google-oauth-java-client improperly verifies cryptographic signature
SummaryThe vulnerability impacts only users of the `IdTokenVerifier` class. The verify method in `IdTokenVerifier` does not validate the signature before verifying the claims (e.g., iss, aud, etc.). Signature verification makes sure that the token's payload comes from valid provider, not from someone else.An attacker can provide a compromised token with modified payload like email or phone number. The token will pass the validation by the library. Once verified, modified payload can be used by the application.If the application sends verified `IdToken` to other service as is like for auth - the risk is low, because the backend of the service is expected to check the signature and fail the request.Reporter: [Tamjid al Rahat](https://github.com/tamjidrahat), contributorPatchesThe issue was fixed in the 1.33.3 version of the libraryProof of ConceptTo reproduce, one needs to call the verify function with an IdToken instance that contains a malformed signature to successfully bypass the checks inside the verify function.Remediation and MitigationUpdate to the version 1.33.3 or higherIf the library used indirectly or cannot be updated for any reason you can use similar IdToken verifiers provided by Google that already has signature verification. For example: 
[google-auth-library-java](https://github.com/googleapis/google-auth-library-java/blob/main/oauth2_http/java/com/google/auth/oauth2/TokenVerifier.java)
[google-api-java-client](https://github.com/googleapis/google-api-java-client/blob/main/google-api-client/src/main/java/com/google/api/client/googleapis/auth/oauth2/GoogleIdTokenVerifier.java)TimelineDate reported: 12 Dec 2021
Date fixed: 13 Apr 2022
Date disclosed: 2 May 2022For more informationIf you have any questions or comments about this advisory:Open an issue in the [google-oauth-java-client](https://github.com/googleapis/google-oauth-java-client) repo