Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2000 Markus Friedl. All rights reserved. |
| 3 | * |
| 4 | * Redistribution and use in source and binary forms, with or without |
| 5 | * modification, are permitted provided that the following conditions |
| 6 | * are met: |
| 7 | * 1. Redistributions of source code must retain the above copyright |
| 8 | * notice, this list of conditions and the following disclaimer. |
| 9 | * 2. Redistributions in binary form must reproduce the above copyright |
| 10 | * notice, this list of conditions and the following disclaimer in the |
| 11 | * documentation and/or other materials provided with the distribution. |
| 12 | * |
| 13 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| 14 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| 15 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| 16 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| 17 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| 18 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 19 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 20 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 21 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| 22 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 23 | */ |
| 24 | |
| 25 | #include "includes.h" |
Damien Miller | 3a961dc | 2003-06-03 10:25:48 +1000 | [diff] [blame] | 26 | RCSID("$OpenBSD: auth2-hostbased.c,v 1.4 2003/06/02 09:17:34 markus Exp $"); |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 27 | |
| 28 | #include "ssh2.h" |
| 29 | #include "xmalloc.h" |
| 30 | #include "packet.h" |
| 31 | #include "buffer.h" |
| 32 | #include "log.h" |
| 33 | #include "servconf.h" |
| 34 | #include "compat.h" |
| 35 | #include "bufaux.h" |
| 36 | #include "auth.h" |
| 37 | #include "key.h" |
| 38 | #include "canohost.h" |
| 39 | #include "monitor_wrap.h" |
| 40 | #include "pathnames.h" |
| 41 | |
| 42 | /* import */ |
| 43 | extern ServerOptions options; |
| 44 | extern u_char *session_id2; |
| 45 | extern int session_id2_len; |
| 46 | |
| 47 | static int |
| 48 | userauth_hostbased(Authctxt *authctxt) |
| 49 | { |
| 50 | Buffer b; |
| 51 | Key *key = NULL; |
| 52 | char *pkalg, *cuser, *chost, *service; |
| 53 | u_char *pkblob, *sig; |
| 54 | u_int alen, blen, slen; |
| 55 | int pktype; |
| 56 | int authenticated = 0; |
| 57 | |
| 58 | if (!authctxt->valid) { |
| 59 | debug2("userauth_hostbased: disabled because of invalid user"); |
| 60 | return 0; |
| 61 | } |
| 62 | pkalg = packet_get_string(&alen); |
| 63 | pkblob = packet_get_string(&blen); |
| 64 | chost = packet_get_string(NULL); |
| 65 | cuser = packet_get_string(NULL); |
| 66 | sig = packet_get_string(&slen); |
| 67 | |
| 68 | debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d", |
| 69 | cuser, chost, pkalg, slen); |
| 70 | #ifdef DEBUG_PK |
| 71 | debug("signature:"); |
| 72 | buffer_init(&b); |
| 73 | buffer_append(&b, sig, slen); |
| 74 | buffer_dump(&b); |
| 75 | buffer_free(&b); |
| 76 | #endif |
| 77 | pktype = key_type_from_name(pkalg); |
| 78 | if (pktype == KEY_UNSPEC) { |
| 79 | /* this is perfectly legal */ |
Damien Miller | 996acd2 | 2003-04-09 20:59:48 +1000 | [diff] [blame] | 80 | logit("userauth_hostbased: unsupported " |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 81 | "public key algorithm: %s", pkalg); |
| 82 | goto done; |
| 83 | } |
| 84 | key = key_from_blob(pkblob, blen); |
| 85 | if (key == NULL) { |
| 86 | error("userauth_hostbased: cannot decode key: %s", pkalg); |
| 87 | goto done; |
| 88 | } |
| 89 | if (key->type != pktype) { |
| 90 | error("userauth_hostbased: type mismatch for decoded key " |
