Zig

Verify JWT Using HS256, HS384, or HS512

See more JSON Web Token (JWT) Examples

Demonstrates how to verify a JWT that was signed using HS256, HS384, or HS512. (HS256 is JWT's acronym for HMAC-SHA256.)

This example verifies the 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.

Zig

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

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

    // Demonstrates how to verify an HMAC JWT using a shared secret (password).

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

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

    const token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDYzNDMxODEyLCJuYmYiOjE0NjM0MzE4MTIsImV4cCI6MTQ2MzQzNTQxMn0.SHnMJ11qJH5pbp22YchT_9fL2HIx0koHiUHLG67_foU";

    // First verify the signature.
    // The password used to create this JWT was "secret".
    var sig_verified: bool = if (jwt.verifyJwt(token, "secret")) true else |_| false;
    std.debug.print("with correct password: {}\n", .{sig_verified});

    // Now try with a different password:
    sig_verified = if (jwt.verifyJwt(token, "secret2")) true else |_| false;
    std.debug.print("with incorrect password {}\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)});
}