1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
|
/* 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"
#endif
/* Produce MD5 pseudo-random pad for TACACS+ encryption.
Use data from packet header and secret, which
should be a global variable */
static void _tac_md5_pad(const HDR *hdr,
u_char *new_digest, u_char *old_digest) {
unsigned tac_secret_len = strlen(tac_secret);
MD5_CTX mdcontext;
/* 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 */
MD5_Init(&mdcontext);
MD5_Update(&mdcontext, (const u_char *) &hdr->session_id, sizeof(hdr->session_id));
MD5_Update(&mdcontext, (const u_char *) tac_secret, tac_secret_len);
MD5_Update(&mdcontext, &hdr->version, sizeof(hdr->version));
MD5_Update(&mdcontext, &hdr->seq_no, sizeof(hdr->seq_no));
/* append previous pad if this is not the first run */
if (old_digest) {
MD5_Update(&mdcontext, old_digest, MD5_LBLOCK);
}
MD5_Final(new_digest, &mdcontext);
} /* _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, const HDR *th) {
unsigned i, j, length = ntohl(th->datalength);
/* null operation if no encryption requested */
if((tac_secret != NULL) && (th->encryption & TAC_PLUS_UNENCRYPTED_FLAG) != TAC_PLUS_UNENCRYPTED_FLAG) {
u_char digest[MD5_LBLOCK];
for (i=0; i<length; i++) {
j = i % MD5_LBLOCK;
/* At the beginning of every block (16 bytes, i.e. the size
* of an MD5 digest), generate a new pad to XOR against.
* For the 2nd and all successive blocks, we prime it with
* the previous digest.
*/
if (j == 0)
_tac_md5_pad(th, digest, ((i > 0) ? digest : NULL));
buf[i] ^= digest[j];
}
} else {
TACSYSLOG(LOG_WARNING, "%s: using no TACACS+ encryption", __FUNCTION__);
}
} /* _tac_crypt */
|
