1 files changed, 127 insertions, 0 deletions
diff --git a/comm/chat/protocols/matrix/lib/matrix-sdk/crypto/aes.js b/comm/chat/protocols/matrix/lib/matrix-sdk/crypto/aes.js
new file mode 100644
index 0000000000..e48c59446c
--- /dev/null
+++ b/comm/chat/protocols/matrix/lib/matrix-sdk/crypto/aes.js
@@ -0,0 +1,127 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.calculateKeyCheck = calculateKeyCheck;
+exports.decryptAES = decryptAES;
+exports.encryptAES = encryptAES;
+var _olmlib = require("./olmlib");
+var _crypto = require("./crypto");
+/*
+Copyright 2020 - 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// salt for HKDF, with 8 bytes of zeros
+const zeroSalt = new Uint8Array(8);
+/**
+ * encrypt a string
+ *
+ * @param data - the plaintext to encrypt
+ * @param key - the encryption key to use
+ * @param name - the name of the secret
+ * @param ivStr - the initialization vector to use
+ */
+async function encryptAES(data, key, name, ivStr) {
+  let iv;
+  if (ivStr) {
+    iv = (0, _olmlib.decodeBase64)(ivStr);
+  } else {
+    iv = new Uint8Array(16);
+    _crypto.crypto.getRandomValues(iv);
+
+    // clear bit 63 of the IV to stop us hitting the 64-bit counter boundary
+    // (which would mean we wouldn't be able to decrypt on Android). The loss
+    // of a single bit of iv is a price we have to pay.
+    iv[8] &= 0x7f;
+  }
+  const [aesKey, hmacKey] = await deriveKeys(key, name);
+  const encodedData = new _crypto.TextEncoder().encode(data);
+  const ciphertext = await _crypto.subtleCrypto.encrypt({
+    name: "AES-CTR",
+    counter: iv,
+    length: 64
+  }, aesKey, encodedData);
+  const hmac = await _crypto.subtleCrypto.sign({
+    name: "HMAC"
+  }, hmacKey, ciphertext);
+  return {
+    iv: (0, _olmlib.encodeBase64)(iv),
+    ciphertext: (0, _olmlib.encodeBase64)(ciphertext),
+    mac: (0, _olmlib.encodeBase64)(hmac)
+  };
+}
+
+/**
+ * decrypt a string
+ *
+ * @param data - the encrypted data
+ * @param key - the encryption key to use
+ * @param name - the name of the secret
+ */
+async function decryptAES(data, key, name) {
+  const [aesKey, hmacKey] = await deriveKeys(key, name);
+  const ciphertext = (0, _olmlib.decodeBase64)(data.ciphertext);
+  if (!(await _crypto.subtleCrypto.verify({
+    name: "HMAC"
+  }, hmacKey, (0, _olmlib.decodeBase64)(data.mac), ciphertext))) {
+    throw new Error(`Error decrypting secret ${name}: bad MAC`);
+  }
+  const plaintext = await _crypto.subtleCrypto.decrypt({
+    name: "AES-CTR",
+    counter: (0, _olmlib.decodeBase64)(data.iv),
+    length: 64
+  }, aesKey, ciphertext);
+  return new TextDecoder().decode(new Uint8Array(plaintext));
+}
+async function deriveKeys(key, name) {
+  const hkdfkey = await _crypto.subtleCrypto.importKey("raw", key, {
+    name: "HKDF"
+  }, false, ["deriveBits"]);
+  const keybits = await _crypto.subtleCrypto.deriveBits({
+    name: "HKDF",
+    salt: zeroSalt,
+    // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+    // @ts-ignore: https://github.com/microsoft/TypeScript-DOM-lib-generator/pull/879
+    info: new _crypto.TextEncoder().encode(name),
+    hash: "SHA-256"
+  }, hkdfkey, 512);
+  const aesKey = keybits.slice(0, 32);
+  const hmacKey = keybits.slice(32);
+  const aesProm = _crypto.subtleCrypto.importKey("raw", aesKey, {
+    name: "AES-CTR"
+  }, false, ["encrypt", "decrypt"]);
+  const hmacProm = _crypto.subtleCrypto.importKey("raw", hmacKey, {
+    name: "HMAC",
+    hash: {
+      name: "SHA-256"
+    }
+  }, false, ["sign", "verify"]);
+  return Promise.all([aesProm, hmacProm]);
+}
+
+// string of zeroes, for calculating the key check
+const ZERO_STR = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
+
+/** Calculate the MAC for checking the key.
+ *
+ * @param key - the key to use
+ * @param iv - The initialization vector as a base64-encoded string.
+ *     If omitted, a random initialization vector will be created.
+ * @returns An object that contains, `mac` and `iv` properties.
+ */
+function calculateKeyCheck(key, iv) {
+  return encryptAES(ZERO_STR, key, "", iv);
+}
+\ No newline at end of file