Annotation of src/usr.bin/ssh/auth2-hostbased.c, Revision 1.18
1.18 ! millert 1: /* $OpenBSD: auth2-hostbased.c,v 1.17 2013/12/30 23:52:27 djm Exp $ */
1.1 markus 2: /*
3: * Copyright (c) 2000 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:
1.9 stevesk 26:
27: #include <sys/types.h>
28:
29: #include <pwd.h>
1.10 stevesk 30: #include <string.h>
1.11 deraadt 31: #include <stdarg.h>
1.1 markus 32:
1.11 deraadt 33: #include "xmalloc.h"
1.1 markus 34: #include "ssh2.h"
35: #include "packet.h"
36: #include "buffer.h"
37: #include "log.h"
1.18 ! millert 38: #include "misc.h"
1.1 markus 39: #include "servconf.h"
40: #include "compat.h"
1.11 deraadt 41: #include "key.h"
42: #include "hostfile.h"
1.1 markus 43: #include "auth.h"
44: #include "canohost.h"
1.11 deraadt 45: #ifdef GSSAPI
46: #include "ssh-gss.h"
47: #endif
1.1 markus 48: #include "monitor_wrap.h"
49: #include "pathnames.h"
50:
51: /* import */
52: extern ServerOptions options;
53: extern u_char *session_id2;
1.5 markus 54: extern u_int session_id2_len;
1.1 markus 55:
1.2 markus 56: static int
1.1 markus 57: userauth_hostbased(Authctxt *authctxt)
58: {
59: Buffer b;
60: Key *key = NULL;
61: char *pkalg, *cuser, *chost, *service;
62: u_char *pkblob, *sig;
63: u_int alen, blen, slen;
64: int pktype;
65: int authenticated = 0;
66:
67: if (!authctxt->valid) {
68: debug2("userauth_hostbased: disabled because of invalid user");
69: return 0;
70: }
71: pkalg = packet_get_string(&alen);
72: pkblob = packet_get_string(&blen);
73: chost = packet_get_string(NULL);
74: cuser = packet_get_string(NULL);
75: sig = packet_get_string(&slen);
76:
77: debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d",
78: cuser, chost, pkalg, slen);
79: #ifdef DEBUG_PK
80: debug("signature:");
81: buffer_init(&b);
82: buffer_append(&b, sig, slen);
83: buffer_dump(&b);
84: buffer_free(&b);
85: #endif
86: pktype = key_type_from_name(pkalg);
87: if (pktype == KEY_UNSPEC) {
88: /* this is perfectly legal */
1.3 itojun 89: logit("userauth_hostbased: unsupported "
1.1 markus 90: "public key algorithm: %s", pkalg);
91: goto done;
92: }
93: key = key_from_blob(pkblob, blen);
94: if (key == NULL) {
95: error("userauth_hostbased: cannot decode key: %s", pkalg);
96: goto done;
97: }
98: if (key->type != pktype) {
99: error("userauth_hostbased: type mismatch for decoded key "
100: "(received %d, expected %d)", key->type, pktype);
1.17 djm 101: goto done;
102: }
103: if (key_type_plain(key->type) == KEY_RSA &&
104: (datafellows & SSH_BUG_RSASIGMD5) != 0) {
105: error("Refusing RSA key because peer uses unsafe "
106: "signature format");
1.1 markus 107: goto done;
108: }
109: service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
110: authctxt->service;
111: buffer_init(&b);
112: buffer_put_string(&b, session_id2, session_id2_len);
113: /* reconstruct packet */
114: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
115: buffer_put_cstring(&b, authctxt->user);
116: buffer_put_cstring(&b, service);
117: buffer_put_cstring(&b, "hostbased");
118: buffer_put_string(&b, pkalg, alen);
119: buffer_put_string(&b, pkblob, blen);
120: buffer_put_cstring(&b, chost);
121: buffer_put_cstring(&b, cuser);
122: #ifdef DEBUG_PK
123: buffer_dump(&b);
124: #endif
1.16 djm 125:
126: pubkey_auth_info(authctxt, key,
127: "client user \"%.100s\", client host \"%.100s\"", cuser, chost);
