Zig Requires Chilkat v11.0.0+

Validate a JWS Using ECDSA P-256 SHA-256

See more JSON Web Signatures (JWS) Examples

Validates a JSON Web Signature (JWS) that uses ECDSA P-256 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 an ECDSA public key to validate and recover the protected header and payload.

    // We only need a public key for signature validation.  This is the ECDSA public key
    // that is used:

    //      {"kty":"EC",
    //       "crv":"P-256",
    //       "x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU",
    //       "y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0"
    //      }

    const sb_pub_key = try chilkat.StringBuilder.init();
    defer sb_pub_key.deinit();
    sb_pub_key.append("{\"kty\":\"EC\",") catch {};
    sb_pub_key.append("\"crv\":\"P-256\",") catch {};
    sb_pub_key.append("\"x\":\"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU\",") catch {};
    sb_pub_key.append("\"y\":\"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0\"") catch {};
    sb_pub_key.append("}") catch {};

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

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

    // Set the ECC public key:
    const signature_index = 0;
    jws.setPublicKey(signature_index, pub_key) catch {};

    // Load the JWS.
    const sb_jws = try chilkat.StringBuilder.init();
    defer sb_jws.deinit();
    sb_jws.append("eyJhbGciOiJFUzI1NiJ9") catch {};
    sb_jws.append(".") catch {};
    sb_jws.append("eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt") catch {};
    sb_jws.append("cGxlLmNvbS9pc19yb290Ijp0cnVlfQ") catch {};
    sb_jws.append(".") catch {};
    sb_jws.append("DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSA") catch {};
    sb_jws.append("pmWQxfKTUJqPP3-Kg6NU1Q") catch {};

    jws.loadJwsSb(sb_jws) catch {
        std.debug.print("{s}\n", .{try jws.getLastErrorText(alloc)});
        return;
    };

    // 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 ECC 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", .{});
    std.debug.print("--\n", .{});

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

    // 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:
    //     {
    //       "alg": "ES256"
    //     }
}