179 lines
8.2 KiB
JavaScript
179 lines
8.2 KiB
JavaScript
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/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
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/* SHA-256 (FIPS 180-4) implementation in JavaScript (c) Chris Veness 2002-2017 */
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/* MIT Licence */
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/* www.movable-type.co.uk/scripts/sha256.html */
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/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
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'use strict';
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/**
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* SHA-256 hash function reference implementation.
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*
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* This is an annotated direct implementation of FIPS 180-4, without any optimisations. It is
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* intended to aid understanding of the algorithm rather than for production use.
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*
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* While it could be used where performance is not critical, I would recommend using the ‘Web
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* Cryptography API’ (developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto/digest) for the browser,
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* or the ‘crypto’ library (nodejs.org/api/crypto.html#crypto_class_hash) in Node.js.
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*
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* See csrc.nist.gov/groups/ST/toolkit/secure_hashing.html
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* csrc.nist.gov/groups/ST/toolkit/examples.html
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*/
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class Sha256 {
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/**
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* Generates SHA-256 hash of string.
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*
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* @param {string} msg - (Unicode) string to be hashed.
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* @param {Object} [options]
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* @param {string} [options.msgFormat=string] - Message format: 'string' for JavaScript string
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* (gets converted to UTF-8 for hashing); 'hex-bytes' for string of hex bytes ('616263' ≡ 'abc') .
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* @param {string} [options.outFormat=hex] - Output format: 'hex' for string of contiguous
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* hex bytes; 'hex-w' for grouping hex bytes into groups of (4 byte / 8 character) words.
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* @returns {string} Hash of msg as hex character string.
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*/
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static hash(msg, options) {
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const defaults = { msgFormat: 'string', outFormat: 'hex' };
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const opt = Object.assign(defaults, options);
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// note use throughout this routine of 'n >>> 0' to coerce Number 'n' to unsigned 32-bit integer
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switch (opt.msgFormat) {
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default: // default is to convert string to UTF-8, as SHA only deals with byte-streams
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case 'string': msg = utf8Encode(msg); break;
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case 'hex-bytes':msg = hexBytesToString(msg); break; // mostly for running tests
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}
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// constants [§4.2.2]
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const K = [
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0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
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0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
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0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
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0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
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0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
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0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
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0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
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0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2 ];
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// initial hash value [§5.3.3]
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const H = [
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0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19 ];
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// PREPROCESSING [§6.2.1]
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msg += String.fromCharCode(0x80); // add trailing '1' bit (+ 0's padding) to string [§5.1.1]
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// convert string msg into 512-bit blocks (array of 16 32-bit integers) [§5.2.1]
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const l = msg.length/4 + 2; // length (in 32-bit integers) of msg + ‘1’ + appended length
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const N = Math.ceil(l/16); // number of 16-integer (512-bit) blocks required to hold 'l' ints
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const M = new Array(N); // message M is N×16 array of 32-bit integers
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for (let i=0; i<N; i++) {
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M[i] = new Array(16);
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for (let j=0; j<16; j++) { // encode 4 chars per integer (64 per block), big-endian encoding
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M[i][j] = (msg.charCodeAt(i*64+j*4+0)<<24) | (msg.charCodeAt(i*64+j*4+1)<<16)
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| (msg.charCodeAt(i*64+j*4+2)<< 8) | (msg.charCodeAt(i*64+j*4+3)<< 0);
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} // note running off the end of msg is ok 'cos bitwise ops on NaN return 0
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}
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// add length (in bits) into final pair of 32-bit integers (big-endian) [§5.1.1]
