compat.c revision 264692 
1/* $OpenBSD: compat.c,v 1.82 2013/12/30 23:52:27 djm Exp $ */
2/* $FreeBSD: stable/10/crypto/openssh/compat.c 264692 2014-04-20 12:46:18Z des $ */
3/*
4 * Copyright (c) 1999, 2000, 2001, 2002 Markus Friedl.  All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#include "includes.h"
28
29#include <sys/types.h>
30
31#include <stdlib.h>
32#include <string.h>
33#include <stdarg.h>
34
35#include "xmalloc.h"
36#include "buffer.h"
37#include "packet.h"
38#include "compat.h"
39#include "log.h"
40#include "match.h"
41
42int compat13 = 0;
43int compat20 = 0;
44int datafellows = 0;
45
46void
47enable_compat20(void)
48{
49	if (compat20)
50		return;
51	debug("Enabling compatibility mode for protocol 2.0");
52	compat20 = 1;
53}
54void
55enable_compat13(void)
56{
57	debug("Enabling compatibility mode for protocol 1.3");
58	compat13 = 1;
59}
60/* datafellows bug compatibility */
61void
62compat_datafellows(const char *version)
63{
64	int i;
65	static struct {
66		char	*pat;
67		int	bugs;
68	} check[] = {
69		{ "OpenSSH-2.0*,"
70		  "OpenSSH-2.1*,"
71		  "OpenSSH_2.1*,"
72		  "OpenSSH_2.2*",	SSH_OLD_SESSIONID|SSH_BUG_BANNER|
73					SSH_OLD_DHGEX|SSH_BUG_NOREKEY|
74					SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR},
75		{ "OpenSSH_2.3.0*",	SSH_BUG_BANNER|SSH_BUG_BIGENDIANAES|
76					SSH_OLD_DHGEX|SSH_BUG_NOREKEY|
77					SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR},
78		{ "OpenSSH_2.3.*",	SSH_BUG_BIGENDIANAES|SSH_OLD_DHGEX|
79					SSH_BUG_NOREKEY|SSH_BUG_EXTEOF|
80					SSH_OLD_FORWARD_ADDR},
81		{ "OpenSSH_2.5.0p1*,"
82		  "OpenSSH_2.5.1p1*",
83					SSH_BUG_BIGENDIANAES|SSH_OLD_DHGEX|
84					SSH_BUG_NOREKEY|SSH_BUG_EXTEOF|
85					SSH_OLD_FORWARD_ADDR},
86		{ "OpenSSH_2.5.0*,"
87		  "OpenSSH_2.5.1*,"
88		  "OpenSSH_2.5.2*",	SSH_OLD_DHGEX|SSH_BUG_NOREKEY|
89					SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR},
90		{ "OpenSSH_2.5.3*",	SSH_BUG_NOREKEY|SSH_BUG_EXTEOF|
91					SSH_OLD_FORWARD_ADDR},
92		{ "OpenSSH_2.*,"
93		  "OpenSSH_3.0*,"
94		  "OpenSSH_3.1*",	SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR},
95		{ "OpenSSH_3.*",	SSH_OLD_FORWARD_ADDR },
96		{ "Sun_SSH_1.0*",	SSH_BUG_NOREKEY|SSH_BUG_EXTEOF},
97		{ "OpenSSH_4*",		0 },
98		{ "OpenSSH_5*",		SSH_NEW_OPENSSH|SSH_BUG_DYNAMIC_RPORT},
99		{ "OpenSSH_6.6.1*",	SSH_NEW_OPENSSH},
100		{ "OpenSSH_6.5*,"
101		  "OpenSSH_6.6*",	SSH_NEW_OPENSSH|SSH_BUG_CURVE25519PAD},
102		{ "OpenSSH*",		SSH_NEW_OPENSSH },
103		{ "*MindTerm*",		0 },
104		{ "2.1.0*",		SSH_BUG_SIGBLOB|SSH_BUG_HMAC|
105					SSH_OLD_SESSIONID|SSH_BUG_DEBUG|
106					SSH_BUG_RSASIGMD5|SSH_BUG_HBSERVICE|
107					SSH_BUG_FIRSTKEX },
