xref: /freebsd/crypto/openssh/compat.c (revision a0ee8cc636cd5c2374ec44ca71226564ea0bca95)
1 /* $OpenBSD: compat.c,v 1.85 2014/04/20 02:49:32 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 __RCSID("$FreeBSD$");
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 
42 int compat13 = 0;
43 int compat20 = 0;
44 int datafellows = 0;
45 
46 void
47 enable_compat20(void)
48 {
49 	if (compat20)
50 		return;
51 	debug("Enabling compatibility mode for protocol 2.0");
52 	compat20 = 1;
53 }
54 void
55 enable_compat13(void)
56 {
57 	debug("Enabling compatibility mode for protocol 1.3");
58 	compat13 = 1;
59 }
60 /* datafellows bug compatibility */
61 void
62 compat_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 			return;
182 		}
183 	}
184 	debug("no match: %s", version);
185 }
186 
187 #define	SEP	","
188 int
189 proto_spec(const char *spec)
190 {
191 	char *s, *p, *q;
192 	int ret = SSH_PROTO_UNKNOWN;
193 
194 	if (spec == NULL)
195 		return ret;
196 	q = s = xstrdup(spec);
197 	for ((p = strsep(&q, SEP)); p && *p != '\0'; (p = strsep(&q, SEP))) {
198 		switch (atoi(p)) {
199 		case 1:
200 			if (ret == SSH_PROTO_UNKNOWN)
201 				ret |= SSH_PROTO_1_PREFERRED;
202 			ret |= SSH_PROTO_1;
203 			break;
204 		case 2:
205 			ret |= SSH_PROTO_2;
206 			break;
207 		default:
208 			logit("ignoring bad proto spec: '%s'.", p);
209 			break;
210 		}
211 	}
212 	free(s);
213 	return ret;
214 }
215 
216 /*
217  * Filters a proposal string, excluding any algorithm matching the 'filter'
218  * pattern list.
219  */
220 static char *
221 filter_proposal(char *proposal, const char *filter)
222 {
223 	Buffer b;
224 	char *orig_prop, *fix_prop;
225 	char *cp, *tmp;
226 
227 	buffer_init(&b);
228 	tmp = orig_prop = xstrdup(proposal);
229 	while ((cp = strsep(&tmp, ",")) != NULL) {
230 		if (match_pattern_list(cp, filter, strlen(cp), 0) != 1) {
231 			if (buffer_len(&b) > 0)
232 				buffer_append(&b, ",", 1);
233 			buffer_append(&b, cp, strlen(cp));
234 		} else
235 			debug2("Compat: skipping algorithm \"%s\"", cp);
236 	}
237 	buffer_append(&b, "\0", 1);
238 	fix_prop = xstrdup(buffer_ptr(&b));
239 	buffer_free(&b);
240 	free(orig_prop);
241 
242 	return fix_prop;
243 }
244 
245 char *
246 compat_cipher_proposal(char *cipher_prop)
247 {
248 	if (!(datafellows & SSH_BUG_BIGENDIANAES))
249 		return cipher_prop;
250 	debug2("%s: original cipher proposal: %s", __func__, cipher_prop);
251 	cipher_prop = filter_proposal(cipher_prop, "aes*");
252 	debug2("%s: compat cipher proposal: %s", __func__, cipher_prop);
253 	if (*cipher_prop == '\0')
254 		fatal("No supported ciphers found");
255 	return cipher_prop;
256 }
257 
258 char *
259 compat_pkalg_proposal(char *pkalg_prop)
260 {
261 	if (!(datafellows & SSH_BUG_RSASIGMD5))
262 		return pkalg_prop;
263 	debug2("%s: original public key proposal: %s", __func__, pkalg_prop);
264 	pkalg_prop = filter_proposal(pkalg_prop, "ssh-rsa");
265 	debug2("%s: compat public key proposal: %s", __func__, pkalg_prop);
266 	if (*pkalg_prop == '\0')
267 		fatal("No supported PK algorithms found");
268 	return pkalg_prop;
269 }
270 
271 char *
272 compat_kex_proposal(char *kex_prop)
273 {
274 	if (!(datafellows & SSH_BUG_CURVE25519PAD))
275 		return kex_prop;
276 	debug2("%s: original KEX proposal: %s", __func__, kex_prop);
277 	kex_prop = filter_proposal(kex_prop, "curve25519-sha256@libssh.org");
278 	debug2("%s: compat KEX proposal: %s", __func__, kex_prop);
279 	if (*kex_prop == '\0')
280 		fatal("No supported key exchange algorithms found");
281 	return kex_prop;
282 }
283 
284