/**
* Cipher base API.
*
* @author Dave Longley
*
* Copyright (c) 2010-2014 Digital Bazaar, Inc.
*/
var forge = require('./forge');
require('./util');
module.exports = forge.cipher = forge.cipher || {};
// registered algorithms
forge.cipher.algorithms = forge.cipher.algorithms || {};
/**
* Creates a cipher object that can be used to encrypt data using the given
* algorithm and key. The algorithm may be provided as a string value for a
* previously registered algorithm or it may be given as a cipher algorithm
* API object.
*
* @param algorithm the algorithm to use, either a string or an algorithm API
* object.
* @param key the key to use, as a binary-encoded string of bytes or a
* byte buffer.
*
* @return the cipher.
*/
forge.cipher.createCipher = function(algorithm, key) {
var api = algorithm;
if(typeof api === 'string') {
api = forge.cipher.getAlgorithm(api);
if(api) {
api = api();
}
}
if(!api) {
throw new Error('Unsupported algorithm: ' + algorithm);
}
// assume block cipher
return new forge.cipher.BlockCipher({
algorithm: api,
key: key,
decrypt: false
});
};
/**
* Creates a decipher object that can be used to decrypt data using the given
* algorithm and key. The algorithm may be provided as a string value for a
* previously registered algorithm or it may be given as a cipher algorithm
* API object.
*
* @param algorithm the algorithm to use, either a string or an algorithm API
* object.
* @param key the key to use, as a binary-encoded string of bytes or a
* byte buffer.
*
* @return the cipher.
*/
forge.cipher.createDecipher = function(algorithm, key) {
var api = algorithm;
if(typeof api === 'string') {
api = forge.cipher.getAlgorithm(api);
if(api) {
api = api();
}
}
if(!api) {
throw new Error('Unsupported algorithm: ' + algorithm);
}
// assume block cipher
return new forge.cipher.BlockCipher({
algorithm: api,
key: key,
decrypt: true
});
};
/**
* Registers an algorithm by name. If the name was already registered, the
* algorithm API object will be overwritten.
*
* @param name the name of the algorithm.
* @param algorithm the algorithm API object.
*/
forge.cipher.registerAlgorithm = function(name, algorithm) {
name = name.toUpperCase();
forge.cipher.algorithms[name] = algorithm;
};
/**
* Gets a registered algorithm by name.
*
* @param name the name of the algorithm.
*
* @return the algorithm, if found, null if not.
*/
forge.cipher.getAlgorithm = function(name) {
name = name.toUpperCase();
if(name in forge.cipher.algorithms) {
return forge.cipher.algorithms[name];
}
return null;
};
var BlockCipher = forge.cipher.BlockCipher = function(options) {
this.algorithm = options.algorithm;
this.mode = this.algorithm.mode;
this.blockSize = this.mode.blockSize;
this._finish = false;
this._input = null;
this.output = null;
this._op = options.decrypt ? this.mode.decrypt : this.mode.encrypt;
this._decrypt = options.decrypt;
this.algorithm.initialize(options);
};
/**
* Starts or restarts the encryption or decryption process, whichever
* was previously configured.
*
* For non-GCM mode, the IV may be a binary-encoded string of bytes, an array
* of bytes, a byte buffer, or an array of 32-bit integers. If the IV is in
* bytes, then it must be Nb (16) bytes in length. If the IV is given in as
* 32-bit integers, then it must be 4 integers long.
*
* Note: an IV is not required or used in ECB mode.
*
* For GCM-mode, the IV must be given as a binary-encoded string of bytes or
* a byte buffer. The number of bytes should be 12 (96 bits) as recommended
* by NIST SP-800-38D but another length may be given.
*
* @param options the options to use:
* iv the initialization vector to use as a binary-encoded string of
* bytes, null to reuse the last ciphered block from a previous
* update() (this "residue" method is for legacy support only).
* additionalData additional authentication data as a binary-encoded
* string of bytes, for 'GCM' mode, (default: none).
* tagLength desired length of authentication tag, in bits, for
* 'GCM' mode (0-128, default: 128).
* tag the authentication tag to check if decrypting, as a
* binary-encoded string of bytes.
* output the output the buffer to write to, null to create one.
*/
BlockCipher.prototype.start = function(options) {
options = options || {};
var opts = {};
for(var key in options) {
opts[key] = options[key];
}
opts.decrypt = this._decrypt;
this._finish = false;
this._input = forge.util.createBuffer();
this.output = options.output || forge.util.createBuffer();
this.mode.start(opts);
};
/**
* Updates the next block according to the cipher mode.
*
* @param input the buffer to read from.
*/
BlockCipher.prototype.update = function(input) {
if(input) {
// input given, so empty it into the input buffer
this._input.putBuffer(input);
}
// do cipher operation until it needs more input and not finished
while(!this._op.call(this.mode, this._input, this.output, this._finish) &&
!this._finish) {}
// free consumed memory from input buffer
this._input.compact();
};
/**
* Finishes encrypting or decrypting.
*
* @param pad a padding function to use in CBC mode, null for default,
* signature(blockSize, buffer, decrypt).
*
* @return true if successful, false on error.
*/
BlockCipher.prototype.finish = function(pad) {
// backwards-compatibility w/deprecated padding API
// Note: will overwrite padding functions even after another start() call
if(pad && (this.mode.name === 'ECB' || this.mode.name === 'CBC')) {
this.mode.pad = function(input) {
return pad(this.blockSize, input, false);
};
this.mode.unpad = function(output) {
return pad(this.blockSize, output, true);
};
}
// build options for padding and afterFinish functions
var options = {};
options.decrypt = this._decrypt;
// get # of bytes that won't fill a block
options.overflow = this._input.length() % this.blockSize;
if(!this._decrypt && this.mode.pad) {
if(!this.mode.pad(this._input, options)) {
return false;
}
}
// do final update
this._finish = true;
this.update();
if(this._decrypt && this.mode.unpad) {
if(!this.mode.unpad(this.output, options)) {
return false;
}
}
if(this.mode.afterFinish) {
if(!this.mode.afterFinish(this.output, options)) {
return false;
}
}
return true;
};