used in contexts where it is inappropriate, since the allowed variation has the potential to cause harm in that it leaves the client unsure exactly what security-related action will be performed by the server. The new treatment will limit use use of MAY to cases in which it is truly necessary, in order to give clients proper notice of cases in which server behavior cannot be determined and limit the work necessary to deal with a large array of possible behaviors.
• There are also cases in which no RFC2119-defined keywords are used but it is stated that certain server implementations do a particular thing, leaving the impression that that action is to be allowed, just as if "MAY" had been used. If the flexibility is necessary, MAY will be used. In other cases, SHOULD will be used with the understanding that maintaining compatibility with clients that have adapted to a particular approach to this issue is a valid reason to bypass the recommendation. However, in no case will it be implied, as it is in the current specifications, that the server MAY do whatever it chooses, with the client having no option but to adapt to that choice.
• There was a case, in , in which the term "SHOULD" was explicitly used intentionally, without it being made clear what the valid reasons to ignore the guidance might be, although there was a reference to servers built to support the now-withdrawn draft definition of POSIX ACLs, which are referred to in this document as "UNIX ACLs", as described in Section 4.1 of . A discussion of the issues for support of for these ACLs appears in . [Author Aside]: Despite the statement, now cited in , that this was to accommodate implementations "POSIX" ACLs, it now appears that this was not complete. I've been given to understand that this was the result of two groups disagreeing on the appropriate mapping from ACLs, and specifying both, using the "intentional" "SHOULD" essentially as a MAY, with the text now in discouraging such use as potentially confusing, not intended to be taken seriously. Since the above information might not be appropriate in a standards-track RFC, we intend to retain this as an Author Aside which the working group might consider as it discusses how to navigate our way out of this situation. The new approach will use the term "RECOMMENDED" without use of the confusing term "intentional". The valid reasons to bypass the recommendation will be clearly explained as will be the consequences of choosing to do other than what is recommended.
• There are many case in which the terms "SHOULD" and "SHOULD NOT" are used without any clear indication why they were used. In this situation it is possible that the "SHOULD" was essentially treated as a "MAY" but also possible that servers chose to follow the recommendation. In order to deal with the many uses of these terms in and included subsections, which have no clear motivation, it is to be assumed that the valid reasons to act contrary to the recommendation given are the difficulty of changing implementations based on previous analogous guidance, which may have given the impression that the server was free to ignore the guidance for any reason the implementer chose. This allows the possibility of more individualized treatment of these instances once compatibility issues have been adequately discussed. [Author Aside]: In each subsection in which the the interpretation of these term in the previous paragraph applies there will be an explicit reference to Consensus Item #63, to draw attention to this change, even in the absence of modified text.

Needed Attribute Coordination On servers that support acl or dacl attributes, to gether with the mode attribute, the server needs to keep the two attributes consistent with one another. The value of the mode attribute (with the exception of the high-order bits reserved for client use as described in Section 5.3.2 of , are to be determined entirely by the value of the ACL, so that use of the mode is never required by ACL-aware clients for anything other than setting and interrogating the three high-order bits. See Sections through for detailed discussion. [Previous Treatment (Item #63b)]: When a mode attribute is set on an object, the ACL attributes may need to be modified in order to not conflict with the new mode. In such cases, it is desirable that the ACL keep as much information as possible. This includes information about inheritance, AUDIT and ALARM ACEs, and permissions granted and denied that do not conflict with the new mode. [Author Aside]: one the things that this formulation leaves uncertain, is whether, if the ACL specifies permission for a named user group or group, it "conflicts" with the node. Ordinarily, one might think it does not, unless the specified user is the owner of the file or a member of the owning group, or the specified group is the owning group. However, while some parts of the existing treatment seem to agree with this, other parts, while unclear, seem to suggest otherwise, while the treatment in is directly in conflict. [Previous Treatment (Item #26a)]: The server that supports both mode and ACL must take care to synchronize the MODE4_*USR, MODE4_*GRP, and MODE4_*OTH bits with the ACEs that have respective who fields of "OWNER@", "GROUP@", and "EVERYONE@". [Author Aside]: This sentence ignores named owners and group, giving the impressions that there is no need to change them. [Previous Treatment (Item #26a)]: This way, the client can see if semantically equivalent access permissions exist whether the client asks for the owner, owner_group, and mode attributes or for just the ACL. [Author Aside, Including List:] The above sentence, while hard to interpret for a number a reasons, is worth looking at in detail because it might suggest an approach different from the one in the previous sentence from the initial paragraph for The Previous Treatment of Item #26a.

• The introductory phrase "this way" adds confusion because it suggests that there are other valid ways of doing this, while not giving any hint about what these might be.
• It is hard to understand the intention of "client can see if semantically equivalent access permissions" especially as the client is told elsewhere that he is not to interpret the ACL himself.
• If this sentence is to have any effect at all it, it would be to suggest that the result be the same "whether the client asks for the owner, owner_group, and mode attributes or for just the ACL." If these are to be semantically equivalent it would be necessary to delete ACEs for named users, which requires a different approach form the first sentence of the original paragraph.

{Consensus Needed, Including List (Items #26a, #28a)]: A server that supports both mode and ACL attributes needs to take care to synchronize the MODE4_*USR, MODE4_*GRP, and MODE4_*OTH bits with the ACEs that have respective who fields of "OWNER@", "GROUP@", and "EVERYONE@". This requires:

• When the mode is changed, in most cases, the ACL attributes will need to be modified as described in .
• When the ACL is changed, the corresponding mode is determined and used to set the nine low-oder bits of the mode attribute. This is relatively straightforward in the case of forward-slope modes, but the case of reverse-slope modes needs to be addressed as well. It is RECOMMENDED that the procedure presented in be used or another one that provides the same results. The valid reasons to bypass this recommendation together with a alternate procedures to be used are discussed in .

