Lianja
Validate a Google ID Token

Demonstrates how to verify the signature of a Google id token.
Chilkat Lianja Downloads

Lianja
llSuccess = .F.

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

loHttp = createobject("CkHttp")

// First get the public key we'll be needing..
lcJwkStr = loHttp.QuickGetStr("https://www.googleapis.com/oauth2/v3/certs")
if (loHttp.LastMethodSuccess = .F.) then
    ? loHttp.LastErrorText
    release loHttp
    return
endif

// 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"
// 	}
//       ]
//     }

loJson = createobject("CkJsonObject")
llSuccess = loJson.Load(lcJwkStr)

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

// 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"
// }

loJsonToken = createobject("CkJsonObject")
llSuccess = loJsonToken.LoadFile("qa_data/tokens/google_sample_id_token.json")
if (llSuccess = .F.) then
    ? "Failed to load the JSON file..."
    release loHttp
    release loJson
    release loJsonToken
    return
endif

// Get the id_token;
loSbIdToken = createobject("CkStringBuilder")
llSuccess = loSbIdToken.Append(loJsonToken.StringOf("id_token"))

// Get the signature in base64url format.
// The header + payload remains in sbIdToken.
lcSig_b64Url = loSbIdToken.GetAfterFinal(".",.T.)
lcHeaderPlusPayload = loSbIdToken.GetAsString()

? lcSig_b64Url
? lcHeaderPlusPayload

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

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

loRsa = createobject("CkRsa")
loRsa.EncodingMode = "base64url"

loJsonKey = createobject("CkJsonObject")
loPubKey = createobject("CkPublicKey")

lnNumKeys = loJson.SizeOfArray("keys")
i = 0
do while i < lnNumKeys
    loJson.I = i

    loJson.ObjectOf2("keys[i]",loJsonKey)

    llSuccess = loPubKey.LoadFromString(loJsonKey.Emit())
    if (llSuccess = .F.) then
        ? loPubKey.LastErrorText
        release loHttp
        release loJson
        release loJsonToken
        release loSbIdToken
        release loRsa
        release loJsonKey
        release loPubKey
        return
    endif

    ? str(i)
    ? loPubKey.GetPem(.T.)

    llSuccess = loRsa.UsePublicKey(loPubKey)

    llBVerified = loRsa.VerifyStringENC(lcHeaderPlusPayload,"sha256",lcSig_b64Url)
    ? "bVerified = " + str(llBVerified)

    i = i + 1
enddo

// 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


release loHttp
release loJson
release loJsonToken
release loSbIdToken
release loRsa
release loJsonKey
release loPubKey