1 files changed, 232 insertions, 0 deletions
diff --git a/services/crypto/modules/WeaveCrypto.sys.mjs b/services/crypto/modules/WeaveCrypto.sys.mjs
new file mode 100644
index 0000000000..63ee51a1a2
--- /dev/null
+++ b/services/crypto/modules/WeaveCrypto.sys.mjs
@@ -0,0 +1,232 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const CRYPT_ALGO = "AES-CBC";
+const CRYPT_ALGO_LENGTH = 256;
+const CRYPT_ALGO_USAGES = ["encrypt", "decrypt"];
+const AES_CBC_IV_SIZE = 16;
+const OPERATIONS = { ENCRYPT: 0, DECRYPT: 1 };
+const UTF_LABEL = "utf-8";
+
+export function WeaveCrypto() {
+  this.init();
+}
+
+WeaveCrypto.prototype = {
+  prefBranch: null,
+  debug: true, // services.sync.log.cryptoDebug
+
+  observer: {
+    _self: null,
+
+    QueryInterface: ChromeUtils.generateQI([
+      "nsIObserver",
+      "nsISupportsWeakReference",
+    ]),
+
+    observe(subject, topic, data) {
+      let self = this._self;
+      self.log("Observed " + topic + " topic.");
+      if (topic == "nsPref:changed") {
+        self.debug = self.prefBranch.getBoolPref("cryptoDebug");
+      }
+    },
+  },
+
+  init() {
+    // Preferences. Add observer so we get notified of changes.
+    this.prefBranch = Services.prefs.getBranch("services.sync.log.");
+    this.prefBranch.addObserver("cryptoDebug", this.observer);
+    this.observer._self = this;
+    this.debug = this.prefBranch.getBoolPref("cryptoDebug", false);
+    ChromeUtils.defineLazyGetter(
+      this,
+      "encoder",
+      () => new TextEncoder(UTF_LABEL)
+    );
+    ChromeUtils.defineLazyGetter(
+      this,
+      "decoder",
+      () => new TextDecoder(UTF_LABEL, { fatal: true })
+    );
+  },
+
+  log(message) {
+    if (!this.debug) {
+      return;
+    }
+    dump("WeaveCrypto: " + message + "\n");
+    Services.console.logStringMessage("WeaveCrypto: " + message);
+  },
+
+  // /!\ Only use this for tests! /!\
+  _getCrypto() {
+    return crypto;
+  },
+
+  async encrypt(clearTextUCS2, symmetricKey, iv) {
+    this.log("encrypt() called");
+    let clearTextBuffer = this.encoder.encode(clearTextUCS2).buffer;
+    let encrypted = await this._commonCrypt(
+      clearTextBuffer,
+      symmetricKey,
+      iv,
+      OPERATIONS.ENCRYPT
+    );
+    return this.encodeBase64(encrypted);
+  },
+
+  async decrypt(cipherText, symmetricKey, iv) {
+    this.log("decrypt() called");
+    if (cipherText.length) {
+      cipherText = atob(cipherText);
+    }
+    let cipherTextBuffer = this.byteCompressInts(cipherText);
+    let decrypted = await this._commonCrypt(
+      cipherTextBuffer,
+      symmetricKey,
+      iv,
+      OPERATIONS.DECRYPT
+    );
+    return this.decoder.decode(decrypted);
+  },
+
+  /**
+   * _commonCrypt
+   *
+   * @args
+   * data: data to encrypt/decrypt (ArrayBuffer)
+   * symKeyStr: symmetric key (Base64 String)
+   * ivStr: initialization vector (Base64 String)
+   * operation: operation to apply (either OPERATIONS.ENCRYPT or OPERATIONS.DECRYPT)
+   * @returns
+   * the encrypted/decrypted data (ArrayBuffer)
+   */
+  async _commonCrypt(data, symKeyStr, ivStr, operation) {
+    this.log("_commonCrypt() called");
+    ivStr = atob(ivStr);
+
+    if (operation !== OPERATIONS.ENCRYPT && operation !== OPERATIONS.DECRYPT) {
+      throw new Error("Unsupported operation in _commonCrypt.");
+    }
+    // We never want an IV longer than the block size, which is 16 bytes
+    // for AES, neither do we want one smaller; throw in both cases.
