xref: /openssh-portable/compat.c (revision 4ca6a1fa)
1 /* $OpenBSD: compat.c,v 1.117 2021/01/27 09:26:54 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 "packet.h"
36 #include "compat.h"
37 #include "log.h"
38 #include "match.h"
39 #include "kex.h"
40 
41 /* determine bug flags from SSH protocol banner */
42 void
compat_banner(struct ssh * ssh,const char * version)43 compat_banner(struct ssh *ssh, const char *version)
44 {
45 	int i;
46 	static struct {
47 		char	*pat;
48 		int	bugs;
49 	} check[] = {
50 		{ "OpenSSH_2.*,"
51 		  "OpenSSH_3.0*,"
52 		  "OpenSSH_3.1*",	SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR|
53 					SSH_BUG_SIGTYPE},
54 		{ "OpenSSH_3.*",	SSH_OLD_FORWARD_ADDR|SSH_BUG_SIGTYPE },
55 		{ "Sun_SSH_1.0*",	SSH_BUG_NOREKEY|SSH_BUG_EXTEOF|
56 					SSH_BUG_SIGTYPE},
57 		{ "OpenSSH_2*,"
58 		  "OpenSSH_3*,"
59 		  "OpenSSH_4*",		SSH_BUG_SIGTYPE },
60 		{ "OpenSSH_5*",		SSH_NEW_OPENSSH|SSH_BUG_DYNAMIC_RPORT|
61 					SSH_BUG_SIGTYPE},
62 		{ "OpenSSH_6.6.1*",	SSH_NEW_OPENSSH|SSH_BUG_SIGTYPE},
63 		{ "OpenSSH_6.5*,"
64 		  "OpenSSH_6.6*",	SSH_NEW_OPENSSH|SSH_BUG_CURVE25519PAD|
65 					SSH_BUG_SIGTYPE},
66 		{ "OpenSSH_7.0*,"
67 		  "OpenSSH_7.1*,"
68 		  "OpenSSH_7.2*,"
69 		  "OpenSSH_7.3*,"
70 		  "OpenSSH_7.4*,"
71 		  "OpenSSH_7.5*,"
72 		  "OpenSSH_7.6*,"
73 		  "OpenSSH_7.7*",	SSH_NEW_OPENSSH|SSH_BUG_SIGTYPE},
74 		{ "OpenSSH*",		SSH_NEW_OPENSSH },
75 		{ "*MindTerm*",		0 },
76 		{ "3.0.*",		SSH_BUG_DEBUG },
77 		{ "3.0 SecureCRT*",	SSH_OLD_SESSIONID },
78 		{ "1.7 SecureFX*",	SSH_OLD_SESSIONID },
79 		{ "1.2.18*,"
80 		  "1.2.19*,"
81 		  "1.2.20*,"
82 		  "1.2.21*,"
83 		  "1.2.22*",		SSH_BUG_IGNOREMSG },
84 		{ "1.3.2*",		/* F-Secure */
85 					SSH_BUG_IGNOREMSG },
86 		{ "Cisco-1.*",		SSH_BUG_DHGEX_LARGE|
87 					SSH_BUG_HOSTKEYS },
88 		{ "*SSH Compatible Server*",			/* Netscreen */
89 					SSH_BUG_PASSWORDPAD },
90 		{ "*OSU_0*,"
91 		  "OSU_1.0*,"
92 		  "OSU_1.1*,"
93 		  "OSU_1.2*,"
94 		  "OSU_1.3*,"
95 		  "OSU_1.4*,"
96 		  "OSU_1.5alpha1*,"
97 		  "OSU_1.5alpha2*,"
98 		  "OSU_1.5alpha3*",	SSH_BUG_PASSWORDPAD },
99 		{ "*SSH_Version_Mapper*",
100 					SSH_BUG_SCANNER },
101 		{ "PuTTY_Local:*,"	/* dev versions < Sep 2014 */
102 		  "PuTTY-Release-0.5*," /* 0.50-0.57, DH-GEX in >=0.52 */
103 		  "PuTTY_Release_0.5*,"	/* 0.58-0.59 */
104 		  "PuTTY_Release_0.60*,"
105 		  "PuTTY_Release_0.61*,"
106 		  "PuTTY_Release_0.62*,"
107 		  "PuTTY_Release_0.63*,"
108 		  "PuTTY_Release_0.64*",
109 					SSH_OLD_DHGEX },
110 		{ "FuTTY*",		SSH_OLD_DHGEX }, /* Putty Fork */
111 		{ "Probe-*",
112 					SSH_BUG_PROBE },
113 		{ "TeraTerm SSH*,"
114 		  "TTSSH/1.5.*,"
115 		  "TTSSH/2.1*,"
116 		  "TTSSH/2.2*,"
117 		  "TTSSH/2.3*,"
118 		  "TTSSH/2.4*,"
119 		  "TTSSH/2.5*,"
120 		  "TTSSH/2.6*,"
121 		  "TTSSH/2.70*,"
122 		  "TTSSH/2.71*,"
123 		  "TTSSH/2.72*",	SSH_BUG_HOSTKEYS },
124 		{ "WinSCP_release_4*,"
