/**
* Partial implementation of PKCS#1 v2.2: RSA-OEAP
*
* Modified but based on the following MIT and BSD licensed code:
*
* https://github.com/kjur/jsjws/blob/master/rsa.js:
*
* The 'jsjws'(JSON Web Signature JavaScript Library) License
*
* Copyright (c) 2012 Kenji Urushima
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*
* http://webrsa.cvs.sourceforge.net/viewvc/webrsa/Client/RSAES-OAEP.js?content-type=text%2Fplain:
*
* RSAES-OAEP.js
* $Id: RSAES-OAEP.js,v 1.1.1.1 2003/03/19 15:37:20 ellispritchard Exp $
* JavaScript Implementation of PKCS #1 v2.1 RSA CRYPTOGRAPHY STANDARD (RSA Laboratories, June 14, 2002)
* Copyright (C) Ellis Pritchard, Guardian Unlimited 2003.
* Contact: ellis@nukinetics.com
* Distributed under the BSD License.
*
* Official documentation: http://www.rsa.com/rsalabs/node.asp?id=2125
*
* @author Evan Jones (http://evanjones.ca/)
* @author Dave Longley
*
* Copyright (c) 2013-2014 Digital Bazaar, Inc.
*/
var forge = require('./forge');
require('./util');
require('./random');
require('./sha1');
// shortcut for PKCS#1 API
var pkcs1 = module.exports = forge.pkcs1 = forge.pkcs1 || {};
/**
* Encode the given RSAES-OAEP message (M) using key, with optional label (L)
* and seed.
*
* This method does not perform RSA encryption, it only encodes the message
* using RSAES-OAEP.
*
* @param key the RSA key to use.
* @param message the message to encode.
* @param options the options to use:
* label an optional label to use.
* seed the seed to use.
* md the message digest object to use, undefined for SHA-1.
* mgf1 optional mgf1 parameters:
* md the message digest object to use for MGF1.
*
* @return the encoded message bytes.
*/
pkcs1.encode_rsa_oaep = function(key, message, options) {
// parse arguments
var label;
var seed;
var md;
var mgf1Md;
// legacy args (label, seed, md)
if(typeof options === 'string') {
label = options;
seed = arguments[3] || undefined;
md = arguments[4] || undefined;
} else if(options) {
label = options.label || undefined;
seed = options.seed || undefined;
md = options.md || undefined;
if(options.mgf1 && options.mgf1.md) {
mgf1Md = options.mgf1.md;
}
}
// default OAEP to SHA-1 message digest
if(!md) {
md = forge.md.sha1.create();
} else {
md.start();
}
// default MGF-1 to same as OAEP
if(!mgf1Md) {
mgf1Md = md;
}
// compute length in bytes and check output
var keyLength = Math.ceil(key.n.bitLength() / 8);
var maxLength = keyLength - 2 * md.digestLength - 2;
if(message.length > maxLength) {
var error = new Error('RSAES-OAEP input message length is too long.');
error.length = message.length;
error.maxLength = maxLength;
throw error;
}
if(!label) {
label = '';
}
md.update(label, 'raw');
var lHash = md.digest();
var PS = '';
var PS_length = maxLength - message.length;
for(var i = 0; i < PS_length; i++) {
PS += '\x00';
}
var DB = lHash.getBytes() + PS + '\x01' + message;
if(!seed) {
seed = forge.random.getBytes(md.digestLength);
} else if(seed.length !== md.digestLength) {
var error = new Error('Invalid RSAES-OAEP seed. The seed length must ' +
'match the digest length.');
error.seedLength = seed.length;
error.digestLength = md.digestLength;
throw error;
}
var dbMask = rsa_mgf1(seed, keyLength - md.digestLength - 1, mgf1Md);
var maskedDB = forge.util.xorBytes(DB, dbMask, DB.length);
var seedMask = rsa_mgf1(maskedDB, md.digestLength, mgf1Md);
var maskedSeed = forge.util.xorBytes(seed, seedMask, seed.length);
// return encoded message
return '\x00' + maskedSeed + maskedDB;
};
/**
* Decode the given RSAES-OAEP encoded message (EM) using key, with optional
* label (L).
