DataFlex

Verify a Google JWT Using Google's Public Key

See more Google APIs Examples

Demonstrates how to verify a JWT that was signed using Google's RSA private key.

This example verifies the RSA signature. It also does the following:

• Checks to see if the time constraints ("nbf" and "exp") are valid.
• Recovers the original JOSE header.
• Recovers the original claims JSON.

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoHttp
    Variant vSbPubKeys
    Handle hoSbPubKeys
    String sToken
    Handle hoJwt
    String sHeader
    Handle hoJson
    String sKid
    Handle hoJsonPubKeys
    Variant vJsonKey
    Handle hoJsonKey
    Handle hoPubKey
    String sTemp1
    Boolean bTemp1

    Move False To iSuccess

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

    Get Create (RefClass(cComChilkatHttp)) To hoHttp
    If (Not(IsComObjectCreated(hoHttp))) Begin
        Send CreateComObject of hoHttp
    End
    Get Create (RefClass(cComChilkatStringBuilder)) To hoSbPubKeys
    If (Not(IsComObjectCreated(hoSbPubKeys))) Begin
        Send CreateComObject of hoSbPubKeys
    End

    Get pvComObject of hoSbPubKeys to vSbPubKeys
    Get ComQuickGetSb Of hoHttp "https://www.googleapis.com/oauth2/v3/certs" vSbPubKeys To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoHttp To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get ComGetAsString Of hoSbPubKeys To sTemp1
    Showln sTemp1

    // Here are the keys:

    // {
    //   "keys": [
    //     {
    //       "e": "AQAB",
    //       "n": "4bAT6C6EeX8Dspje3FrAXw-nnhNk04e1RmNa4kjc0CHf6Pk7ryARlwA-6YilyPABqQfYHx60s8oSnxvUVprFfQ2-Q8aAZO7bPKSxnoGlcKERL2oLNA4Msvc89N9Y5ycThZUplf_QC19e6jyYXN6Nz-UnJSCLrtQY8tVhhVRs61j4A2N_p-enAi-r704Qi1-v-DKV4eVRkClKViploo8NyjUaT9L4vbBssPCjyimJzsWnEe1fED5c4LnHeArYzA_FEn3JJotqDIz9t2VnvZNTMhizHEX4VnORlEWMEfR8n4CEHQx7PcQUOmfqyw08gWeXQl1-uTjtIGaE-sRIv9u_vQ",
    //       "kty": "RSA",
    //       "use": "sig",
    //       "alg": "RS256",
    //       "kid": "2af90e87be140c20038898a6efa11283dab6031d"
    //     },
    //     {
    //       "n": "nzGsrziOYrMVYMpvUZOwkKNiPWcOPTYRYlDSdRW4UpAHdWPbPlyqaaphYhoMB5DXrVxI3bdvm7DOlo-sHNnulmAFQa-7TsQMxrZCvVdAbyXGID9DZYEqf8mkCV1Ohv7WY5lDUqlybIk1OSHdK7-1et0QS8nn-5LojGg8FK4ssLf3mV1APpujl27D1bDhyRb1MGumXYElwlUms7F9p9OcSp5pTevXCLmXs9MJJk4o9E1zzPpQ9Ko0lH9l_UqFpA7vwQhnw0nbh73rXOX2TUDCUqL4ThKU5Z9Pd-eZCEOatKe0mJTpQ00XGACBME_6ojCdfNIJr84Y_IpGKvkAEksn9w",
    //       "use": "sig",
    //       "kid": "87bbe0815b064e6d449cac999f0e50e72a3e4374",
    //       "e": "AQAB",
    //       "alg": "RS256",
    //       "kty": "RSA"
    //     }
    //   ]
    // }

