Zig

Verify JWT with EdDSA / Ed25519 Signature

See more JSON Web Token (JWT) Examples

Note: This example requires Chilkat v9.5.0.84 or greater.

Demonstrates how to verify a JWT that was signed using an Ed25519 private key.

This example verifies the EdDSA 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 data.

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 a JWT with an EdDSA/Ed25519 Signature
    // *** Requires Chilkat v9.5.0.84 or greater.

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

    // Use this Ed25519 public key for verification

    const json_pub_key = "{\"kty\": \"OKP\",\"alg\": \"EdDSA\",\"crv\": \"Ed25519\",\"x\": \"11qYAYKxCrfVS_7TyWQHOg7hcvPapiMlrwIaaPcHURo\"}";

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

    const jwt = try chilkat.Jwt.init();
    defer jwt.deinit();
    const token = "eyJhbGciOiJFZERTQSJ9.RXhhbXBsZSBvZiBFZDI1NTE5IHNpZ25pbmc.hgyY0il_MGCjP0JzlnLWG1PPOt7-09PGcvMg3AIbQR6dWbhijcNR4ki4iylGjg5BhVsPt9g7sVvpAr_MuM0KAg";

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

    if (!sig_verified) {
        std.debug.print("{s}\n", .{try jwt.getLastErrorText(alloc)});
        return;
    }

    // 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});

    // Recover the original data (the payload).
    const payload = try jwt.getPayload(alloc, token);
    std.debug.print("{s}\n", .{payload});

    // Recover the original JOSE header in the same way:
    const jose_header = try jwt.getHeader(alloc, token);
    std.debug.print("{s}\n", .{jose_header});
}