53 lines
2.0 KiB
Plaintext
53 lines
2.0 KiB
Plaintext
import { encode, concat, uint32be } from './buffer_utils.js';
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import { checkEncCryptoKey } from './crypto_key.js';
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import { digest } from './helpers.js';
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function lengthAndInput(input) {
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return concat(uint32be(input.length), input);
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}
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async function concatKdf(Z, L, OtherInfo) {
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const dkLen = L >> 3;
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const hashLen = 32;
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const reps = Math.ceil(dkLen / hashLen);
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const dk = new Uint8Array(reps * hashLen);
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for (let i = 1; i <= reps; i++) {
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const hashInput = new Uint8Array(4 + Z.length + OtherInfo.length);
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hashInput.set(uint32be(i), 0);
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hashInput.set(Z, 4);
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hashInput.set(OtherInfo, 4 + Z.length);
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const hashResult = await digest('sha256', hashInput);
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dk.set(hashResult, (i - 1) * hashLen);
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}
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return dk.slice(0, dkLen);
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}
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export async function deriveKey(publicKey, privateKey, algorithm, keyLength, apu = new Uint8Array(), apv = new Uint8Array()) {
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checkEncCryptoKey(publicKey, 'ECDH');
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checkEncCryptoKey(privateKey, 'ECDH', 'deriveBits');
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const algorithmID = lengthAndInput(encode(algorithm));
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const partyUInfo = lengthAndInput(apu);
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const partyVInfo = lengthAndInput(apv);
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const suppPubInfo = uint32be(keyLength);
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const suppPrivInfo = new Uint8Array();
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const otherInfo = concat(algorithmID, partyUInfo, partyVInfo, suppPubInfo, suppPrivInfo);
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const Z = new Uint8Array(await crypto.subtle.deriveBits({
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name: publicKey.algorithm.name,
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public: publicKey,
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}, privateKey, getEcdhBitLength(publicKey)));
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return concatKdf(Z, keyLength, otherInfo);
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}
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function getEcdhBitLength(publicKey) {
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if (publicKey.algorithm.name === 'X25519') {
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return 256;
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}
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return (Math.ceil(parseInt(publicKey.algorithm.namedCurve.slice(-3), 10) / 8) << 3);
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}
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export function allowed(key) {
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switch (key.algorithm.namedCurve) {
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case 'P-256':
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case 'P-384':
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case 'P-521':
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return true;
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default:
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return key.algorithm.name === 'X25519';
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}
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}
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