(Ruby) Validate a Google ID Token

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

Chilkat Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

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

http = Chilkat::CkHttp.new()

# 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() + "\n";
    exit
end

# 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.new()
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.new()
success = jsonToken.LoadFile("qa_data/tokens/google_sample_id_token.json")
if (success == false)
    print "Failed to load the JSON file..." + "\n";
    exit
end

# Get the id_token;
sbIdToken = Chilkat::CkStringBuilder.new()
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 + "\n";
print headerPlusPayload + "\n";

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

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

rsa = Chilkat::CkRsa.new()
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.new()
    success = pubKey.LoadFromString(jsonKey.emit())
    if (success == false)
        print pubKey.lastErrorText() + "\n";
        exit
    end

    print i.to_s() + "\n";
    print pubKey.getPem(true) + "\n";

    success = rsa.ImportPublicKeyObj(pubKey)

    bVerified = rsa.VerifyStringENC(headerPlusPayload,"sha256",sig_b64Url)
    print "bVerified = " + bVerified.to_s() + "\n";

    i = i + 1
end

# 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