1 /* $OpenBSD: compat.c,v 1.120 2022/07/01 03:35:45 dtucker 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_7.4*", SSH_NEW_OPENSSH|SSH_BUG_SIGTYPE|
67 SSH_BUG_SIGTYPE74},
68 { "OpenSSH_7.0*,"
69 "OpenSSH_7.1*,"
70 "OpenSSH_7.2*,"
71 "OpenSSH_7.3*,"
72 "OpenSSH_7.5*,"
73 "OpenSSH_7.6*,"
74 "OpenSSH_7.7*", SSH_NEW_OPENSSH|SSH_BUG_SIGTYPE},
75 { "OpenSSH*", SSH_NEW_OPENSSH },
76 { "*MindTerm*", 0 },
77 { "3.0.*", SSH_BUG_DEBUG },
78 { "3.0 SecureCRT*", SSH_OLD_SESSIONID },
79 { "1.7 SecureFX*", SSH_OLD_SESSIONID },
80 { "1.2.18*,"
81 "1.2.19*,"
82 "1.2.20*,"
83 "1.2.21*,"
84 "1.2.22*", SSH_BUG_IGNOREMSG },
85 { "1.3.2*", /* F-Secure */
86 SSH_BUG_IGNOREMSG },
87 { "Cisco-1.*", SSH_BUG_DHGEX_LARGE|
88 SSH_BUG_HOSTKEYS },
89 { "*SSH Compatible Server*", /* Netscreen */
90 SSH_BUG_PASSWORDPAD },
91 { "*OSU_0*,"
92 "OSU_1.0*,"
93 "OSU_1.1*,"
94 "OSU_1.2*,"
95 "OSU_1.3*,"
96 "OSU_1.4*,"
97 "OSU_1.5alpha1*,"
98 "OSU_1.5alpha2*,"
99 "OSU_1.5alpha3*", SSH_BUG_PASSWORDPAD },
100 { "*SSH_Version_Mapper*",
101 SSH_BUG_SCANNER },
102 { "PuTTY_Local:*," /* dev versions < Sep 2014 */
103 "PuTTY-Release-0.5*," /* 0.50-0.57, DH-GEX in >=0.52 */
104 "PuTTY_Release_0.5*," /* 0.58-0.59 */
105 "PuTTY_Release_0.60*,"
106 "PuTTY_Release_0.61*,"
107 "PuTTY_Release_0.62*,"
108 "PuTTY_Release_0.63*,"
109 "PuTTY_Release_0.64*",
110 SSH_OLD_DHGEX },
111 { "FuTTY*", SSH_OLD_DHGEX }, /* Putty Fork */
112 { "Probe-*",
113 SSH_BUG_PROBE },
114 { "TeraTerm SSH*,"
115 "TTSSH/1.5.*,"
116 "TTSSH/2.1*,"
117 "TTSSH/2.2*,"
118 "TTSSH/2.3*,"
119 "TTSSH/2.4*,"
120 "TTSSH/2.5*,"
121 "TTSSH/2.6*,"
122 "TTSSH/2.70*,"
123 "TTSSH/2.71*,"
124 "TTSSH/2.72*", SSH_BUG_HOSTKEYS },
125 { "WinSCP_release_4*,"
126 "WinSCP_release_5.0*,"
127 "WinSCP_release_5.1,"
128 "WinSCP_release_5.1.*,"
129 "WinSCP_release_5.5,"
130 "WinSCP_release_5.5.*,"
131 "WinSCP_release_5.6,"
132 "WinSCP_release_5.6.*,"
133 "WinSCP_release_5.7,"
134 "WinSCP_release_5.7.1,"
135 "WinSCP_release_5.7.2,"
136 "WinSCP_release_5.7.3,"
137 "WinSCP_release_5.7.4",
138 SSH_OLD_DHGEX },
139 { "ConfD-*",
140 SSH_BUG_UTF8TTYMODE },
141 { "Twisted_*", 0 },
142 { "Twisted*", SSH_BUG_DEBUG },
143 { NULL, 0 }
144 };
145
146 /* process table, return first match */
147 ssh->compat = 0;
148 for (i = 0; check[i].pat; i++) {
149 if (match_pattern_list(version, check[i].pat, 0) == 1) {
150 debug_f("match: %s pat %s compat 0x%08x",
151 version, check[i].pat, check[i].bugs);
152 ssh->compat = check[i].bugs;
153 return;
154 }
155 }
156 debug_f("no match: %s", version);
157 }
158
159 /* Always returns pointer to allocated memory, caller must free. */
160 char *
compat_cipher_proposal(struct ssh * ssh,char * cipher_prop)161 compat_cipher_proposal(struct ssh *ssh, char *cipher_prop)
162 {
163 if (!(ssh->compat & SSH_BUG_BIGENDIANAES))
164 return xstrdup(cipher_prop);
165 debug2_f("original cipher proposal: %s", cipher_prop);
166 if ((cipher_prop = match_filter_denylist(cipher_prop, "aes*")) == NULL)
167 fatal("match_filter_denylist failed");
168 debug2_f("compat cipher proposal: %s", cipher_prop);
169 if (*cipher_prop == '\0')
170 fatal("No supported ciphers found");
171 return cipher_prop;
172 }
173
174 /* Always returns pointer to allocated memory, caller must free. */
175 char *
compat_pkalg_proposal(struct ssh * ssh,char * pkalg_prop)176 compat_pkalg_proposal(struct ssh *ssh, char *pkalg_prop)
177 {
178 if (!(ssh->compat & SSH_BUG_RSASIGMD5))
179 return xstrdup(pkalg_prop);
180 debug2_f("original public key proposal: %s", pkalg_prop);
181 if ((pkalg_prop = match_filter_denylist(pkalg_prop, "ssh-rsa")) == NULL)
182 fatal("match_filter_denylist failed");
183 debug2_f("compat public key proposal: %s", pkalg_prop);
184 if (*pkalg_prop == '\0')
185 fatal("No supported PK algorithms found");
186 return pkalg_prop;
187 }
188
189 /* Always returns pointer to allocated memory, caller must free. */
190 char *
compat_kex_proposal(struct ssh * ssh,char * p)191 compat_kex_proposal(struct ssh *ssh, char *p)
192 {
193 char *cp = NULL;
194
195 if ((ssh->compat & (SSH_BUG_CURVE25519PAD|SSH_OLD_DHGEX)) == 0)
196 return xstrdup(p);
197 debug2_f("original KEX proposal: %s", p);
198 if ((ssh->compat & SSH_BUG_CURVE25519PAD) != 0)
199 if ((p = match_filter_denylist(p,
200 "curve25519-sha256@libssh.org")) == NULL)
201 fatal("match_filter_denylist failed");
202 if ((ssh->compat & SSH_OLD_DHGEX) != 0) {
203 cp = p;
204 if ((p = match_filter_denylist(p,
205 "diffie-hellman-group-exchange-sha256,"
206 "diffie-hellman-group-exchange-sha1")) == NULL)
207 fatal("match_filter_denylist failed");
208 free(cp);
209 }
210 debug2_f("compat KEX proposal: %s", p);
211 if (*p == '\0')
212 fatal("No supported key exchange algorithms found");
213 return p;
214 }
215
216