61 lines
2.5 KiB
JavaScript
61 lines
2.5 KiB
JavaScript
/*
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* Copyright 2024 The Matrix.org Foundation C.I.C.
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*
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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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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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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 { decodeBase64, encodeBase64 } from "../base64.js";
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import { deriveKeys } from "./internal/deriveKeys.js";
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/**
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* Encrypt a string as a secret storage item, using AES-CTR.
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*
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* @param data - the plaintext to encrypt
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* @param key - the encryption key to use as an input to the HKDF function which is used to derive the AES key for
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* encryption. Obviously, the same key must be provided when decrypting.
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* @param name - the name of the secret. Used as an input to the HKDF operation which is used to derive the AES key,
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* so again the same value must be provided when decrypting.
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* @param ivStr - the base64-encoded initialization vector to use. If not supplied, a random one will be generated.
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*
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* @returns The encrypted result, including the ciphertext itself, the initialization vector (as supplied in `ivStr`,
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* or generated), and an HMAC on the ciphertext — all base64-encoded.
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*/
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export default async function encryptAESSecretStorageItem(data, key, name, ivStr) {
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let iv;
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if (ivStr) {
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iv = decodeBase64(ivStr);
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} else {
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iv = new Uint8Array(16);
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globalThis.crypto.getRandomValues(iv);
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// clear bit 63 of the IV to stop us hitting the 64-bit counter boundary
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// (which would mean we wouldn't be able to decrypt on Android). The loss
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// of a single bit of iv is a price we have to pay.
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iv[8] &= 0x7f;
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}
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const [aesKey, hmacKey] = await deriveKeys(key, name);
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const encodedData = new TextEncoder().encode(data);
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const ciphertext = await globalThis.crypto.subtle.encrypt({
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name: "AES-CTR",
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counter: iv,
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length: 64
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}, aesKey, encodedData);
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const hmac = await globalThis.crypto.subtle.sign({
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name: "HMAC"
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}, hmacKey, ciphertext);
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return {
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iv: encodeBase64(iv),
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ciphertext: encodeBase64(new Uint8Array(ciphertext)),
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mac: encodeBase64(new Uint8Array(hmac))
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};
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}
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//# sourceMappingURL=encryptAESSecretStorageItem.js.map
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