120 lines
3.7 KiB
TypeScript
120 lines
3.7 KiB
TypeScript
// Copyright 2020 Signal Messenger, LLC
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// SPDX-License-Identifier: AGPL-3.0-only
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/* eslint-disable max-classes-per-file */
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import type { KeyPairType } from './Types.d';
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import * as Bytes from '../Bytes';
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import {
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decryptAes256CbcPkcsPadding,
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deriveSecrets,
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verifyHmacSha256,
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} from '../Crypto';
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import { calculateAgreement, createKeyPair, generateKeyPair } from '../Curve';
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import { SignalService as Proto } from '../protobuf';
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import type { PniString, AciString } from '../types/ServiceId';
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import { normalizeAci, normalizePni } from '../types/ServiceId';
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import { strictAssert } from '../util/assert';
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type ProvisionDecryptResult = {
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aciKeyPair: KeyPairType;
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pniKeyPair?: KeyPairType;
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number?: string;
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aci?: AciString;
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pni?: PniString;
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provisioningCode?: string;
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userAgent?: string;
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readReceipts?: boolean;
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profileKey?: Uint8Array;
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};
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class ProvisioningCipherInner {
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keyPair?: KeyPairType;
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async decrypt(
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provisionEnvelope: Proto.ProvisionEnvelope
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): Promise<ProvisionDecryptResult> {
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strictAssert(
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provisionEnvelope.publicKey && provisionEnvelope.body,
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'Missing required fields in ProvisionEnvelope'
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);
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const masterEphemeral = provisionEnvelope.publicKey;
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const message = provisionEnvelope.body;
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if (new Uint8Array(message)[0] !== 1) {
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throw new Error('Bad version number on ProvisioningMessage');
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}
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const iv = message.slice(1, 16 + 1);
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const mac = message.slice(message.byteLength - 32, message.byteLength);
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const ivAndCiphertext = message.slice(0, message.byteLength - 32);
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const ciphertext = message.slice(16 + 1, message.byteLength - 32);
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if (!this.keyPair) {
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throw new Error('ProvisioningCipher.decrypt: No keypair!');
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}
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const ecRes = calculateAgreement(masterEphemeral, this.keyPair.privKey);
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const keys = deriveSecrets(
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ecRes,
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new Uint8Array(32),
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Bytes.fromString('TextSecure Provisioning Message')
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);
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verifyHmacSha256(ivAndCiphertext, keys[1], mac, 32);
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const plaintext = decryptAes256CbcPkcsPadding(keys[0], ciphertext, iv);
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const provisionMessage = Proto.ProvisionMessage.decode(plaintext);
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const aciPrivKey = provisionMessage.aciIdentityKeyPrivate;
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const pniPrivKey = provisionMessage.pniIdentityKeyPrivate;
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strictAssert(aciPrivKey, 'Missing aciKeyPrivate in ProvisionMessage');
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const aciKeyPair = createKeyPair(aciPrivKey);
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const pniKeyPair = pniPrivKey?.length
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? createKeyPair(pniPrivKey)
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: undefined;
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const { aci, pni } = provisionMessage;
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strictAssert(aci, 'Missing aci in provisioning message');
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const ret: ProvisionDecryptResult = {
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aciKeyPair,
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pniKeyPair,
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number: provisionMessage.number,
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aci: normalizeAci(aci, 'ProvisionMessage.aci'),
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pni: pni ? normalizePni(pni, 'ProvisionMessage.pni') : undefined,
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provisioningCode: provisionMessage.provisioningCode,
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userAgent: provisionMessage.userAgent,
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readReceipts: provisionMessage.readReceipts,
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};
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if (provisionMessage.profileKey) {
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ret.profileKey = provisionMessage.profileKey;
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}
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return ret;
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}
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async getPublicKey(): Promise<Uint8Array> {
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if (!this.keyPair) {
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this.keyPair = generateKeyPair();
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}
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if (!this.keyPair) {
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throw new Error('ProvisioningCipher.decrypt: No keypair!');
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}
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return this.keyPair.pubKey;
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}
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}
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export default class ProvisioningCipher {
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constructor() {
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const inner = new ProvisioningCipherInner();
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this.decrypt = inner.decrypt.bind(inner);
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this.getPublicKey = inner.getPublicKey.bind(inner);
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}
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decrypt: (
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provisionEnvelope: Proto.ProvisionEnvelope
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) => Promise<ProvisionDecryptResult>;
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getPublicKey: () => Promise<Uint8Array>;
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}
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