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openssh/compat.c

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/* $OpenBSD: compat.c,v 1.118 2021/06/06 03:40:39 djm Exp $ */
/*
* Copyright (c) 1999, 2000, 2001, 2002 Markus Friedl. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
#include <sys/types.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include "xmalloc.h"
#include "packet.h"
#include "compat.h"
#include "log.h"
#include "match.h"
#include "kex.h"
/* determine bug flags from SSH protocol banner */
void
compat_banner(struct ssh *ssh, const char *version)
{
int i;
static struct {
char *pat;
int bugs;
} check[] = {
{ "OpenSSH_2.*,"
"OpenSSH_3.0*,"
"OpenSSH_3.1*", SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR|
SSH_BUG_SIGTYPE},
{ "OpenSSH_3.*", SSH_OLD_FORWARD_ADDR|SSH_BUG_SIGTYPE },
{ "Sun_SSH_1.0*", SSH_BUG_NOREKEY|SSH_BUG_EXTEOF|
SSH_BUG_SIGTYPE},
{ "OpenSSH_2*,"
"OpenSSH_3*,"
"OpenSSH_4*", SSH_BUG_SIGTYPE },
{ "OpenSSH_5*", SSH_NEW_OPENSSH|SSH_BUG_DYNAMIC_RPORT|
SSH_BUG_SIGTYPE},
{ "OpenSSH_6.6.1*", SSH_NEW_OPENSSH|SSH_BUG_SIGTYPE},
{ "OpenSSH_6.5*,"
"OpenSSH_6.6*", SSH_NEW_OPENSSH|SSH_BUG_CURVE25519PAD|
SSH_BUG_SIGTYPE},
{ "OpenSSH_7.4*", SSH_NEW_OPENSSH|SSH_BUG_SIGTYPE|
SSH_BUG_SIGTYPE74},
{ "OpenSSH_7.0*,"
"OpenSSH_7.1*,"
"OpenSSH_7.2*,"
"OpenSSH_7.3*,"
"OpenSSH_7.4*,"
"OpenSSH_7.5*,"
"OpenSSH_7.6*,"
"OpenSSH_7.7*", SSH_NEW_OPENSSH|SSH_BUG_SIGTYPE},
{ "OpenSSH*", SSH_NEW_OPENSSH },
{ "*MindTerm*", 0 },
{ "3.0.*", SSH_BUG_DEBUG },
{ "3.0 SecureCRT*", SSH_OLD_SESSIONID },
{ "1.7 SecureFX*", SSH_OLD_SESSIONID },
{ "1.2.18*,"
"1.2.19*,"
"1.2.20*,"
"1.2.21*,"
"1.2.22*", SSH_BUG_IGNOREMSG },
{ "1.3.2*", /* F-Secure */
SSH_BUG_IGNOREMSG },
{ "Cisco-1.*", SSH_BUG_DHGEX_LARGE|
SSH_BUG_HOSTKEYS },
{ "*SSH Compatible Server*", /* Netscreen */
SSH_BUG_PASSWORDPAD },
{ "*OSU_0*,"
"OSU_1.0*,"
"OSU_1.1*,"
"OSU_1.2*,"
"OSU_1.3*,"
"OSU_1.4*,"
"OSU_1.5alpha1*,"
"OSU_1.5alpha2*,"
"OSU_1.5alpha3*", SSH_BUG_PASSWORDPAD },
{ "*SSH_Version_Mapper*",
SSH_BUG_SCANNER },
{ "PuTTY_Local:*," /* dev versions < Sep 2014 */
"PuTTY-Release-0.5*," /* 0.50-0.57, DH-GEX in >=0.52 */
"PuTTY_Release_0.5*," /* 0.58-0.59 */
"PuTTY_Release_0.60*,"
"PuTTY_Release_0.61*,"
"PuTTY_Release_0.62*,"
"PuTTY_Release_0.63*,"
"PuTTY_Release_0.64*",
SSH_OLD_DHGEX },
{ "FuTTY*", SSH_OLD_DHGEX }, /* Putty Fork */
{ "Probe-*",
SSH_BUG_PROBE },
{ "TeraTerm SSH*,"
"TTSSH/1.5.*,"
"TTSSH/2.1*,"
"TTSSH/2.2*,"
