JOSE: Deprecate 'none' and 'RSA1

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 document 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.

Note that RSA signatures using PKCS#1 version 1.5 padding (RS256, RS384, and RS512) are unchanged by this specification and can still be used. Additionally, this document also updates the Review Instructions for the JOSE Designated Experts, to establish baseline security requirements for future JOSE algorithm registrations. Only algorithms that are reasonably believed to satisfy these requirements should be registered in future.

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. The IANA algorithm registry distinguishes between algorithms that are "Deprecated" and those that are "Prohibited". The algorithms identified in this document are to be marked as Deprecated only. Existing specifications and applictions that make use of these algorithms can continue to do so, but should consider adopting alternatives in future updates.

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 these additional review criteria:

For JWS signature algorithms, only algorithms that are reasonably conjectured to 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 are reasonably conjectured to 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 are reasonably conjectured to meet the standard security goal of authenticated encryption with associated data (AEAD) should be considered for approval.