(CkPython) Validate a Google ID Token

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

Chilkat Python Downloads install with pip pip3 install chilkat or download... Python Module for Windows, MacOS, Linux, Alpine Linux, Solaris

import sys
import chilkat

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

http = chilkat.CkHttp()

# First get the public key we'll be needing..
jwkStr = http.quickGetStr("https://www.googleapis.com/oauth2/v3/certs")
if (http.get_LastMethodSuccess() == False):
    print(http.lastErrorText())
    sys.exit()

# 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"
# 	}
#       ]
#     }

json = chilkat.CkJsonObject()
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"
# }

jsonToken = chilkat.CkJsonObject()
success = jsonToken.LoadFile("qa_data/tokens/google_sample_id_token.json")
if (success == False):
    print("Failed to load the JSON file...")
    sys.exit()

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

# Get the signature in base64url format.
# The header + payload remains in sbIdToken.
sig_b64Url = sbIdToken.getAfterFinal(".",True)
headerPlusPayload = sbIdToken.getAsString()

print(sig_b64Url)
print(headerPlusPayload)

# ---------------------------------------------

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

rsa = chilkat.CkRsa()
rsa.put_EncodingMode("base64url")

numKeys = json.SizeOfArray("keys")
i = 0
while i < numKeys :
    json.put_I(i)
    # jsonKey is a CkJsonObject
    jsonKey = json.ObjectOf("keys[i]")
    pubKey = chilkat.CkPublicKey()
    success = pubKey.LoadFromString(jsonKey.emit())
    if (success == False):
        print(pubKey.lastErrorText())
        sys.exit()

    print(str(i))
    print(pubKey.getPem(True))

    success = rsa.ImportPublicKeyObj(pubKey)

    bVerified = rsa.VerifyStringENC(headerPlusPayload,"sha256",sig_b64Url)
    print("bVerified = " + str(bVerified))

    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