318 lines
11 KiB
JavaScript
318 lines
11 KiB
JavaScript
/**
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* [ChaCha20](https://cr.yp.to/chacha.html) stream cipher, released
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* in 2008. Developed after Salsa20, ChaCha aims to increase diffusion per round.
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* It was standardized in [RFC 8439](https://datatracker.ietf.org/doc/html/rfc8439) and
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* is now used in TLS 1.3.
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*
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* [XChaCha20](https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-xchacha)
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* extended-nonce variant is also provided. Similar to XSalsa, it's safe to use with
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* randomly-generated nonces.
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*
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* Check out [PDF](http://cr.yp.to/chacha/chacha-20080128.pdf) and
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* [wiki](https://en.wikipedia.org/wiki/Salsa20).
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* @module
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*/
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import { createCipher, rotl } from './_arx.js';
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import { poly1305 } from './_poly1305.js';
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import { clean, createView, equalBytes, getOutput, setBigUint64, wrapCipher, } from './utils.js';
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/**
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* ChaCha core function.
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*/
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// prettier-ignore
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function chachaCore(s, k, n, out, cnt, rounds = 20) {
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let y00 = s[0], y01 = s[1], y02 = s[2], y03 = s[3], // "expa" "nd 3" "2-by" "te k"
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y04 = k[0], y05 = k[1], y06 = k[2], y07 = k[3], // Key Key Key Key
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y08 = k[4], y09 = k[5], y10 = k[6], y11 = k[7], // Key Key Key Key
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y12 = cnt, y13 = n[0], y14 = n[1], y15 = n[2]; // Counter Counter Nonce Nonce
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// Save state to temporary variables
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let x00 = y00, x01 = y01, x02 = y02, x03 = y03, x04 = y04, x05 = y05, x06 = y06, x07 = y07, x08 = y08, x09 = y09, x10 = y10, x11 = y11, x12 = y12, x13 = y13, x14 = y14, x15 = y15;
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for (let r = 0; r < rounds; r += 2) {
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x00 = (x00 + x04) | 0;
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x12 = rotl(x12 ^ x00, 16);
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x08 = (x08 + x12) | 0;
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x04 = rotl(x04 ^ x08, 12);
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x00 = (x00 + x04) | 0;
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x12 = rotl(x12 ^ x00, 8);
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x08 = (x08 + x12) | 0;
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x04 = rotl(x04 ^ x08, 7);
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x01 = (x01 + x05) | 0;
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x13 = rotl(x13 ^ x01, 16);
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x09 = (x09 + x13) | 0;
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x05 = rotl(x05 ^ x09, 12);
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x01 = (x01 + x05) | 0;
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x13 = rotl(x13 ^ x01, 8);
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x09 = (x09 + x13) | 0;
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x05 = rotl(x05 ^ x09, 7);
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x02 = (x02 + x06) | 0;
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x14 = rotl(x14 ^ x02, 16);
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x10 = (x10 + x14) | 0;
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x06 = rotl(x06 ^ x10, 12);
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x02 = (x02 + x06) | 0;
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x14 = rotl(x14 ^ x02, 8);
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x10 = (x10 + x14) | 0;
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x06 = rotl(x06 ^ x10, 7);
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x03 = (x03 + x07) | 0;
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x15 = rotl(x15 ^ x03, 16);
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x11 = (x11 + x15) | 0;
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x07 = rotl(x07 ^ x11, 12);
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x03 = (x03 + x07) | 0;
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x15 = rotl(x15 ^ x03, 8);
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x11 = (x11 + x15) | 0;
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x07 = rotl(x07 ^ x11, 7);
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x00 = (x00 + x05) | 0;
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x15 = rotl(x15 ^ x00, 16);
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x10 = (x10 + x15) | 0;
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x05 = rotl(x05 ^ x10, 12);
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x00 = (x00 + x05) | 0;
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x15 = rotl(x15 ^ x00, 8);
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x10 = (x10 + x15) | 0;
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x05 = rotl(x05 ^ x10, 7);
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x01 = (x01 + x06) | 0;
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x12 = rotl(x12 ^ x01, 16);
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x11 = (x11 + x12) | 0;
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x06 = rotl(x06 ^ x11, 12);
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x01 = (x01 + x06) | 0;
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x12 = rotl(x12 ^ x01, 8);
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x11 = (x11 + x12) | 0;
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x06 = rotl(x06 ^ x11, 7);
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x02 = (x02 + x07) | 0;
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x13 = rotl(x13 ^ x02, 16);
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x08 = (x08 + x13) | 0;
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x07 = rotl(x07 ^ x08, 12);
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x02 = (x02 + x07) | 0;
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x13 = rotl(x13 ^ x02, 8);
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x08 = (x08 + x13) | 0;
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x07 = rotl(x07 ^ x08, 7);
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x03 = (x03 + x04) | 0;
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x14 = rotl(x14 ^ x03, 16);
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x09 = (x09 + x14) | 0;
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x04 = rotl(x04 ^ x09, 12);
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x03 = (x03 + x04) | 0;
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x14 = rotl(x14 ^ x03, 8);
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x09 = (x09 + x14) | 0;
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x04 = rotl(x04 ^ x09, 7);
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}
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// Write output
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let oi = 0;
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out[oi++] = (y00 + x00) | 0;
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out[oi++] = (y01 + x01) | 0;
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out[oi++] = (y02 + x02) | 0;
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out[oi++] = (y03 + x03) | 0;
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out[oi++] = (y04 + x04) | 0;
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out[oi++] = (y05 + x05) | 0;
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out[oi++] = (y06 + x06) | 0;
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out[oi++] = (y07 + x07) | 0;
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out[oi++] = (y08 + x08) | 0;
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out[oi++] = (y09 + x09) | 0;
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out[oi++] = (y10 + x10) | 0;
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out[oi++] = (y11 + x11) | 0;
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out[oi++] = (y12 + x12) | 0;
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out[oi++] = (y13 + x13) | 0;
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out[oi++] = (y14 + x14) | 0;
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out[oi++] = (y15 + x15) | 0;
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}
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/**
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* hchacha helper method, used primarily in xchacha, to hash
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* key and nonce into key' and nonce'.
