diff options
Diffstat (limited to 'libtac/lib/crypt.c')
| -rw-r--r-- | libtac/lib/crypt.c | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/libtac/lib/crypt.c b/libtac/lib/crypt.c new file mode 100644 index 0000000..49a071c --- /dev/null +++ b/libtac/lib/crypt.c @@ -0,0 +1,114 @@ +/* crypt.c - TACACS+ encryption related functions + * + * Copyright (C) 2010, Pawel Krawczyk <pawel.krawczyk@hush.com> and + * Jeroen Nijhof <jeroen@jeroennijhof.nl> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program 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 General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program - see the file COPYING. + * + * See `CHANGES' file for revision history. + */ + +#include "libtac.h" +#include "xalloc.h" + +#ifdef HAVE_CONFIG_H + #include "config.h" +#endif + +#if defined(HAVE_OPENSSL_MD5_H) && defined(HAVE_LIBCRYPTO) +# include <openssl/md5.h> +#else +# include "md5.h" +# ifndef MD5_LBLOCK /* should be always, since it's in openssl */ +# define MD5_LBLOCK MD5_LEN +# endif +#endif + +/* Produce MD5 pseudo-random pad for TACACS+ encryption. + Use data from packet header and secret, which + should be a global variable */ +u_char *_tac_md5_pad(int len, HDR *hdr) { + int n, i, bufsize; + int bp = 0; /* buffer pointer */ + int pp = 0; /* pad pointer */ + u_char *pad; + u_char *buf; + MD5_CTX mdcontext; + + /* make pseudo pad */ + n = (int)(len/16)+1; /* number of MD5 runs */ + bufsize = sizeof(hdr->session_id) + strlen(tac_secret) + sizeof(hdr->version) + + sizeof(hdr->seq_no) + MD5_LBLOCK + 10; + buf = (u_char *) tac_xcalloc(1, bufsize); + pad = (u_char *) tac_xcalloc(n, MD5_LBLOCK); + + for (i=0; i<n; i++) { + /* MD5_1 = MD5{session_id, secret, version, seq_no} + MD5_2 = MD5{session_id, secret, version, seq_no, MD5_1} */ + + /* place session_id, key, version and seq_no in buffer */ + bp = 0; + bcopy(&hdr->session_id, buf, sizeof(session_id)); + bp += sizeof(session_id); + bcopy(tac_secret, buf+bp, strlen(tac_secret)); + bp += strlen(tac_secret); + bcopy(&hdr->version, buf+bp, sizeof(hdr->version)); + bp += sizeof(hdr->version); + bcopy(&hdr->seq_no, buf+bp, sizeof(hdr->seq_no)); + bp += sizeof(hdr->seq_no); + + /* append previous pad if this is not the first run */ + if (i) { + bcopy(pad+((i-1)*MD5_LBLOCK), buf+bp, MD5_LBLOCK); + bp+=MD5_LBLOCK; + } + +#if defined(HAVE_OPENSSL_MD5_H) && defined(HAVE_LIBCRYPTO) + MD5_Init(&mdcontext); + MD5_Update(&mdcontext, buf, bp); + MD5_Final(pad+pp, &mdcontext); +#else + MD5Init(&mdcontext); + MD5Update(&mdcontext, buf, bp); + MD5Final(pad+pp, &mdcontext); +#endif + + pp += MD5_LBLOCK; + } + + free(buf); + return pad; + +} /* _tac_md5_pad */ + +/* Perform encryption/decryption on buffer. This means simply XORing + each byte from buffer with according byte from pseudo-random + pad. */ +void _tac_crypt(u_char *buf, HDR *th, int length) { + int i; + u_char *pad; + + /* null operation if no encryption requested */ + if((tac_secret != NULL) && (th->encryption == TAC_PLUS_ENCRYPTED_FLAG)) { + pad = _tac_md5_pad(length, th); + + for (i=0; i<length; i++) { + *(buf+i) ^= pad[i]; + } + + free(pad); + } else { + TACSYSLOG((LOG_WARNING, "%s: using no TACACS+ encryption", __func__)) + } +} /* _tac_crypt */ |