compat.c revision 323121 
1/* $OpenBSD: compat.c,v 1.97 2015/08/19 23:21:42 djm Exp $ */
2/*
3 * Copyright (c) 1999, 2000, 2001, 2002 Markus Friedl.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#include "includes.h"
27
28#include <sys/types.h>
29
30#include <stdlib.h>
31#include <string.h>
32#include <stdarg.h>
33
34#include "xmalloc.h"
35#include "buffer.h"
36#include "packet.h"
37#include "compat.h"
38#include "log.h"
39#include "match.h"
40
41int compat13 = 0;
42int compat20 = 0;
43int datafellows = 0;
44
45void
46enable_compat20(void)
47{
48	if (compat20)
49		return;
50	debug("Enabling compatibility mode for protocol 2.0");
51	compat20 = 1;
52}
53void
54enable_compat13(void)
55{
56	debug("Enabling compatibility mode for protocol 1.3");
57	compat13 = 1;
58}
59/* datafellows bug compatibility */
60u_int
61compat_datafellows(const char *version)
62{
63	int i;
64	static struct {
65		char	*pat;
66		int	bugs;
67	} check[] = {
68		{ "OpenSSH-2.0*,"
69		  "OpenSSH-2.1*,"
70		  "OpenSSH_2.1*,"
71		  "OpenSSH_2.2*",	SSH_OLD_SESSIONID|SSH_BUG_BANNER|
72					SSH_OLD_DHGEX|SSH_BUG_NOREKEY|
73					SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR},
74		{ "OpenSSH_2.3.0*",	SSH_BUG_BANNER|SSH_BUG_BIGENDIANAES|
75					SSH_OLD_DHGEX|SSH_BUG_NOREKEY|
76					SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR},
77		{ "OpenSSH_2.3.*",	SSH_BUG_BIGENDIANAES|SSH_OLD_DHGEX|
78					SSH_BUG_NOREKEY|SSH_BUG_EXTEOF|
79					SSH_OLD_FORWARD_ADDR},
80		{ "OpenSSH_2.5.0p1*,"
81		  "OpenSSH_2.5.1p1*",
82					SSH_BUG_BIGENDIANAES|SSH_OLD_DHGEX|
83					SSH_BUG_NOREKEY|SSH_BUG_EXTEOF|
84					SSH_OLD_FORWARD_ADDR},
85		{ "OpenSSH_2.5.0*,"
86		  "OpenSSH_2.5.1*,"
87		  "OpenSSH_2.5.2*",	SSH_OLD_DHGEX|SSH_BUG_NOREKEY|
88					SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR},
89		{ "OpenSSH_2.5.3*",	SSH_BUG_NOREKEY|SSH_BUG_EXTEOF|
90					SSH_OLD_FORWARD_ADDR},
91		{ "OpenSSH_2.*,"
92		  "OpenSSH_3.0*,"
93		  "OpenSSH_3.1*",	SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR},
94		{ "OpenSSH_3.*",	SSH_OLD_FORWARD_ADDR },
95		{ "Sun_SSH_1.0*",	SSH_BUG_NOREKEY|SSH_BUG_EXTEOF},
96		{ "OpenSSH_4*",		0 },
97		{ "OpenSSH_5*",		SSH_NEW_OPENSSH|SSH_BUG_DYNAMIC_RPORT},
98		{ "OpenSSH_6.6.1*",	SSH_NEW_OPENSSH},
99		{ "OpenSSH_6.5*,"
100		  "OpenSSH_6.6*",	SSH_NEW_OPENSSH|SSH_BUG_CURVE25519PAD},
101		{ "OpenSSH*",		SSH_NEW_OPENSSH },
102		{ "*MindTerm*",		0 },
103		{ "2.1.0*",		SSH_BUG_SIGBLOB|SSH_BUG_HMAC|
104					SSH_OLD_SESSIONID|SSH_BUG_DEBUG|
105					SSH_BUG_RSASIGMD5|SSH_BUG_HBSERVICE|
106					SSH_BUG_FIRSTKEX },
107		{ "2.1 *",		SSH_BUG_SIGBLOB|SSH_BUG_HMAC|
108					SSH_OLD_SESSIONID|SSH_BUG_DEBUG|
109					SSH_BUG_RSASIGMD5|SSH_BUG_HBSERVICE|
110					SSH_BUG_FIRSTKEX },
111		{ "2.0.13*,"
112		  "2.0.14*,"
113		  "2.0.15*,"
114		  "2.0.16*,"
115		  "2.0.17*,"
116		  "2.0.18*,"
117		  "2.0.19*",		SSH_BUG_SIGBLOB|SSH_BUG_HMAC|
118					SSH_OLD_SESSIONID|SSH_BUG_DEBUG|
119					SSH_BUG_PKSERVICE|SSH_BUG_X11FWD|
120					SSH_BUG_PKOK|SSH_BUG_RSASIGMD5|
121					SSH_BUG_HBSERVICE|SSH_BUG_OPENFAILURE|
