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Diffstat (limited to 'services/crypto/modules/WeaveCrypto.sys.mjs')
| -rw-r--r-- | services/crypto/modules/WeaveCrypto.sys.mjs | 234 |
1 files changed, 234 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..06268ce65d --- /dev/null +++ b/services/crypto/modules/WeaveCrypto.sys.mjs @@ -0,0 +1,234 @@ +/* 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/. */ + +import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs"; + +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); + 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; + }, + + 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); + }, +}; |