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/* 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/. */
/**
* Class to handle encryption and decryption of logins stored in Chrome/Chromium
* on Windows.
*/
import { ChromeMigrationUtils } from "resource:///modules/ChromeMigrationUtils.sys.mjs";
import { OSCrypto } from "resource://gre/modules/OSCrypto_win.sys.mjs";
/**
* These constants should match those from Chromium.
*
* @see https://source.chromium.org/chromium/chromium/src/+/master:components/os_crypt/os_crypt_win.cc
*/
const AEAD_KEY_LENGTH = 256 / 8;
const ALGORITHM_NAME = "AES-GCM";
const DPAPI_KEY_PREFIX = "DPAPI";
const ENCRYPTION_VERSION_PREFIX = "v10";
const NONCE_LENGTH = 96 / 8;
const gTextDecoder = new TextDecoder();
const gTextEncoder = new TextEncoder();
/**
* Instances of this class have a shape similar to OSCrypto so it can be dropped
* into code which uses that. The algorithms here are
* specific to what is needed for Chrome login storage on Windows.
*/
export class ChromeWindowsLoginCrypto {
/**
* @param {string} userDataPathSuffix The unique identifier for the variant of
* Chrome that is having its logins imported. These are the keys in the
* SUB_DIRECTORIES object in ChromeMigrationUtils.getDataPath.
*/
constructor(userDataPathSuffix) {
this.osCrypto = new OSCrypto();
// Lazily decrypt the key from "Chrome"s local state using OSCrypto and save
// it as the master key to decrypt or encrypt passwords.
ChromeUtils.defineLazyGetter(this, "_keyPromise", async () => {
let keyData;
try {
// NB: For testing, allow directory service to be faked before getting.
const localState = await ChromeMigrationUtils.getLocalState(
userDataPathSuffix
);
const withHeader = atob(localState.os_crypt.encrypted_key);
if (!withHeader.startsWith(DPAPI_KEY_PREFIX)) {
throw new Error("Invalid key format");
}
const encryptedKey = withHeader.slice(DPAPI_KEY_PREFIX.length);
keyData = this.osCrypto.decryptData(encryptedKey, null, "bytes");
} catch (ex) {
console.error(`${userDataPathSuffix} os_crypt key:`, ex);
// Use a generic key that will fail for actually encrypted data, but for
// testing it'll be consistent for both encrypting and decrypting.
keyData = AEAD_KEY_LENGTH;
}
return crypto.subtle.importKey(
"raw",
new Uint8Array(keyData),
ALGORITHM_NAME,
false,
["decrypt", "encrypt"]
);
});
}
/**
* Must be invoked once after last use of any of the provided helpers.
*/
finalize() {
this.osCrypto.finalize();
}
/**
* Convert an array containing only two bytes unsigned numbers to a string.
*
* @param {number[]} arr - the array that needs to be converted.
* @returns {string} the string representation of the array.
*/
arrayToString(arr) {
let str = "";
for (let i = 0; i < arr.length; i++) {
str += String.fromCharCode(arr[i]);
}
return str;
}
stringToArray(binary_string) {
const len = binary_string.length;
const bytes = new Uint8Array(len);
for (let i = 0; i < len; i++) {
bytes[i] = binary_string.charCodeAt(i);
}
return bytes;
}
/**
* @param {string} ciphertext ciphertext optionally prefixed by the encryption version
* (see ENCRYPTION_VERSION_PREFIX).
* @returns {string} plaintext password
*/
async decryptData(ciphertext) {
const ciphertextString = this.arrayToString(ciphertext);
return ciphertextString.startsWith(ENCRYPTION_VERSION_PREFIX)
? this._decryptV10(ciphertext)
: this._decryptUnversioned(ciphertextString);
}
async _decryptUnversioned(ciphertext) {
return this.osCrypto.decryptData(ciphertext);
}
async _decryptV10(ciphertext) {
const key = await this._keyPromise;
if (!key) {
throw new Error("Cannot decrypt without a key");
}
// Split the nonce/iv from the rest of the encrypted value and decrypt.
const nonceIndex = ENCRYPTION_VERSION_PREFIX.length;
const cipherIndex = nonceIndex + NONCE_LENGTH;
const iv = new Uint8Array(ciphertext.slice(nonceIndex, cipherIndex));
const algorithm = {
name: ALGORITHM_NAME,
iv,
};
const cipherArray = new Uint8Array(ciphertext.slice(cipherIndex));
const plaintext = await crypto.subtle.decrypt(algorithm, key, cipherArray);
return gTextDecoder.decode(new Uint8Array(plaintext));
}
/**
* @param {USVString} plaintext to encrypt
* @param {?string} version to encrypt default unversioned
* @returns {string} encrypted string consisting of UTF-16 code units prefixed
* by the ENCRYPTION_VERSION_PREFIX.
*/
async encryptData(plaintext, version = undefined) {
return version === ENCRYPTION_VERSION_PREFIX
? this._encryptV10(plaintext)
: this._encryptUnversioned(plaintext);
}
async _encryptUnversioned(plaintext) {
return this.osCrypto.encryptData(plaintext);
}
async _encryptV10(plaintext) {
const key = await this._keyPromise;
if (!key) {
throw new Error("Cannot encrypt without a key");
}
// Encrypt and concatenate the prefix, nonce/iv and encrypted value.
const iv = crypto.getRandomValues(new Uint8Array(NONCE_LENGTH));
const algorithm = {
name: ALGORITHM_NAME,
iv,
};
const plainArray = gTextEncoder.encode(plaintext);
const ciphertext = await crypto.subtle.encrypt(algorithm, key, plainArray);
return (
ENCRYPTION_VERSION_PREFIX +
this.arrayToString(iv) +
this.arrayToString(new Uint8Array(ciphertext))
);
}
}
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