(Go) 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.

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

    http := chilkat.NewHttp()
    sbPubKeys := chilkat.NewStringBuilder()

    success := http.QuickGetSb("https://www.googleapis.com/oauth2/v3/certs",sbPubKeys)
    if success == false {
        fmt.Println(http.LastErrorText())
        http.DisposeHttp()
        sbPubKeys.DisposeStringBuilder()
        return
    }

    fmt.Println(*sbPubKeys.GetAsString())

    // 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.
    // -------------------------------------------------------------------------------------------
    token := "eyJhbGciOiJSUzI1NiIsImtpZCI6IjQyZmY5MGQ3ZDM0OGM5NzM4MWE3YzExOWVmMWY1MzI0ZWEzZjViZWIifQ.eyJpc3MiOiJodHRwczovL2FjY291bnRzLmdvb2dsZS5jb20iLCJzdWIiOiIxMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExIiwiaWF0IjoxNjExMTE1MTQzLCJleHAiOjE2MTEyMDE1NDMsImF1ZCI6IjQyOTc1NzExNTE0ODg0OSJ9.pLem5i0bx3M7lJYj7jKv2Nq7c07X5YpZz-x1uM5RniW-v4LsX-lKIVvOq2x3-WoPqkzLXJfP0kG0dx1uD2q1NfFQK60YwKH4FnFtB6INnUP1dRVpP9_pTTKyAE28I3s5Tay4PbPdrCl7ZLCIJzCfpCW1TiWeVoPjp5HgZKTBHdP_sEkN_yO5dQerQXAkFJkV3kNgF9jI3ayT-KPqOIH6GVoWXjHFDyA2EYgJPEFRo5WSe6XycJ85p5duwT-OoBcb_kJZG9PxYd91eHlPCzp8vGxzIb2dVROCBxyM8e8W0cd9v15hfmpg9R-eG9vCM5y63ZLChZLFeHFx0Pd7hvAqfKg"

    jwt := chilkat.NewJwt()
    header := jwt.GetHeader(token)

    fmt.Println(*header)

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

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

    json := chilkat.NewJsonObject()
    json.Load(*header)
    kid := json.StringOf("kid")

    fmt.Println("kid = ", *kid)

    jsonPubKeys := chilkat.NewJsonObject()
    jsonPubKeys.LoadSb(sbPubKeys)

    jsonKey := jsonPubKeys.FindRecord("keys","kid",*kid,true)
    if jsonPubKeys.LastMethodSuccess() == false {
        fmt.Println("Did not find a matching public key based on the kid.")
        http.DisposeHttp()
        sbPubKeys.DisposeStringBuilder()
        jwt.DisposeJwt()
        json.DisposeJsonObject()
        jsonPubKeys.DisposeJsonObject()
        return
    }

    fmt.Println(*jsonKey.Emit())

    // Load the matching public key into a Chilkat public key object.
    pubKey := chilkat.NewPublicKey()
    success = pubKey.LoadFromString(*jsonKey.Emit())
    jsonKey.DisposeJsonObject()
    if success == false {
        fmt.Println(pubKey.LastErrorText())
        http.DisposeHttp()
        sbPubKeys.DisposeStringBuilder()
        jwt.DisposeJwt()
        json.DisposeJsonObject()
        jsonPubKeys.DisposeJsonObject()
        pubKey.DisposePublicKey()
        return
    }

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

    http.DisposeHttp()
    sbPubKeys.DisposeStringBuilder()
    jwt.DisposeJwt()
    json.DisposeJsonObject()
    jsonPubKeys.DisposeJsonObject()
    pubKey.DisposePublicKey()