108		{ "2.1 *",		SSH_BUG_SIGBLOB|SSH_BUG_HMAC|
109					SSH_OLD_SESSIONID|SSH_BUG_DEBUG|
110					SSH_BUG_RSASIGMD5|SSH_BUG_HBSERVICE|
111					SSH_BUG_FIRSTKEX },
112		{ "2.0.13*,"
113		  "2.0.14*,"
114		  "2.0.15*,"
115		  "2.0.16*,"
116		  "2.0.17*,"
117		  "2.0.18*,"
118		  "2.0.19*",		SSH_BUG_SIGBLOB|SSH_BUG_HMAC|
119					SSH_OLD_SESSIONID|SSH_BUG_DEBUG|
120					SSH_BUG_PKSERVICE|SSH_BUG_X11FWD|
121					SSH_BUG_PKOK|SSH_BUG_RSASIGMD5|
122					SSH_BUG_HBSERVICE|SSH_BUG_OPENFAILURE|
123					SSH_BUG_DUMMYCHAN|SSH_BUG_FIRSTKEX },
124		{ "2.0.11*,"
125		  "2.0.12*",		SSH_BUG_SIGBLOB|SSH_BUG_HMAC|
126					SSH_OLD_SESSIONID|SSH_BUG_DEBUG|
127					SSH_BUG_PKSERVICE|SSH_BUG_X11FWD|
128					SSH_BUG_PKAUTH|SSH_BUG_PKOK|
129					SSH_BUG_RSASIGMD5|SSH_BUG_OPENFAILURE|
130					SSH_BUG_DUMMYCHAN|SSH_BUG_FIRSTKEX },
131		{ "2.0.*",		SSH_BUG_SIGBLOB|SSH_BUG_HMAC|
132					SSH_OLD_SESSIONID|SSH_BUG_DEBUG|
133					SSH_BUG_PKSERVICE|SSH_BUG_X11FWD|
134					SSH_BUG_PKAUTH|SSH_BUG_PKOK|
135					SSH_BUG_RSASIGMD5|SSH_BUG_OPENFAILURE|
136					SSH_BUG_DERIVEKEY|SSH_BUG_DUMMYCHAN|
137					SSH_BUG_FIRSTKEX },
138		{ "2.2.0*,"
139		  "2.3.0*",		SSH_BUG_HMAC|SSH_BUG_DEBUG|
140					SSH_BUG_RSASIGMD5|SSH_BUG_FIRSTKEX },
141		{ "2.3.*",		SSH_BUG_DEBUG|SSH_BUG_RSASIGMD5|
142					SSH_BUG_FIRSTKEX },
143		{ "2.4",		SSH_OLD_SESSIONID },	/* Van Dyke */
144		{ "2.*",		SSH_BUG_DEBUG|SSH_BUG_FIRSTKEX|
145					SSH_BUG_RFWD_ADDR },
146		{ "3.0.*",		SSH_BUG_DEBUG },
147		{ "3.0 SecureCRT*",	SSH_OLD_SESSIONID },
148		{ "1.7 SecureFX*",	SSH_OLD_SESSIONID },
149		{ "1.2.18*,"
150		  "1.2.19*,"
151		  "1.2.20*,"
152		  "1.2.21*,"
153		  "1.2.22*",		SSH_BUG_IGNOREMSG },
154		{ "1.3.2*",		/* F-Secure */
155					SSH_BUG_IGNOREMSG },
156		{ "*SSH Compatible Server*",			/* Netscreen */
157					SSH_BUG_PASSWORDPAD },
158		{ "*OSU_0*,"
159		  "OSU_1.0*,"
160		  "OSU_1.1*,"
161		  "OSU_1.2*,"
162		  "OSU_1.3*,"
163		  "OSU_1.4*,"
164		  "OSU_1.5alpha1*,"
165		  "OSU_1.5alpha2*,"
166		  "OSU_1.5alpha3*",	SSH_BUG_PASSWORDPAD },
167		{ "*SSH_Version_Mapper*",
168					SSH_BUG_SCANNER },
169		{ "Probe-*",
170					SSH_BUG_PROBE },
171		{ NULL,			0 }
172	};
173
174	/* process table, return first match */
175	for (i = 0; check[i].pat; i++) {
176		if (match_pattern_list(version, check[i].pat,
177		    strlen(check[i].pat), 0) == 1) {
178			datafellows = check[i].bugs;
179			debug("match: %s pat %s compat 0x%08x",
180			    version, check[i].pat, datafellows);
181			/*
182			 * Check to see if the remote side is OpenSSH and not
183			 * HPN.  It is utterly strange to check it from the
184			 * version string and expose the option that way.
