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<h1 class="page-title">Source: type/openpgp.type.s2k.js</h1>
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<pre class="prettyprint source"><code>// 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
/**
* @class
* @classdesc Implementation of the String-to-key specifier (RFC4880 3.7)
* String-to-key (S2K) specifiers are used to convert passphrase strings
into symmetric-key encryption/decryption keys. They are used in two
places, currently: to encrypt the secret part of private keys in the
private keyring, and to convert passphrases to encryption keys for
symmetrically encrypted messages.
*/
function openpgp_type_s2k() {
/**
* Parsing function for a string-to-key specifier (RFC 4880 3.7).
* @param {String} input Payload of string-to-key specifier
* @param {Integer} position Position to start reading from the input string
* @return {openpgp_type_s2k} Object representation
*/
function read(input, position) {
var mypos = position;
this.type = input[mypos++].charCodeAt();
switch (this.type) {
case 0: // Simple S2K
// Octet 1: hash algorithm
this.hashAlgorithm = input[mypos++].charCodeAt();
this.s2kLength = 1;
break;
case 1: // Salted S2K
// Octet 1: hash algorithm
this.hashAlgorithm = input[mypos++].charCodeAt();
// Octets 2-9: 8-octet salt value
this.saltValue = input.substring(mypos, mypos+8);
mypos += 8;
this.s2kLength = 9;
break;
case 3: // Iterated and Salted S2K
// Octet 1: hash algorithm
this.hashAlgorithm = input[mypos++].charCodeAt();
// Octets 2-9: 8-octet salt value
this.saltValue = input.substring(mypos, mypos+8);
mypos += 8;
// Octet 10: count, a one-octet, coded value
this.EXPBIAS = 6;
var c = input[mypos++].charCodeAt();
this.count = (16 + (c & 15)) << ((c >> 4) + this.EXPBIAS);
this.s2kLength = 10;
break;
case 101:
if(input.substring(mypos+1, mypos+4) == "GNU") {
this.hashAlgorithm = input[mypos++].charCodeAt();
mypos += 3; // GNU
var gnuExtType = 1000 + input[mypos++].charCodeAt();
if(gnuExtType == 1001) {
this.type = gnuExtType;
this.s2kLength = 5;
// GnuPG extension mode 1001 -- don't write secret key at all
} else {
util.print_error("unknown s2k gnu protection mode! "+this.type);
}
} else {
util.print_error("unknown s2k type! "+this.type);
}
break;
case 2: // Reserved value
default:
util.print_error("unknown s2k type! "+this.type);
break;
}
return this;
}
/**
* writes an s2k hash based on the inputs.
* @return {String} Produced key of hashAlgorithm hash length
*/
function write(type, hash, passphrase, salt, c){
this.type = type;
if(this.type == 3){this.saltValue = salt;
this.hashAlgorithm = hash;
this.count = (16 + (c & 15)) << ((c >> 4) + 6);
this.s2kLength = 10;
}
return this.produce_key(passphrase);
}
/**
* Produces a key using the specified passphrase and the defined
* hashAlgorithm
* @param {String} passphrase Passphrase containing user input
* @return {String} Produced key with a length corresponding to
* hashAlgorithm hash length
*/
function produce_key(passphrase, numBytes) {
passphrase = util.encode_utf8(passphrase);
if (this.type == 0) {
return openpgp_crypto_hashData(this.hashAlgorithm,passphrase);
} else if (this.type == 1) {
return openpgp_crypto_hashData(this.hashAlgorithm,this.saltValue+passphrase);
} else if (this.type == 3) {
var isp = [];
isp[0] = this.saltValue+passphrase;
while (isp.length*(this.saltValue+passphrase).length < this.count)
isp.push(this.saltValue+passphrase);
isp = isp.join('');
if (isp.length > this.count)
isp = isp.substr(0, this.count);
if(numBytes && (numBytes == 24 || numBytes == 32)){ //This if accounts for RFC 4880 3.7.1.1 -- If hash size is greater than block size, use leftmost bits. If blocksize larger than hash size, we need to rehash isp and prepend with 0.
var key = openpgp_crypto_hashData(this.hashAlgorithm,isp);
return key + openpgp_crypto_hashData(this.hashAlgorithm,String.fromCharCode(0)+isp);
}
return openpgp_crypto_hashData(this.hashAlgorithm,isp);
} else return null;
}
this.read = read;
this.write = write;
this.produce_key = produce_key;
}
</code></pre>
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