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2 actionable advisories, newest first. Withdrawn advisories and news are excluded. Coverage is partial.
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…
Recommended action: Upgrade to 5.0.0 or later, then redeploy and verify.A vendor fix does not resolve your finding until you verify it in your own systems.
Impact The paper Cryptanalysis of Aggregate Γ-Signature and Practical Countermeasures in Application to Bitcoin defines a way to forge valid Γ-signatures, an algorithm that is used in the Biscuit specification version 1. It would allow an attacker to create a token with any access level. As Biscuit v1 was still an early version and not broadly deployed, we were able to contact all known users of Biscuit v1 and help them migrate to Biscuit v2. We are not aware of any active exploitation of this vulnerability. Patches The version 2 of the specification mandates a different algorithm than gamma signatures and as such is not affected by this vulnerability. The Biscuit implementations in Rust, Haskell, Go, Java and Javascript all have published versions following the v2 specification. Workarounds There is no known workaround, any use of Biscuit v1 should be migrated to v2. References Cryptanalysis of Aggregate Γ-Signature and Practical Countermeasures in Application to Bitcoin For more…
Recommended action: Upgrade to 2.0.0 or later, then redeploy and verify.A vendor fix does not resolve your finding until you verify it in your own systems.