92 lines
3.3 KiB
Plaintext
92 lines
3.3 KiB
Plaintext
import { concat, uint64be } from '../lib/buffer_utils.js';
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import checkIvLength from '../lib/check_iv_length.js';
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import checkCekLength from './check_cek_length.js';
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import timingSafeEqual from './timing_safe_equal.js';
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import { JOSENotSupported, JWEDecryptionFailed, JWEInvalid } from '../util/errors.js';
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import crypto, { isCryptoKey } from './webcrypto.js';
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import { checkEncCryptoKey } from '../lib/crypto_key.js';
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import invalidKeyInput from '../lib/invalid_key_input.js';
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import { types } from './is_key_like.js';
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async function cbcDecrypt(enc, cek, ciphertext, iv, tag, aad) {
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if (!(cek instanceof Uint8Array)) {
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throw new TypeError(invalidKeyInput(cek, 'Uint8Array'));
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}
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const keySize = parseInt(enc.slice(1, 4), 10);
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const encKey = await crypto.subtle.importKey('raw', cek.subarray(keySize >> 3), 'AES-CBC', false, ['decrypt']);
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const macKey = await crypto.subtle.importKey('raw', cek.subarray(0, keySize >> 3), {
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hash: `SHA-${keySize << 1}`,
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name: 'HMAC',
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}, false, ['sign']);
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const macData = concat(aad, iv, ciphertext, uint64be(aad.length << 3));
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const expectedTag = new Uint8Array((await crypto.subtle.sign('HMAC', macKey, macData)).slice(0, keySize >> 3));
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let macCheckPassed;
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try {
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macCheckPassed = timingSafeEqual(tag, expectedTag);
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}
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catch {
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}
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if (!macCheckPassed) {
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throw new JWEDecryptionFailed();
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}
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let plaintext;
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try {
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plaintext = new Uint8Array(await crypto.subtle.decrypt({ iv, name: 'AES-CBC' }, encKey, ciphertext));
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}
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catch {
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}
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if (!plaintext) {
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throw new JWEDecryptionFailed();
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}
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return plaintext;
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}
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async function gcmDecrypt(enc, cek, ciphertext, iv, tag, aad) {
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let encKey;
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if (cek instanceof Uint8Array) {
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encKey = await crypto.subtle.importKey('raw', cek, 'AES-GCM', false, ['decrypt']);
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}
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else {
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checkEncCryptoKey(cek, enc, 'decrypt');
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encKey = cek;
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}
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try {
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return new Uint8Array(await crypto.subtle.decrypt({
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additionalData: aad,
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iv,
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name: 'AES-GCM',
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tagLength: 128,
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}, encKey, concat(ciphertext, tag)));
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}
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catch {
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throw new JWEDecryptionFailed();
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}
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}
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const decrypt = async (enc, cek, ciphertext, iv, tag, aad) => {
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if (!isCryptoKey(cek) && !(cek instanceof Uint8Array)) {
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throw new TypeError(invalidKeyInput(cek, ...types, 'Uint8Array'));
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}
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if (!iv) {
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throw new JWEInvalid('JWE Initialization Vector missing');
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}
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if (!tag) {
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throw new JWEInvalid('JWE Authentication Tag missing');
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}
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checkIvLength(enc, iv);
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switch (enc) {
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case 'A128CBC-HS256':
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case 'A192CBC-HS384':
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case 'A256CBC-HS512':
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if (cek instanceof Uint8Array)
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checkCekLength(cek, parseInt(enc.slice(-3), 10));
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return cbcDecrypt(enc, cek, ciphertext, iv, tag, aad);
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case 'A128GCM':
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case 'A192GCM':
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case 'A256GCM':
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if (cek instanceof Uint8Array)
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checkCekLength(cek, parseInt(enc.slice(1, 4), 10));
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return gcmDecrypt(enc, cek, ciphertext, iv, tag, aad);
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default:
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throw new JOSENotSupported('Unsupported JWE Content Encryption Algorithm');
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}
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};
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export default decrypt;
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