{Consensus Needed (Item #26a)]: How other ACEs are dealt with when setting mode is described in . This includes ACEs with other who values, all AUDIT and ALARM ACEs, and all ACES that affect ACL inheritance. [Previous Treatment (Item #27a)]: In this section, much depends on the method in specified . Many requirements refer to this section. It needs to be noted that the methods have behaviors specified with "SHOULD" and that alternate approaches are discussed in . This is intentional, to avoid invalidating existing implementations that compute the mode according to the withdrawn POSIX ACL draft (1003.1e draft 17), rather than by actual permissions on owner, group, and other. [Consensus (Item #27a)]: In performing the co-ordinarion discussed in this section, the method used to compute the mode from the ACL has an important role. While the approach specified in is RECOMMENDED, it needs to be noted that the alternate approaches discussed in are valid in some cases. As discussed in that section, an important reason for allowing multiple ways of doing this is to accommodate server implementations that compute the mode according to the withdrawn POSIX ACL draft (1003.1e draft 17), rather than by actual permissions on owner, group, and other. While, this means that a client, having no way of determining the method the server uses may face interoperability difficulties in moving between servers which approach this matter differently, these problems need to be accepted for the time being. A more complete discussion of handling of the UNIX ACLs is to be found in . [Consensus Needed, Including List (Items #27a, #28a)]: All valid methods of computing the mode from an ACL use the following procedure to derive a set of mode bits from a set of three ACL masks, with the only difference being in how the set of ACL masks is constructed. The calculated mask for for each set of bits in mode are derived from the ACL mask for owner, group, other are derived as follows:

1. Set the read bit (MODE4_RUSR, MODE4_RGRP, or MODE4_ROTH) if and only if ACE4_READ_DATA is set in the corresponding mask.
2. Set the write bit (MODE4_WUSR, MODE4_WGRP, or MODE4_WOTH) if and only if ACE4_WRITE_DATA and ACE4_APPEND_DATA are both set in the corresponding mask.
3. Set the execute bit (MODE4_XUSR, MODE4_XGRP, or MODE4_XOTH), if and only if ACE4_EXECUTE is set in the corresponding mask.

Computing a Mode Attribute from an ACL [Previous Treatment (Item #27b)]: The following method can be used to calculate the MODE4_R*, MODE4_W*, and MODE4_X* bits of a mode attribute, based upon an ACL. [Author Aside]: "can be used" says essentially "do whatever you choose" and would make essentially pointless. Would prefer "is to be used" or "MUST", with "SHOULD" available if valid reasons to do otherwise can be found. [Consensus Needed (Items #27b, #28b, #61g)}: The following method (or another one providing exactly the same results) SHOULD be used to calculate the MODE4_R*, MODE4_W*, and MODE4_X* bits of a mode attribute, based upon an ACL when that ACL is one providing NFSv4 semantics. In this case, one of the valid reasons to bypass the recommendation includes implementor reliance on previous specifications which ignored the cases of the owner having less access than the owning group or the owning group having less access than others. Further, in implementing or the maintaining an implementation previously believed to be valid, the implementor needs to be aware that this will result in invalid values in some uncommon cases. Other reasons to bypass the recommendation are discussed in , along with the case of ACLs providing UNIX ACL semantics. [Author Aside, Including List]: The algorithm specified below, now considered the Previous Treatment associated with Item #24a, has an important flaw in does not deal with the (admittedly uncommon) case in which the owner_group has less access than the owner or others have less access than the owner-group. In essence, this algorithm ignores the following facts:

• That GROUP@ includes the owning user while group bits in the mode do not affect the owning user.
• That EVERYONE includes the owning group while other bits in the mode do not affect users within the owning group.

[Previous Treatment (Item #28b)]: First, for each of the special identifiers OWNER@, GROUP@, and EVERYONE@, evaluate the ACL in order, considering only ALLOW and DENY ACEs for the identifier EVERYONE@ and for the identifier under consideration. The result of the evaluation will be an NFSv4 ACL mask showing exactly which bits are permitted to that identifier. [Previous Treatment (Item #28b)]: Then translate the calculated mask for OWNER@, GROUP@, and EVERYONE@ into mode bits for, respectively, the user, group, and other, as follows: [Consensus Needed, including List(Item #28b)]: First, for each of the sets of mode bits (i.e., user, group other, evaluate the ACL in order, with a specific evaluation procedure depending on the specific set of mode bits being determined. For each set there will be one or more special identifiers considered in a positive sense so that ALLOW and DENY ACE's are considered in arriving at the mode bit. In addition, for some sets of bits, there will be one or more special identifiers to be considered only in a negative sense, so that only DENY ACE's are considered in arriving at the mode it. The users to be considered are as follows:

• For the owner bits, "OWNER@" and "EVERYONE@" are to be considered, both in a positive sense.
• For the group bits, "GROUP@" and "EVERYONE@" are to be considered, both in a positive sense, while "OWNER@" is to be considered in a negative sense.
• For the other bit, "EVERYONE@" is to be considered in a positive sense, while "OWNER@" and "GROUP@" are to be considered in a negative sense.

[Consensus Needed (Item #28b)]: Once these ACL masks are constructed, the mode bits for, user, group, and other can be obtained as described in above.