| 91 | "(received %d, expected %d)", key->type, pktype); |
| 92 | goto done; |
| 93 | } |
| 94 | service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" : |
| 95 | authctxt->service; |
| 96 | buffer_init(&b); |
| 97 | buffer_put_string(&b, session_id2, session_id2_len); |
| 98 | /* reconstruct packet */ |
| 99 | buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST); |
| 100 | buffer_put_cstring(&b, authctxt->user); |
| 101 | buffer_put_cstring(&b, service); |
| 102 | buffer_put_cstring(&b, "hostbased"); |
| 103 | buffer_put_string(&b, pkalg, alen); |
| 104 | buffer_put_string(&b, pkblob, blen); |
| 105 | buffer_put_cstring(&b, chost); |
| 106 | buffer_put_cstring(&b, cuser); |
| 107 | #ifdef DEBUG_PK |
| 108 | buffer_dump(&b); |
| 109 | #endif |
| 110 | /* test for allowed key and correct signature */ |
| 111 | authenticated = 0; |
| 112 | if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) && |
| 113 | PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b), |
| 114 | buffer_len(&b))) == 1) |
| 115 | authenticated = 1; |
| 116 | |
| 117 | buffer_clear(&b); |
| 118 | done: |
| 119 | debug2("userauth_hostbased: authenticated %d", authenticated); |
| 120 | if (key != NULL) |
| 121 | key_free(key); |
| 122 | xfree(pkalg); |
| 123 | xfree(pkblob); |
| 124 | xfree(cuser); |
| 125 | xfree(chost); |
| 126 | xfree(sig); |
| 127 | return authenticated; |
| 128 | } |
| 129 | |
| 130 | /* return 1 if given hostkey is allowed */ |
| 131 | int |
| 132 | hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost, |
| 133 | Key *key) |
| 134 | { |
| 135 | const char *resolvedname, *ipaddr, *lookup; |
| 136 | HostStatus host_status; |
| 137 | int len; |
| 138 | |
Damien Miller | 3a961dc | 2003-06-03 10:25:48 +1000 | [diff] [blame] | 139 | resolvedname = get_canonical_hostname(options.use_dns); |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 140 | ipaddr = get_remote_ipaddr(); |
| 141 | |
| 142 | debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s", |
| 143 | chost, resolvedname, ipaddr); |
| 144 | |
| 145 | if (options.hostbased_uses_name_from_packet_only) { |
| 146 | if (auth_rhosts2(pw, cuser, chost, chost) == 0) |
| 147 | return 0; |
| 148 | lookup = chost; |
| 149 | } else { |
| 150 | if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') { |
| 151 | debug2("stripping trailing dot from chost %s", chost); |
| 152 | chost[len - 1] = '\0'; |
| 153 | } |
| 154 | if (strcasecmp(resolvedname, chost) != 0) |
Damien Miller | 996acd2 | 2003-04-09 20:59:48 +1000 | [diff] [blame] | 155 | logit("userauth_hostbased mismatch: " |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 156 | "client sends %s, but we resolve %s to %s", |
| 157 | chost, ipaddr, resolvedname); |
| 158 | if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) |
| 159 | return 0; |
| 160 | lookup = resolvedname; |
| 161 | } |
| 162 | debug2("userauth_hostbased: access allowed by auth_rhosts2"); |
| 163 | |
| 164 | host_status = check_key_in_hostfiles(pw, key, lookup, |
| 165 | _PATH_SSH_SYSTEM_HOSTFILE, |
| 166 | options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE); |
| 167 | |
| 168 | /* backward compat if no key has been found. */ |
| 169 | if (host_status == HOST_NEW) |
| 170 | host_status = check_key_in_hostfiles(pw, key, lookup, |
| 171 | _PATH_SSH_SYSTEM_HOSTFILE2, |
| 172 | options.ignore_user_known_hosts ? NULL : |
| 173 | _PATH_SSH_USER_HOSTFILE2); |
| 174 | |
| 175 | return (host_status == HOST_OK); |
| 176 | } |
| 177 | |
| 178 | Authmethod method_hostbased = { |
| 179 | "hostbased", |
| 180 | userauth_hostbased, |
| 181 | &options.hostbased_authentication |
| 182 | }; |