fix: bind BJJ signature proof signing key to issuer published state#411
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Alexander-frenki wants to merge 3 commits into
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fix: bind BJJ signature proof signing key to issuer published state#411Alexander-frenki wants to merge 3 commits into
Alexander-frenki wants to merge 3 commits into
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verifyBJJSignatureProof trusted the public key embedded in proof.issuerData.authCoreClaim and only checked that the state value was published on-chain, never verifying that the auth claim is included in that state's claims tree (issuerData.mtp was parsed but unused). An attacker could put their own key in authCoreClaim, sign with it, and forge a credential from any issuer DID that verifyProofs would accept. Bind the signing key to the published state: - state.value === poseidon(claimsTreeRoot, revocationTreeRoot, rootOfRoots) - rootFromProof(issuerData.mtp, hiAuth, hvAuth) === state.claimsTreeRoot Also verify fetched credential proofs in FetchHandler's plaintext offer and issuance-response paths before saving (previously only the encrypted path verified), so received credentials are validated, not blindly trusted. Add regression test covering a forged credential re-signed by a key not in the issuer claims tree.
vmidyllic
approved these changes
Jun 12, 2026
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Summary
verifyBJJSignatureProoftrusted the public key embedded inproof.issuerData.authCoreClaimand only checked thatstate.valuewas published on-chain — it never verified that the auth claim is included in that state's claims tree (proof.issuerData.mtpwas parsed but unused). An attacker could place their own key inauthCoreClaim, sign with it, and forge a credential from any issuer DID thatverifyProofswould accept.Bind the signing key to the issuer's published state:
state.value === poseidon(claimsTreeRoot, revocationTreeRoot, rootOfRoots)rootFromProof(issuerData.mtp, hiAuth, hvAuth) === state.claimsTreeRootAlso verify fetched credential proofs in
FetchHandler's plaintext offer and issuance-response paths before saving (previously only the encrypted path verified), so received credentials are validated rather than blindly trusted.Adds a regression test covering a forged credential re-signed by a key not in the issuer's claims tree.