Alternatives in Computing Mode Bits [Author Aside]: All unannotated paragraphs within this section are to be considered the Previous Treatment corresponding to Consensus Item #27c. Some server implementations also add bits permitted to named users and groups to the group bits (MODE4_RGRP, MODE4_WGRP, and MODE4_XGRP). Implementations are discouraged from doing this, because it has been found to cause confusion for users who see members of a file's group denied access that the mode bits appear to allow. (The presence of DENY ACEs may also lead to such behavior, but DENY ACEs are expected to be more rarely used.) [Author Aside]: The text does not seem to really discourage this practice and makes no reference to the need to standardize behavior so the clients know what to expect or any other reason for providing standardization of server behavior. The same user confusion seen when fetching the mode also results if setting the mode does not effectively control permissions for the owner, group, and other users; this motivates some of the requirements that follow. [Author Aside]: The part before the semicolon appears to be relevant to Consensus Item #23 but does not point us to a clear conclusion. The statement certainly suggests that the 512-ACL approach is more desirable but the absence of a more direct statement to that effect suggest that this is a server implementer choice. [Author Aside]: The part after the semicolon is hard to interpret in that it is not clear what "this" refers to or which which requirements are referred to by "some of the requirements that follow". The author would appreciate hearing from anyone who has insight about what might have been intended here. [Consensus Needed, Including List (Item #27c, #61h)]: In cases in which the mode is not computed as described in , one of the following analogous procedures or their equivalents, MUST be used. This includes cases in which the ACL in question is one providing UNIX ACL semantics.

• First, for each of the special identifiers OWNER@ and EVERYONE@, evaluate the ACL in order, considering only ALLOW and DENY ACEs for the identifier EVERYONE@ and for the identifier under consideration. For the special identifier GROUP@, ALLOW and DENY ACEs for GROUP@ and EVERYONE@ are to be considered, together with ALLOW ACEs for named users and groups. This represents the approach previously recommended to compute mode in previous specification, as modified to reflect the UNIX ACL practice of reflecting permissions for named users and groups. It does not deal properly with reverse-slope modes.
• Compute a set of ACL mask according to the procedure in and then, for the mask associated with GROUP@, or in the masks for all ALLOW ACEs for named users and groups. This represents the approach currently recommended to compute mode in as modified to reflect the UNIX ACL practice of reflecting permissions for named users and groups.

[Consensus Needed, Including List (Item #27c)]: In both cases, The results of the evaluation will be a set of NFSv4 ACL masks which can be converted to the set on nine low-order mode bits using the procedure appearing in above. [Consensus Needed, Including List (Item #27c)]: When the recommendation to use is bypassed, it needs to be understood, that the modes derived will differ from the expected values and might cause interoperability issues. This is particularly the case when clients have no way to determine that the server's behavior is other than standard.

Handling of UNIX ACLs [Author Aside]: All paragraphs in this section are consider part of Consensus Item #63c. Although the working group did not adopt the acls in the withdrawn POSIX draft, their continued existence in UNIX contexts has created protocol difficulties that need to be resolved. In many cases these ACLS and their associated semantics are the basis for ACL support in UNIX client APIs and in UNIX file systems supported by NFSv4 Although the semantic range of UNIX ACLs is a subset of that for NFSv4 ACLs, expecting clients to perform that mapping on their own has not worked well, leading to the following issues which will, at some point, need to be addressed:

• There is a considerable uncertainty about the proper mapping from ACLs to modes.
• The corresponding mapping from modes to ACLs is dealt with different ways by different sections of the spec.
• These individual uncertainties are compounded since it is difficult, in this environment, to ensure that these independently chosen mappings are inverses of one another, as they are intended to be.

Some possible approaches to these issues are discussed in MAINSPEC(FUTURE-acl).

Setting Multiple ACL Attributes In the case where a server supports the sacl or dacl attribute, in addition to the acl attribute, the server MUST fail a request to set the acl attribute simultaneously with a dacl or sacl attribute. The error to be given is NFS4ERR_ATTRNOTSUPP.

Setting Mode and not ACL (overall)

Setting Mode and not ACL (vestigial) [Author Aside]: All unannotated paragraphs are to be considered the Previous treatment of Consensus Item #30b. [Previous Treatment (Item #?a)]: When any of the nine low-order mode bits are subject to change, either because the mode attribute was set or because the mode_set_masked attribute was set and the mask included one or more bits from the nine low-order mode bits, and no ACL attribute is explicitly set, the acl and dacl attributes must be modified in accordance with the updated value of those bits. This must happen even if the value of the low-order bits is the same after the mode is set as before. Note that any AUDIT or ALARM ACEs (hence any ACEs in the sacl attribute) are unaffected by changes to the mode. In cases in which the permissions bits are subject to change, the acl and dacl attributes MUST be modified such that the mode computed via the method in yields the low-order nine bits (MODE4_R*, MODE4_W*, MODE4_X*) of the mode attribute as modified by the attribute change. The ACL attributes SHOULD also be modified such that:

1. If MODE4_RGRP is not set, entities explicitly listed in the ACL other than OWNER@ and EVERYONE@ SHOULD NOT be granted ACE4_READ_DATA.
2. If MODE4_WGRP is not set, entities explicitly listed in the ACL other than OWNER@ and EVERYONE@ SHOULD NOT be granted ACE4_WRITE_DATA or ACE4_APPEND_DATA.
3. If MODE4_XGRP is not set, entities explicitly listed in the ACL other than OWNER@ and EVERYONE@ SHOULD NOT be granted ACE4_EXECUTE.

