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SEC LAMPS Working Group Public Key Infrastructure Cryptographic Message Syntax Certificate Management Transport Protocols This document defines a number of transport mechanisms that are used to move CMC (Certificate Management over CMS (Cryptographic Message Syntax)) messages. The transport mechanisms described in this document are HTTP, file, mail, and TCP. This document obsoletes RFC 5273 and RFC 6402. Status information for this document may be found at . Discussion of this document takes place on the WG LAMPS mailing list (), which is archived at . Subscribe at . Source for this draft and an issue tracker can be found at .

Introduction This document defines a number of transport methods that are used to move CMC messages (defined in ). The transport mechanisms described in this document are HTTP, file, mail, and TCP. This document obsoletes RFC 5273 and RFC 6402 . This document also incorporates .

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

Changes Since 5273 and 6402 Merged text. IANA assigned TCP port 5318 for the use of CMC. Clarified the file extensions for Full PKI Requests and Responses. Replaced TLS 1.0 for TLS 1.2 or later, and added that implemetations are required to follow the recommendations in . Addressed .

File-Based Protocol Enrollment messages and responses may be transferred between clients and servers using file-system-based mechanisms, such as when enrollment is performed for an off-line client. When files are used to transport binary, Full PKI Request or Full PKI Response messages, there MUST be only one instance of a request or response message in a single file. crq and crp stand for Full PKI Request/Response, respectively; for clarity we define file extensions for them. The following file type extensions SHOULD be used: Message Type File Extension Simple PKI Request .p10 Full PKI Request .crq Simple PKI Response .p7c Full PKI Response .crp

Mail-Based Protocol MIME wrapping is defined for those environments that are MIME native. The basic mime wrapping in this section is taken from . When using a mail-based protocol, MIME wrapping between the layers of CMS wrapping is optional. Note that this is different from the standard S/MIME (Secure MIME) message. Simple enrollment requests are encoded using the "application/pkcs10" content type. A file name MUST be included either in a content-type or a content-disposition statement. The extension for the file MUST be ".p10". Simple enrollment response messages MUST be encoded as content type "application/pkcs7-mime". An smime-type parameter MUST be on the content-type statement with a value of "certs-only". A file name with the ".p7c" extension MUST be specified as part of the content- type or content-disposition statement. Full enrollment request messages MUST be encoded as content type "application/pkcs7-mime". The smime-type parameter MUST be included with a value of "CMC-request". A file name with the ".p7m" extension MUST be specified as part of the content-type or content-disposition statement. Full enrollment response messages MUST be encoded as content type "application/pkcs7-mime". The smime-type parameter MUST be included with a value of "CMC-response". A file name with the ".p7m" extension MUST be specified as part of the content-type or content- disposition statement. Item MIME Type File Extension SMIME Type Simple PKI Request application/pkcs10 .p10 N/A Full PKI Request application/pkcs7-mime .p7m CMC-request Simple PKI Response application/pkcs7-mime .p7c certs-only Full PKI Response application/pkcs7-mime .p7m CMC-response

HTTP/HTTPS-Based Protocol This section describes the conventions for use of HTTP as a transport layer. In most circumstances, the use of HTTP over TLS provides any necessary content protection from eavesdroppers. In order for CMC clients and servers using HTTP to interoperate, the following rules apply.

• Clients MUST use the POST method to submit their requests.

• Servers MUST use the 200 response code for successful responses.

• Clients MAY attempt to send HTTP requests using TLS 1.2 or later, although servers are not required to support TLS. If TLS is supported by an implementation, then the implementation MUST folow the recommendations in .

• Servers MUST NOT assume client support for any type of HTTP authentication such as cookies, Basic authentication, or Digest authentication.

• Clients and servers are expected to follow the other rules and restrictions in . Note that some of those rules are for HTTP methods other than POST; clearly, only the rules that apply to POST are relevant for this specification.

PKI Request A PKI Request using the POST method is constructed as follows: The Content-Type header MUST have the appropriate value from . A Content-Type header for a request:

• Content-Type: application/pkcs7-mime; smime-type=CMC-request; name=request.p7m

The body of the message is the binary value of the encoding of the PKI Request.

PKI Response An HTTP-based PKI Response is composed of the appropriate HTTP headers, followed by the binary value of the BER (Basic Encoding Rules) encoding of either a Simple or Full PKI Response. The Content-Type header MUST have the appropriate value from . A Content-Type header for a response:

• Content-Type: application/pkcs7-mime; smime-type=CMC-response; name=response.p7m

TCP-Based Protocol When CMC messages are sent over a TCP-based connection, no wrapping is required of the message. Messages are sent in their binary encoded form. The client closes a connection after receiving a response, or it issues another request to the server using the same connection. Reusing one connection for multiple successive requests, instead of opening multiple connections that are only used for a single request, is RECOMMENDED for performance and resource conservation reasons. A server MAY close a connection after it has been idle for some period of time; this timeout would typically be several minutes long. CMC requires a registered port number to send and receive CMC messages over TCP. The Service Name is "pkix-cmc". The value of this TCP port is 5318. Prior to , CMC did not have a registered port number and used an externally configured port from the Private Port range. Client implementations MAY want to continue to allow for this to occur. Servers SHOULD change to use the new port. It is expected that HTTP will continue to be the primary transport method used by CMC installations.

