1/*	$NetBSD: compat.c,v 1.26 2023/07/26 17:58:15 christos Exp $	*/
2/* $OpenBSD: compat.c,v 1.126 2023/03/06 12:14:48 dtucker Exp $ */
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("$NetBSD: compat.c,v 1.26 2023/07/26 17:58:15 christos Exp $");
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 "packet.h"
37#include "compat.h"
38#include "log.h"
39#include "match.h"
40
41/* determine bug flags from SSH protocol banner */
42void
43compat_banner(struct ssh *ssh, const char *version)
44{
45	int i;
46	static struct {
47		const 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		{ "Cisco-1.*",		SSH_BUG_DHGEX_LARGE|
81					SSH_BUG_HOSTKEYS },
82		{ "*SSH_Version_Mapper*",
83					SSH_BUG_SCANNER },
84		{ "PuTTY_Local:*,"	/* dev versions < Sep 2014 */
85		  "PuTTY-Release-0.5*," /* 0.50-0.57, DH-GEX in >=0.52 */
86		  "PuTTY_Release_0.5*,"	/* 0.58-0.59 */
87		  "PuTTY_Release_0.60*,"
88		  "PuTTY_Release_0.61*,"
89		  "PuTTY_Release_0.62*,"
90		  "PuTTY_Release_0.63*,"
91		  "PuTTY_Release_0.64*",
92					SSH_OLD_DHGEX },
93		{ "FuTTY*",		SSH_OLD_DHGEX }, /* Putty Fork */
94		{ "Probe-*",
95					SSH_BUG_PROBE },
96		{ "TeraTerm SSH*,"
97		  "TTSSH/1.5.*,"
98		  "TTSSH/2.1*,"
99		  "TTSSH/2.2*,"
100		  "TTSSH/2.3*,"
101		  "TTSSH/2.4*,"
102		  "TTSSH/2.5*,"
103		  "TTSSH/2.6*,"
104		  "TTSSH/2.70*,"
105		  "TTSSH/2.71*,"
106		  "TTSSH/2.72*",	SSH_BUG_HOSTKEYS },
107		{ "WinSCP_release_4*,"
108		  "WinSCP_release_5.0*,"
109		  "WinSCP_release_5.1,"
110		  "WinSCP_release_5.1.*,"
111		  "WinSCP_release_5.5,"
112		  "WinSCP_release_5.5.*,"
113		  "WinSCP_release_5.6,"
114		  "WinSCP_release_5.6.*,"
115		  "WinSCP_release_5.7,"
116		  "WinSCP_release_5.7.1,"
117		  "WinSCP_release_5.7.2,"
118		  "WinSCP_release_5.7.3,"
119		  "WinSCP_release_5.7.4",
120					SSH_OLD_DHGEX },
121		{ "ConfD-*",
122					SSH_BUG_UTF8TTYMODE },
123		{ "Twisted_*",		0 },
124		{ "Twisted*",		SSH_BUG_DEBUG },
125		{ NULL,			0 }
126	};
127
128	/* process table, return first match */
129	ssh->compat = 0;
130	for (i = 0; check[i].pat; i++) {
131		if (match_pattern_list(version, check[i].pat, 0) == 1) {
132			debug_f("match: %s pat %s compat 0x%08x",
133			    version, check[i].pat, check[i].bugs);
134			ssh->compat = check[i].bugs;
135			return;
136		}
137	}
138	debug_f("no match: %s", version);
139}
140
141/* Always returns pointer to allocated memory, caller must free. */
142char *
143compat_kex_proposal(struct ssh *ssh, const char *p)
144{
145	char *cp = NULL, *cp2 = NULL;
146
147	if ((ssh->compat & (SSH_BUG_CURVE25519PAD|SSH_OLD_DHGEX)) == 0)
148		return xstrdup(p);
149	debug2_f("original KEX proposal: %s", p);
150	if ((ssh->compat & SSH_BUG_CURVE25519PAD) != 0)
151		if ((cp = match_filter_denylist(p,
152		    "curve25519-sha256@libssh.org")) == NULL)
153			fatal("match_filter_denylist failed");
154	if ((ssh->compat & SSH_OLD_DHGEX) != 0) {
155		if ((cp2 = match_filter_denylist(cp ? cp : p,
156		    "diffie-hellman-group-exchange-sha256,"
157		    "diffie-hellman-group-exchange-sha1")) == NULL)
158			fatal("match_filter_denylist failed");
159		free(cp);
160		cp = cp2;
161	}
162	if (cp == NULL || *cp == '\0')
163		fatal("No supported key exchange algorithms found");
164	debug2_f("compat KEX proposal: %s", cp);
165	return cp;
166}
167
168