1/* $OpenBSD: compat.c,v 1.126 2023/03/06 12:14:48 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
40/* determine bug flags from SSH protocol banner */
41void
42compat_banner(struct ssh *ssh, const char *version)
43{
44	int i;
45	static struct {
46		char	*pat;
47		int	bugs;
48	} check[] = {
49		{ "OpenSSH_2.*,"
50		  "OpenSSH_3.0*,"
51		  "OpenSSH_3.1*",	SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR|
52					SSH_BUG_SIGTYPE},
53		{ "OpenSSH_3.*",	SSH_OLD_FORWARD_ADDR|SSH_BUG_SIGTYPE },
54		{ "Sun_SSH_1.0*",	SSH_BUG_NOREKEY|SSH_BUG_EXTEOF|
55					SSH_BUG_SIGTYPE},
56		{ "OpenSSH_2*,"
57		  "OpenSSH_3*,"
58		  "OpenSSH_4*",		SSH_BUG_SIGTYPE },
59		{ "OpenSSH_5*",		SSH_NEW_OPENSSH|SSH_BUG_DYNAMIC_RPORT|
60					SSH_BUG_SIGTYPE},
61		{ "OpenSSH_6.6.1*",	SSH_NEW_OPENSSH|SSH_BUG_SIGTYPE},
62		{ "OpenSSH_6.5*,"
63		  "OpenSSH_6.6*",	SSH_NEW_OPENSSH|SSH_BUG_CURVE25519PAD|
64					SSH_BUG_SIGTYPE},
65		{ "OpenSSH_7.4*",	SSH_NEW_OPENSSH|SSH_BUG_SIGTYPE|
66					SSH_BUG_SIGTYPE74},
67		{ "OpenSSH_7.0*,"
68		  "OpenSSH_7.1*,"
69		  "OpenSSH_7.2*,"
70		  "OpenSSH_7.3*,"
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		{ "Cisco-1.*",		SSH_BUG_DHGEX_LARGE|
80					SSH_BUG_HOSTKEYS },
81		{ "*SSH_Version_Mapper*",
82					SSH_BUG_SCANNER },
83		{ "PuTTY_Local:*,"	/* dev versions < Sep 2014 */
84		  "PuTTY-Release-0.5*," /* 0.50-0.57, DH-GEX in >=0.52 */
85		  "PuTTY_Release_0.5*,"	/* 0.58-0.59 */
86		  "PuTTY_Release_0.60*,"
87		  "PuTTY_Release_0.61*,"
88		  "PuTTY_Release_0.62*,"
89		  "PuTTY_Release_0.63*,"
90		  "PuTTY_Release_0.64*",
91					SSH_OLD_DHGEX },
92		{ "FuTTY*",		SSH_OLD_DHGEX }, /* Putty Fork */
93		{ "Probe-*",
94					SSH_BUG_PROBE },
95		{ "TeraTerm SSH*,"
96		  "TTSSH/1.5.*,"
97		  "TTSSH/2.1*,"
98		  "TTSSH/2.2*,"
99		  "TTSSH/2.3*,"
100		  "TTSSH/2.4*,"
101		  "TTSSH/2.5*,"
102		  "TTSSH/2.6*,"
103		  "TTSSH/2.70*,"
104		  "TTSSH/2.71*,"
105		  "TTSSH/2.72*",	SSH_BUG_HOSTKEYS },
106		{ "WinSCP_release_4*,"
107		  "WinSCP_release_5.0*,"
108		  "WinSCP_release_5.1,"
109		  "WinSCP_release_5.1.*,"
110		  "WinSCP_release_5.5,"
111		  "WinSCP_release_5.5.*,"
112		  "WinSCP_release_5.6,"
113		  "WinSCP_release_5.6.*,"
114		  "WinSCP_release_5.7,"
115		  "WinSCP_release_5.7.1,"
116		  "WinSCP_release_5.7.2,"
117		  "WinSCP_release_5.7.3,"
118		  "WinSCP_release_5.7.4",
119					SSH_OLD_DHGEX },
120		{ "ConfD-*",
121					SSH_BUG_UTF8TTYMODE },
122		{ "Twisted_*",		0 },
123		{ "Twisted*",		SSH_BUG_DEBUG },
124		{ NULL,			0 }
125	};
126
127	/* process table, return first match */
128	ssh->compat = 0;
129	for (i = 0; check[i].pat; i++) {
130		if (match_pattern_list(version, check[i].pat, 0) == 1) {
131			debug_f("match: %s pat %s compat 0x%08x",
132			    version, check[i].pat, check[i].bugs);
133			ssh->compat = check[i].bugs;
134			return;
135		}
136	}
137	debug_f("no match: %s", version);
138}
139
140/* Always returns pointer to allocated memory, caller must free. */
141char *
142compat_kex_proposal(struct ssh *ssh, const char *p)
143{
144	char *cp = NULL, *cp2 = NULL;
145
146	if ((ssh->compat & (SSH_BUG_CURVE25519PAD|SSH_OLD_DHGEX)) == 0)
147		return xstrdup(p);
148	debug2_f("original KEX proposal: %s", p);
149	if ((ssh->compat & SSH_BUG_CURVE25519PAD) != 0)
150		if ((cp = match_filter_denylist(p,
151		    "curve25519-sha256@libssh.org")) == NULL)
152			fatal("match_filter_denylist failed");
153	if ((ssh->compat & SSH_OLD_DHGEX) != 0) {
154		if ((cp2 = match_filter_denylist(cp ? cp : p,
155		    "diffie-hellman-group-exchange-sha256,"
156		    "diffie-hellman-group-exchange-sha1")) == NULL)
157			fatal("match_filter_denylist failed");
158		free(cp);
159		cp = cp2;
160	}
161	if (cp == NULL || *cp == '\0')
162		fatal("No supported key exchange algorithms found");
163	debug2_f("compat KEX proposal: %s", cp);
164	return cp;
165}
166
167