fix(sdk-lib-mpc): authenticate signatureR in DKLS DSG round 4 messages#8470
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mrdanish26 wants to merge 1 commit intomasterfrom
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fix(sdk-lib-mpc): authenticate signatureR in DKLS DSG round 4 messages#8470mrdanish26 wants to merge 1 commit intomasterfrom
mrdanish26 wants to merge 1 commit intomasterfrom
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signatureR was wrapped with signature: "" (hardcoded empty string) in encryptAndAuthOutgoingMessages(), leaving the ECDSA nonce commitment R unauthenticated. A MITM could substitute a crafted R value and have it used by combinePartialSignatures() to produce an attacker-controlled signature component. Fix: - Sign signatureR bytes with the party GPG key via detachSignData in encryptAndAuthOutgoingMessages() - Verify signatureR in decryptAndVerifyIncomingMessages() and return it in the result so callers can use the authenticated value - Transmit signatureRSignature in getSignatureShareRoundThree() so the server can authenticate signatureR before combining - Update signBitgoMPCv2Round3 (server simulation) to pass signatureR to decryptAndVerifyIncomingMessages for end-to-end verification - Add unit tests covering sign, verify, tamper detection, and wrong-key rejection for signatureR Ticket: WAL-376 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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| const parsedSignatureShare = JSON.parse(userShare.share) as MPCv2SignatureShareRound3Input & { | ||
| data: { msg4: { signatureRSignature?: string } }; | ||
| }; |
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why not update the type instead of casting it?
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I agree, I have added signatureRSignature on the shared round‑3 msg4 type in @bitgo/public-types: https://github.com/BitGo/public-types/pull/339 . Will remove the cast once that is merged
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Summary
signatureRbytes with the party GPG key inencryptAndAuthOutgoingMessages()— previously hardcodedsignature: ""left the ECDSA nonce commitment R unauthenticated (F-04, severity: HIGH)signatureRindecryptAndVerifyIncomingMessages()before returning it to callerssignatureRSignatureingetSignatureShareRoundThree()so the server can authenticate R before passing it tocombinePartialSignatures()Test plan
sdk-lib-mpcunit tests passsdk-coreunit tests passTicket: WAL-376