+    if (ivStr.length !== AES_CBC_IV_SIZE) {
+      throw new Error(`Invalid IV size; must be ${AES_CBC_IV_SIZE} bytes.`);
+    }
+
+    let iv = this.byteCompressInts(ivStr);
+    let symKey = await this.importSymKey(symKeyStr, operation);
+    let cryptMethod = (
+      operation === OPERATIONS.ENCRYPT
+        ? crypto.subtle.encrypt
+        : crypto.subtle.decrypt
+    ).bind(crypto.subtle);
+    let algo = { name: CRYPT_ALGO, iv };
+
+    let keyBytes = await cryptMethod.call(crypto.subtle, algo, symKey, data);
+    return new Uint8Array(keyBytes);
+  },
+
+  async generateRandomKey() {
+    this.log("generateRandomKey() called");
+    let algo = {
+      name: CRYPT_ALGO,
+      length: CRYPT_ALGO_LENGTH,
+    };
+    let key = await crypto.subtle.generateKey(algo, true, CRYPT_ALGO_USAGES);
+    let keyBytes = await crypto.subtle.exportKey("raw", key);
+    return this.encodeBase64(new Uint8Array(keyBytes));
+  },
+
+  generateRandomIV() {
+    return this.generateRandomBytes(AES_CBC_IV_SIZE);
+  },
+
+  generateRandomBytes(byteCount) {
+    this.log("generateRandomBytes() called");
+
+    let randBytes = new Uint8Array(byteCount);
+    crypto.getRandomValues(randBytes);
+
+    return this.encodeBase64(randBytes);
+  },
+
+  //
+  // SymKey CryptoKey memoization.
+  //
+
+  // Memoize the import of symmetric keys. We do this by using the base64
+  // string itself as a key.
+  _encryptionSymKeyMemo: {},
+  _decryptionSymKeyMemo: {},
+  async importSymKey(encodedKeyString, operation) {
+    let memo;
+
+    // We use two separate memos for thoroughness: operation is an input to
+    // key import.
+    switch (operation) {
+      case OPERATIONS.ENCRYPT:
+        memo = this._encryptionSymKeyMemo;
+        break;
+      case OPERATIONS.DECRYPT:
+        memo = this._decryptionSymKeyMemo;
+        break;
+      default:
+        throw new Error("Unsupported operation in importSymKey.");
+    }
+
+    if (encodedKeyString in memo) {
+      return memo[encodedKeyString];
+    }
+
+    let symmetricKeyBuffer = this.makeUint8Array(encodedKeyString, true);
+    let algo = { name: CRYPT_ALGO };
+    let usages = [operation === OPERATIONS.ENCRYPT ? "encrypt" : "decrypt"];
+    let symKey = await crypto.subtle.importKey(
+      "raw",
+      symmetricKeyBuffer,
+      algo,
+      false,
+      usages
+    );
+    memo[encodedKeyString] = symKey;
+    return symKey;
+  },
+
+  //
+  // Utility functions
+  //
+
+  /**
+   * Returns an Uint8Array filled with a JS string,
+   * which means we only keep utf-16 characters from 0x00 to 0xFF.
+   */
+  byteCompressInts(str) {
+    let arrayBuffer = new Uint8Array(str.length);
+    for (let i = 0; i < str.length; i++) {
+      arrayBuffer[i] = str.charCodeAt(i) & 0xff;
+    }
+    return arrayBuffer;
+  },
+
+  expandData(data) {
+    let expanded = "";
+    for (let i = 0; i < data.length; i++) {
+      expanded += String.fromCharCode(data[i]);
+    }
+    return expanded;
+  },
+
+  encodeBase64(data) {
+    return btoa(this.expandData(data));
+  },
+
+  makeUint8Array(input, isEncoded) {
+    if (isEncoded) {
+      input = atob(input);
+    }
+    return this.byteCompressInts(input);
+  },
+};