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// OpenPGP.js - An OpenPGP implementation in javascript
// Copyright (C) 2018 ProtonTech AG
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 3.0 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
/**
* @fileoverview This module implements AES-EAX en/decryption on top of
* native AES-CTR using either the WebCrypto API or Node.js' crypto API.
* @module crypto/mode/eax
* @private
*/
import { AES_CTR } from '@openpgp/asmcrypto.js/dist_es8/aes/ctr';
import CMAC from '../cmac';
import util from '../../util';
import enums from '../../enums';
const webCrypto = util.getWebCrypto();
const nodeCrypto = util.getNodeCrypto();
const Buffer = util.getNodeBuffer();
const blockLength = 16;
const ivLength = blockLength;
const tagLength = blockLength;
const zero = new Uint8Array(blockLength);
const one = new Uint8Array(blockLength); one[blockLength - 1] = 1;
const two = new Uint8Array(blockLength); two[blockLength - 1] = 2;
async function OMAC(key) {
const cmac = await CMAC(key);
return function(t, message) {
return cmac(util.concatUint8Array([t, message]));
};
}
async function CTR(key) {
if (
util.getWebCrypto() &&
key.length !== 24 && // WebCrypto (no 192 bit support) see: https://www.chromium.org/blink/webcrypto#TOC-AES-support
navigator.userAgent.indexOf('Edge') === -1
) {
key = await webCrypto.importKey('raw', key, { name: 'AES-CTR', length: key.length * 8 }, false, ['encrypt']);
return async function(pt, iv) {
const ct = await webCrypto.encrypt({ name: 'AES-CTR', counter: iv, length: blockLength * 8 }, key, pt);
return new Uint8Array(ct);
};
}
if (util.getNodeCrypto()) { // Node crypto library
return async function(pt, iv) {
const en = new nodeCrypto.createCipheriv('aes-' + (key.length * 8) + '-ctr', key, iv);
const ct = Buffer.concat([en.update(pt), en.final()]);
return new Uint8Array(ct);
};
}
// asm.js fallback
return async function(pt, iv) {
return AES_CTR.encrypt(pt, key, iv);
};
}
/**
* Class to en/decrypt using EAX mode.
* @param {enums.symmetric} cipher - The symmetric cipher algorithm to use
* @param {Uint8Array} key - The encryption key
*/
async function EAX(cipher, key) {
if (cipher !== enums.symmetric.aes128 &&
cipher !== enums.symmetric.aes192 &&
cipher !== enums.symmetric.aes256) {
throw new Error('EAX mode supports only AES cipher');
}
const [
omac,
ctr
] = await Promise.all([
OMAC(key),
CTR(key)
]);
return {
/**
* Encrypt plaintext input.
* @param {Uint8Array} plaintext - The cleartext input to be encrypted
* @param {Uint8Array} nonce - The nonce (16 bytes)
* @param {Uint8Array} adata - Associated data to sign
* @returns {Promise<Uint8Array>} The ciphertext output.
*/
encrypt: async function(plaintext, nonce, adata) {
const [
omacNonce,
omacAdata
] = await Promise.all([
omac(zero, nonce),
omac(one, adata)
]);
const ciphered = await ctr(plaintext, omacNonce);
const omacCiphered = await omac(two, ciphered);
const tag = omacCiphered; // Assumes that omac(*).length === tagLength.
for (let i = 0; i < tagLength; i++) {
tag[i] ^= omacAdata[i] ^ omacNonce[i];
}
return util.concatUint8Array([ciphered, tag]);
},
/**
* Decrypt ciphertext input.
* @param {Uint8Array} ciphertext - The ciphertext input to be decrypted
* @param {Uint8Array} nonce - The nonce (16 bytes)
* @param {Uint8Array} adata - Associated data to verify
* @returns {Promise<Uint8Array>} The plaintext output.
*/
decrypt: async function(ciphertext, nonce, adata) {
if (ciphertext.length < tagLength) throw new Error('Invalid EAX ciphertext');
const ciphered = ciphertext.subarray(0, -tagLength);
const ctTag = ciphertext.subarray(-tagLength);
const [
omacNonce,
omacAdata,
omacCiphered
] = await Promise.all([
omac(zero, nonce),
omac(one, adata),
omac(two, ciphered)
]);
const tag = omacCiphered; // Assumes that omac(*).length === tagLength.
for (let i = 0; i < tagLength; i++) {
tag[i] ^= omacAdata[i] ^ omacNonce[i];
}
if (!util.equalsUint8Array(ctTag, tag)) throw new Error('Authentication tag mismatch');
const plaintext = await ctr(ciphered, omacNonce);
return plaintext;
}
};
}
/**
* Get EAX nonce as defined by {@link https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-04#section-5.16.1|RFC4880bis-04, section 5.16.1}.
* @param {Uint8Array} iv - The initialization vector (16 bytes)
* @param {Uint8Array} chunkIndex - The chunk index (8 bytes)
*/
EAX.getNonce = function(iv, chunkIndex) {
const nonce = iv.slice();
for (let i = 0; i < chunkIndex.length; i++) {
nonce[8 + i] ^= chunkIndex[i];
}
return nonce;
};
EAX.blockLength = blockLength;
EAX.ivLength = ivLength;
EAX.tagLength = tagLength;
export default EAX;
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