102 lines
3.4 KiB
Plaintext
102 lines
3.4 KiB
Plaintext
import { createDecipheriv, KeyObject } from 'node:crypto';
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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 { concat } from '../lib/buffer_utils.js';
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import { JOSENotSupported, JWEDecryptionFailed, JWEInvalid } from '../util/errors.js';
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import timingSafeEqual from './timing_safe_equal.js';
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import cbcTag from './cbc_tag.js';
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import { isCryptoKey } from './webcrypto.js';
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import { checkEncCryptoKey } from '../lib/crypto_key.js';
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import isKeyObject from './is_key_object.js';
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import invalidKeyInput from '../lib/invalid_key_input.js';
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import supported from './ciphers.js';
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import { types } from './is_key_like.js';
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function cbcDecrypt(enc, cek, ciphertext, iv, tag, aad) {
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const keySize = parseInt(enc.slice(1, 4), 10);
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if (isKeyObject(cek)) {
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cek = cek.export();
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}
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const encKey = cek.subarray(keySize >> 3);
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const macKey = cek.subarray(0, keySize >> 3);
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const macSize = parseInt(enc.slice(-3), 10);
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const algorithm = `aes-${keySize}-cbc`;
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if (!supported(algorithm)) {
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throw new JOSENotSupported(`alg ${enc} is not supported by your javascript runtime`);
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}
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const expectedTag = cbcTag(aad, iv, ciphertext, macSize, macKey, keySize);
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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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const decipher = createDecipheriv(algorithm, encKey, iv);
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plaintext = concat(decipher.update(ciphertext), decipher.final());
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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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function gcmDecrypt(enc, cek, ciphertext, iv, tag, aad) {
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const keySize = parseInt(enc.slice(1, 4), 10);
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const algorithm = `aes-${keySize}-gcm`;
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if (!supported(algorithm)) {
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throw new JOSENotSupported(`alg ${enc} is not supported by your javascript runtime`);
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}
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try {
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const decipher = createDecipheriv(algorithm, cek, iv, { authTagLength: 16 });
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decipher.setAuthTag(tag);
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if (aad.byteLength) {
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decipher.setAAD(aad, { plaintextLength: ciphertext.length });
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}
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const plaintext = decipher.update(ciphertext);
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decipher.final();
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return plaintext;
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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 = (enc, cek, ciphertext, iv, tag, aad) => {
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let key;
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if (isCryptoKey(cek)) {
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checkEncCryptoKey(cek, enc, 'decrypt');
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key = KeyObject.from(cek);
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}
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else if (cek instanceof Uint8Array || isKeyObject(cek)) {
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key = cek;
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}
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else {
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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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checkCekLength(enc, key);
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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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return cbcDecrypt(enc, key, 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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return gcmDecrypt(enc, key, 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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