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 <sys/types.h> 27 28 #include <stdlib.h> 29 #include <string.h> 30 #include <stdarg.h> 31 32 #include "xmalloc.h" 33 #include "packet.h" 34 #include "compat.h" 35 #include "log.h" 36 #include "match.h" 37 #include "kex.h" 38 39 /* determine bug flags from SSH protocol banner */ 40 void 41 compat_banner(struct ssh *ssh, const char *version) 42 { 43 int i; 44 static struct { 45 char *pat; 46 int bugs; 47 } check[] = { 48 { "OpenSSH_2.*," 49 "OpenSSH_3.0*," 50 "OpenSSH_3.1*", SSH_BUG_EXTEOF|SSH_OLD_FORWARD_ADDR| 51 SSH_BUG_SIGTYPE}, 52 { "OpenSSH_3.*", SSH_OLD_FORWARD_ADDR|SSH_BUG_SIGTYPE }, 53 { "Sun_SSH_1.0*", SSH_BUG_NOREKEY|SSH_BUG_EXTEOF| 54 SSH_BUG_SIGTYPE}, 55 { "OpenSSH_2*," 56 "OpenSSH_3*," 57 "OpenSSH_4*", SSH_BUG_SIGTYPE }, 58 { "OpenSSH_5*", SSH_NEW_OPENSSH|SSH_BUG_DYNAMIC_RPORT| 59 SSH_BUG_SIGTYPE}, 60 { "OpenSSH_6.6.1*", SSH_NEW_OPENSSH|SSH_BUG_SIGTYPE}, 61 { "OpenSSH_6.5*," 62 "OpenSSH_6.6*", SSH_NEW_OPENSSH|SSH_BUG_CURVE25519PAD| 63 SSH_BUG_SIGTYPE}, 64 { "OpenSSH_7.4*", SSH_NEW_OPENSSH|SSH_BUG_SIGTYPE| 65 SSH_BUG_SIGTYPE74}, 66 { "OpenSSH_7.0*," 67 "OpenSSH_7.1*," 68 "OpenSSH_7.2*," 69 "OpenSSH_7.3*," 70 "OpenSSH_7.5*," 71 "OpenSSH_7.6*," 72 "OpenSSH_7.7*", SSH_NEW_OPENSSH|SSH_BUG_SIGTYPE}, 73 { "OpenSSH*", SSH_NEW_OPENSSH }, 74 { "*MindTerm*", 0 }, 75 { "3.0.*", SSH_BUG_DEBUG }, 76 { "3.0 SecureCRT*", SSH_OLD_SESSIONID }, 77 { "1.7 SecureFX*", SSH_OLD_SESSIONID }, 78 { "1.2.18*," 79 "1.2.19*," 80 "1.2.20*," 81 "1.2.21*," 82 "1.2.22*", SSH_BUG_IGNOREMSG }, 83 { "1.3.2*", /* F-Secure */ 84 SSH_BUG_IGNOREMSG }, 85 { "Cisco-1.*", SSH_BUG_DHGEX_LARGE| 86 SSH_BUG_HOSTKEYS }, 87 { "*SSH Compatible Server*", /* Netscreen */ 88 SSH_BUG_PASSWORDPAD }, 89 { "*OSU_0*," 90 "OSU_1.0*," 91 "OSU_1.1*," 92 "OSU_1.2*," 93 "OSU_1.3*," 94 "OSU_1.4*," 95 "OSU_1.5alpha1*," 96 "OSU_1.5alpha2*," 97 "OSU_1.5alpha3*", SSH_BUG_PASSWORDPAD }, 98 { "*SSH_Version_Mapper*", 99 SSH_BUG_SCANNER }, 100 { "PuTTY_Local:*," /* dev versions < Sep 2014 */ 101 "PuTTY-Release-0.5*," /* 0.50-0.57, DH-GEX in >=0.52 */ 102 "PuTTY_Release_0.5*," /* 0.58-0.59 */ 103 "PuTTY_Release_0.60*," 104 "PuTTY_Release_0.61*," 105 "PuTTY_Release_0.62*," 106 "PuTTY_Release_0.63*," 107 "PuTTY_Release_0.64*", 108 SSH_OLD_DHGEX }, 109 { "FuTTY*", SSH_OLD_DHGEX }, /* Putty Fork */ 110 { "Probe-*", 111 SSH_BUG_PROBE }, 112 { "TeraTerm SSH*," 113 "TTSSH/1.5.*," 114 "TTSSH/2.1*," 115 "TTSSH/2.2*," 116 "TTSSH/2.3*," 117 "TTSSH/2.4*," 118 "TTSSH/2.5*," 119 "TTSSH/2.6*," 120 "TTSSH/2.70*," 121 "TTSSH/2.71*," 122 "TTSSH/2.72*", SSH_BUG_HOSTKEYS }, 123 { "WinSCP_release_4*," 124 "WinSCP_release_5.0*," 125 "WinSCP_release_5.1," 126 "WinSCP_release_5.1.