Google OAuth2 JWT token verification exception

Question

I'm facing OAuth2 JWT token verification exception last hour (so no one can access my application):

java.security.SignatureException: Signature length not correct: got 256 but was expecting 128. I'm using google-http-client 1.20.0 and Java 1.7.0 . Same configuration worked so far - any ideas?

Stacktrace

java.security.SignatureException: Signature length not correct: got 256 but was expecting 128
    at sun.security.rsa.RSASignature.engineVerify(Unknown Source) ~[na:1.7.0_45]
    at java.security.Signature$Delegate.engineVerify(Unknown Source) ~[na:1.7.0_45]
    at java.security.Signature.verify(Unknown Source) ~[na:1.7.0_45]
    at com.google.api.client.util.SecurityUtils.verify(SecurityUtils.java:164) ~[google-http-client-1.20.0.jar:1.20.0]

Answer 1

Same problem here, I added the source code of GoogleIdTokenVerifier to my project and changed the method:

 public boolean verify(GoogleIdToken googleIdToken) throws GeneralSecurityException, IOException {
    // check the payload
    if (!super.verify(googleIdToken)) {
      return false;
    }
    // verify signature
    for (PublicKey publicKey : publicKeys.getPublicKeys()) {
      try {
        if (googleIdToken.verifySignature(publicKey)) {
            return true;
          }
    } catch (Exception e) {
        System.err.println("Verify Token:" + e);
    }
    }
    return false;
  }

just handle the exception, the second certificate works fine.

Edit: you can subclass as Erik-z suggested if you want to make it more clean:

Edit 2: I can't make it work using the code below, I will stick to the ugly hack above.

package com.my.project.package;

import java.io.IOException;
import java.security.GeneralSecurityException;
import java.security.PublicKey;

import com.google.api.client.auth.openidconnect.IdTokenVerifier;
import com.google.api.client.googleapis.auth.oauth2.GoogleIdToken;
import com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier;
import com.google.api.client.http.HttpTransport;
import com.google.api.client.json.JsonFactory;

// Remember to remove this class later by making it deprecated
@Deprecated
public class GoogleIdTokenVerifier2 extends GoogleIdTokenVerifier {

    // Add constructors as needed
    public GoogleIdTokenVerifier2(HttpTransport transport, JsonFactory jsonFactory) {
        super(transport, jsonFactory);
    }

    @Override
    public boolean verify(GoogleIdToken googleIdToken) throws GeneralSecurityException, IOException {
        // check the payload
        if (!((IdTokenVerifier)this).verify(googleIdToken)) {
            return false;
        }
        // verify signature
        for (PublicKey publicKey : getPublicKeysManager().getPublicKeys()) {
            try {
                if (googleIdToken.verifySignature(publicKey)) {
                    return true;
                }
            } catch (Exception e) {
                System.err.println("Verify Token:" + e);
            }
        }
        return false;
    }
}

Answer 2

Don't think it's the final solution but a temporary work-around which definitely works is to change the audience of the verifier to the tokenId.

GoogleIdTokenVerifier verifier = new GoogleIdTokenVerifier.Builder(transport, jsonFactory).setAudience(Arrays.asList(clientId)).build();

to

GoogleIdTokenVerifier verifier = new GoogleIdTokenVerifier.Builder(transport, jsonFactory)
                    .setAudience(Arrays.asList(tokenResponse.getIdToken())).build();

Answer 3

The root cause is on the Google side, the certs in the JSON is in bad order:

https://www.googleapis.com/oauth2/v1/certs

You can adjust the order of them, like this:

http://test.gacivs.info/frontend/certs.json

After, you can specify your custom URL (or using mine :) of the JSON with the GooglePublicKeysManager.setPublicCertsEncodedUrl(...) method:

final GoogleIdToken idToken = GoogleIdToken.parse(JSON_FACTORY, token);
final GooglePublicKeysManager manager = new GooglePublicKeysManager.Builder(HTTP_TRANSPORT, JSON_FACTORY).setPublicCertsEncodedUrl(CUSTOM_CERTS_URL).build();
final GoogleIdTokenVerifier verifier = new GoogleIdTokenVerifier.Builder(manager).setAudience(Arrays.asList(CLIENT_ID)).build();
verifier.verify(idToken);

...and it works.