128:
1.1 markus 129: /* test for allowed key and correct signature */
130: authenticated = 0;
131: if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&
132: PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
133: buffer_len(&b))) == 1)
134: authenticated = 1;
135:
1.6 markus 136: buffer_free(&b);
1.1 markus 137: done:
138: debug2("userauth_hostbased: authenticated %d", authenticated);
139: if (key != NULL)
140: key_free(key);
1.15 djm 141: free(pkalg);
142: free(pkblob);
143: free(cuser);
144: free(chost);
145: free(sig);
1.1 markus 146: return authenticated;
147: }
148:
149: /* return 1 if given hostkey is allowed */
150: int
151: hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
152: Key *key)
153: {
1.14 djm 154: const char *resolvedname, *ipaddr, *lookup, *reason;
1.1 markus 155: HostStatus host_status;
156: int len;
1.14 djm 157: char *fp;
1.13 djm 158:
159: if (auth_key_is_revoked(key))
160: return 0;
1.1 markus 161:
1.4 markus 162: resolvedname = get_canonical_hostname(options.use_dns);
1.1 markus 163: ipaddr = get_remote_ipaddr();
164:
165: debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s",
166: chost, resolvedname, ipaddr);
167:
1.12 djm 168: if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
169: debug2("stripping trailing dot from chost %s", chost);
170: chost[len - 1] = '\0';
171: }
172:
1.1 markus 173: if (options.hostbased_uses_name_from_packet_only) {
174: if (auth_rhosts2(pw, cuser, chost, chost) == 0)
175: return 0;
176: lookup = chost;
177: } else {
178: if (strcasecmp(resolvedname, chost) != 0)
1.3 itojun 179: logit("userauth_hostbased mismatch: "
1.1 markus 180: "client sends %s, but we resolve %s to %s",
181: chost, ipaddr, resolvedname);
182: if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0)
183: return 0;
184: lookup = resolvedname;
185: }
186: debug2("userauth_hostbased: access allowed by auth_rhosts2");
187:
1.14 djm 188: if (key_is_cert(key) &&
189: key_cert_check_authority(key, 1, 0, lookup, &reason)) {
190: error("%s", reason);
191: auth_debug_add("%s", reason);
192: return 0;
193: }
194:
1.1 markus 195: host_status = check_key_in_hostfiles(pw, key, lookup,
196: _PATH_SSH_SYSTEM_HOSTFILE,
197: options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
198:
199: /* backward compat if no key has been found. */
1.14 djm 200: if (host_status == HOST_NEW) {
1.1 markus 201: host_status = check_key_in_hostfiles(pw, key, lookup,
202: _PATH_SSH_SYSTEM_HOSTFILE2,
203: options.ignore_user_known_hosts ? NULL :
204: _PATH_SSH_USER_HOSTFILE2);
1.14 djm 205: }
206:
207: if (host_status == HOST_OK) {
208: if (key_is_cert(key)) {
209: fp = key_fingerprint(key->cert->signature_key,
210: SSH_FP_MD5, SSH_FP_HEX);
211: verbose("Accepted certificate ID \"%s\" signed by "
212: "%s CA %s from %s@%s", key->cert->key_id,
213: key_type(key->cert->signature_key), fp,
214: cuser, lookup);
215: } else {
216: fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
217: verbose("Accepted %s public key %s from %s@%s",
218: key_type(key), fp, cuser, lookup);
219: }
1.15 djm 220: free(fp);
1.14 djm 221: }
1.1 markus 222:
223: return (host_status == HOST_OK);
224: }
1.2 markus 225:
226: Authmethod method_hostbased = {
227: "hostbased",
228: userauth_hostbased,
229: &options.hostbased_authentication
230: };
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