IANA Considerations IANA has assigned a TCP port number in the Registered Port Number range for the use of CMC.

IANA is requested to update the existing references to in the Media Type Sub-Parameter Registries for CMC-Request and CMC-Response to [ RFC-to-be ].

Security Considerations Mechanisms for thwarting replay attacks may be required in particular implementations of this protocol depending on the operational environment. In cases where the Certification Authority (CA) maintains significant state information, replay attacks may be detectable without the inclusion of the optional nonce mechanisms. Implementers of this protocol need to carefully consider environmental conditions before choosing whether or not to implement the senderNonce and recipientNonce attributes described in . Developers of state-constrained PKI clients are strongly encouraged to incorporate the use of these attributes. Initiation of a secure communications channel between an end-entity and a CA or Registration Authority (RA) -- and, similarly, between an RA and another RA or CA -- necessarily requires an out-of-band trust initiation mechanism. For example, a secure channel may be constructed between the end-entity and the CA via IPsec or TLS . Many such schemes exist, and the choice of any particular scheme for trust initiation is outside the scope of this document. Implementers of this protocol are strongly encouraged to consider generally accepted principles of secure key management when integrating this capability within an overall security architecture. In some instances, no prior out-of-band trust will have been initiated prior to use of this protocol. This can occur when the protocol itself is being used to download onto the system the set of trust anchors to be used for these protocols. In these instances, the Enveloped Data content type () must be used to provide the same shrouding that TLS would have provided.

Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) are used to protect data exchanged over a wide range of application protocols and can also form the basis for secure transport protocols. Over the years, the industry has witnessed several serious attacks on TLS and DTLS, including attacks on the most commonly used cipher suites and their modes of operation. This document provides the latest recommendations for ensuring the security of deployed services that use TLS and DTLS. These recommendations are applicable to the majority of use cases. RFC 7525, an earlier version of the TLS recommendations, was published when the industry was transitioning to TLS 1.2. Years later, this transition is largely complete, and TLS 1.3 is widely available. This document updates the guidance given the new environment and obsoletes RFC 7525. In addition, this document updates RFCs 5288 and 6066 in view of recent attacks. AKAYLA, Inc. sn3rd This document defines the base syntax for CMC, a Certificate Management protocol using the Cryptographic Message Syntax (CMS). This protocol addresses two immediate needs within the Internet Public Key Infrastructure (PKI) community: The Hypertext Transfer Protocol (HTTP) is a stateless application-level protocol for distributed, collaborative, hypertext information systems. This document describes the overall architecture of HTTP, establishes common terminology, and defines aspects of the protocol that are shared by all versions. In this definition are core protocol elements, extensibility mechanisms, and the "http" and "https" Uniform Resource Identifier (URI) schemes. This document updates RFC 3864 and obsoletes RFCs 2818, 7231, 7232, 7233, 7235, 7538, 7615, 7694, and portions of 7230. This document defines Secure/Multipurpose Internet Mail Extensions (S/MIME) version 4.0. S/MIME provides a consistent way to send and receive secure MIME data. Digital signatures provide authentication, message integrity, and non-repudiation with proof of origin. Encryption provides data confidentiality. Compression can be used to reduce data size. This document obsoletes RFC 5751. In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. This document specifies Version 1.2 of the Transport Layer Security (TLS) protocol. The TLS protocol provides communications security over the Internet. The protocol allows client/server applications to communicate in a way that is designed to prevent eavesdropping, tampering, or message forgery. [STANDARDS-TRACK] This document defines a number of transport mechanisms that are used to move CMC (Certificate Management over CMS (Cryptographic Message Syntax)) messages. The transport mechanisms described in this document are HTTP, file, mail, and TCP. [STANDARDS-TRACK] This document contains a set of updates to the base syntax for CMC, a Certificate Management protocol using the Cryptographic Message Syntax (CMS). This document updates RFC 5272, RFC 5273, and RFC 5274. The new items in this document are: new controls for future work in doing server side key generation, definition of a Subject Information Access value to identify CMC servers, and the registration of a port number for TCP/IP for the CMC service to run on. [STANDARDS-TRACK] This document describes an updated version of the "Security Architecture for IP", which is designed to provide security services for traffic at the IP layer. This document obsoletes RFC 2401 (November 1998). [STANDARDS-TRACK]

Acknowledgements Obviously, the authors of this version of the document would like to thank Jim Schaad and Michael Myers for their work on the previous version of this document. The acknowledgment from the previous version of this document follows: The authors and the PKIX Working Group are grateful for the participation of Xiaoyi Liu and Jeff Weinstein in helping to author the original versions of this document. The authors would like to thank Brian LaMacchia for his work in developing and writing up many of the concepts presented in this document. The authors would also like to thank Alex Deacon and Barb Fox for their contributions.

Contributors August Cellars

TraceRoute Security, Inc.