95 lines
2.4 KiB
JavaScript
95 lines
2.4 KiB
JavaScript
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var parseKeys = require('parse-asn1');
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var randomBytes = require('randombytes');
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var createHash = require('create-hash');
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var mgf = require('./mgf');
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var xor = require('./xor');
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var bn = require('bn.js');
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var withPublic = require('./withPublic');
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var crt = require('browserify-rsa');
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var constants = {
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RSA_PKCS1_OAEP_PADDING: 4,
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RSA_PKCS1_PADDIN: 1,
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RSA_NO_PADDING: 3
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};
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module.exports = function publicEncrypt(public_key, msg, reverse) {
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var padding;
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if (public_key.padding) {
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padding = public_key.padding;
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} else if (reverse) {
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padding = 1;
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} else {
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padding = 4;
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}
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var key = parseKeys(public_key);
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var paddedMsg;
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if (padding === 4) {
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paddedMsg = oaep(key, msg);
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} else if (padding === 1) {
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paddedMsg = pkcs1(key, msg, reverse);
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} else if (padding === 3) {
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paddedMsg = new bn(msg);
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if (paddedMsg.cmp(key.modulus) >= 0) {
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throw new Error('data too long for modulus');
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}
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} else {
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throw new Error('unknown padding');
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}
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if (reverse) {
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return crt(paddedMsg, key);
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} else {
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return withPublic(paddedMsg, key);
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}
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};
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function oaep(key, msg){
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var k = key.modulus.byteLength();
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var mLen = msg.length;
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var iHash = createHash('sha1').update(new Buffer('')).digest();
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var hLen = iHash.length;
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var hLen2 = 2 * hLen;
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if (mLen > k - hLen2 - 2) {
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throw new Error('message too long');
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}
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var ps = new Buffer(k - mLen - hLen2 - 2);
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ps.fill(0);
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var dblen = k - hLen - 1;
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var seed = randomBytes(hLen);
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var maskedDb = xor(Buffer.concat([iHash, ps, new Buffer([1]), msg], dblen), mgf(seed, dblen));
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var maskedSeed = xor(seed, mgf(maskedDb, hLen));
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return new bn(Buffer.concat([new Buffer([0]), maskedSeed, maskedDb], k));
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}
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function pkcs1(key, msg, reverse){
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var mLen = msg.length;
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var k = key.modulus.byteLength();
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if (mLen > k - 11) {
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throw new Error('message too long');
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}
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var ps;
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if (reverse) {
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ps = new Buffer(k - mLen - 3);
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ps.fill(0xff);
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} else {
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ps = nonZero(k - mLen - 3);
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}
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return new bn(Buffer.concat([new Buffer([0, reverse?1:2]), ps, new Buffer([0]), msg], k));
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}
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function nonZero(len, crypto) {
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var out = new Buffer(len);
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var i = 0;
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var cache = randomBytes(len*2);
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var cur = 0;
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var num;
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while (i < len) {
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if (cur === cache.length) {
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cache = randomBytes(len*2);
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cur = 0;
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}
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num = cache[cur++];
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if (num) {
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out[i++] = num;
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}
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}
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return out;
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}
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