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* Same as chachaCore, but there doesn't seem to be a way to move the block
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* out without 25% performance hit.
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*/
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// prettier-ignore
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export function hchacha(s, k, i, o32) {
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let x00 = s[0], x01 = s[1], x02 = s[2], x03 = s[3], x04 = k[0], x05 = k[1], x06 = k[2], x07 = k[3], x08 = k[4], x09 = k[5], x10 = k[6], x11 = k[7], x12 = i[0], x13 = i[1], x14 = i[2], x15 = i[3];
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for (let r = 0; r < 20; r += 2) {
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x00 = (x00 + x04) | 0;
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x12 = rotl(x12 ^ x00, 16);
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x08 = (x08 + x12) | 0;
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x04 = rotl(x04 ^ x08, 12);
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x00 = (x00 + x04) | 0;
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x12 = rotl(x12 ^ x00, 8);
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x08 = (x08 + x12) | 0;
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x04 = rotl(x04 ^ x08, 7);
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x01 = (x01 + x05) | 0;
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x13 = rotl(x13 ^ x01, 16);
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x09 = (x09 + x13) | 0;
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x05 = rotl(x05 ^ x09, 12);
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x01 = (x01 + x05) | 0;
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x13 = rotl(x13 ^ x01, 8);
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x09 = (x09 + x13) | 0;
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x05 = rotl(x05 ^ x09, 7);
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x02 = (x02 + x06) | 0;
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x14 = rotl(x14 ^ x02, 16);
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x10 = (x10 + x14) | 0;
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x06 = rotl(x06 ^ x10, 12);
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x02 = (x02 + x06) | 0;
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x14 = rotl(x14 ^ x02, 8);
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x10 = (x10 + x14) | 0;
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x06 = rotl(x06 ^ x10, 7);
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x03 = (x03 + x07) | 0;
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x15 = rotl(x15 ^ x03, 16);
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x11 = (x11 + x15) | 0;
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x07 = rotl(x07 ^ x11, 12);
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x03 = (x03 + x07) | 0;
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x15 = rotl(x15 ^ x03, 8);
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x11 = (x11 + x15) | 0;
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x07 = rotl(x07 ^ x11, 7);
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x00 = (x00 + x05) | 0;
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x15 = rotl(x15 ^ x00, 16);
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x10 = (x10 + x15) | 0;
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x05 = rotl(x05 ^ x10, 12);
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x00 = (x00 + x05) | 0;
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x15 = rotl(x15 ^ x00, 8);
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x10 = (x10 + x15) | 0;
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x05 = rotl(x05 ^ x10, 7);
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x01 = (x01 + x06) | 0;
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x12 = rotl(x12 ^ x01, 16);
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x11 = (x11 + x12) | 0;
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x06 = rotl(x06 ^ x11, 12);
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x01 = (x01 + x06) | 0;
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x12 = rotl(x12 ^ x01, 8);
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x11 = (x11 + x12) | 0;
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x06 = rotl(x06 ^ x11, 7);
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x02 = (x02 + x07) | 0;
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x13 = rotl(x13 ^ x02, 16);
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x08 = (x08 + x13) | 0;
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x07 = rotl(x07 ^ x08, 12);
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x02 = (x02 + x07) | 0;
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x13 = rotl(x13 ^ x02, 8);
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x08 = (x08 + x13) | 0;
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x07 = rotl(x07 ^ x08, 7);
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x03 = (x03 + x04) | 0;
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x14 = rotl(x14 ^ x03, 16);
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x09 = (x09 + x14) | 0;
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x04 = rotl(x04 ^ x09, 12);
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x03 = (x03 + x04) | 0;
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x14 = rotl(x14 ^ x03, 8);
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x09 = (x09 + x14) | 0;
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x04 = rotl(x04 ^ x09, 7);
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}
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let oi = 0;
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o32[oi++] = x00;
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o32[oi++] = x01;
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o32[oi++] = x02;
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o32[oi++] = x03;
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o32[oi++] = x12;
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o32[oi++] = x13;
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o32[oi++] = x14;
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o32[oi++] = x15;
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}
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/**
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* Original, non-RFC chacha20 from DJB. 8-byte nonce, 8-byte counter.
