Lilia's Webcrypto branch rebased and a few very tiny tweaks

js/webcrypto.js

@@ -0,0 +1,74 @@
+/* Web Crypto polyfill. TODO: replace with web crypto */
+// All inputs/outputs are arraybuffers!
+window.crypto.subtle = (function() {
+	if (window.crypto.subtle !== undefined && window.crypto.subtle !== null) {
+			return window.crypto.subtle;
+	} else {
+		// private implementation functions
+		function HmacSHA256(key, input) {
+			return CryptoJS.HmacSHA256(
+					CryptoJS.lib.WordArray.create(toArrayBuffer(input)),
+					CryptoJS.enc.Latin1.parse(getString(key))
+				).toString(CryptoJS.enc.Latin1);
+		};
+
+		function encryptAESCTR(plaintext, key, 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) {
+				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 decryptAESCBC(ciphertext, key, 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 new Promise(function(resolve) {
+				resolve(implementation.apply(this, args));
+			});
+		}
+
+		// public interface functions
+		function encrypt(algorithm, key, data) {
+			if (algorithm.name === "AES-CTR") {
+					return promise(encryptAESCTR, data, key, algorithm.counter);
+			}
+		};
+		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,
+		}
+	}
+})();