"TTSSH/2.3*,"
"TTSSH/2.4*,"
"TTSSH/2.5*,"
"TTSSH/2.6*,"
"TTSSH/2.70*,"
"TTSSH/2.71*,"
"TTSSH/2.72*", SSH_BUG_HOSTKEYS },
{ "WinSCP_release_4*,"
"WinSCP_release_5.0*,"
"WinSCP_release_5.1,"
"WinSCP_release_5.1.*,"
"WinSCP_release_5.5,"
"WinSCP_release_5.5.*,"
"WinSCP_release_5.6,"
"WinSCP_release_5.6.*,"
"WinSCP_release_5.7,"
"WinSCP_release_5.7.1,"
"WinSCP_release_5.7.2,"
"WinSCP_release_5.7.3,"
"WinSCP_release_5.7.4",
SSH_OLD_DHGEX },
{ "ConfD-*",
SSH_BUG_UTF8TTYMODE },
{ "Twisted_*", 0 },
{ "Twisted*", SSH_BUG_DEBUG },
{ NULL, 0 }
};
/* process table, return first match */
ssh->compat = 0;
for (i = 0; check[i].pat; i++) {
if (match_pattern_list(version, check[i].pat, 0) == 1) {
debug_f("match: %s pat %s compat 0x%08x",
version, check[i].pat, check[i].bugs);
ssh->compat = check[i].bugs;
return;
}
}
debug_f("no match: %s", version);
}
char *
compat_cipher_proposal(struct ssh *ssh, char *cipher_prop)
{
if (!(ssh->compat & SSH_BUG_BIGENDIANAES))
return cipher_prop;
debug2_f("original cipher proposal: %s", cipher_prop);
if ((cipher_prop = match_filter_denylist(cipher_prop, "aes*")) == NULL)
fatal("match_filter_denylist failed");
debug2_f("compat cipher proposal: %s", cipher_prop);
if (*cipher_prop == '\0')
fatal("No supported ciphers found");
return cipher_prop;
}
char *
compat_pkalg_proposal(struct ssh *ssh, char *pkalg_prop)
{
if (!(ssh->compat & SSH_BUG_RSASIGMD5))
return pkalg_prop;
debug2_f("original public key proposal: %s", pkalg_prop);
if ((pkalg_prop = match_filter_denylist(pkalg_prop, "ssh-rsa")) == NULL)
fatal("match_filter_denylist failed");
debug2_f("compat public key proposal: %s", pkalg_prop);
if (*pkalg_prop == '\0')
fatal("No supported PK algorithms found");
return pkalg_prop;
}
char *
compat_kex_proposal(struct ssh *ssh, char *p)
{
if ((ssh->compat & (SSH_BUG_CURVE25519PAD|SSH_OLD_DHGEX)) == 0)
return p;
debug2_f("original KEX proposal: %s", p);
if ((ssh->compat & SSH_BUG_CURVE25519PAD) != 0)
if ((p = match_filter_denylist(p,
"curve25519-sha256@libssh.org")) == NULL)
fatal("match_filter_denylist failed");
if ((ssh->compat & SSH_OLD_DHGEX) != 0) {
if ((p = match_filter_denylist(p,
"diffie-hellman-group-exchange-sha256,"
"diffie-hellman-group-exchange-sha1")) == NULL)
fatal("match_filter_denylist failed");
}
debug2_f("compat KEX proposal: %s", p);
if (*p == '\0')
fatal("No supported key exchange algorithms found");
return p;
}
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