// GPG4Browsers - An OpenPGP implementation in javascript
// Copyright (C) 2011 Recurity Labs GmbH
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
/**
* Implementation of the Key Material Packet (Tag 5,6,7,14)<br/>
* <br/>
* RFC4480 5.5:
* A key material packet contains all the information about a public or
* private key. There are four variants of this packet type, and two
* major versions. Consequently, this section is complex.
* @requires crypto
* @requires enums
* @requires packet/public_key
* @requires type/mpi
* @requires type/s2k
* @requires util
* @module packet/secret_key
*/
var publicKey = require('./public_key.js'),
enums = require('../enums.js'),
util = require('../util'),
crypto = require('../crypto'),
type_mpi = require('../type/mpi.js'),
type_s2k = require('../type/s2k.js');
/**
* @constructor
* @extends module:packet/public_key
*/
module.exports = function secret_key() {
publicKey.call(this);
// encrypted secret-key data
this.encrypted = null;
// indicator if secret-key data is available in decrypted form
this.isDecrypted = false;
function get_hash_len(hash) {
if (hash == 'sha1')
return 20;
else
return 2;
}
function get_hash_fn(hash) {
if (hash == 'sha1')
return crypto.hash.sha1;
else
return function(c) {
return util.writeNumber(util.calc_checksum(c), 2);
};
}
// Helper function
function parse_cleartext_mpi(hash_algorithm, cleartext, algorithm) {
var hashlen = get_hash_len(hash_algorithm),
hashfn = get_hash_fn(hash_algorithm);
var hashtext = cleartext.substr(cleartext.length - hashlen);
cleartext = cleartext.substr(0, cleartext.length - hashlen);
var hash = hashfn(cleartext);
if (hash != hashtext)
return new Error("Hash mismatch.");
var mpis = crypto.getPrivateMpiCount(algorithm);
var j = 0;
var mpi = [];
for (var i = 0; i < mpis && j < cleartext.length; i++) {
mpi[i] = new type_mpi();
j += mpi[i].read(cleartext.substr(j));
}
return mpi;
}
function write_cleartext_mpi(hash_algorithm, algorithm, mpi) {
var bytes = '';
var discard = crypto.getPublicMpiCount(algorithm);
for (var i = discard; i < mpi.length; i++) {
bytes += mpi[i].write();
}
bytes += get_hash_fn(hash_algorithm)(bytes);
return bytes;
}
// 5.5.3. Secret-Key Packet Formats
/**
* Internal parser for private keys as specified in RFC 4880 section 5.5.3
* @param {String} bytes Input string to read the packet from
*/
this.read = function (bytes) {
// - A Public-Key or Public-Subkey packet, as described above.
var len = this.readPublicKey(bytes);
bytes = bytes.substr(len);
// - One octet indicating string-to-key usage conventions. Zero
// indicates that the secret-key data is not encrypted. 255 or 254
// indicates that a string-to-key specifier is being given. Any
// other value is a symmetric-key encryption algorithm identifier.
var isEncrypted = bytes.charCodeAt(0);
if (isEncrypted) {
this.encrypted = bytes;
} else {
// - Plain or encrypted multiprecision integers comprising the secret
// key data. These algorithm-specific fields are as described
// below.
var parsedMPI = parse_cleartext_mpi('mod', bytes.substr(1), this.algorithm);
if (parsedMPI instanceof Error)
throw parsedMPI;
this.mpi = this.mpi.concat(parsedMPI);
this.isDecrypted = true;
}
};
/** Creates an OpenPGP key packet for the given key.
* @return {String} A string of bytes containing the secret key OpenPGP packet
*/
this.write = function () {
var bytes = this.writePublicKey();
if (!this.encrypted) {
bytes += String.fromCharCode(0);
bytes += write_cleartext_mpi('mod', this.algorithm, this.mpi);
} else {
bytes += this.encrypted;
}
return bytes;
};
/** Encrypt the payload. By default, we use aes256 and iterated, salted string
* to key specifier
* @param {String} passphrase
*/
this.encrypt = function (passphrase) {
var s2k = new type_s2k(),
symmetric = 'aes256',
cleartext = write_cleartext_mpi('sha1', this.algorithm, this.mpi),
key = produceEncryptionKey(s2k, passphrase, symmetric),
blockLen = crypto.cipher[symmetric].blockSize,
iv = crypto.random.getRandomBytes(blockLen);
this.encrypted = '';
this.encrypted += String.fromCharCode(254);
this.encrypted += String.fromCharCode(enums.write(enums.symmetric, symmetric));
this.encrypted += s2k.write();
this.encrypted += iv;
this.encrypted += crypto.cfb.normalEncrypt(symmetric, key, cleartext, iv);
};
function produceEncryptionKey(s2k, passphrase, algorithm) {
return s2k.produce_key(passphrase,
crypto.cipher[algorithm].keySize);
}
/**
* Decrypts the private key MPIs which are needed to use the key.
* @link module:packet/secret_key.isDecrypted should be
* false otherwise a call to this function is not needed
*
* @param {String} str_passphrase The passphrase for this private key
* as string
* @return {Boolean} True if the passphrase was correct or MPI already
* decrypted; false if not
*/
this.decrypt = function (passphrase) {
if (this.isDecrypted)
return true;
var i = 0,
symmetric,
key;
var s2k_usage = this.encrypted.charCodeAt(i++);
// - [Optional] If string-to-key usage octet was 255 or 254, a one-
// octet symmetric encryption algorithm.
if (s2k_usage == 255 || s2k_usage == 254) {
symmetric = this.encrypted.charCodeAt(i++);
symmetric = enums.read(enums.symmetric, symmetric);
// - [Optional] If string-to-key usage octet was 255 or 254, a
// string-to-key specifier. The length of the string-to-key
// specifier is implied by its type, as described above.
var s2k = new type_s2k();
i += s2k.read(this.encrypted.substr(i));
key = produceEncryptionKey(s2k, passphrase, symmetric);
} else {
symmetric = s2k_usage;
symmetric = enums.read(enums.symmetric, symmetric);
key = crypto.hash.md5(passphrase);
}
// - [Optional] If secret data is encrypted (string-to-key usage octet
// not zero), an Initial Vector (IV) of the same length as the
// cipher's block size.
var iv = this.encrypted.substr(i,
crypto.cipher[symmetric].blockSize);
i += iv.length;
var cleartext,
ciphertext = this.encrypted.substr(i);
cleartext = crypto.cfb.normalDecrypt(symmetric, key, ciphertext, iv);
var hash = s2k_usage == 254 ?
'sha1' :
'mod';
var parsedMPI = parse_cleartext_mpi(hash, cleartext, this.algorithm);
if (parsedMPI instanceof Error)
return false;
this.mpi = this.mpi.concat(parsedMPI);
this.isDecrypted = true;
return true;
};
this.generate = function (bits) {
this.mpi = crypto.generateMpi(this.algorithm, bits);
this.isDecrypted = true;
};
}
module.exports.prototype = new publicKey();