Zig Requires Chilkat v11.0.0+

Validate a Google ID Token

See more OAuth2 Examples

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

const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

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

    const http = try chilkat.Http.init();
    defer http.deinit();

    // First get the public key we'll be needing..
    const jwk_str = http.quickGetStr(alloc, "https://www.googleapis.com/oauth2/v3/certs") catch {
        std.debug.print("{s}\n", .{try http.getLastErrorText(alloc)});
        return;
    };

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

    const json = try chilkat.JsonObject.init();
    defer json.deinit();
    try json.load(jwk_str);

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

    // 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"
    // }

    const json_token = try chilkat.JsonObject.init();
    defer json_token.deinit();
    json_token.loadFile("qa_data/tokens/google_sample_id_token.json") catch {
        std.debug.print("Failed to load the JSON file...\n", .{});
        return;
    };

    // Get the id_token;
    const sb_id_token = try chilkat.StringBuilder.init();
    defer sb_id_token.deinit();
    try sb_id_token.append(try json_token.stringOf(alloc, "id_token"));

    // Get the signature in base64url format.
    // The header + payload remains in sbIdToken.
    const sig_b64_url = try sb_id_token.getAfterFinal(alloc, ".", true);
    const header_plus_payload = try sb_id_token.getAsString(alloc);

    std.debug.print("{s}\n", .{sig_b64_url});
    std.debug.print("{s}\n", .{header_plus_payload});

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

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

    const rsa = try chilkat.Rsa.init();
    defer rsa.deinit();
    rsa.setEncodingMode("base64url");

    const json_key = try chilkat.JsonObject.init();
    defer json_key.deinit();
    const pub_key = try chilkat.PublicKey.init();
    defer pub_key.deinit();

    const num_keys = json.sizeOfArray("keys");
    var i: i32 = 0;
    while (i < num_keys) {
        json.setI(i);

        json.objectOf2("keys[i]", json_key) catch {};

        pub_key.loadFromString(try json_key.emit(alloc)) catch {
            std.debug.print("{s}\n", .{try pub_key.getLastErrorText(alloc)});
            return;
        };

        std.debug.print("{d}\n", .{i});
        std.debug.print("{s}\n", .{try pub_key.getPem(alloc, true)});

        try rsa.usePublicKey(pub_key);

        const b_verified = if (rsa.verifyStringENC(header_plus_payload, "sha256", sig_b64_url)) true else |_| false;
        std.debug.print("bVerified = {}\n", .{b_verified});

        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
}