Cable-Desktop/js/webcrypto.js

/*
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

// All inputs/outputs are arraybuffers!
window.textsecure.subtle = (function() {
	var StaticArrayBufferProto = new ArrayBuffer().__proto__;
	function assertIsArrayBuffer(thing) {
		if (thing !== Object(thing) || thing.__proto__ != StaticArrayBufferProto)
			throw new Error("Needed a ArrayBuffer");
	}

	// private implementation functions
	function HmacSHA256(key, input) {
		assertIsArrayBuffer(key);
		assertIsArrayBuffer(input);
		return CryptoJS.HmacSHA256(
				CryptoJS.lib.WordArray.create(input),
				CryptoJS.enc.Latin1.parse(getString(key))
			).toString(CryptoJS.enc.Latin1);
	};

	function encryptAESCTR(plaintext, key, counter) {
		assertIsArrayBuffer(plaintext);
		assertIsArrayBuffer(key);
		assertIsArrayBuffer(counter);
			return CryptoJS.AES.encrypt(CryptoJS.enc.Latin1.parse(getString(plaintext)),
					CryptoJS.enc.Latin1.parse(getString(key)),
					{mode: CryptoJS.mode.CTR, iv: CryptoJS.enc.Latin1.parse(getString(counter)),
						padding: CryptoJS.pad.NoPadding})
				.ciphertext.toString(CryptoJS.enc.Latin1);
	};

	function decryptAESCTR(ciphertext, key, counter) {
		assertIsArrayBuffer(ciphertext);
		assertIsArrayBuffer(key);
		assertIsArrayBuffer(counter);
			return CryptoJS.AES.decrypt(btoa(getString(ciphertext)),
					CryptoJS.enc.Latin1.parse(getString(key)),
					{mode: CryptoJS.mode.CTR, iv: CryptoJS.enc.Latin1.parse(getString(counter)),
						padding: CryptoJS.pad.NoPadding})
				.toString(CryptoJS.enc.Latin1);
	};

	function encryptAESCBC(plaintext, key, iv) {
		assertIsArrayBuffer(plaintext);
		assertIsArrayBuffer(key);
		assertIsArrayBuffer(iv);
		return CryptoJS.AES.encrypt(CryptoJS.enc.Latin1.parse(getString(plaintext)),
				CryptoJS.enc.Latin1.parse(getString(key)),
				{iv: CryptoJS.enc.Latin1.parse(getString(iv))})
			.ciphertext.toString(CryptoJS.enc.Latin1);
	};
	function decryptAESCBC(ciphertext, key, iv) {
		assertIsArrayBuffer(ciphertext);
		assertIsArrayBuffer(key);
		assertIsArrayBuffer(iv);
		return CryptoJS.AES.decrypt(btoa(getString(ciphertext)),
				CryptoJS.enc.Latin1.parse(getString(key)),
				{iv: CryptoJS.enc.Latin1.parse(getString(iv))})
			.toString(CryptoJS.enc.Latin1);
	};

	// utility function for connecting front and back ends via promises
	// Takes an implementation function and 0 or more arguments
	function promise(implementation) {
		var args = Array.prototype.slice.call(arguments);
		args.shift();
		return Promise.resolve(toArrayBuffer(implementation.apply(this, args)));
	}

	// public interface functions
	function encrypt(algorithm, key, data) {
		if (algorithm.name === "AES-CTR")
			return promise(encryptAESCTR, data, key, algorithm.counter);
		if (algorithm.name === "AES-CBC")
			return promise(encryptAESCBC, data, key, algorithm.iv);
	};
	function decrypt(algorithm, key, data) {
		if (algorithm.name === "AES-CTR")
			return promise(decryptAESCTR, data, key, algorithm.counter);
		if (algorithm.name === "AES-CBC")
			return promise(decryptAESCBC, data, key, algorithm.iv);
	};
	function sign(algorithm, key, data) {
		if (algorithm.name === "HMAC" && algorithm.hash === "SHA-256")
			return promise(HmacSHA256, key, data);
	};

	return {
		encrypt	 : encrypt,
		decrypt	 : decrypt,
		sign     : sign,
	}
})();