Use constant-time comparison for HMAC signature verification#3997
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duanemay wants to merge 1 commit into
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Use constant-time comparison for HMAC signature verification#3997duanemay wants to merge 1 commit into
duanemay wants to merge 1 commit into
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UaaMacSigner.verify compared the token's signature to the recomputed signature using String.equals via Base64URL, which short-circuits on the first differing character and can leak timing information about the expected HMAC value. Switch to MessageDigest.isEqual on the decoded signature bytes.
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Summary
UaaMacSigner.verifycompared the recomputed HMAC signature to the token's signature viaBase64URL.equals(backed byString.equals), which short-circuits on the first differing byte and can leak timing information useful for forging a valid HMAC.MessageDigest.isEqualon the decoded signature bytes, matching the constant-time comparison pattern already used elsewhere in the codebase (e.g.PasswordComparisonAuthenticator).Test plan
./gradlew :cloudfoundry-identity-server:compileJava./gradlew :cloudfoundry-identity-server:test --tests JwtHelperTest --tests CommonSignerTest --tests JwtTokenSignedByThisUAATest