Access mask bits other than those listed above, appearing in ALLOW ACEs, MAY also be disabled. Note that ACEs with the flag ACE4_INHERIT_ONLY_ACE set do not affect the permissions of the ACL itself, nor do ACEs of the type AUDIT and ALARM. As such, it is desirable to leave these ACEs unmodified when modifying the ACL attributes. Also note that the requirement may be met by discarding the acl and dacl, in favor of an ACL that represents the mode and only the mode. This is permitted, but it is preferable for a server to preserve as much of the ACL as possible without violating the above requirements. Discarding the ACL makes it effectively impossible for a file created with a mode attribute to inherit an ACL (see ).

Setting Mode and not ACL (Discussion) [Author Aside]: All unannotated paragraphs are to be considered Author Asides relating to Consensus Item #30c. Existing documents are unclear about the changes to be made to an existing ACL when the nine low-order bits of the mode attribute are subject to modification using SETATTR. A new treatment needs to apply to all minor versions. It will be necessary to specify that, for all minor versions, setting of the mode attribute, subjects the low-order nine bits to modification. One important source of this lack of clarity is the following paragraph from , which we refer to later as the trivial-implementation-remark".

• Also note that the requirement may be met by discarding the acl and dacl, in favor of an ACL that represents the mode and only the mode. This is permitted, but it is preferable for a server to preserve as much of the ACL as possible without violating the above requirements. Discarding the ACL makes it effectively impossible for a file created with a mode attribute to inherit an ACL (see ).

The only "requirement" which might be met by the procedure mentioned above is the text quoted below.

• In cases in which the permissions bits are subject to change, the acl and dacl attributes MUST be modified such that the mode computed via the method in yields the low-order nine bits (MODE4_R*, MODE4_W*, MODE4_X*) of the mode attribute as modified by the attribute change.

While it is true that this requirement could be met by the specified treatment, this fact does not, in itself, affect the numerous recommendations that appear between the above requirement and the trivial-implementation-remark. It may well be that there are are implementations that have treated the trivial-implementation-remark as essentially allowing them to essentially ignore all of those recommendations, resulting in a situation in which were treated as if it were a trivial-implementation-ok indication. How that issue will be dealt with in a replacement for will be affected by the working group's examination of compatibility issues. The following specific issues need to be addressed:

• Handling of inheritance. Beyond the possible issues that arise from the trivial-implementation-ok interpretation, the treatment in , by pointing specifically to existing INHERIT_ONLY ACEs obscures the corresponding need to convert ACE's that specify both inheritance and access permissions to be converted to INHERIT_ONLY ACEs.
• Reverse-slope modes
• Named users and groups.
• The exact bounds of what within the ACL is covered by the low-order bits of the mode.

It appears that for many of the issues, there are many possible readings of the existing specs, leading to the possibility of multiple inconsistent server behaviors. Furthermore, there are cases in which none of the possible behaviors described in existing specifications meets the needs. As a result of these issues, the existing specifications do not provide a reliable basis for client-side implementations of the ACL feature which a Proposed Standard is normally expected to provide.

Setting Mode and not ACL (Proposed) [Author Aside]: This proposed section is part of Consensus Item #30d and all unannotated paragraphs within it are to be considered part of that Item. Since the proposed text includes support for reverse-slope modes, treats all minor versions together and assumes decisions about handling of ACEs for named users and groups, the relevance of consensus items #26, #28, and #29 needs to be noted. [Author Aside]: As with all such Consensus Items, it is expected that the eventual text in a published RFC might be substantially different based on working group discussion of client and server needs and possible compatibility issues. In this particular case, that divergence can be expected to be larger, because the author was forced to guess about compatibility issues and because earlier material, on which it is based left such a wide range of matters to the discretion of server implementers. It is the author's hope that, as the working group discusses matters, sufficient attention is placed on the need for client-side implementations to have reliable information about expected server-side actions. This section describes how ACLs are to be updated in response to actual or potential changes in the mode attribute, when the attributes needed by both of the file access authorization models are supported. It supersedes the discussions of the subject in and , each of which appeared in Section 6.4.1.1 of the corresponding document. It is necessary to approach the matter differently than in the past because:

• Organizational changes are necessary to address all minor versions together.
• Those previous discussions are often internally inconsistent leaving it unclear what specification-mandated actions were being specified..
• In many cases, servers were granted an extraordinary degree of freedom to choose the action to take, either explicitly or via an apparently unmotivated use of "SHOULD", leaving it unclear what might be considered "valid" reasons to ignore the recommendation.
• There appears to have been no concern for the problems that clients and applications might encounter dealing ACLs in such an uncertain environment.
• Cases involving reverse-slope modes were not adequately addressed.
• The security-related effects of SVTX were not addressed.

While that sort of approach might have been workable at one time, it made it difficult to devise client-side ACL implementations, even if there had been any interest in doing so. In order to enable this situation to eventually be rectified, we will define the preferred implementation here, but in order to provide temporary compatibility with existing implementations based on reasonable interpretations of . To enable such compatibility the term "SHOULD" will be used, with the understanding that valid reasons to bypass the recommendation, are limited to implementers' previous reliance on these earlier specifications and the difficulty of changing them now. When the recommendation is bypassed in this way, it is necessary to understand, that, until the divergence is rectified, or the client is given a way to determine the detail of the server's non-standard behavior, client-side implementations may find it difficult to implement a client-side implementation that correctly interoperates with the existing server. When mode bits involved in determining file access authorization are subject to modification, the server MUST, when ACL-related attributes have been set, modify the associated ACEs so as not to conflict with the new value of the mode attribute. The occasions to which this requirement applies, vary with the attribute being set and the type of object being dealt with:

• For all minor versions, any change to the mode attribute, triggers this requirement
• When the set_mode_masked attribute is being set on an object which is not a directory, whether this requirement is triggered depends on whether any of the nine low-order bits of the mode is included in the mask.
• When the set_mode_masked attribute is being set on a directory, whether this requirement is triggered depends on whether any of the nine low-order bits of the mode or the SVTX bit is included in the mask of bit whose values are to be set.

