JWT Library

jwt.mo

import Array "mo:base/Array";
import Blob "mo:base/Blob";
import Buffer "mo:base/Buffer";
import Nat8 "mo:base/Nat8";
import Text "mo:base/Text";
import Time "mo:base/Time";
import Base64 "mo:encoding/Base64";
import JSON "mo:json/JSON";
import CRC32 "mo:hash/CRC32";

actor JWTLibrary {
// Define the interface for the management canister
type IC = actor {
sign_with_ecdsa : ({
message_hash : Blob;
derivation_path : [Blob];
key_id : { curve: { #secp256k1; } ; name: Text };
}) -> async ({ signature : Blob });

ecdsa_public_key : ({
        canister_id : ?Principal;
        derivation_path : [Blob];
        key_id : { curve: { #secp256k1; } ; name: Text };
    }) -> async ({ public_key : Blob; chain_code : Blob; });
};

let ic : IC = actor("aaaaa-aa");

// JWT Header
private func createHeader() : Text {
    let header = {
        alg = "ES256";
        typ = "JWT";
    };
    Base64.encode(Text.encodeUtf8(JSON.show(#Object(header))));
};

// JWT Payload
private func createPayload(subject : Text, expiresIn : Nat) : async Text {
    let now = Time.now();
    let payload = {
        sub = subject;
        iat = now;
        exp = now + expiresIn;
    };
    Base64.encode(Text.encodeUtf8(JSON.show(#Object(payload))));
};

// Sign the JWT
private func signJWT(message : Text) : async Blob {
    let messageHash = Blob.fromArray(CRC32.crc32(Blob.toArray(Text.encodeUtf8(message))));

    let { signature } = await ic.sign_with_ecdsa({
        message_hash = messageHash;
        derivation_path = [];
        key_id = { curve = #secp256k1; name = "decide_id_pub_key" };
    });

    signature
};

// Create JWT
public func createJWT(subject : Text, expiresIn : Nat) : async Text {
    let header = createHeader();
    let payload = await createPayload(subject, expiresIn);
    let message = header # "." # payload;
    let signature = await signJWT(message);

    message # "." # Base64.encode(Blob.toArray(signature))
};

// Get Public Key
public func getPublicKey() : async Text {
    let { public_key } = await ic.ecdsa_public_key({
        canister_id = null;
        derivation_path = [];
        key_id = { curve = #secp256k1; name = "decide_id_pub_key" };
    });

    Base64.encode(Blob.toArray(public_key))
};