Zig Requires Chilkat v11.0.0+

Verify a JWT Created by the Amazon Cognito Service

See more JSON Web Token (JWT) Examples

Demonstrates how to verify a JWT created by the Amazon Cognito Service. 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.

    // The public keys for this example are at https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json
    // Let's get them:

    const http = try chilkat.Http.init();
    defer http.deinit();
    const sb_json_keys = try chilkat.StringBuilder.init();
    defer sb_json_keys.deinit();
    http.quickGetSb("https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json", sb_json_keys) catch {
        std.debug.print("{s}\n", .{try http.getLastErrorText(alloc)});
        return;
    };

    const json_keys = try chilkat.JsonObject.init();
    defer json_keys.deinit();
    json_keys.loadSb(sb_json_keys) catch {};
    json_keys.setEmitCompact(false);
    std.debug.print("{s}\n", .{try json_keys.emit(alloc)});

    // Here are the keys:

    // {
    //   "keys": [
    //     {
    //       "alg": "RS256",
    //       "e": "AQAB",
    //       "kid": "1A/L5Fsb2EsEwxy5E0cmCMS1BnMe6Jl6NXiMig4iNwU=",
    //       "kty": "RSA",
    //       "n": "y0w7BJrIJYi ... jKG27z2P3OKw",
    //       "use": "sig"
    //     },
    //     {
    //       "alg": "RS256",
    //       "e": "AQAB",
    //       "kid": "mos6VTJnvDwurY3ghJg6IAPUq+dMwl6CL/iThzJOkzg=",
    //       "kty": "RSA",
    //       "n": "qbIEH-7tg6yrT ... 3Fj94ooTd0w",
    //       "use": "sig"
    //     }
    //   ]
    // }

    // Try the 1st key.
    const json_key1 = try chilkat.JsonObject.init();
    defer json_key1.deinit();
    json_keys.objectOf2("keys[0]", json_key1) catch {};

    const pub_key1 = try chilkat.PublicKey.init();
    defer pub_key1.deinit();
    pub_key1.loadFromString(try json_key1.emit(alloc)) catch {
        std.debug.print("{s}\n", .{try pub_key1.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("Success\n", .{});

    const jwt = try chilkat.Jwt.init();
    defer jwt.deinit();

    // I did not include the an actual AWS Cognito token here because our test sample used customer-provided data..
    const token = "eyJ..asXg";

    // First verify the signature.
    const sig_verified = if (jwt.verifyJwtPk(token, pub_key1)) true else |_| false;
    std.debug.print("verified: {}\n", .{sig_verified});

    // Let's see if the time constraints, if any, are valid.
    // The above JWT was created on the afternoon of 16-May-2016, with an expiration of 1 hour.
    // If the current system time is before the "nbf" time, or after the "exp" time,
    // then IsTimeValid will return false/0.
    // Also, we'll allow a leeway of 60 seconds to account for any clock skew.
    // Note: If the token has no "nbf" or "exp" claim fields, then IsTimeValid is always true.
    const leeway = 60;
    const b_time_valid = jwt.isTimeValid(token, leeway);
    std.debug.print("time constraints valid: {}\n", .{b_time_valid});

    // Now let's recover the original claims JSON (the payload).
    const payload = try jwt.getPayload(alloc, token);
    // The payload will likely be in compact form:
    std.debug.print("{s}\n", .{payload});

    // We can format for human viewing by loading it into Chilkat's JSON object
    // and emit.
    const json = try chilkat.JsonObject.init();
    defer json.deinit();
    try json.load(payload);
    json.setEmitCompact(false);
    std.debug.print("{s}\n", .{try json.emit(alloc)});

    // We can recover the original JOSE header in the same way:
    const jose_header = try jwt.getHeader(alloc, token);
    // The payload will likely be in compact form:
    std.debug.print("{s}\n", .{jose_header});

    // We can format for human viewing by loading it into Chilkat's JSON object
    // and emit.
    try json.load(jose_header);
    json.setEmitCompact(false);
    std.debug.print("{s}\n", .{try json.emit(alloc)});
}