When the requirement is triggered, ACEs need to be updated to be consistent with the new mode attribute. In the case of AUDIT and ALARM ACEs, which are outside of file access authorization, no change is to be made. For ALLOW and DENY ACEs, changes are necessary to avoid conflicts with the mode in a number of areas:

• The handling of ACEs that have consequences relating to ACL inheritance.
• The handling of ACEs with a who-value of OWNER@, GROUP@, or EVERYONE@ need to be adapted to the new mode.
• ACEs whose who-value is a named user or group, are to be retained or not based on the mode being set as described below.
• ACEs whose who-value is one of the other special values defined in are to be left unmodified.

In order to deal with inheritance issues, the following SHOULD be done:

• ACEs that specify inheritance-only need to be retained, regardless of the value of who specified, since inheritance issues are outside of the semantic range of the mode attribute.
• ACEs that specify inheritance, in addition to allowing or denying authorization for the current object need to be converted into inheritance-only ACEs. This needs to occur irrespective of the value of who appearing in the ACE.

For NFSv4 servers that support the dacl attribute, at least the first of the above MUST be done. Other ACEs are to be treated are classified based on the ACE's who-value:

• ACEs whose who-value is OWNER@, GROUP@, or EVERYONE@ are referred to as mode-directed ACEs and are subject to extensive modification.
• ACEs whose who-value is a named user or group are either left alone or subject to extensive modification, as described below.
• ACEs whose who-value is one of the other special values defined in are left as they are.

Mode-directed ACEs need to be modified so that they reflect the mode being set. In effecting this modification, the server will need to distinguish mask bits deriving from mode attributes from those that have no such connection. The former can be categorized as follows:

• For non-directory objects, the mask bits ACE4_READ_DATA (from the read bit in the mode), ACE4_EXECUTE (from the execute bit in the mode), and ACE4_WRITE_DATA together with ACE4_APPEND_DATA (from the write bit in the mode) are all derived from the set of three mode bits appropriate to the current who-value.
• For directories, analogous mask bits are included: ACE4_LIST_DIRECTORY (from the read in the mode), ACE4_EXECUTE (from the execute bit in the mode), and ACE4_ADD_FILE together with ACE4_ADD_SUBDIRECTORY and ACE4_DELETE_CHILD> (from the write bit in the mode) are all included based on the set of three mode bits appropriate to the current who-value. When the SVTX bit is set, ACE4_DELETE_CHILD is set, regardless of the values of the low-order nine bit of the mode.
• When named attributes are supported for the object whose mode is subject to change, ACE4_READ_NAMED_ATTRIBUTES is set based on the read bit and ACE4_WRITE_NAMED_ATTRIBUTES is set based on the write bit based on the set of three mode bits appropriate to the current who-value.
• In the case of OWNER@, ACE4_WRITE_ACL, ACE4_WRITE_ATTRIBUTES ACE4_WRITE_ACL, ACE4_WRITE_OWNER are all set.

The union of these groups of mode bit are referred to as the mode-relevant mask bits. [Author Aside]: Except for the case of ACE4_SYNCHRONIZE, the handling of mask bits which are not mode-relevant is yet to be clarified. For tracking purposes, the handling of mask bits ACE4_READ_ATTRIBUTES, ACE4_WRITE_RETENTION, ACE4_WRITE_RETENTION_HOLD, ACE4_READ_ACL will be dealt with as Consensus Item #31. If the mode is of forward-slope, then each set of three bits is translated into a corresponding set of mode bits. Then, for each ALLOW ACE with one of these who values, all mask bits in this class are deleted and the computed mode bits for that who-value substituted. For DENY ACEs, all mask bits in this class are reset, and, if none remain, the ACE MAY be deleted. In the case of reverse-slope modes, the following SHOULD be done:

• For mode-directed ACEs all mode-relevant mask bits are reset, and, if none remain, the ACE MAY be deleted.
• Then, proceeding from owner to others, ALLOW ACEs are generated based on the computed mode-relevant mask bits. At each stage, if the mode-relevant mask bits for the current stage includes mask bits not set for the previous stage, then a DENY ACE needs to be added before the new ALLOW ACE. That ACE will have a who-value based on the previous stage and a mask consisting of the bit included in the current stage that were not included in the previous stage.

In cases in which the above recommendation is not followed, the server MUST follow a procedure which arrives at an ACL which behaves identically for all cases involving forward-slope mode values. When dealing with ACEs whose who-value is a named user or group, they SHOULD be processed as follows:

• DENY ACEs are left as they are.
• ALLOW ACES are subject to filtering to effect mode changes that deny access to any principal other than the owner. To determine the set of mode bits to which this filtering applies, the mode bits for group are combined with those for others, to get a set of three mode bits to determine which of the mode privileges (read, write, execute) are denied to all principals other than the owner, i.e. the set of bits not present in either the bits for group or the bits for others. Those three bits are converted to the corresponding set of mask bits, according to the rules above. All such mask bits are reset in the ACE, and, if none remain, the ACE MAY be deleted.

