77 lines
2.8 KiB
JavaScript
77 lines
2.8 KiB
JavaScript
/*
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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 base64 from "../../../lib/base64-arraybuffer/index.js";
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/**
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* Decrypt an attachment.
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* @param {ArrayBuffer} ciphertextBuffer The encrypted attachment data buffer.
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* @param {Object} info The information needed to decrypt the attachment.
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* @param {Object} info.key AES-CTR JWK key object.
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* @param {string} info.iv Base64 encoded 16 byte AES-CTR IV.
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* @param {string} info.hashes.sha256 Base64 encoded SHA-256 hash of the ciphertext.
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* @return {Promise} A promise that resolves with an ArrayBuffer when the attachment is decrypted.
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*/
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export async function decryptAttachment(crypto, ciphertextBuffer, info) {
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if (info === undefined || info.key === undefined || info.iv === undefined
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|| info.hashes === undefined || info.hashes.sha256 === undefined) {
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throw new Error("Invalid info. Missing info.key, info.iv or info.hashes.sha256 key");
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}
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var ivArray = base64.decode(info.iv);
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// re-encode to not deal with padded vs unpadded
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var expectedSha256base64 = base64.encode(base64.decode(info.hashes.sha256));
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// Check the sha256 hash
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const digestResult = await crypto.digest("SHA-256", ciphertextBuffer);
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if (base64.encode(new Uint8Array(digestResult)) != expectedSha256base64) {
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throw new Error("Mismatched SHA-256 digest");
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}
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var counterLength;
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if (info.v == "v1" || info.v == "v2") {
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// Version 1 and 2 use a 64 bit counter.
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counterLength = 64;
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} else {
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// Version 0 uses a 128 bit counter.
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counterLength = 128;
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}
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const decryptedBuffer = await crypto.aes.decryptCTR({
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jwkKey: info.key,
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iv: ivArray,
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data: ciphertextBuffer,
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counterLength
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});
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return decryptedBuffer;
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}
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export async function encryptAttachment(crypto, data) {
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const iv = await crypto.aes.generateIV();
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const key = await crypto.aes.generateKey("jwk", 256);
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const ciphertext = await crypto.aes.encryptCTR({key, iv, data});
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const digest = await crypto.digest("SHA-256", ciphertext);
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return {
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data: ciphertext,
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info: {
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v: "v2",
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key,
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iv: base64.encode(iv),
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hashes: {
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sha256: base64.encode(digest)
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}
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}
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};
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}
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