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56 lines
1.9 KiB
56 lines
1.9 KiB
2 years ago
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'use strict';
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const crypto = require('crypto');
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const Encryptor = {
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/**
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* Calculate a hash of the concatenated buffers with the given algorithm.
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* @param {string} algorithm - The hash algorithm.
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* @returns {Buffer} The hash
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*/
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hash(algorithm, ...buffers) {
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const hash = crypto.createHash(algorithm);
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hash.update(Buffer.concat(buffers));
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return hash.digest();
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},
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/**
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* Convert a password into an encryption key
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* @param {string} password - The password
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* @param {string} hashAlgorithm - The hash algoritm
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* @param {string} saltValue - The salt value
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* @param {number} spinCount - The spin count
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* @param {number} keyBits - The length of the key in bits
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* @param {Buffer} blockKey - The block key
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* @returns {Buffer} The encryption key
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*/
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convertPasswordToHash(password, hashAlgorithm, saltValue, spinCount) {
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hashAlgorithm = hashAlgorithm.toLowerCase();
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const hashes = crypto.getHashes();
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if (hashes.indexOf(hashAlgorithm) < 0) {
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throw new Error(`Hash algorithm '${hashAlgorithm}' not supported!`);
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}
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// Password must be in unicode buffer
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const passwordBuffer = Buffer.from(password, 'utf16le');
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// Generate the initial hash
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let key = this.hash(hashAlgorithm, Buffer.from(saltValue, 'base64'), passwordBuffer);
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// Now regenerate until spin count
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for (let i = 0; i < spinCount; i++) {
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const iterator = Buffer.alloc(4);
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// this is the 'special' element of Excel password hashing
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// that stops us from using crypto.pbkdf2()
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iterator.writeUInt32LE(i, 0);
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key = this.hash(hashAlgorithm, key, iterator);
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}
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return key.toString('base64');
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},
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/**
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* Generates cryptographically strong pseudo-random data.
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* @param size The size argument is a number indicating the number of bytes to generate.
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*/
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randomBytes(size) {
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return crypto.randomBytes(size);
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},
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};
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module.exports = Encryptor;
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