In cases in which the above recommendation is not followed, the server MUST follow a procedure which arrives at an ACL which behaves identically for all cases involving forward-slope mode values. This would be accomplished if the mask bits were reset based on the group bits alone, as had been recommended in earlier specifications.

Setting ACL and Not Mode [Author Aside]: The handling of SHOULD in this section is considered as part of Consensus Item #63d. When setting the acl or dacl and not setting the mode or mode_set_masked attributes, the permission bits of the mode need to be derived from the ACL. In this case, the ACL attribute SHOULD be set as given. The nine low-order bits of the mode attribute (MODE4_R*, MODE4_W*, MODE4_X*) MUST be modified to match the result of the method in . The three high-order bits of the mode (MODE4_SUID, MODE4_SGID, MODE4_SVTX) SHOULD remain unchanged.

Setting Both ACL and Mode When setting both the mode (includes use of either the mode attribute or the mode_set_masked attribute) and the acl or dacl attributes in the same operation, the attributes MUST be applied in the following order order: mode (or mode_set_masked), then ACL. The mode-related attribute is set as given, then the ACL attribute is set as given, possibly changing the final mode, as described above in .

Retrieving the Mode and/or ACL Attributes [Author Aside]: The handling of SHOULD in this section is considered as part of Consensus Item #63e. If a server supports any ACL attributes, it may use the ACL attributes on the parent directory to compute an initial ACL attribute for a newly created object. This will be referred to as the inherited ACL within this section. The act of adding one or more ACEs to the inherited ACL that are based upon ACEs in the parent directory's ACL will be referred to as inheriting an ACE within this section. Implementors need to base the behavior of CREATE and OPEN depending on the presence or absence of the mode and ACL attributes by following the directions below:

1. If just the mode is given in the call: In this case, inheritance SHOULD take place, but the mode MUST be applied to the inherited ACL as described in , thereby modifying the ACL.
2. If just the ACL is given in the call: In this case, inheritance SHOULD NOT take place, and the ACL as defined in the CREATE or OPEN will be set without modification, and the mode modified as in .
3. If both mode and ACL are given in the call: In this case, inheritance SHOULD NOT take place, and both attributes will be set as described in .
4. If neither mode nor ACL is given in the call: In the case where an object is being created without any initial attributes at all, e.g., an OPEN operation with an opentype4 of OPEN4_CREATE and a createmode4 of EXCLUSIVE4, inheritance SHOULD NOT take place (note that EXCLUSIVE4_1 is a better choice of createmode4, since it does permit initial attributes). Instead, the server SHOULD set permissions to deny all access to the newly created object. It is expected that the appropriate client will set the desired attributes in a subsequent SETATTR operation, and the server SHOULD allow that operation to succeed, regardless of what permissions the object is created with. For example, an empty ACL denies all permissions, but the server need to allow the owner's SETATTR to succeed even though WRITE_ACL is implicitly denied. In other cases, inheritance SHOULD take place, and no modifications to the ACL will happen. The mode attribute, if supported, MUST be as computed in , with the MODE4_SUID, MODE4_SGID, and MODE4_SVTX bits clear. If no inheritable ACEs exist on the parent directory, the rules for creating acl, dacl, or sacl attributes are implementation defined. If either the dacl or sacl attribute is supported, then the ACL4_DEFAULTED flag SHOULD be set on the newly created attributes.

Use of Inherited ACL When Creating Objects [Author Aside]: The handling of SHOULD in this section is considered as part of Consensus Item #63f. If the object being created is not a directory, the inherited ACL SHOULD NOT inherit ACEs from the parent directory ACL unless the ACE4_FILE_INHERIT_ACE flag is set. If the object being created is a directory, the inherited ACL is to inherit all inheritable ACEs from the parent directory, that is, those that have the ACE4_FILE_INHERIT_ACE or ACE4_DIRECTORY_INHERIT_ACE flag set. If the inheritable ACE has ACE4_FILE_INHERIT_ACE set but ACE4_DIRECTORY_INHERIT_ACE is clear, the inherited ACE on the newly created directory MUST have the ACE4_INHERIT_ONLY_ACE flag set to prevent the directory from being affected by ACEs meant for non-directories. When a new directory is created, the server MAY split any inherited ACE that is both inheritable and effective (in other words, that has neither ACE4_INHERIT_ONLY_ACE nor ACE4_NO_PROPAGATE_INHERIT_ACE set), into two ACEs, one with no inheritance flags and one with ACE4_INHERIT_ONLY_ACE set. (In the case of a dacl or sacl attribute, both of those ACEs SHOULD also have the ACE4_INHERITED_ACE flag set.) This makes it simpler to modify the effective permissions on the directory without modifying the ACE that is to be inherited to the new directory's children.

Combined Authorization Models for NFSv4.2 The NFSv4 server implementation requirements described in the subsections above apply to NFSv4.2 as well and NFSv4.2 clients can assume that the server follows them. NFSv4.2 contains an OPTIONAL extension, defined in , which is intended to reduce the interference of modes, restricted by the umask mechanism, with the acl inheritance mechanism. The extension allows the client to specify the umask separately from the mask attribute.

Other Uses of Access Control Lists Whether the acl or sacl attributes are used, AUDIT and ALARM ACEs provide security-related facilities separate from the the file access authorization provided by ALLOW and DENY ACEs

• AUDIT ACEs provide a means to audit attempts to access a specified file by specified sets of principals.
• ALARM ACEs provide a means to draw special attention to attempts to access specified files by specified sets of principals.

