B4X Requires Chilkat v11.0.0+

Validate a Google ID Token

See more OAuth2 Examples

Demonstrates how to verify the signature of a Google id token. B4X

Dim success As Boolean = False

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

Dim http As ChilkatHttp
http.Initialize("http")

'  First get the public key we'll be needing..
Dim jwkStr As String = http.QuickGetStr("https://www.googleapis.com/oauth2/v3/certs")
If http.LastMethodSuccess = False Then
    Log(http.LastErrorText)
    Return
End If


'  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"
'  	}
'        ]
'      }

Dim json As ChilkatJsonObject
json.Initialize
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"
'  }

Dim jsonToken As ChilkatJsonObject
jsonToken.Initialize
success = jsonToken.LoadFile("qa_data/tokens/google_sample_id_token.json")
If success = False Then
    Log("Failed to load the JSON file...")
    Return
End If


'  Get the id_token;
Dim sbIdToken As ChilkatStringBuilder
sbIdToken.Initialize
success = sbIdToken.Append(jsonToken.StringOf("id_token"))

'  Get the signature in base64url format.
'  The header + payload remains in sbIdToken.
Dim sig_b64Url As String = sbIdToken.GetAfterFinal(".", True)
Dim headerPlusPayload As String = sbIdToken.GetAsString

Log(sig_b64Url)
Log(headerPlusPayload)

'  ---------------------------------------------

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

Dim rsa As ChilkatRsa
rsa.Initialize
rsa.EncodingMode = "base64url"

Dim jsonKey As ChilkatJsonObject
jsonKey.Initialize
Dim pubKey As ChilkatPublicKey
pubKey.Initialize

Dim numKeys As Int = json.SizeOfArray("keys")
Dim i As Int = 0
Do While i < numKeys
    json.I = i

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

    success = pubKey.LoadFromString(jsonKey.Emit)
    If success = False Then
        Log(pubKey.LastErrorText)
        Return
    End If


    Log(i)
    Log(pubKey.GetPem(True))

    success = rsa.UsePublicKey(pubKey)

    Dim bVerified As Boolean = rsa.VerifyStringENC(headerPlusPayload, "sha256", sig_b64Url)
    Log("bVerified = " & bVerified)

    i = i + 1
Loop

'  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