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5fd7ef370f
Asm.js has now been deprecated for many years, and no performance gain is recorded for AES compared to vanilla JS. The relevant AES fallback code is primarily used if the WebCrypto (resp. NodeCrypto) implementation is not available.
104 lines
3.4 KiB
JavaScript
104 lines
3.4 KiB
JavaScript
/**
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* @fileoverview This module implements AES-CMAC on top of
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* native AES-CBC using either the WebCrypto API or Node.js' crypto API.
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* @module crypto/cmac
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*/
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import { cbc as nobleAesCbc } from '@noble/ciphers/aes';
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import util from '../util';
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const webCrypto = util.getWebCrypto();
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const nodeCrypto = util.getNodeCrypto();
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/**
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* This implementation of CMAC is based on the description of OMAC in
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* http://web.cs.ucdavis.edu/~rogaway/papers/eax.pdf. As per that
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* document:
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*
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* We have made a small modification to the OMAC algorithm as it was
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* originally presented, changing one of its two constants.
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* Specifically, the constant 4 at line 85 was the constant 1/2 (the
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* multiplicative inverse of 2) in the original definition of OMAC [14].
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* The OMAC authors indicate that they will promulgate this modification
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* [15], which slightly simplifies implementations.
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*/
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const blockLength = 16;
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/**
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* xor `padding` into the end of `data`. This function implements "the
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* operation xor→ [which] xors the shorter string into the end of longer
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* one". Since data is always as least as long as padding, we can
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* simplify the implementation.
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* @param {Uint8Array} data
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* @param {Uint8Array} padding
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*/
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function rightXORMut(data, padding) {
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const offset = data.length - blockLength;
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for (let i = 0; i < blockLength; i++) {
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data[i + offset] ^= padding[i];
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}
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return data;
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}
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function pad(data, padding, padding2) {
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// if |M| in {n, 2n, 3n, ...}
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if (data.length && data.length % blockLength === 0) {
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// then return M xor→ B,
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return rightXORMut(data, padding);
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}
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// else return (M || 10^(n−1−(|M| mod n))) xor→ P
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const padded = new Uint8Array(data.length + (blockLength - (data.length % blockLength)));
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padded.set(data);
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padded[data.length] = 0b10000000;
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return rightXORMut(padded, padding2);
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}
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const zeroBlock = new Uint8Array(blockLength);
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export default async function CMAC(key) {
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const cbc = await CBC(key);
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// L ← E_K(0^n); B ← 2L; P ← 4L
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const padding = util.double(await cbc(zeroBlock));
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const padding2 = util.double(padding);
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return async function(data) {
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// return CBC_K(pad(M; B, P))
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return (await cbc(pad(data, padding, padding2))).subarray(-blockLength);
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};
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}
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async function CBC(key) {
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if (util.getNodeCrypto()) { // Node crypto library
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return async function(pt) {
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const en = new nodeCrypto.createCipheriv('aes-' + (key.length * 8) + '-cbc', key, zeroBlock);
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const ct = en.update(pt);
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return new Uint8Array(ct);
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};
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}
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if (util.getWebCrypto()) {
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try {
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key = await webCrypto.importKey('raw', key, { name: 'AES-CBC', length: key.length * 8 }, false, ['encrypt']);
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return async function(pt) {
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const ct = await webCrypto.encrypt({ name: 'AES-CBC', iv: zeroBlock, length: blockLength * 8 }, key, pt);
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return new Uint8Array(ct).subarray(0, ct.byteLength - blockLength);
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};
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} catch (err) {
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// no 192 bit support in Chromium, which throws `OperationError`, see: https://www.chromium.org/blink/webcrypto#TOC-AES-support
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if (err.name !== 'NotSupportedError' &&
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!(key.length === 24 && err.name === 'OperationError')) {
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throw err;
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}
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util.printDebugError('Browser did not support operation: ' + err.message);
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}
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}
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return async function(pt) {
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return nobleAesCbc(key, zeroBlock, { disablePadding: true }).encrypt(pt);
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};
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}
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