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f5799ae1 | 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" | |
cdd66111 | 26 | RCSID("$OpenBSD: auth2-hostbased.c,v 1.6 2004/01/19 21:25:15 markus Exp $"); |
f5799ae1 | 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; | |
0fff78ff | 45 | extern u_int session_id2_len; |
f5799ae1 | 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 */ | |
0fff78ff | 80 | logit("userauth_hostbased: unsupported " |
f5799ae1 | 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 | ||
cdd66111 | 117 | buffer_free(&b); |
f5799ae1 | 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 | ||
0fff78ff | 139 | resolvedname = get_canonical_hostname(options.use_dns); |
f5799ae1 | 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) | |
0fff78ff | 155 | logit("userauth_hostbased mismatch: " |
f5799ae1 | 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 | }; |