125 		  "WinSCP_release_5.0*,"
126 		  "WinSCP_release_5.1,"
127 		  "WinSCP_release_5.1.*,"
128 		  "WinSCP_release_5.5,"
129 		  "WinSCP_release_5.5.*,"
130 		  "WinSCP_release_5.6,"
131 		  "WinSCP_release_5.6.*,"
132 		  "WinSCP_release_5.7,"
133 		  "WinSCP_release_5.7.1,"
134 		  "WinSCP_release_5.7.2,"
135 		  "WinSCP_release_5.7.3,"
136 		  "WinSCP_release_5.7.4",
137 					SSH_OLD_DHGEX },
138 		{ "ConfD-*",
139 					SSH_BUG_UTF8TTYMODE },
140 		{ "Twisted_*",		0 },
141 		{ "Twisted*",		SSH_BUG_DEBUG },
142 		{ NULL,			0 }
143 	};
144 
145 	/* process table, return first match */
146 	ssh->compat = 0;
147 	for (i = 0; check[i].pat; i++) {
148 		if (match_pattern_list(version, check[i].pat, 0) == 1) {
149 			debug_f("match: %s pat %s compat 0x%08x",
150 			    version, check[i].pat, check[i].bugs);
151 			ssh->compat = check[i].bugs;
152 			return;
153 		}
154 	}
155 	debug_f("no match: %s", version);
156 }
157 
158 char *
compat_cipher_proposal(struct ssh * ssh,char * cipher_prop)159 compat_cipher_proposal(struct ssh *ssh, char *cipher_prop)
160 {
161 	if (!(ssh->compat & SSH_BUG_BIGENDIANAES))
162 		return cipher_prop;
163 	debug2_f("original cipher proposal: %s", cipher_prop);
164 	if ((cipher_prop = match_filter_denylist(cipher_prop, "aes*")) == NULL)
165 		fatal("match_filter_denylist failed");
166 	debug2_f("compat cipher proposal: %s", cipher_prop);
167 	if (*cipher_prop == '\0')
168 		fatal("No supported ciphers found");
169 	return cipher_prop;
170 }
171 
172 char *
compat_pkalg_proposal(struct ssh * ssh,char * pkalg_prop)173 compat_pkalg_proposal(struct ssh *ssh, char *pkalg_prop)
174 {
175 	if (!(ssh->compat & SSH_BUG_RSASIGMD5))
176 		return pkalg_prop;
177 	debug2_f("original public key proposal: %s", pkalg_prop);
178 	if ((pkalg_prop = match_filter_denylist(pkalg_prop, "ssh-rsa")) == NULL)
179 		fatal("match_filter_denylist failed");
180 	debug2_f("compat public key proposal: %s", pkalg_prop);
181 	if (*pkalg_prop == '\0')
182 		fatal("No supported PK algorithms found");
183 	return pkalg_prop;
184 }
185 
186 char *
compat_kex_proposal(struct ssh * ssh,char * p)187 compat_kex_proposal(struct ssh *ssh, char *p)
188 {
189 	if ((ssh->compat & (SSH_BUG_CURVE25519PAD|SSH_OLD_DHGEX)) == 0)
190 		return p;
191 	debug2_f("original KEX proposal: %s", p);
192 	if ((ssh->compat & SSH_BUG_CURVE25519PAD) != 0)
193 		if ((p = match_filter_denylist(p,
194 		    "curve25519-sha256@libssh.org")) == NULL)
195 			fatal("match_filter_denylist failed");
196 	if ((ssh->compat & SSH_OLD_DHGEX) != 0) {
197 		if ((p = match_filter_denylist(p,
198 		    "diffie-hellman-group-exchange-sha256,"
199 		    "diffie-hellman-group-exchange-sha1")) == NULL)
200 			fatal("match_filter_denylist failed");
201 	}
202 	debug2_f("compat KEX proposal: %s", p);
203 	if (*p == '\0')
204 		fatal("No supported key exchange algorithms found");
205 	return p;
206 }
207 
208