C++

Validate a Google ID Token

See more OAuth2 Examples

Demonstrates how to verify the signature of a Google id token. C++

#include <CkHttp.h>
#include <CkJsonObject.h>
#include <CkStringBuilder.h>
#include <CkRsa.h>
#include <CkPublicKey.h>

void ChilkatSample(void)
    {
    bool success = false;

    //  This example requires the Chilkat API to have been previously unlocked.
    //  See Global Unlock Sample for sample code.

    CkHttp http;

    //  First get the public key we'll be needing..
    const char *jwkStr = http.quickGetStr("https://www.googleapis.com/oauth2/v3/certs");
    if (http.get_LastMethodSuccess() == false) {
        std::cout << http.lastErrorText() << "\r\n";
        return;
    }

    //  We have the following:

    //      {
    //        "keys": [
    //  	{
    //  	  "kid": "e8732db06287515556213b80acbcfd08cfb302a9",
    //  	  "n": "4RIrO30287Wsq3gqXCMkUYMVAeI3H8...w2mbMNEBQ",
    //  	  "kty": "RSA",
    //  	  "e": "AQAB",
    //  	  "alg": "RS256",
    //  	  "use": "sig"
    //  	},
    //  	{
    //  	  "kid": "8462a71da4f6d611fc0fecf0fc4ba9c37d65e6cd",
    //  	  "e": "AQAB",
    //  	  "n": "xT_ngLZNmT5GBtJZeTB...Ft4gK0eoFi0d3l8bcw",
    //  	  "alg": "RS256",
    //  	  "use": "sig",
    //  	  "kty": "RSA"
    //  	}
    //        ]
    //      }

    CkJsonObject json;
    success = json.Load(jwkStr);

    //  -------------------------------------------------

    //  Load the following..

    //   {
    //    "access_token": "ya29.a0...0f",
    //    "expires_in": 3599,
    //    "scope": "openid https://www.googleapis.com/auth/userinfo.email",
    //    "token_type": "Bearer",
    //    "id_token": "eyJhb...o5nQ"
    //  }

    CkJsonObject jsonToken;
    success = jsonToken.LoadFile("qa_data/tokens/google_sample_id_token.json");
    if (success == false) {
        std::cout << "Failed to load the JSON file..." << "\r\n";
        return;
    }

    //  Get the id_token;
    CkStringBuilder sbIdToken;
    success = sbIdToken.Append(jsonToken.stringOf("id_token"));

    //  Get the signature in base64url format.
    //  The header + payload remains in sbIdToken.
    const char *sig_b64Url = sbIdToken.getAfterFinal(".",true);
    const char *headerPlusPayload = sbIdToken.getAsString();

    std::cout << sig_b64Url << "\r\n";
    std::cout << headerPlusPayload << "\r\n";

    //  ---------------------------------------------

    //  Try validating with each cert's public key.
    //  Hopefully one will be the key that verifies.

    CkRsa rsa;
    rsa.put_EncodingMode("base64url");

    CkJsonObject jsonKey;
    CkPublicKey pubKey;

    int numKeys = json.SizeOfArray("keys");
    int i = 0;
    while (i < numKeys) {
        json.put_I(i);

        json.ObjectOf2("keys[i]",jsonKey);

        success = pubKey.LoadFromString(jsonKey.emit());
        if (success == false) {
            std::cout << pubKey.lastErrorText() << "\r\n";
            return;
        }

        std::cout << i << "\r\n";
        std::cout << pubKey.getPem(true) << "\r\n";

        success = rsa.UsePublicKey(pubKey);

        bool bVerified = rsa.VerifyStringENC(headerPlusPayload,"sha256",sig_b64Url);
        std::cout << "bVerified = " << bVerified << "\r\n";

        i = i + 1;
    }

    //  The output is:

    //  0
    //  -----BEGIN RSA PUBLIC KEY-----
    //  MIIBCgKCAQEA4RIrO30287Wsq3gqXCMkUYMVAeI3H8LVE6IXR1krdFeGnZLiGUPw
    //  cbkeVpXf3lmJdsStOg+jijces2DZCfPyIBiQuLYfxxmAZE6ErJ0QJFg1stwli2Pz
    //  9ncYhFoqi8pXr7kEzEJBTzX4thuw56ydbGsshSEznPXoerCJOc7UI2+n0wFCWQ4Y
    //  LHbh/PrWt4vdadyUUUW/QpQHXQLdD8q/Qwqdj0O9zlJE7R6Elw2E9EqnHyIGu1hm
    //  LxhqrTru1M18SUhONYbVskV/BCEdVKs//X96849HorWQDCAgVMWfGsdMVq55FAdJ
    //  680N5UmQDRynIZ4+PeNGN4S9iw2mbMNEBQIDAQAB
    //  -----END RSA PUBLIC KEY-----
    //  
    //  bVerified = True
    //  1
    //  -----BEGIN RSA PUBLIC KEY-----
    //  MIIBCgKCAQEAxT/ngLZNmT5GBdkLtJZjNeTB+8B5yWgrq/e5eMZ1hrZhcmLK+dSn
    //  IkpOPV8/OekV67EnQ7I4II2rcNJnHGrGKZziXO3XN2gtUHE+mBJC99oULSbX/QwB
    //  Kz7gC/IBPq9EuxTt6Oq6fPkVQ9DbRIgWJSEGBF/KRaNl3kyAlIZfpY7XgHyJTTv8
    //  E7yAcYKPR+36gzdl+ps0sDLKzUuAtZNq8llK0u80z6AtAUIYwWdkEhM9upy6keKI
    //  TasIxcsO7M6kZPINUSbh6t5VAm8FuqRmxpgg+9c9/GQSGd89InVypoVzWLQ+wOGg
    //  5G4H6JqIgtj0TRFt4gK0eoFi2U0d3l8bcwIDAQAB
    //  -----END RSA PUBLIC KEY-----
    //  
    //  bVerified = False
    }