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Текущая директория: /usr/lib/node_modules/bitgo/node_modules/@noble/ciphers/esm
Просмотр файла: _arx.js
/**
* Basic utils for ARX (add-rotate-xor) salsa and chacha ciphers.
RFC8439 requires multi-step cipher stream, where
authKey starts with counter: 0, actual msg with counter: 1.
For this, we need a way to re-use nonce / counter:
const counter = new Uint8Array(4);
chacha(..., counter, ...); // counter is now 1
chacha(..., counter, ...); // counter is now 2
This is complicated:
- 32-bit counters are enough, no need for 64-bit: max ArrayBuffer size in JS is 4GB
- Original papers don't allow mutating counters
- Counter overflow is undefined [^1]
- Idea A: allow providing (nonce | counter) instead of just nonce, re-use it
- Caveat: Cannot be re-used through all cases:
- * chacha has (counter | nonce)
- * xchacha has (nonce16 | counter | nonce16)
- Idea B: separate nonce / counter and provide separate API for counter re-use
- Caveat: there are different counter sizes depending on an algorithm.
- salsa & chacha also differ in structures of key & sigma:
salsa20: s[0] | k(4) | s[1] | nonce(2) | ctr(2) | s[2] | k(4) | s[3]
chacha: s(4) | k(8) | ctr(1) | nonce(3)
chacha20orig: s(4) | k(8) | ctr(2) | nonce(2)
- Idea C: helper method such as `setSalsaState(key, nonce, sigma, data)`
- Caveat: we can't re-use counter array
xchacha [^2] uses the subkey and remaining 8 byte nonce with ChaCha20 as normal
(prefixed by 4 NUL bytes, since [RFC8439] specifies a 12-byte nonce).
[^1]: https://mailarchive.ietf.org/arch/msg/cfrg/gsOnTJzcbgG6OqD8Sc0GO5aR_tU/
[^2]: https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-xchacha#appendix-A.2
* @module
*/
// prettier-ignore
import { abool, abytes, anumber, checkOpts, clean, copyBytes, u32 } from "./utils.js";
// We can't make top-level var depend on utils.utf8ToBytes
// because it's not present in all envs. Creating a similar fn here
const _utf8ToBytes = (str) => Uint8Array.from(str.split('').map((c) => c.charCodeAt(0)));
const sigma16 = _utf8ToBytes('expand 16-byte k');
const sigma32 = _utf8ToBytes('expand 32-byte k');
const sigma16_32 = u32(sigma16);
const sigma32_32 = u32(sigma32);
export function rotl(a, b) {
return (a << b) | (a >>> (32 - b));
}
// Is byte array aligned to 4 byte offset (u32)?
function isAligned32(b) {
return b.byteOffset % 4 === 0;
}
// Salsa and Chacha block length is always 512-bit
const BLOCK_LEN = 64;
const BLOCK_LEN32 = 16;
// new Uint32Array([2**32]) // => Uint32Array(1) [ 0 ]
// new Uint32Array([2**32-1]) // => Uint32Array(1) [ 4294967295 ]
const MAX_COUNTER = 2 ** 32 - 1;
const U32_EMPTY = new Uint32Array();
function runCipher(core, sigma, key, nonce, data, output, counter, rounds) {
const len = data.length;
const block = new Uint8Array(BLOCK_LEN);
const b32 = u32(block);
// Make sure that buffers aligned to 4 bytes
const isAligned = isAligned32(data) && isAligned32(output);
const d32 = isAligned ? u32(data) : U32_EMPTY;
const o32 = isAligned ? u32(output) : U32_EMPTY;
for (let pos = 0; pos < len; counter++) {
core(sigma, key, nonce, b32, counter, rounds);
if (counter >= MAX_COUNTER)
throw new Error('arx: counter overflow');
const take = Math.min(BLOCK_LEN, len - pos);
// aligned to 4 bytes
if (isAligned && take === BLOCK_LEN) {
const pos32 = pos / 4;
if (pos % 4 !== 0)
throw new Error('arx: invalid block position');
for (let j = 0, posj; j < BLOCK_LEN32; j++) {
posj = pos32 + j;
o32[posj] = d32[posj] ^ b32[j];
}
pos += BLOCK_LEN;
continue;
}
for (let j = 0, posj; j < take; j++) {
posj = pos + j;
output[posj] = data[posj] ^ block[j];
}
pos += take;
}
}
/** Creates ARX-like (ChaCha, Salsa) cipher stream from core function. */
export function createCipher(core, opts) {
const { allowShortKeys, extendNonceFn, counterLength, counterRight, rounds } = checkOpts({ allowShortKeys: false, counterLength: 8, counterRight: false, rounds: 20 }, opts);
if (typeof core !== 'function')
throw new Error('core must be a function');
anumber(counterLength);
anumber(rounds);
abool(counterRight);
abool(allowShortKeys);
return (key, nonce, data, output, counter = 0) => {
abytes(key);
abytes(nonce);
abytes(data);
const len = data.length;
if (output === undefined)
output = new Uint8Array(len);
abytes(output);
anumber(counter);
if (counter < 0 || counter >= MAX_COUNTER)
throw new Error('arx: counter overflow');
if (output.length < len)
throw new Error(`arx: output (${output.length}) is shorter than data (${len})`);
const toClean = [];
// Key & sigma
// key=16 -> sigma16, k=key|key
// key=32 -> sigma32, k=key
let l = key.length;
let k;
let sigma;
if (l === 32) {
toClean.push((k = copyBytes(key)));
sigma = sigma32_32;
}
else if (l === 16 && allowShortKeys) {
k = new Uint8Array(32);
k.set(key);
k.set(key, 16);
sigma = sigma16_32;
toClean.push(k);
}
else {
throw new Error(`arx: invalid 32-byte key, got length=${l}`);
}
// Nonce
// salsa20: 8 (8-byte counter)
// chacha20orig: 8 (8-byte counter)
// chacha20: 12 (4-byte counter)
// xsalsa20: 24 (16 -> hsalsa, 8 -> old nonce)
// xchacha20: 24 (16 -> hchacha, 8 -> old nonce)
// Align nonce to 4 bytes
if (!isAligned32(nonce))
toClean.push((nonce = copyBytes(nonce)));
const k32 = u32(k);
// hsalsa & hchacha: handle extended nonce
if (extendNonceFn) {
if (nonce.length !== 24)
throw new Error(`arx: extended nonce must be 24 bytes`);
extendNonceFn(sigma, k32, u32(nonce.subarray(0, 16)), k32);
nonce = nonce.subarray(16);
}
// Handle nonce counter
const nonceNcLen = 16 - counterLength;
if (nonceNcLen !== nonce.length)
throw new Error(`arx: nonce must be ${nonceNcLen} or 16 bytes`);
// Pad counter when nonce is 64 bit
if (nonceNcLen !== 12) {
const nc = new Uint8Array(12);
nc.set(nonce, counterRight ? 0 : 12 - nonce.length);
nonce = nc;
toClean.push(nonce);
}
const n32 = u32(nonce);
runCipher(core, sigma, k32, n32, data, output, counter, rounds);
clean(...toClean);
return output;
};
}
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