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Diffstat (limited to 'lib/rc4.c')
| -rw-r--r-- | lib/rc4.c | 189 |
1 files changed, 0 insertions, 189 deletions
diff --git a/lib/rc4.c b/lib/rc4.c deleted file mode 100644 index 635b802a..00000000 --- a/lib/rc4.c +++ /dev/null @@ -1,189 +0,0 @@ -/***************************************************************************\ -* * -* BitlBee - An IRC to IM gateway * -* Simple (but secure) RC4 implementation for safer password storage. * -* * -* Copyright 2006 Wilmer van der Gaast <wilmer@gaast.net> * -* * -* 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, version * -* 2.1. * -* * -* 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 St, Fifth Floor, Boston, MA 02110-1301 USA * -* * -\***************************************************************************/ - -/* - This file implements RC4-encryption, which will mainly be used to save IM - passwords safely in the new XML-format. Possibly other uses will come up - later. It's supposed to be quite reliable (thanks to the use of a 6-byte - IV/seed), certainly compared to the old format. The only realistic way to - crack BitlBee passwords now is to use a sniffer to get your hands on the - user's password. - - If you see that something's wrong in this implementation (I asked a - couple of people to look at it already, but who knows), please tell me. - - The reason I chose for RC4 is because it's pretty simple but effective, - so it will work without adding several KBs or an extra library dependency. -*/ - - -#include <glib.h> -#include <gmodule.h> -#include <stdlib.h> -#include <string.h> -#include "misc.h" -#include "rc4.h" - -/* Add some seed to the password, to make sure we *never* use the same key. - This defines how many bytes we use as a seed. */ -#define RC4_IV_LEN 6 - -/* To defend against a "Fluhrer, Mantin and Shamir attack", it is recommended - to shuffle S[] just a bit more before you start to use it. This defines how - many bytes we'll request before we'll really use them for encryption. */ -#define RC4_CYCLES 1024 - -struct rc4_state *rc4_keymaker( unsigned char *key, int kl, int cycles ) -{ - struct rc4_state *st; - int i, j, tmp; - - st = g_malloc( sizeof( struct rc4_state ) ); - st->i = st->j = 0; - for( i = 0; i < 256; i ++ ) - st->S[i] = i; - - if( kl <= 0 ) - kl = strlen( (char*) key ); - - for( i = j = 0; i < 256; i ++ ) - { - j = ( j + st->S[i] + key[i%kl] ) & 0xff; - tmp = st->S[i]; - st->S[i] = st->S[j]; - st->S[j] = tmp; - } - - for( i = 0; i < cycles; i ++ ) - rc4_getbyte( st ); - - return st; -} - -/* - For those who don't know, RC4 is basically an algorithm that generates a - stream of bytes after you give it a key. Just get a byte from it and xor - it with your cleartext. To decrypt, just give it the same key again and - start xorring. - - The function above initializes the RC4 byte generator, the next function - can be used to get bytes from the generator (and shuffle things a bit). -*/ - -unsigned char rc4_getbyte( struct rc4_state *st ) -{ - unsigned char tmp; - - /* Unfortunately the st-> stuff doesn't really improve readability here... */ - st->i ++; - st->j += st->S[st->i]; - tmp = st->S[st->i]; - st->S[st->i] = st->S[st->j]; - st->S[st->j] = tmp; - - return st->S[(st->S[st->i] + st->S[st->j]) & 0xff]; -} - -/* - The following two functions can be used for reliable encryption and - decryption. Known plaintext attacks are prevented by adding some (6, - by default) random bytes to the password before setting up the RC4 - structures. These 6 bytes are also saved in the results, because of - course we'll need them in rc4_decode(). - - Because the length of the resulting string is unknown to the caller, - it should pass a char**. Since the encode/decode functions allocate - memory for the string, make sure the char** points at a NULL-pointer - (or at least to something you already free()d), or you'll leak - memory. And of course, don't forget to free() the result when you - don't need it anymore. - - Both functions return the number of bytes in the result string. -*/ - -int rc4_encode( char *clear, int clear_len, unsigned char **crypt, char *password ) -{ - struct rc4_state *st; - unsigned char *key; - int key_len, i; - - key_len = strlen( password ) + RC4_IV_LEN; - if( clear_len <= 0 ) - clear_len = strlen( clear ); - - /* Prepare buffers and the key + IV */ - *crypt = g_malloc( clear_len + RC4_IV_LEN ); - key = g_malloc( key_len ); - strcpy( (char*) key, password ); - - /* Add the salt. Save it for later (when decrypting) and, of course, - add it to the encryption key. */ - random_bytes( crypt[0], RC4_IV_LEN ); - memcpy( key + key_len - RC4_IV_LEN, crypt[0], RC4_IV_LEN ); - - /* Generate the initial S[] from the IVed key. */ - st = rc4_keymaker( key, key_len, RC4_CYCLES ); - g_free( key ); - - for( i = 0; i < clear_len; i ++ ) - crypt[0][i+RC4_IV_LEN] = clear[i] ^ rc4_getbyte( st ); - - g_free( st ); - - return clear_len + RC4_IV_LEN; -} - -int rc4_decode( unsigned char *crypt, int crypt_len, char **clear, char *password ) -{ - struct rc4_state *st; - unsigned char *key; - int key_len, clear_len, i; - - key_len = strlen( password ) + RC4_IV_LEN; - clear_len = crypt_len - RC4_IV_LEN; - - if( clear_len < 0 ) - { - *clear = g_strdup( "" ); - return 0; - } - - /* Prepare buffers and the key + IV */ - *clear = g_malloc( clear_len + 1 ); - key = g_malloc( key_len ); - strcpy( (char*) key, password ); - for( i = 0; i < RC4_IV_LEN; i ++ ) - key[key_len-RC4_IV_LEN+i] = crypt[i]; - - /* Generate the initial S[] from the IVed key. */ - st = rc4_keymaker( key, key_len, RC4_CYCLES ); - g_free( key ); - - for( i = 0; i < clear_len; i ++ ) - clear[0][i] = crypt[i+RC4_IV_LEN] ^ rc4_getbyte( st ); - clear[0][i] = 0; /* Nice to have for plaintexts. */ - - g_free( st ); - - return clear_len; -} |