compat.c revision 264693 
1/* $OpenBSD: compat.c,v 1.82 2013/12/30 23:52:27 djm Exp $ */
2/* $FreeBSD: stable/9/crypto/openssh/compat.c 264693 2014-04-20 13:12:32Z 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__RCSID("$FreeBSD: stable/9/crypto/openssh/compat.c 264693 2014-04-20 13:12:32Z des $");
29
30#include <sys/types.h>
31
32#include <stdlib.h>
33#include <string.h>
34#include <stdarg.h>
35
36#include "xmalloc.h"
37#include "buffer.h"
38#include "packet.h"
39#include "compat.h"
40#include "log.h"
41#include "match.h"
42
43int compat13 = 0;
44int compat20 = 0;
45int datafellows = 0;
46
47void
48enable_compat20(void)
49{
50	if (compat20)
51		return;
52	debug("Enabling compatibility mode for protocol 2.0");
53	compat20 = 1;
54}
55void
56enable_compat13(void)
57{
58	debug("Enabling compatibility mode for protocol 1.3");
59	compat13 = 1;
60}
61/* datafellows bug compatibility */
62void
63compat_datafellows(const char *version)
64{
65	int i;
66	static struct {
67		char	*pat;
68		int	bugs;
69	} check[] = {
70		{ "OpenSSH-2.0*,"
71		  "OpenSSH-2.1*,"
72		  "OpenSSH_2.1*,"
73		  "OpenSSH_2.2*",	SSH_OLD_SESSIONID|SSH_BUG_BANNER|
74					SSH_OLD_DHGEX|SSH_BUG_NOREKEY|
75					SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR},
76		{ "OpenSSH_2.3.0*",	SSH_BUG_BANNER|SSH_BUG_BIGENDIANAES|
77					SSH_OLD_DHGEX|SSH_BUG_NOREKEY|
78					SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR},
79		{ "OpenSSH_2.3.*",	SSH_BUG_BIGENDIANAES|SSH_OLD_DHGEX|
80					SSH_BUG_NOREKEY|SSH_BUG_EXTEOF|
81					SSH_OLD_FORWARD_ADDR},
82		{ "OpenSSH_2.5.0p1*,"
83		  "OpenSSH_2.5.1p1*",
84					SSH_BUG_BIGENDIANAES|SSH_OLD_DHGEX|
85					SSH_BUG_NOREKEY|SSH_BUG_EXTEOF|
86					SSH_OLD_FORWARD_ADDR},
87		{ "OpenSSH_2.5.0*,"
88		  "OpenSSH_2.5.1*,"
89		  "OpenSSH_2.5.2*",	SSH_OLD_DHGEX|SSH_BUG_NOREKEY|
90					SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR},
91		{ "OpenSSH_2.5.3*",	SSH_BUG_NOREKEY|SSH_BUG_EXTEOF|
92					SSH_OLD_FORWARD_ADDR},
93		{ "OpenSSH_2.*,"
94		  "OpenSSH_3.0*,"
95		  "OpenSSH_3.1*",	SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR},
96		{ "OpenSSH_3.*",	SSH_OLD_FORWARD_ADDR },
97		{ "Sun_SSH_1.0*",	SSH_BUG_NOREKEY|SSH_BUG_EXTEOF},
98		{ "OpenSSH_4*",		0 },
99		{ "OpenSSH_5*",		SSH_NEW_OPENSSH|SSH_BUG_DYNAMIC_RPORT},
100		{ "OpenSSH_6.6.1*",	SSH_NEW_OPENSSH},
101		{ "OpenSSH_6.5*,"
102		  "OpenSSH_6.6*",	SSH_NEW_OPENSSH|SSH_BUG_CURVE25519PAD},
103		{ "OpenSSH*",		SSH_NEW_OPENSSH },
104		{ "*MindTerm*",		0 },
