Zig Requires Chilkat v11.0.0+

Validate JWS Using HMAC SHA-256

See more JSON Web Signatures (JWS) Examples

Validates a JSON Web Signature (JWS) using HMAC SHA-256. Zig

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

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

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

    // This example takes a JSON signature in compact serialization format,
    // and uses a MAC key to validate and recover the protected header and payload.

    const jws = try chilkat.Jws.init();
    defer jws.deinit();

    // Set the HMAC key:
    const hmac_key = "AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow";
    const signature_index = 0;
    jws.setMacKey(signature_index, hmac_key, "base64url") catch {};

    // Load the JWS.
    const jws_compact = "eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ.dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk";
    try jws.loadJws(jws_compact);

    // Validate the 1st (and only) signature at index 0..
    const v = jws.validate(signature_index);
    if (v < 0) {
        // Perhaps Chilkat was not unlocked or the trial expired..
        std.debug.print("Method call failed for some other reason.\n", .{});
        std.debug.print("{s}\n", .{try jws.getLastErrorText(alloc)});
        return;
    }

    if (v == 0) {
        std.debug.print("Invalid signature.  The MAC key was incorrect, the JWS was invalid, or both.\n", .{});
        return;
    }

    // If we get here, the signature was validated..
    std.debug.print("Signature validated.\n", .{});

    // Recover the original content:
    std.debug.print("Recovered content:\n", .{});
    std.debug.print("{s}\n", .{try jws.getPayload(alloc, "utf-8")});

    // Examine the protected header:

    const jose_header = try chilkat.JsonObject.init();
    defer jose_header.deinit();
    jws.getProtectedH(signature_index, jose_header) catch {
        std.debug.print("{s}\n", .{try jws.getLastErrorText(alloc)});
        return;
    };

    jose_header.setEmitCompact(false);

    std.debug.print("Protected (JOSE) header:\n", .{});
    std.debug.print("{s}\n", .{try jose_header.emit(alloc)});

    // Output:

    //     Signature validated.
    //     Recovered content:
    //     {"iss":"joe",
    //      "exp":1300819380,
    //      "http://example.com/is_root":true}
    //     Protected (JOSE) header:
    //     {
    //       "typ": "JWT",
    //       "alg": "HS256"
    //     }
}