Security Considerations There are no Security considerations specific to this document. Security considerations for NFSv4 as a whole are dealt with in the Security Considerations section of .

IANA Considerations This document requires no actions from IANA>

References Normative References Informative References

Issues for which Consensus Needs to be Ascertained This section helps to keep track of specific changes which the author has made or intends to make to deal with issues found in RFCs 7530 and 8881. The changes listed here exclude those which are clearly editorial but includes some that the author believes are editorial but for which the issues are sufficiently complicated that working group consensus on the issue is probably necessary. These changes are presented in the table below, organized into a set of "Consensus Items" identified by the numeric code appearing in annotations in the proposed document text. For each such item, a type code is assigned with separate sets of code define for pending items and for those which are no longer pending. The following codes are defined for pending consensus items:

• "NM" denotes a change which is new material that is not purely editorial and thus requires Working Group consensus for eventual publication.
• "BE" denotes a change which the author believes is editorial but for which the change is sufficiently complex that the judgment is best confirmed by the Working Group.
• "BC" denotes a change which is a substantive change that the author believes is correct. This does not exclude the possibility of compatibility issues becoming an issue but is used to indicate that the author believes any such issues are unlikely to prevent its eventual acceptance.
• "CI" denotes a change for which the potential for compatibility issues is a major concern with the expected result that working group discussion of change will focus on clarifying our knowledge of how existing clients and server deal with the issue and how they might be affected by the change or the change modified to accommodate them.
• "NS" denotes a change which represents the author's best effort to resolve a difficulty but for which the author is not yet confident that it will be adopted in its present form, principally because of the possibility of troublesome compatibility issues.
• "NE" denotes change based on an existing issue in the spec but for which the replacement text is incomplete and needs further elaboration.
• "WI" denotes a potential change based on an existing issue in the spec but for which replacement text is not yet available because further working group input is necessary before drafting. It is expected that replacement text will be available in a later draft once that discussion is done.
• "LD" denotes a potential change based on an existing issue in the spec but for which replacement text is not yet available due to the press of time. It is expected that replacement text will be available in a later draft.
• "EV" denote a potential change which is tentative or incomplete because further details need to be provide or because the author is unsure that he has a correct explanation of the issue. It is expected that replacement text will be available in a later draft.

The following codes are defined for consensus items which are no longer pending.

• "RT" designates a former item which has been retired, because it has been merged with another one or otherwise organized out of existence. Such items no longer are referred to the document source although the item id is never reassigned. They are no longer counted among the set of total items.
• "CA" designates a former item for which consensus has been achieved in the judgment of the author, although not by any official process. Items reaching this state are effected in the document source including the deletion of annotations and the elimination of obsoleted previous treatments. Items in this state are still counted among the total of item but are no longer considered pending
• "CV" designates a former item for which consensus has been achieved and officially verified. Even though the author is a Working Group co-chair,it is probably best if he is not involved in this process and intends to leave it to the other co-chairs, the Document Shepherd and the Area Director. Items in this state are not counted among the item totals. They may be kept in the table but only to indicate that the item id is still reserved.
• "DR" designates a former item which has been dropped, because it appears that working group acceptance of it, even with some modification, is unlikely. Such items no longer are referred to the document source although the item id is never reassigned. They are no longer counted among the set of total items.

When asterisk is appended to a state of "NM", "BC" or "BE" it that there has been adequate working group discussion leading one to reasonably expect it will be adopted, without major change, in a subsequent document revision. Such general acceptance is not equivalent to a formal working group consensus and it not expected to result in major changes to the draft document, On the other hand, once there is a working group consensus with regard to a particular issue, the document will be modified to remove associated annotations, with the previously conditional text appearing just as other document text does. The issue will remain in this table as a non-pending item. It will be mentioned in Appendix A of , to summarize the changes that have been made. It is to be expected that these designations will change as discussion proceeds and new document versions are published. It is hoped that most such shifts will be upward in the above list or result in the deletion of a pending item, by reaching a consensus to accept or reject it. This would enable, once all items are dealt with, an eventual request for publication as an RFC, with this appendix having been deleted. The consensus item in the followig table can be divided into three groups, based on the ssociated numeric id.

• Those with ids less than 62 were created as part of the security and transferred to this on as part of the doument split.
• Those with ids between 62 and 65 are the result of splitting item created as part of the security that now adress issues in bo both documents
• Those with id 100 and aboved were created after the document split. In most case, there is no connection to material within the security document.