122					SSH_BUG_DUMMYCHAN|SSH_BUG_FIRSTKEX },
123		{ "2.0.11*,"
124		  "2.0.12*",		SSH_BUG_SIGBLOB|SSH_BUG_HMAC|
125					SSH_OLD_SESSIONID|SSH_BUG_DEBUG|
126					SSH_BUG_PKSERVICE|SSH_BUG_X11FWD|
127					SSH_BUG_PKAUTH|SSH_BUG_PKOK|
128					SSH_BUG_RSASIGMD5|SSH_BUG_OPENFAILURE|
129					SSH_BUG_DUMMYCHAN|SSH_BUG_FIRSTKEX },
130		{ "2.0.*",		SSH_BUG_SIGBLOB|SSH_BUG_HMAC|
131					SSH_OLD_SESSIONID|SSH_BUG_DEBUG|
132					SSH_BUG_PKSERVICE|SSH_BUG_X11FWD|
133					SSH_BUG_PKAUTH|SSH_BUG_PKOK|
134					SSH_BUG_RSASIGMD5|SSH_BUG_OPENFAILURE|
135					SSH_BUG_DERIVEKEY|SSH_BUG_DUMMYCHAN|
136					SSH_BUG_FIRSTKEX },
137		{ "2.2.0*,"
138		  "2.3.0*",		SSH_BUG_HMAC|SSH_BUG_DEBUG|
139					SSH_BUG_RSASIGMD5|SSH_BUG_FIRSTKEX },
140		{ "2.3.*",		SSH_BUG_DEBUG|SSH_BUG_RSASIGMD5|
141					SSH_BUG_FIRSTKEX },
142		{ "2.4",		SSH_OLD_SESSIONID },	/* Van Dyke */
143		{ "2.*",		SSH_BUG_DEBUG|SSH_BUG_FIRSTKEX|
144					SSH_BUG_RFWD_ADDR },
145		{ "3.0.*",		SSH_BUG_DEBUG },
146		{ "3.0 SecureCRT*",	SSH_OLD_SESSIONID },
147		{ "1.7 SecureFX*",	SSH_OLD_SESSIONID },
148		{ "1.2.18*,"
149		  "1.2.19*,"
150		  "1.2.20*,"
151		  "1.2.21*,"
152		  "1.2.22*",		SSH_BUG_IGNOREMSG },
153		{ "1.3.2*",		/* F-Secure */
154					SSH_BUG_IGNOREMSG },
155		{ "Cisco-1.*",		SSH_BUG_DHGEX_LARGE|
156					SSH_BUG_HOSTKEYS },
157		{ "*SSH Compatible Server*",			/* Netscreen */
158					SSH_BUG_PASSWORDPAD },
159		{ "*OSU_0*,"
160		  "OSU_1.0*,"
161		  "OSU_1.1*,"
162		  "OSU_1.2*,"
163		  "OSU_1.3*,"
164		  "OSU_1.4*,"
165		  "OSU_1.5alpha1*,"
166		  "OSU_1.5alpha2*,"
167		  "OSU_1.5alpha3*",	SSH_BUG_PASSWORDPAD },
168		{ "*SSH_Version_Mapper*",
169					SSH_BUG_SCANNER },
170		{ "PuTTY_Local:*,"	/* dev versions < Sep 2014 */
171		  "PuTTY-Release-0.5*," /* 0.50-0.57, DH-GEX in >=0.52 */
172		  "PuTTY_Release_0.5*,"	/* 0.58-0.59 */
173		  "PuTTY_Release_0.60*,"
174		  "PuTTY_Release_0.61*,"
175		  "PuTTY_Release_0.62*,"
176		  "PuTTY_Release_0.63*,"
177		  "PuTTY_Release_0.64*",
178					SSH_OLD_DHGEX },
179		{ "FuTTY*",		SSH_OLD_DHGEX }, /* Putty Fork */
180		{ "Probe-*",
181					SSH_BUG_PROBE },
182		{ "TeraTerm SSH*,"
183		  "TTSSH/1.5.*,"
184		  "TTSSH/2.1*,"
185		  "TTSSH/2.2*,"
186		  "TTSSH/2.3*,"
187		  "TTSSH/2.4*,"
188		  "TTSSH/2.5*,"
189		  "TTSSH/2.6*,"
190		  "TTSSH/2.70*,"
191		  "TTSSH/2.71*,"
192		  "TTSSH/2.72*",	SSH_BUG_HOSTKEYS },
193		{ "WinSCP_release_4*,"
194		  "WinSCP_release_5.0*,"
195		  "WinSCP_release_5.1*,"
196		  "WinSCP_release_5.5*,"
197		  "WinSCP_release_5.6*,"
198		  "WinSCP_release_5.7,"
199		  "WinSCP_release_5.7.1,"
200		  "WinSCP_release_5.7.2,"
201		  "WinSCP_release_5.7.3,"
202		  "WinSCP_release_5.7.4",
203					SSH_OLD_DHGEX },
204		{ NULL,			0 }
205	};
206
207	/* process table, return first match */
208	for (i = 0; check[i].pat; i++) {
209		if (match_pattern_list(version, check[i].pat, 0) == 1) {
210			debug("match: %s pat %s compat 0x%08x",
211			    version, check[i].pat, check[i].bugs);
212			datafellows = check[i].bugs;	/* XXX for now */