*
* This method does not perform RSA decryption, it only decodes the message
* using RSAES-OAEP.
*
* @param key the RSA key to use.
* @param em the encoded message to decode.
* @param options the options to use:
* label an optional label to use.
* md the message digest object to use for OAEP, undefined for SHA-1.
* mgf1 optional mgf1 parameters:
* md the message digest object to use for MGF1.
*
* @return the decoded message bytes.
*/
pkcs1.decode_rsa_oaep = function(key, em, options) {
// parse args
var label;
var md;
var mgf1Md;
// legacy args
if(typeof options === 'string') {
label = options;
md = arguments[3] || undefined;
} else if(options) {
label = options.label || undefined;
md = options.md || undefined;
if(options.mgf1 && options.mgf1.md) {
mgf1Md = options.mgf1.md;
}
}
// compute length in bytes
var keyLength = Math.ceil(key.n.bitLength() / 8);
if(em.length !== keyLength) {
var error = new Error('RSAES-OAEP encoded message length is invalid.');
error.length = em.length;
error.expectedLength = keyLength;
throw error;
}
// default OAEP to SHA-1 message digest
if(md === undefined) {
md = forge.md.sha1.create();
} else {
md.start();
}
// default MGF-1 to same as OAEP
if(!mgf1Md) {
mgf1Md = md;
}
if(keyLength < 2 * md.digestLength + 2) {
throw new Error('RSAES-OAEP key is too short for the hash function.');
}
if(!label) {
label = '';
}
md.update(label, 'raw');
var lHash = md.digest().getBytes();
// split the message into its parts
var y = em.charAt(0);
var maskedSeed = em.substring(1, md.digestLength + 1);
var maskedDB = em.substring(1 + md.digestLength);
var seedMask = rsa_mgf1(maskedDB, md.digestLength, mgf1Md);
var seed = forge.util.xorBytes(maskedSeed, seedMask, maskedSeed.length);
var dbMask = rsa_mgf1(seed, keyLength - md.digestLength - 1, mgf1Md);
var db = forge.util.xorBytes(maskedDB, dbMask, maskedDB.length);
var lHashPrime = db.substring(0, md.digestLength);
// constant time check that all values match what is expected
var error = (y !== '\x00');
// constant time check lHash vs lHashPrime
for(var i = 0; i < md.digestLength; ++i) {
error |= (lHash.charAt(i) !== lHashPrime.charAt(i));
}
// "constant time" find the 0x1 byte separating the padding (zeros) from the
// message
// TODO: It must be possible to do this in a better/smarter way?
var in_ps = 1;
var index = md.digestLength;
for(var j = md.digestLength; j < db.length; j++) {
var code = db.charCodeAt(j);
var is_0 = (code & 0x1) ^ 0x1;
// non-zero if not 0 or 1 in the ps section
var error_mask = in_ps ? 0xfffe : 0x0000;
error |= (code & error_mask);
// latch in_ps to zero after we find 0x1
in_ps = in_ps & is_0;
index += in_ps;
}
if(error || db.charCodeAt(index) !== 0x1) {
throw new Error('Invalid RSAES-OAEP padding.');
}
return db.substring(index + 1);
};
function rsa_mgf1(seed, maskLength, hash) {
// default to SHA-1 message digest
if(!hash) {
hash = forge.md.sha1.create();
}
var t = '';
var count = Math.ceil(maskLength / hash.digestLength);
for(var i = 0; i < count; ++i) {
var c = String.fromCharCode(
(i >> 24) & 0xFF, (i >> 16) & 0xFF, (i >> 8) & 0xFF, i & 0xFF);
hash.start();
hash.update(seed + c);
t += hash.digest().getBytes();
}
return t.substring(0, maskLength);
}