#	Type	...References...	Substance
3	BE	#3a in S	Conversion of mask bit descriptions from being about "permissions" to being about the action permitted, denied, or specified as being audited or generating alarms.
4	CI	#4a in S	Elimination of uses of SHOULD believed inappropriate in .
5	NI	#5a in S #5b in S	Changes needes in treatment of ACCESS, including the following: ACCESS is listed as an operation in all cases in which one of the bits returned by the operation ould be affected. There is now explcit indication of which bit(s) returned by ACCESS might be affected. There is now a discussion of differences between the effect on authorization and that on other uses of the associated mask biks for ACEs not conncted with authorization. Given the inability of the server to determine which bits are being tested by the client, determiing when success or failure has occurred is impossible. As a result it appears best to given the server freedom, in any particular case, to decide whether ACCESS constitutes a recordable evenr
14	BC	#14a in S #14b in S	Explicit discussion of the case in which aclsupport is not supported.
15	BC	#15a in S	Handling of the proper relationship between support for ALLOW and DENY ACEs.
16	NM	#16a in S	Discussion of coherence of acl, sacl, and dacl attributes.
62	NI	#62a in S	New/revised description of the role of the "sticky bit" for directories, with respect to ACL/ACE handling. Needs to be considered together with Item #6 in the security document proper.
63	CI	#63a in S #63b in S #63c in S #63d in S #63e in S #63f in S	Revised description of co-ordination of acl and mode attributes to apply to NFSv4 as a whole. While this includes many aspects of the shift to be more specific about the co-ordination requirements including addressing apparently unmotivated uses of the terms "SHOULD" and "SHOULD NOT", it excludes some arguably related matters dealt with as Consensus Items #26 and #27. Needs to be considered together with Item #25 in the security document proper.
64	WI	#64a in S	Discussion of issues related to the handling of allowed variants of the NFSv4 ACL model, including subsets based on the Unix ACL model. Needs to be considered together with Item #56 in the security document proper.
65	NS	#65a #65b #65c	Designation of the acl, dacl, and sacl attributes as Experimental, even though still formally OPTIONAL. Note that this is separate from the possibility of sufficiently clarifying the description of the acl, dacl, and sacl attributes to make the Experimental designation unnecessary, which will be covered as Item #XX. Needs to be considered together with Item #58 in the security document proper.
100	NI		Needs to be considered together with Item #66 in the security document wich deal with parallel issues regarding POSIX-based authorization. Address issues regarding ACE4_{READ,WRITE}_NAMED_ATTRIBUTES.
10A	NM	#10Aa in S	Inclusion of the action of READLINK as authorized by ACE4_READ_DATA
10B	BC	#10Ba in S	Specification of one set of mask bits as always supported.
10C	NM	#10Ca in S	Classification of masks bits based on relationship to permission bits and existence of implementations.
10D	NI	#10Da in S	Presentation of UNIX ACLs as the basis of the feature, rather than the possibly aspirational NFSv4 ACLs Includes work to mention of Extension features that were never implemented, where the WG agrees
10E	NI	#10Ea in S	Support for discovety of ACL extensions using the Aclfeature attribute or inference rules, to help in those case in which it is not supported.
10F	BC		More detail about cases in which OPEN is affected by ACE mask bits, including the dependence on the type of OPEN.
10G	BC		More detail about use of ACE4_WRITE_DATA and the dependence on the support for finer-grained bits in descriptions of ACE mask bits.
10H	BC		Distinguish mask bit treatments depending on the type of the objects
10I	BC		More detail about cases in which RENAME is affected by ACE mask bits including the dependence on the directories for wich the mask bits, distinguising the within-directory and cross-directory cases, and dealing appropiately with the rename-over case.
20B	NI		Needs to be considered together with Item #6 in the security document wich deal with parallel issues regarding POSIX-based authorization. New/revised description of the role of the "sticky bit" for directories, with respect to ACL handling.

The following table summarizes the issues in each particular pending state, dividing them into those associated with the motivating changes for this new document and those that derive from other issues, that were uncovered later, once work on a new treatment of NFSv4 security had begun.

Type	Cnt	Issues
BC(M)	1	32
CI(M)	5	36, 38, 39, 40, 41
WI(M)	1	47
NE(M)	1	35
EV(M)	3	53, 54, 55
All(M)	11	As listed above.
NM(O)	1	16
NS(O)	1	52
BE(O)	4	3, 5, 7, 24
BC(O)	14	9, 10, 12, 13, 14, 15, 17, 18, 21, 22, 23, 29, 50, 51
CI(O)	10	4, 6, 8, 11, 19, 25, 26, 27, 30, 37
WI(O)	4	20, 28, 31, 56
All(O)	34	As described above
*All*	45	Grand total for above table.

The following table summarizes the issues in each particular non-pending state, dividing them into those associated with the motivating changes for this new document and those that derive from other issues, that were uncovered later, once work on a new treatment of NFSv4 security had begun.

Type	Cnt	Issues
CA(M)	2	1, 2
RT(M)	5	42, 43, 44, 45, 46
RJ(M)	4	33, 34, 48, 49
All(M)	11	As listed above.
All(O)	0	Nothing yet.
*All*	11	Grand total for above table.

Acknowledgments The author wishes to thank Tom Haynes for his helpful suggestion to deal with security for all NFSv4 minor versions in the same document. The author wishes to draw people's attention to Nico Williams' remark that NFSv4 security was not so bad, except that there was no provision for authentication of the client peer. This perceptive remark, which now seems like common sense, did not seem so when made, but it has served as a beacon for those working on putting NFSv4 security on a firmer footing. We appreciate Nico's perceptive guidance. The author wishes to thank Bruce Fields for his helpful comments regarding ACL support which had a major role in the evolution of this document. The author wishes to acknowledge the important role of the authors of RPC-with-TLS, Chuck Lever and Trond Myklebust, in moving the NFS security agenda forward and thank them for all their efforts to improve NFS security. The author wishes to thank Chuck Lever for his many helpful comments about nfsv4 security issues, his explanation of many unclear points, and much important guidance he provided that is reflected in this document, including his work to streamline the security negotiation process by the definition of new pseudo-flavors. The author wishes to thank Rick Macklem for his help in resolving NFSv4 security issues. These include clarifying possible server policies regarding RPC-with-TLS, helping to clarify "owner-override semantics" and bringing to the Working Group's attention the possibility of deriving limited principal identification from client peer authentication while still staying within the boundaries of RPC-with-TLS.