*," 127 "WinSCP_release_5.5," 128 "WinSCP_release_5.5.*," 129 "WinSCP_release_5.6," 130 "WinSCP_release_5.6.*," 131 "WinSCP_release_5.7," 132 "WinSCP_release_5.7.1," 133 "WinSCP_release_5.7.2," 134 "WinSCP_release_5.7.3," 135 "WinSCP_release_5.7.4", 136 SSH_OLD_DHGEX }, 137 { "ConfD-*", 138 SSH_BUG_UTF8TTYMODE }, 139 { "Twisted_*", 0 }, 140 { "Twisted*", SSH_BUG_DEBUG }, 141 { NULL, 0 } 142 }; 143 144 /* process table, return first match */ 145 ssh->compat = 0; 146 for (i = 0; check[i].pat; i++) { 147 if (match_pattern_list(version, check[i].pat, 0) == 1) { 148 debug_f("match: %s pat %s compat 0x%08x", 149 version, check[i].pat, check[i].bugs); 150 ssh->compat = check[i].bugs; 151 return; 152 } 153 } 154 debug_f("no match: %s", version); 155 } 156 157 /* Always returns pointer to allocated memory, caller must free. */ 158 char * 159 compat_cipher_proposal(struct ssh *ssh, char *cipher_prop) 160 { 161 if (!(ssh->compat & SSH_BUG_BIGENDIANAES)) 162 return xstrdup(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 /* Always returns pointer to allocated memory, caller must free. */ 173 char * 174 compat_pkalg_proposal(struct ssh *ssh, char *pkalg_prop) 175 { 176 if (!(ssh->compat & SSH_BUG_RSASIGMD5)) 177 return xstrdup(pkalg_prop); 178 debug2_f("original public key proposal: %s", pkalg_prop); 179 if ((pkalg_prop = match_filter_denylist(pkalg_prop, "ssh-rsa")) == NULL) 180 fatal("match_filter_denylist failed"); 181 debug2_f("compat public key proposal: %s", pkalg_prop); 182 if (*pkalg_prop == '\0') 183 fatal("No supported PK algorithms found"); 184 return pkalg_prop; 185 } 186 187 /* Always returns pointer to allocated memory, caller must free. */ 188 char * 189 compat_kex_proposal(struct ssh *ssh, char *p) 190 { 191 char *cp = NULL; 192 193 if ((ssh->compat & (SSH_BUG_CURVE25519PAD|SSH_OLD_DHGEX)) == 0) 194 return xstrdup(p); 195 debug2_f("original KEX proposal: %s", p); 196 if ((ssh->compat & SSH_BUG_CURVE25519PAD) != 0) 197 if ((p = match_filter_denylist(p, 198 "curve25519-sha256@libssh.org")) == NULL) 199 fatal("match_filter_denylist failed"); 200 if ((ssh->compat & SSH_OLD_DHGEX) != 0) { 201 cp = p; 202 if ((p = match_filter_denylist(p, 203 "diffie-hellman-group-exchange-sha256," 204 "diffie-hellman-group-exchange-sha1")) == NULL) 205 fatal("match_filter_denylist failed"); 206 free(cp); 207 } 208 debug2_f("compat KEX proposal: %s", p); 209 if (*p == '\0') 210 fatal("No supported key exchange algorithms found"); 211 return p; 212 } 213 214