105		{ "2.1.0*",		SSH_BUG_SIGBLOB|SSH_BUG_HMAC|
106					SSH_OLD_SESSIONID|SSH_BUG_DEBUG|
107					SSH_BUG_RSASIGMD5|SSH_BUG_HBSERVICE|
108					SSH_BUG_FIRSTKEX },
109		{ "2.1 *",		SSH_BUG_SIGBLOB|SSH_BUG_HMAC|
110					SSH_OLD_SESSIONID|SSH_BUG_DEBUG|
111					SSH_BUG_RSASIGMD5|SSH_BUG_HBSERVICE|
112					SSH_BUG_FIRSTKEX },
113		{ "2.0.13*,"
114		  "2.0.14*,"
115		  "2.0.15*,"
116		  "2.0.16*,"
117		  "2.0.17*,"
118		  "2.0.18*,"
119		  "2.0.19*",		SSH_BUG_SIGBLOB|SSH_BUG_HMAC|
120					SSH_OLD_SESSIONID|SSH_BUG_DEBUG|
121					SSH_BUG_PKSERVICE|SSH_BUG_X11FWD|
122					SSH_BUG_PKOK|SSH_BUG_RSASIGMD5|
123					SSH_BUG_HBSERVICE|SSH_BUG_OPENFAILURE|
124					SSH_BUG_DUMMYCHAN|SSH_BUG_FIRSTKEX },
125		{ "2.0.11*,"
126		  "2.0.12*",		SSH_BUG_SIGBLOB|SSH_BUG_HMAC|
127					SSH_OLD_SESSIONID|SSH_BUG_DEBUG|
128					SSH_BUG_PKSERVICE|SSH_BUG_X11FWD|
129					SSH_BUG_PKAUTH|SSH_BUG_PKOK|
130					SSH_BUG_RSASIGMD5|SSH_BUG_OPENFAILURE|
131					SSH_BUG_DUMMYCHAN|SSH_BUG_FIRSTKEX },
132		{ "2.0.*",		SSH_BUG_SIGBLOB|SSH_BUG_HMAC|
133					SSH_OLD_SESSIONID|SSH_BUG_DEBUG|
134					SSH_BUG_PKSERVICE|SSH_BUG_X11FWD|
135					SSH_BUG_PKAUTH|SSH_BUG_PKOK|
136					SSH_BUG_RSASIGMD5|SSH_BUG_OPENFAILURE|
137					SSH_BUG_DERIVEKEY|SSH_BUG_DUMMYCHAN|
138					SSH_BUG_FIRSTKEX },
139		{ "2.2.0*,"
140		  "2.3.0*",		SSH_BUG_HMAC|SSH_BUG_DEBUG|
141					SSH_BUG_RSASIGMD5|SSH_BUG_FIRSTKEX },
142		{ "2.3.*",		SSH_BUG_DEBUG|SSH_BUG_RSASIGMD5|
143					SSH_BUG_FIRSTKEX },
144		{ "2.4",		SSH_OLD_SESSIONID },	/* Van Dyke */
145		{ "2.*",		SSH_BUG_DEBUG|SSH_BUG_FIRSTKEX|
146					SSH_BUG_RFWD_ADDR },
147		{ "3.0.*",		SSH_BUG_DEBUG },
148		{ "3.0 SecureCRT*",	SSH_OLD_SESSIONID },
149		{ "1.7 SecureFX*",	SSH_OLD_SESSIONID },
150		{ "1.2.18*,"
151		  "1.2.19*,"
152		  "1.2.20*,"
153		  "1.2.21*,"
154		  "1.2.22*",		SSH_BUG_IGNOREMSG },
155		{ "1.3.2*",		/* F-Secure */
156					SSH_BUG_IGNOREMSG },
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		{ "Probe-*",
171					SSH_BUG_PROBE },
172		{ NULL,			0 }
173	};
174
175	/* process table, return first match */
176	for (i = 0; check[i].pat; i++) {
177		if (match_pattern_list(version, check[i].pat,
178		    strlen(check[i].pat), 0) == 1) {
179			datafellows = check[i].bugs;
180			debug("match: %s pat %s compat 0x%08x",
181			    version, check[i].pat, datafellows);
182			/*
183			 * Check to see if the remote side is OpenSSH and not
184			 * HPN.  It is utterly strange to check it from the
185			 * version string and expose the option that way.