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// note: most significant word would be (len-1)*8 >>> 32, but since JS converts
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// bitwise-op args to 32 bits, we need to simulate this by arithmetic operators
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const lenHi = ((msg.length-1)*8) / Math.pow(2, 32);
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const lenLo = ((msg.length-1)*8) >>> 0;
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M[N-1][14] = Math.floor(lenHi);
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M[N-1][15] = lenLo;
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// HASH COMPUTATION [§6.2.2]
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for (let i=0; i<N; i++) {
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const W = new Array(64);
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// 1 - prepare message schedule 'W'
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for (let t=0; t<16; t++) W[t] = M[i][t];
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for (let t=16; t<64; t++) {
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W[t] = (Sha256.σ1(W[t-2]) + W[t-7] + Sha256.σ0(W[t-15]) + W[t-16]) >>> 0;
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}
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// 2 - initialise working variables a, b, c, d, e, f, g, h with previous hash value
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let a = H[0], b = H[1], c = H[2], d = H[3], e = H[4], f = H[5], g = H[6], h = H[7];
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// 3 - main loop (note '>>> 0' for 'addition modulo 2^32')
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for (let t=0; t<64; t++) {
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const T1 = h + Sha256.Σ1(e) + Sha256.Ch(e, f, g) + K[t] + W[t];
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const T2 = Sha256.Σ0(a) + Sha256.Maj(a, b, c);
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h = g;
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g = f;
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f = e;
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e = (d + T1) >>> 0;
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d = c;
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c = b;
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b = a;
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a = (T1 + T2) >>> 0;
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}
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// 4 - compute the new intermediate hash value (note '>>> 0' for 'addition modulo 2^32')
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H[0] = (H[0]+a) >>> 0;
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H[1] = (H[1]+b) >>> 0;
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H[2] = (H[2]+c) >>> 0;
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H[3] = (H[3]+d) >>> 0;
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H[4] = (H[4]+e) >>> 0;
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H[5] = (H[5]+f) >>> 0;
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H[6] = (H[6]+g) >>> 0;
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H[7] = (H[7]+h) >>> 0;
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}
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// convert H0..H7 to hex strings (with leading zeros)
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for (let h=0; h<H.length; h++) H[h] = ('00000000'+H[h].toString(16)).slice(-8);
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// concatenate H0..H7, with separator if required
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const separator = opt.outFormat=='hex-w' ? ' ' : '';
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return H.join(separator);
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/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
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function utf8Encode(str) {
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try {
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return new TextEncoder().encode(str, 'utf-8').reduce((prev, curr) => prev + String.fromCharCode(curr), '');
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} catch (e) { // no TextEncoder available?
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return unescape(encodeURIComponent(str)); // monsur.hossa.in/2012/07/20/utf-8-in-javascript.html
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}
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}
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function hexBytesToString(hexStr) { // convert string of hex numbers to a string of chars (eg '616263' -> 'abc').
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const str = hexStr.replace(' ', ''); // allow space-separated groups
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return str=='' ? '' : str.match(/.{2}/g).map(byte => String.fromCharCode(parseInt(byte, 16))).join('');
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}
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}
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/**
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* Rotates right (circular right shift) value x by n positions [§3.2.4].
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* @private
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*/
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static ROTR(n, x) {
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return (x >>> n) | (x << (32-n));
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}
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/**
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* Logical functions [§4.1.2].
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* @private
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*/
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static Σ0(x) { return Sha256.ROTR(2, x) ^ Sha256.ROTR(13, x) ^ Sha256.ROTR(22, x); }
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static Σ1(x) { return Sha256.ROTR(6, x) ^ Sha256.ROTR(11, x) ^ Sha256.ROTR(25, x); }
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static σ0(x) { return Sha256.ROTR(7, x) ^ Sha256.ROTR(18, x) ^ (x>>>3); }
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static σ1(x) { return Sha256.ROTR(17, x) ^ Sha256.ROTR(19, x) ^ (x>>>10); }
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static Ch(x, y, z) { return (x & y) ^ (~x & z); } // 'choice'
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static Maj(x, y, z) { return (x & y) ^ (x & z) ^ (y & z); } // 'majority'
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}
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/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
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if (typeof module != 'undefined' && module.exports) module.exports = Sha256; // ≡ export default Sha256
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