Ecosyste.ms: Advisories

Security Advisories: GSA_kwCzR0hTQS1wOXc0LTU4NWgtZzNjN84AA-TH

biscuit-auth vulnerable to public key confusion in third party block

Third-party blocks can be generated without transferring the whole token to the third-party authority. Instead, a ThirdPartyBlock request can be sent, providing only the necessary info to generate a third-party block and to sign it:

• the public key of the previous block (used in the signature)
• the public keys part of the token symbol table (for public key interning in datalog expressions)

A third-part block request forged by a malicious user can trick the third-party authority into generating datalog trusting the wrong keypair.

Consider the following example (nominal case)

• Authority A emits the following token: check if thirdparty("b") trusting ${pubkeyB}
• The well-behaving holder then generates a third-party block request based on the token and sends it to third-party authority B
• Third-party B generates the following third-party block thirdparty("b"); check if thirdparty("c") trusting ${pubkeyC}
• The token holder now must obtain a third-party block from third party C to be able to use the token

Now, with a malicious user:

• Authority A emits the following token: check if thirdparty("b") trusting ${pubkeyB}
• The holder then attenuates the token with the following third party block thirdparty("c"), signed with a keypair pubkeyD, privkeyD) they generate
• The holder then generates a third-party block request based on this token, but alter the ThirdPartyBlockRequest publicKeys field and replace pubkeyD with pubkeyC
• Third-party B generates the following third-party block thirdparty("b"); check if thirdparty("c") trusting ${pubkeyC}
• Due to the altered symbol table, the actual meaning of the block is thirdparty("b"); check if thirdparty("c") trusting ${pubkeyD}
• The attacker can now use the token without obtaining a third-party block from C.

Impact

Tokens with third-party blocks containing trusted annotations generated through a third party block request

Permalink: https://github.com/advisories/GHSA-p9w4-585h-g3c7
JSON: https://advisories.ecosyste.ms/api/v1/advisories/GSA_kwCzR0hTQS1wOXc0LTU4NWgtZzNjN84AA-TH
Source: GitHub Advisory Database
Origin: Unspecified
Severity: Low
Classification: General
Published: 3 months ago
Updated: 3 months ago

CVSS Score: 3.0
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:N/I:L/A:N

Identifiers: GHSA-p9w4-585h-g3c7, CVE-2024-41949
References:

• https://github.com/biscuit-auth/biscuit-rust/security/advisories/GHSA-p9w4-585h-g3c7
• https://nvd.nist.gov/vuln/detail/CVE-2024-41949
• https://github.com/biscuit-auth/biscuit/security/advisories/GHSA-rgqv-mwc3-c78m
• https://github.com/advisories/GHSA-p9w4-585h-g3c7

Repository: https://github.com/biscuit-auth/biscuit-rust
Blast Radius: 2.3

Affected Packages