185			 */
186			if (strstr(version,"OpenSSH") != NULL &&
187			    strstr(version,"hpn") == NULL) {
188				datafellows |= SSH_BUG_LARGEWINDOW;
189				debug("Remote is not HPN-aware");
190			}
191			return;
192		}
193	}
194	debug("no match: %s", version);
195}
196
197#define	SEP	","
198int
199proto_spec(const char *spec)
200{
201	char *s, *p, *q;
202	int ret = SSH_PROTO_UNKNOWN;
203
204	if (spec == NULL)
205		return ret;
206	q = s = xstrdup(spec);
207	for ((p = strsep(&q, SEP)); p && *p != '\0'; (p = strsep(&q, SEP))) {
208		switch (atoi(p)) {
209		case 1:
210			if (ret == SSH_PROTO_UNKNOWN)
211				ret |= SSH_PROTO_1_PREFERRED;
212			ret |= SSH_PROTO_1;
213			break;
214		case 2:
215			ret |= SSH_PROTO_2;
216			break;
217		default:
218			logit("ignoring bad proto spec: '%s'.", p);
219			break;
220		}
221	}
222	free(s);
223	return ret;
224}
225
226/*
227 * Filters a proposal string, excluding any algorithm matching the 'filter'
228 * pattern list.
229 */
230static char *
231filter_proposal(char *proposal, const char *filter)
232{
233	Buffer b;
234	char *orig_prop, *fix_prop;
235	char *cp, *tmp;
236
237	buffer_init(&b);
238	tmp = orig_prop = xstrdup(proposal);
239	while ((cp = strsep(&tmp, ",")) != NULL) {
240		if (match_pattern_list(cp, filter, strlen(cp), 0) != 1) {
241			if (buffer_len(&b) > 0)
242				buffer_append(&b, ",", 1);
243			buffer_append(&b, cp, strlen(cp));
244		} else
245			debug2("Compat: skipping algorithm \"%s\"", cp);
246	}
247	buffer_append(&b, "\0", 1);
248	fix_prop = xstrdup(buffer_ptr(&b));
249	buffer_free(&b);
250	free(orig_prop);
251
252	return fix_prop;
253}
254
255char *
256compat_cipher_proposal(char *cipher_prop)
257{
258	if (!(datafellows & SSH_BUG_BIGENDIANAES))
259		return cipher_prop;
260	debug2("%s: original cipher proposal: %s", __func__, cipher_prop);
261	cipher_prop = filter_proposal(cipher_prop, "aes*");
262	debug2("%s: compat cipher proposal: %s", __func__, cipher_prop);
263	if (*cipher_prop == '\0')
264		fatal("No supported ciphers found");
265	return cipher_prop;
266}
267
268char *
269compat_pkalg_proposal(char *pkalg_prop)
270{
271	if (!(datafellows & SSH_BUG_RSASIGMD5))
272		return pkalg_prop;
273	debug2("%s: original public key proposal: %s", __func__, pkalg_prop);
274	pkalg_prop = filter_proposal(pkalg_prop, "ssh-rsa");
275	debug2("%s: compat public key proposal: %s", __func__, pkalg_prop);
276	if (*pkalg_prop == '\0')
277		fatal("No supported PK algorithms found");
278	return pkalg_prop;
279}
280
281char *
282compat_kex_proposal(char *kex_prop)
283{
284	if (!(datafellows & SSH_BUG_CURVE25519PAD))
285		return kex_prop;
286	debug2("%s: original KEX proposal: %s", __func__, kex_prop);
287	kex_prop = filter_proposal(kex_prop, "curve25519-sha256@libssh.org");
288	debug2("%s: compat KEX proposal: %s", __func__, kex_prop);
289	if (*kex_prop == '\0')
290		fatal("No supported key exchange algorithms found");
291	return kex_prop;
292}
293
294