1 files changed, 266 insertions, 0 deletions
diff --git a/services/crypto/modules/WeaveCrypto.js b/services/crypto/modules/WeaveCrypto.js
new file mode 100644
index 000000000..c040c4f6f
--- /dev/null
+++ b/services/crypto/modules/WeaveCrypto.js
@@ -0,0 +1,266 @@
+/* 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/. */
+
+this.EXPORTED_SYMBOLS = ["WeaveCrypto"];
+
+var {classes: Cc, interfaces: Ci, results: Cr, utils: Cu} = Components;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://services-common/async.js");
+
+Cu.importGlobalProperties(['crypto']);
+
+const CRYPT_ALGO        = "AES-CBC";
+const CRYPT_ALGO_LENGTH = 256;
+const AES_CBC_IV_SIZE   = 16;
+const OPERATIONS        = { ENCRYPT: 0, DECRYPT: 1 };
+const UTF_LABEL          = "utf-8";
+
+const KEY_DERIVATION_ALGO         = "PBKDF2";
+const KEY_DERIVATION_HASHING_ALGO = "SHA-1";
+const KEY_DERIVATION_ITERATIONS   = 4096; // PKCS#5 recommends at least 1000.
+const DERIVED_KEY_ALGO            = CRYPT_ALGO;
+
+this.WeaveCrypto = function WeaveCrypto() {
+    this.init();
+};
+
+WeaveCrypto.prototype = {
+    prefBranch : null,
+    debug      : true,  // services.sync.log.cryptoDebug
+
+    observer : {
+        _self : null,
+
+        QueryInterface : XPCOMUtils.generateQI([Ci.nsIObserver,
+                                                Ci.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, false);
+        this.observer._self = this;
+        try {
+          this.debug = this.prefBranch.getBoolPref("cryptoDebug");
+        } catch (x) {
+          this.debug = false;
+        }
+        XPCOMUtils.defineLazyGetter(this, 'encoder', () => new TextEncoder(UTF_LABEL));
+        XPCOMUtils.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;
+    },
+
+    encrypt(clearTextUCS2, symmetricKey, iv) {
+        this.log("encrypt() called");
+        let clearTextBuffer = this.encoder.encode(clearTextUCS2).buffer;
+        let encrypted = this._commonCrypt(clearTextBuffer, symmetricKey, iv, OPERATIONS.ENCRYPT);
+        return this.encodeBase64(encrypted);
+    },
+
+    decrypt(cipherText, symmetricKey, iv) {
+        this.log("decrypt() called");
+        if (cipherText.length) {
+            cipherText = atob(cipherText);
+        }
+        let cipherTextBuffer = this.byteCompressInts(cipherText);
+        let decrypted = 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)
+    */
+    _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 "Invalid IV size; must be " + AES_CBC_IV_SIZE + " bytes.";
+        }
+
+        let iv = this.byteCompressInts(ivStr);
+        let symKey = this.importSymKey(symKeyStr, operation);
+        let cryptMethod = (operation === OPERATIONS.ENCRYPT
+                           ? crypto.subtle.encrypt
+                           : crypto.subtle.decrypt)
+                          .bind(crypto.subtle);
+        let algo = { name: CRYPT_ALGO, iv: iv };
+
+
+        return Async.promiseSpinningly(
+            cryptMethod(algo, symKey, data)
+            .then(keyBytes => new Uint8Array(keyBytes))
+        );
+    },
+
+
+    generateRandomKey() {
+        this.log("generateRandomKey() called");
+        let algo = {
+            name: CRYPT_ALGO,
+            length: CRYPT_ALGO_LENGTH
+        };
+        return Async.promiseSpinningly(
+            crypto.subtle.generateKey(algo, true, [])
+            .then(key => crypto.subtle.exportKey("raw", key))
+            .then(keyBytes => {
+                keyBytes = new Uint8Array(keyBytes);
+                return this.encodeBase64(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: {},
+    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 "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"];
+
+        return Async.promiseSpinningly(
+            crypto.subtle.importKey("raw", symmetricKeyBuffer, algo, false, usages)
+            .then(symKey => {
+                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);
+    },
+
+    /**
+     * Returns the expanded data string for the derived key.
+     */
+    deriveKeyFromPassphrase(passphrase, saltStr, keyLength = 32) {
+        this.log("deriveKeyFromPassphrase() called.");
+        let keyData = this.makeUint8Array(passphrase, false);
+        let salt = this.makeUint8Array(saltStr, true);
+        let importAlgo = { name: KEY_DERIVATION_ALGO };
+        let deriveAlgo = {
+            name: KEY_DERIVATION_ALGO,
+            salt: salt,
+            iterations: KEY_DERIVATION_ITERATIONS,
+            hash: { name: KEY_DERIVATION_HASHING_ALGO },
+        };
+        let derivedKeyType = {
+            name: DERIVED_KEY_ALGO,
+            length: keyLength * 8,
+        };
+        return Async.promiseSpinningly(
+            crypto.subtle.importKey("raw", keyData, importAlgo, false, ["deriveKey"])
+            .then(key => crypto.subtle.deriveKey(deriveAlgo, key, derivedKeyType, true, []))
+            .then(derivedKey => crypto.subtle.exportKey("raw", derivedKey))
+            .then(keyBytes => {
+                keyBytes = new Uint8Array(keyBytes);
+                return this.expandData(keyBytes);
+            })
+        );
+    },
+};