miscreant/release/providers/polyfill/aes_ctr.js

Misuse resistant symmetric encryption library providing AES-SIV (RFC 5297), AES-PMAC-SIV, and STREAM constructions

"use strict";
// Copyright (C) 2016 Dmitry Chestnykh
// MIT License. See LICENSE file for details.
var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
    return new (P || (P = Promise))(function (resolve, reject) {
        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
        step((generator = generator.apply(thisArg, _arguments || [])).next());
    });
};
Object.defineProperty(exports, "__esModule", { value: true });
const block_1 = require("../../internals/block");
/**
 * Polyfill for the AES-CTR (counter) mode of operation.
 *
 * Uses a non-constant-time (lookup table-based) AES polyfill.
 * See polyfill/aes.ts for more information on the security impact.
 *
 * Note that CTR mode is malleable and generally should not be used without
 * authentication. Instead, use an authenticated encryption mode, like AES-SIV!
 */
class PolyfillAesCtr {
    constructor(cipher) {
        // Set cipher.
        this._cipher = cipher;
        // Allocate space for counter.
        this._counter = new block_1.default();
        // Allocate buffer for encrypted block.
        this._buffer = new block_1.default();
    }
    clear() {
        this._buffer.clear();
        this._counter.clear();
        this._cipher.clear();
        return this;
    }
    encryptCtr(iv, plaintext) {
        return __awaiter(this, void 0, void 0, function* () {
            if (iv.length !== block_1.default.SIZE) {
                throw new Error("CTR: iv length must be equal to cipher block size");
            }
            // Copy IV to counter, overwriting it.
            this._counter.data.set(iv);
            // Set buffer position to length of buffer
            // so that the first cipher block is generated.
            let bufferPos = block_1.default.SIZE;
            const result = new Uint8Array(plaintext.length);
            for (let i = 0; i < plaintext.length; i++) {
                if (bufferPos === block_1.default.SIZE) {
                    this._buffer.copy(this._counter);
                    this._cipher.encryptBlock(this._buffer);
                    bufferPos = 0;
                    incrementCounter(this._counter);
                }
                result[i] = plaintext[i] ^ this._buffer.data[bufferPos++];
            }
            return result;
        });
    }
}
exports.default = PolyfillAesCtr;
// Increment an AES-CTR mode counter, intentionally wrapping/overflowing
function incrementCounter(counter) {
    let carry = 1;
    for (let i = block_1.default.SIZE - 1; i >= 0; i--) {
        carry += (counter.data[i] & 0xff) | 0;
        counter.data[i] = carry & 0xff;
        carry >>>= 8;
    }
}