]> JOSE: Deprecate 'none' and 'RSA1_5' Illuminated Security Ltd
neil@illuminated-security.com
Security Javascript Object Signing and Encryption Internet-Draft This draft updates to deprecate the JWS algorithm "none" and the JWE algorithm "RSA1_5". These algorithms have known security weaknesses. About This Document The latest revision of this draft can be found at . Status information for this document may be found at . Discussion of this document takes place on the Javascript Object Signing and Encryption Working Group mailing list (), which is archived at . Subscribe at . Source for this draft and an issue tracker can be found at .
Introduction JSON Web Algorithms (JWA, ) introduced several standard algorithms for both JSON Web Signature (JWS) and JSON Web Encryption (JWE). Many of these algorithms have stood the test of time and are still in widespread use. However, some algorithms have proved to be difficult to implement correctly leading to exploitable vulnerabilities. This draft deprecates two such algorithms:
  • The JWS "none" algorithm, which indicates that no security is applied to the message at all.
  • The JWE "RSA1_5" algorithm, which indicates RSA encryption with PKCS#1 version 1.5 padding.
The 'none' algorithm The "none" algorithm creates an Unsecured JWS, whose contents are completely unsecured as the name implies. Despite strong guidance in the original RFC around not accepting Unsecured JWS by default, many implementations have had serious bugs due to accepting this algorithm. In some cases, this has led to a complete loss of security as authenticity and integrity checking can be disabled by an adversary simply by changing the algorithm ("alg") header in the JWS. The website tracks public vulnerabilities due to implementations mistakenly accepting the "none" algorithm. It currently lists 12 reports, many of which have high impact ratings. The following is a partial list of issues known to have been caused by misuse of the "none" algorithm, with a Common Vulnerability Enumeration identifier, and a Common Vulnerability Scoring System score indicating the severity of the impact:
  • CVE-2018-1000531 - CVSS: 7.5 (High)
  • CVE-2017-10862 - CVSS: 5.3 (Medium)
  • CVE-2022-23540 - CVSS: 7.6 (High)
  • CVE-2020-15957 - CVSS: 7.5 (High)
  • CVE-2021-29500 - CVSS: 7.5 (High)
  • CVE-2021-29451 - CVSS: 9.1 (Critical)
  • CVE-2021-29455 - CVSS: 7.5 (High)
  • CVE-2021-22160 - CVSS: 9.8 (Critical)
  • CVE-2021-32631 - CVSS: 6.5 (Medium)
  • CVE-2023-29357 - CVSS: 9.8 (Critical)
Many other vulnerabilities have been reported without an accompanying CVE, which we do not list here. Although there are some legitimate use-cases for Unsecured JWS, these are relatively few in number and can easily be satisfied by alternative means. The small risk of breaking some of these use-cases is far outweighed by the improvement in security for the majority of JWS users who may be impacted by accidental acceptance of the "none" algorithm.
The 'RSA1_5' algorithm The "RSA1_5" algorithm implements RSA encryption using PKCS#1 version 1.5 padding . This padding mode has long been known to have security issues, since at least Bleichenbacher's attack in 1998. It was supported in JWE due to the wide deployment of this algorithm, especially in legacy hardware. However, more secure replacements such as OAEP or elliptic curve encryption algorithms are now widely available. NIST has disallowed the use of this encryption mode for federal use since the end of 2023 and a CFRG draft also deprecates this encryption mode for IETF protocols. This document therefore also deprecates this algorithm for JWE.
Guidance on deprecation Both of the algorithms listed above are deprecated for use in JWS and JWE. JOSE library developers SHOULD deprecate support for these algorithms and commit to a timeline for removal. Application developers SHOULD disable support for these algorithms by default. New specifications building on top of JOSE MUST NOT allow the use of either algorithm.
Conventions and Definitions 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.
Security Considerations No security issues are introduced by this specification.
IANA Considerations
JOSE Algorithm Deprecations The following changes are to be made to the IANA JOSE Web Signature and Encryption Algorithms registry:
  • For the entry with Algorithm Name "none", update the JOSE Implementation Requirements to "Deprecated".
  • For the entry with Algorithm Name "RSA1_5", update the JOSE Implementation Requirements to "Deprecated".
Updated Review Instructions for Designated Experts The review instructions for the designated experts for the IANA "JSON Web Signature and Encryption Algorithms" registry in Section 7.1 of are updated to add this additional review criteria:
  • For JWS signature algorithms, only algorithms that meet the standard security goal of existential unforgeability under a chosen message attack (EUF-CMA) should be considered for approval.
  • For JWE key management algorithms (specified with the "alg" header), only algorithms that meet the standard security goal of indistinguishability under an adaptive chosen ciphertext attack (IND-CCA2) should be considered for approval.
  • For JWE content encryption methods (specified with the "enc" header), only algorithms that meet the standard security goal of authenticated encryption with associated data (AEAD) should be considered for approval.
References Normative References JSON Web Algorithms (JWA) This specification registers cryptographic algorithms and identifiers to be used with the JSON Web Signature (JWS), JSON Web Encryption (JWE), and JSON Web Key (JWK) specifications. It defines several IANA registries for these identifiers. Key words for use in RFCs to Indicate Requirement Levels 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. Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words 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. Informative References How Many Days Has It Been Since a JWT alg:none Vulnerability? PKCS #1: RSA Cryptography Specifications Version 2.2 This document provides recommendations for the implementation of public-key cryptography based on the RSA algorithm, covering cryptographic primitives, encryption schemes, signature schemes with appendix, and ASN.1 syntax for representing keys and for identifying the schemes. This document represents a republication of PKCS #1 v2.2 from RSA Laboratories' Public-Key Cryptography Standards (PKCS) series. By publishing this RFC, change control is transferred to the IETF. This document also obsoletes RFC 3447. Implementation Guidance for the PKCS #1 RSA Cryptography Specification Red Hat, Inc. This document specifies additions and amendments to RFC 8017. Specifically, it provides guidance to implementers of the standard to protect against side-channel attacks. It also deprecates the RSAES- PKCS-v1_5 encryption scheme, but provides an alternative depadding algorithm that protects against side-channel attacks raising from users of vulnerable APIs. The purpose of this specification is to increase security of RSA implementations. NIST SP 800-131A Rev. 2: Transitioning the Use of Cryptographic Algorithms and Key Lengths NIST NIST Common Vulnerability Enumeration Database MITRE n.d. Common Vulnerability Scoring System FIRST n.d. JOSE Algorithms IANA n.d.
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