I hope, the Google fix the issue soon... :)

Answer 4

This is copied from my answer here , but more relevant for those not using Google Cloud Endpoint (matching this question). The problem is caused by this:

• RSA has variable length signatures, depending on the key size.
• Google updated the key pairs it uses for signing, and now one of the key pairs generates a different length signature from the other
• java.security.Signature.verify(byte[] signature) throws an exception if a signature of the wrong length is passed (instead of returning false which is normally done when a signature does not match the key)

The simplest solution is to wrap the verify call ( try...catch ), and return false if you get an exception

Looking at the example code on http://android-developers.blogspot.com/2013/01/verifying-back-end-calls-from-android.html , it looks like you can change this line:

GoogleIdToken token = GoogleIdToken.parse(mJFactory, tokenString);

to

JsonWebSignature jws = JsonWebSignature.parser(mJFactory).setPayloadClass(Payload.class).parse(tokenString);
GoogleIdToken token = new GoogleIdToken(jws.getHeader(), (Payload) jws.getPayload(), jws.getSignatureBytes(), jws.getSignedContentBytes()) {
   public boolean verify(GoogleIdTokenVerifier verifier)
  throws GeneralSecurityException, IOException {
       try {
           return verifier.verify(this);
       } catch (java.security.SignatureException e) {
           return false;
       }
   }
};

I unfortunately don't have an exact setup to test this, let me know if this works for you.

Answer 5

It looks to me like the libraries may be behaving badly. As an alternative to offline token verification, you can use Google's OAuth2 endpoints for verifying tokens. A basic example from the API explorer can be seen here .

You can check a token with a curl command curl https://www.googleapis.com/oauth2/v2/tokeninfo?id_token=[id_token] , for example:

curl https://www.googleapis.com/oauth2/v2/tokeninfo?id_token=eyJhbGciOiJSUzI1NiIsImtpZCI6IjRlYjczOTg0MzBkNTNjZjZjNGZkMGU5YmM4NzkzZWViZWNkMWY1NWUifQ.eyJpc3MiOiJhY2NvdW50cy5nb29nbGUuY29tIiwic3ViIjoiMTA3Mzc3MTkxNjgxODAyNjY5ODY2IiwiYXpwIjoiMTE2MjY4ODY3NTIuYXBwcy5nb29nbGV1c2VyY29udGVudC5jb20iLCJhdF9oYXNoIjoieGJSVGJOdFJYRnJzcUJHTkRtRTR6USIsImF1ZCI6IjExNjI2ODg2NzUyLmFwcHMuZ29vZ2xldXNlcmNvbnRlbnQuY29tIiwiY19oYXNoIjoiU3JFa25WczRUejhQSWJicExnNXF2QSIsImlhdCI6MTQzNDA0MTY5OSwiZXhwIjoxNDM0MDQ1Mjk5fQ.vqQXCTFfbDqpTYnfFrDD7m68oEuGqd8NWa4s9wstOrrcyuVKUsqFXM_2bH-un_4C8UBvqtQEyzU_-53DxgvhCHQ7S0W-wtQ9YMoJcy7iL1wDjcy1p7aFVoeGCoqxWv1vzlWTUDu_FnD9oIBSAawyDexvRwwGxN8O1D8nzyj__1DQ_ivxIMF-j1W89mc7adK4p5B8ioZA_PI-AGawX2Nm8t58yBMIYrTk0XExr9Pf4eHHRGbrQxcd0ERGHbRMYuG6k-MzdnVNHIScgZ3Cixx9v15PbQ5hXExNvleifG_Wk3Thnz0j6Uacr4fbi-mO93-h8c0r3BSvQ270_JqlpL5q5Q

Answer 6

If you don't want to (or can't) change the source of the google library, you can just extend the GoogleIdTokenVerifier. (you have to duplicate another method which accesses some private variables - fortunately all of them are accessible via get-members). This works for me:

GoogleIdTokenVerifier myVerifier = new GoogleIdTokenVerifier(httpTransport, jsonFactory) {

    public boolean superVerify(IdToken idToken) {
              return (getIssuer()== null || idToken.verifyIssuer(getIssuer()))
                  && (getAudience() == null || idToken.verifyAudience(getAudience()))
                  && idToken.verifyTime(getClock().currentTimeMillis(), getAcceptableTimeSkewSeconds());
    }


    @Override
  public boolean verify(GoogleIdToken googleIdToken) throws GeneralSecurityException, IOException {
      // check the payload
      if (!superVerify(googleIdToken)) {
          log.info("superVerify returned false");
        return false;
      }
      // verify signature
      for (PublicKey publicKey : getPublicKeysManager().getPublicKeys()) {
              try {
                      if (googleIdToken.verifySignature(publicKey)) {
                              log.info("verifySignature: success!");
                              return true;
                      }
              } catch (Exception e) {
                      log.info("error verifying!", e);
              }
      }
      return false;
    }

};