    // -------------------------------------------------------------------------------------------
    // Replace this with your actual token.
    // This sample token contains a kid that does not match any of the above Google public keys.
    // -------------------------------------------------------------------------------------------
    Move "eyJhbGciOiJSUzI1NiIsImtpZCI6IjQyZmY5MGQ3ZDM0OGM5NzM4MWE3YzExOWVmMWY1MzI0ZWEzZjViZWIifQ.eyJpc3MiOiJodHRwczovL2FjY291bnRzLmdvb2dsZS5jb20iLCJzdWIiOiIxMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExIiwiaWF0IjoxNjExMTE1MTQzLCJleHAiOjE2MTEyMDE1NDMsImF1ZCI6IjQyOTc1NzExNTE0ODg0OSJ9.pLem5i0bx3M7lJYj7jKv2Nq7c07X5YpZz-x1uM5RniW-v4LsX-lKIVvOq2x3-WoPqkzLXJfP0kG0dx1uD2q1NfFQK60YwKH4FnFtB6INnUP1dRVpP9_pTTKyAE28I3s5Tay4PbPdrCl7ZLCIJzCfpCW1TiWeVoPjp5HgZKTBHdP_sEkN_yO5dQerQXAkFJkV3kNgF9jI3ayT-KPqOIH6GVoWXjHFDyA2EYgJPEFRo5WSe6XycJ85p5duwT-OoBcb_kJZG9PxYd91eHlPCzp8vGxzIb2dVROCBxyM8e8W0cd9v15hfmpg9R-eG9vCM5y63ZLChZLFeHFx0Pd7hvAqfKg" To sToken

    Get Create (RefClass(cComChilkatJwt)) To hoJwt
    If (Not(IsComObjectCreated(hoJwt))) Begin
        Send CreateComObject of hoJwt
    End
    Get ComGetHeader Of hoJwt sToken To sHeader

    Showln sHeader

    // Sample header:
    // {"alg":"RS256","kid":"87bbe0815b064e6d449cac999f0e50e72a3e4374"}

    // Load the public key matching the "kid" into a Chilkat public key object, then verify..

    Get Create (RefClass(cComChilkatJsonObject)) To hoJson
    If (Not(IsComObjectCreated(hoJson))) Begin
        Send CreateComObject of hoJson
    End
    Get ComLoad Of hoJson sHeader To iSuccess
    Get ComStringOf Of hoJson "kid" To sKid

    Showln "kid = " sKid

    Get Create (RefClass(cComChilkatJsonObject)) To hoJsonPubKeys
    If (Not(IsComObjectCreated(hoJsonPubKeys))) Begin
        Send CreateComObject of hoJsonPubKeys
    End
    Get pvComObject of hoSbPubKeys to vSbPubKeys
    Get ComLoadSb Of hoJsonPubKeys vSbPubKeys To iSuccess

    Get ComFindRecord Of hoJsonPubKeys "keys" "kid" sKid True To vJsonKey
    If (IsComObject(vJsonKey)) Begin
        Get Create (RefClass(cComChilkatJsonObject)) To hoJsonKey
        Set pvComObject Of hoJsonKey To vJsonKey
    End
    Get ComLastMethodSuccess Of hoJsonPubKeys To bTemp1
    If (bTemp1 = False) Begin
        Showln "Did not find a matching public key based on the kid."
        Procedure_Return
    End

    Get ComEmit Of hoJsonKey To sTemp1
    Showln sTemp1

    // Load the matching public key into a Chilkat public key object.
    Get Create (RefClass(cComChilkatPublicKey)) To hoPubKey
    If (Not(IsComObjectCreated(hoPubKey))) Begin
        Send CreateComObject of hoPubKey
    End
    Get ComEmit Of hoJsonKey To sTemp1
    Get ComLoadFromString Of hoPubKey sTemp1 To iSuccess
    Send Destroy of hoJsonKey
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoPubKey To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // ----------------------------------------------------------------------------------------
    // Now we can validate the JWT using Google's public key as shown in this example:
    // (Except we use the public key obtained as shown above instead of a public key loaded from a PEM file.
    // 
    // See Verify JWT Using an RSA Public Key


End_Procedure