213			return check[i].bugs;
214		}
215	}
216	debug("no match: %s", version);
217	return 0;
218}
219
220#define	SEP	","
221int
222proto_spec(const char *spec)
223{
224	char *s, *p, *q;
225	int ret = SSH_PROTO_UNKNOWN;
226
227	if (spec == NULL)
228		return ret;
229	q = s = strdup(spec);
230	if (s == NULL)
231		return ret;
232	for ((p = strsep(&q, SEP)); p && *p != '\0'; (p = strsep(&q, SEP))) {
233		switch (atoi(p)) {
234		case 1:
235#ifdef WITH_SSH1
236			if (ret == SSH_PROTO_UNKNOWN)
237				ret |= SSH_PROTO_1_PREFERRED;
238			ret |= SSH_PROTO_1;
239#endif
240			break;
241		case 2:
242			ret |= SSH_PROTO_2;
243			break;
244		default:
245			logit("ignoring bad proto spec: '%s'.", p);
246			break;
247		}
248	}
249	free(s);
250	return ret;
251}
252
253/*
254 * Filters a proposal string, excluding any algorithm matching the 'filter'
255 * pattern list.
256 */
257static char *
258filter_proposal(char *proposal, const char *filter)
259{
260	Buffer b;
261	char *orig_prop, *fix_prop;
262	char *cp, *tmp;
263
264	buffer_init(&b);
265	tmp = orig_prop = xstrdup(proposal);
266	while ((cp = strsep(&tmp, ",")) != NULL) {
267		if (match_pattern_list(cp, filter, 0) != 1) {
268			if (buffer_len(&b) > 0)
269				buffer_append(&b, ",", 1);
270			buffer_append(&b, cp, strlen(cp));
271		} else
272			debug2("Compat: skipping algorithm \"%s\"", cp);
273	}
274	buffer_append(&b, "\0", 1);
275	fix_prop = xstrdup((char *)buffer_ptr(&b));
276	buffer_free(&b);
277	free(orig_prop);
278
279	return fix_prop;
280}
281
282char *
283compat_cipher_proposal(char *cipher_prop)
284{
285	if (!(datafellows & SSH_BUG_BIGENDIANAES))
286		return cipher_prop;
287	debug2("%s: original cipher proposal: %s", __func__, cipher_prop);
288	cipher_prop = filter_proposal(cipher_prop, "aes*");
289	debug2("%s: compat cipher proposal: %s", __func__, cipher_prop);
290	if (*cipher_prop == '\0')
291		fatal("No supported ciphers found");
292	return cipher_prop;
293}
294
295char *
296compat_pkalg_proposal(char *pkalg_prop)
297{
298	if (!(datafellows & SSH_BUG_RSASIGMD5))
299		return pkalg_prop;
300	debug2("%s: original public key proposal: %s", __func__, pkalg_prop);
301	pkalg_prop = filter_proposal(pkalg_prop, "ssh-rsa");
302	debug2("%s: compat public key proposal: %s", __func__, pkalg_prop);
303	if (*pkalg_prop == '\0')
304		fatal("No supported PK algorithms found");
305	return pkalg_prop;
306}
307
308char *
309compat_kex_proposal(char *p)
310{
311	if ((datafellows & (SSH_BUG_CURVE25519PAD|SSH_OLD_DHGEX)) == 0)
312		return p;
313	debug2("%s: original KEX proposal: %s", __func__, p);
314	if ((datafellows & SSH_BUG_CURVE25519PAD) != 0)
315		p = filter_proposal(p, "curve25519-sha256@libssh.org");
316	if ((datafellows & SSH_OLD_DHGEX) != 0) {
317		p = filter_proposal(p, "diffie-hellman-group-exchange-sha256");
318		p = filter_proposal(p, "diffie-hellman-group-exchange-sha1");
319	}
320	debug2("%s: compat KEX proposal: %s", __func__, p);
321	if (*p == '\0')
322		fatal("No supported key exchange algorithms found");
323	return p;
324}
325
326