186			 */
187			if (strstr(version,"OpenSSH") != NULL &&
188			    strstr(version,"hpn") == NULL) {
189				datafellows |= SSH_BUG_LARGEWINDOW;
190				debug("Remote is not HPN-aware");
191			}
192			return;
193		}
194	}
195	debug("no match: %s", version);
196}
197
198#define	SEP	","
199int
200proto_spec(const char *spec)
201{
202	char *s, *p, *q;
203	int ret = SSH_PROTO_UNKNOWN;
204
205	if (spec == NULL)
206		return ret;
207	q = s = xstrdup(spec);
208	for ((p = strsep(&q, SEP)); p && *p != '\0'; (p = strsep(&q, SEP))) {
209		switch (atoi(p)) {
210		case 1:
211			if (ret == SSH_PROTO_UNKNOWN)
212				ret |= SSH_PROTO_1_PREFERRED;
213			ret |= SSH_PROTO_1;
214			break;
215		case 2:
216			ret |= SSH_PROTO_2;
217			break;
218		default:
219			logit("ignoring bad proto spec: '%s'.", p);
220			break;
221		}
222	}
223	free(s);
224	return ret;
225}
226
227/*
228 * Filters a proposal string, excluding any algorithm matching the 'filter'
229 * pattern list.
230 */
231static char *
232filter_proposal(char *proposal, const char *filter)
233{
234	Buffer b;
235	char *orig_prop, *fix_prop;
236	char *cp, *tmp;
237
238	buffer_init(&b);
239	tmp = orig_prop = xstrdup(proposal);
240	while ((cp = strsep(&tmp, ",")) != NULL) {
241		if (match_pattern_list(cp, filter, strlen(cp), 0) != 1) {
242			if (buffer_len(&b) > 0)
243				buffer_append(&b, ",", 1);
244			buffer_append(&b, cp, strlen(cp));
245		} else
246			debug2("Compat: skipping algorithm \"%s\"", cp);
247	}
248	buffer_append(&b, "\0", 1);
249	fix_prop = xstrdup(buffer_ptr(&b));
250	buffer_free(&b);
251	free(orig_prop);
252
253	return fix_prop;
254}
255
256char *
257compat_cipher_proposal(char *cipher_prop)
258{
259	if (!(datafellows & SSH_BUG_BIGENDIANAES))
260		return cipher_prop;
261	debug2("%s: original cipher proposal: %s", __func__, cipher_prop);
262	cipher_prop = filter_proposal(cipher_prop, "aes*");
263	debug2("%s: compat cipher proposal: %s", __func__, cipher_prop);
264	if (*cipher_prop == '\0')
265		fatal("No supported ciphers found");
266	return cipher_prop;
267}
268
269char *
270compat_pkalg_proposal(char *pkalg_prop)
271{
272	if (!(datafellows & SSH_BUG_RSASIGMD5))
273		return pkalg_prop;
274	debug2("%s: original public key proposal: %s", __func__, pkalg_prop);
275	pkalg_prop = filter_proposal(pkalg_prop, "ssh-rsa");
276	debug2("%s: compat public key proposal: %s", __func__, pkalg_prop);
277	if (*pkalg_prop == '\0')
278		fatal("No supported PK algorithms found");
279	return pkalg_prop;
280}
281
282char *
283compat_kex_proposal(char *kex_prop)
284{
285	if (!(datafellows & SSH_BUG_CURVE25519PAD))
286		return kex_prop;
287	debug2("%s: original KEX proposal: %s", __func__, kex_prop);
288	kex_prop = filter_proposal(kex_prop, "curve25519-sha256@libssh.org");
289	debug2("%s: compat KEX proposal: %s", __func__, kex_prop);
290	if (*kex_prop == '\0')
291		fatal("No supported key exchange algorithms found");
292	return kex_prop;
293}
294
295