forked from mystiq/hydrogen-web
83 lines
2.8 KiB
TypeScript
83 lines
2.8 KiB
TypeScript
/*
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Copyright 2020 The Matrix.org Foundation C.I.C.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import type {Key} from "./common";
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import type {Platform} from "../../platform/web/Platform.js";
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import type {Transaction} from "../storage/idb/Transaction";
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type EncryptedData = {
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iv: string;
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ciphertext: string;
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mac: string;
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}
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export class SecretStorage {
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private readonly _key: Key;
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private readonly _platform: Platform;
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constructor({key, platform}: {key: Key, platform: Platform}) {
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this._key = key;
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this._platform = platform;
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}
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async readSecret(name: string, txn: Transaction): Promise<string | undefined> {
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const accountData = await txn.accountData.get(name);
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if (!accountData) {
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return;
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}
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const encryptedData = accountData?.content?.encrypted?.[this._key.id] as EncryptedData;
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if (!encryptedData) {
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throw new Error(`Secret ${accountData.type} is not encrypted for key ${this._key.id}`);
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}
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if (this._key.algorithm === "m.secret_storage.v1.aes-hmac-sha2") {
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return await this._decryptAESSecret(accountData.type, encryptedData);
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} else {
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throw new Error(`Unsupported algorithm for key ${this._key.id}: ${this._key.algorithm}`);
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}
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}
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async _decryptAESSecret(type: string, encryptedData: EncryptedData): Promise<string> {
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const {base64, utf8} = this._platform.encoding;
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// now derive the aes and mac key from the 4s key
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const hkdfKey = await this._platform.crypto.derive.hkdf(
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this._key.binaryKey,
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new Uint8Array(8).buffer, //zero salt
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utf8.encode(type), // info
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"SHA-256",
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512 // 512 bits or 64 bytes
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);
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const aesKey = hkdfKey.slice(0, 32);
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const hmacKey = hkdfKey.slice(32);
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const ciphertextBytes = base64.decode(encryptedData.ciphertext);
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const isVerified = await this._platform.crypto.hmac.verify(
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hmacKey, base64.decode(encryptedData.mac),
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ciphertextBytes, "SHA-256");
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if (!isVerified) {
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throw new Error("Bad MAC");
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}
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const plaintextBytes = await this._platform.crypto.aes.decryptCTR({
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key: aesKey,
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iv: base64.decode(encryptedData.iv),
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data: ciphertextBytes
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});
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return utf8.decode(plaintextBytes);
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}
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}
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