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*/
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export const chacha20orig = /* @__PURE__ */ createCipher(chachaCore, {
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counterRight: false,
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counterLength: 8,
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allowShortKeys: true,
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});
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/**
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* ChaCha stream cipher. Conforms to RFC 8439 (IETF, TLS). 12-byte nonce, 4-byte counter.
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* With 12-byte nonce, it's not safe to use fill it with random (CSPRNG), due to collision chance.
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*/
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export const chacha20 = /* @__PURE__ */ createCipher(chachaCore, {
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counterRight: false,
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counterLength: 4,
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allowShortKeys: false,
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});
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/**
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* XChaCha eXtended-nonce ChaCha. 24-byte nonce.
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* With 24-byte nonce, it's safe to use fill it with random (CSPRNG).
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* https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-xchacha
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*/
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export const xchacha20 = /* @__PURE__ */ createCipher(chachaCore, {
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counterRight: false,
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counterLength: 8,
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extendNonceFn: hchacha,
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allowShortKeys: false,
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});
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/**
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* Reduced 8-round chacha, described in original paper.
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*/
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export const chacha8 = /* @__PURE__ */ createCipher(chachaCore, {
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counterRight: false,
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counterLength: 4,
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rounds: 8,
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});
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/**
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* Reduced 12-round chacha, described in original paper.
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*/
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export const chacha12 = /* @__PURE__ */ createCipher(chachaCore, {
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counterRight: false,
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counterLength: 4,
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rounds: 12,
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});
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const ZEROS16 = /* @__PURE__ */ new Uint8Array(16);
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// Pad to digest size with zeros
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const updatePadded = (h, msg) => {
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h.update(msg);
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const left = msg.length % 16;
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if (left)
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h.update(ZEROS16.subarray(left));
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};
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const ZEROS32 = /* @__PURE__ */ new Uint8Array(32);
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function computeTag(fn, key, nonce, data, AAD) {
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const authKey = fn(key, nonce, ZEROS32);
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const h = poly1305.create(authKey);
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if (AAD)
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updatePadded(h, AAD);
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updatePadded(h, data);
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const num = new Uint8Array(16);
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const view = createView(num);
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setBigUint64(view, 0, BigInt(AAD ? AAD.length : 0), true);
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setBigUint64(view, 8, BigInt(data.length), true);
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h.update(num);
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const res = h.digest();
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clean(authKey, num);
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return res;
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}
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/**
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* AEAD algorithm from RFC 8439.
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* Salsa20 and chacha (RFC 8439) use poly1305 differently.
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* We could have composed them similar to:
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* https://github.com/paulmillr/scure-base/blob/b266c73dde977b1dd7ef40ef7a23cc15aab526b3/index.ts#L250
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* But it's hard because of authKey:
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* In salsa20, authKey changes position in salsa stream.
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* In chacha, authKey can't be computed inside computeTag, it modifies the counter.
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*/
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export const _poly1305_aead = (xorStream) => (key, nonce, AAD) => {
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const tagLength = 16;
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return {
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encrypt(plaintext, output) {
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const plength = plaintext.length;
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output = getOutput(plength + tagLength, output, false);
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output.set(plaintext);
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const oPlain = output.subarray(0, -tagLength);
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xorStream(key, nonce, oPlain, oPlain, 1);
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const tag = computeTag(xorStream, key, nonce, oPlain, AAD);
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output.set(tag, plength); // append tag
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clean(tag);
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return output;
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},
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decrypt(ciphertext, output) {
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output = getOutput(ciphertext.length - tagLength, output, false);
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const data = ciphertext.subarray(0, -tagLength);
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const passedTag = ciphertext.subarray(-tagLength);
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const tag = computeTag(xorStream, key, nonce, data, AAD);
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if (!equalBytes(passedTag, tag))
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throw new Error('invalid tag');
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output.set(ciphertext.subarray(0, -tagLength));
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xorStream(key, nonce, output, output, 1); // start stream with i=1
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clean(tag);
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return output;
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},
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};
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};
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/**
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* ChaCha20-Poly1305 from RFC 8439.
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*
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* Unsafe to use random nonces under the same key, due to collision chance.
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* Prefer XChaCha instead.
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*/
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export const chacha20poly1305 = /* @__PURE__ */ wrapCipher({ blockSize: 64, nonceLength: 12, tagLength: 16 }, _poly1305_aead(chacha20));
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/**
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* XChaCha20-Poly1305 extended-nonce chacha.
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*
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* Can be safely used with random nonces (CSPRNG).
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* See [IRTF draft](https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-xchacha).
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*/
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export const xchacha20poly1305 = /* @__PURE__ */ wrapCipher({ blockSize: 64, nonceLength: 24, tagLength: 16 }, _poly1305_aead(xchacha20));
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//# sourceMappingURL=chacha.js.map
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