/***************************************************************************\ * * * BitlBee - An IRC to IM gateway * * Simple (but secure) ArcFour implementation for safer password storage. * * * * Copyright 2006 Wilmer van der Gaast * * * * 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 ArcFour-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 picked ArcFour is because it's pretty simple but effective, so it will work without adding several KBs or an extra library dependency. (ArcFour is an RC4-compatible cipher. See for details: http://www.mozilla.org/projects/security/pki/nss/draft-kaukonen-cipher-arcfour-03.txt) */ #include #include #include #include #include "misc.h" #include "arc.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 ARC_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 ARC_CYCLES 1024 struct arc_state *arc_keymaker( unsigned char *key, int kl, int cycles ) { struct arc_state *st; int i, j, tmp; unsigned char S2[256]; st = g_malloc( sizeof( struct arc_state ) ); st->i = st->j = 0; if( kl <= 0 ) kl = strlen( (char*) key ); for( i = 0; i < 256; i ++ ) { st->S[i] = i; S2[i] = key[i%kl]; } for( i = j = 0; i < 256; i ++ ) { j = ( j + st->S[i] + S2[i] ) & 0xff; tmp = st->S[i]; st->S[i] = st->S[j]; st->S[j] = tmp; } memset( S2, 0, 256 ); i = j = 0; for( i = 0; i < cycles; i ++ ) arc_getbyte( st ); return st; } /* For those who don't know, ArcFour 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 byte generator, the next function can be used to get bytes from the generator (and shuffle things a bit). */ unsigned char arc_getbyte( struct arc_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