Annotation of src/usr.bin/ssh/auth2-hostbased.c, Revision 1.17
1.17 ! djm 1: /* $OpenBSD: auth2-hostbased.c,v 1.16 2013/06/21 00:34:49 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"
38: #include "servconf.h"
39: #include "compat.h"
1.11 deraadt 40: #include "key.h"
41: #include "hostfile.h"
1.1 markus 42: #include "auth.h"
43: #include "canohost.h"
1.11 deraadt 44: #ifdef GSSAPI
45: #include "ssh-gss.h"
46: #endif
1.1 markus 47: #include "monitor_wrap.h"
48: #include "pathnames.h"
49:
50: /* import */
51: extern ServerOptions options;
52: extern u_char *session_id2;
1.5 markus 53: extern u_int session_id2_len;
1.1 markus 54:
1.2 markus 55: static int
1.1 markus 56: userauth_hostbased(Authctxt *authctxt)
57: {
58: Buffer b;
59: Key *key = NULL;
60: char *pkalg, *cuser, *chost, *service;
61: u_char *pkblob, *sig;
62: u_int alen, blen, slen;
63: int pktype;
64: int authenticated = 0;
65:
66: if (!authctxt->valid) {
67: debug2("userauth_hostbased: disabled because of invalid user");
68: return 0;
69: }
70: pkalg = packet_get_string(&alen);
71: pkblob = packet_get_string(&blen);
72: chost = packet_get_string(NULL);
73: cuser = packet_get_string(NULL);
74: sig = packet_get_string(&slen);
75:
76: debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d",
77: cuser, chost, pkalg, slen);
78: #ifdef DEBUG_PK
79: debug("signature:");
80: buffer_init(&b);
81: buffer_append(&b, sig, slen);
82: buffer_dump(&b);
83: buffer_free(&b);
84: #endif
85: pktype = key_type_from_name(pkalg);
86: if (pktype == KEY_UNSPEC) {
87: /* this is perfectly legal */
1.3 itojun 88: logit("userauth_hostbased: unsupported "
1.1 markus 89: "public key algorithm: %s", pkalg);
90: goto done;
91: }
92: key = key_from_blob(pkblob, blen);
93: if (key == NULL) {
94: error("userauth_hostbased: cannot decode key: %s", pkalg);
95: goto done;
96: }
97: if (key->type != pktype) {
98: error("userauth_hostbased: type mismatch for decoded key "
99: "(received %d, expected %d)", key->type, pktype);
1.17 ! djm 100: goto done;
! 101: }
! 102: if (key_type_plain(key->type) == KEY_RSA &&
! 103: (datafellows & SSH_BUG_RSASIGMD5) != 0) {
! 104: error("Refusing RSA key because peer uses unsafe "
! 105: "signature format");
1.1 markus 106: goto done;
107: }
108: service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
109: authctxt->service;
110: buffer_init(&b);
111: buffer_put_string(&b, session_id2, session_id2_len);
112: /* reconstruct packet */
113: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
114: buffer_put_cstring(&b, authctxt->user);
115: buffer_put_cstring(&b, service);
116: buffer_put_cstring(&b, "hostbased");
117: buffer_put_string(&b, pkalg, alen);
118: buffer_put_string(&b, pkblob, blen);
119: buffer_put_cstring(&b, chost);
120: buffer_put_cstring(&b, cuser);
121: #ifdef DEBUG_PK
122: buffer_dump(&b);
123: #endif
1.16 djm 124:
125: pubkey_auth_info(authctxt, key,
126: "client user \"%.100s\", client host \"%.100s\"", cuser, chost);
127:
1.1 markus 128: /* test for allowed key and correct signature */
129: authenticated = 0;
130: if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&
131: PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
132: buffer_len(&b))) == 1)
133: authenticated = 1;
134:
1.6 markus 135: buffer_free(&b);
1.1 markus 136: done:
137: debug2("userauth_hostbased: authenticated %d", authenticated);
138: if (key != NULL)
139: key_free(key);
1.15 djm 140: free(pkalg);
141: free(pkblob);
142: free(cuser);
143: free(chost);
144: free(sig);
1.1 markus 145: return authenticated;
146: }
147:
148: /* return 1 if given hostkey is allowed */
149: int
150: hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
151: Key *key)
152: {
1.14 djm 153: const char *resolvedname, *ipaddr, *lookup, *reason;
1.1 markus 154: HostStatus host_status;
155: int len;
1.14 djm 156: char *fp;
1.13 djm 157:
158: if (auth_key_is_revoked(key))
159: return 0;
1.1 markus 160:
1.4 markus 161: resolvedname = get_canonical_hostname(options.use_dns);
1.1 markus 162: ipaddr = get_remote_ipaddr();
163:
164: debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s",
165: chost, resolvedname, ipaddr);
166:
1.12 djm 167: if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
168: debug2("stripping trailing dot from chost %s", chost);
169: chost[len - 1] = '\0';
170: }
171:
1.1 markus 172: if (options.hostbased_uses_name_from_packet_only) {
173: if (auth_rhosts2(pw, cuser, chost, chost) == 0)
174: return 0;
175: lookup = chost;
176: } else {
177: if (strcasecmp(resolvedname, chost) != 0)
1.3 itojun 178: logit("userauth_hostbased mismatch: "
1.1 markus 179: "client sends %s, but we resolve %s to %s",
180: chost, ipaddr, resolvedname);
181: if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0)
182: return 0;
183: lookup = resolvedname;
184: }
185: debug2("userauth_hostbased: access allowed by auth_rhosts2");
186:
1.14 djm 187: if (key_is_cert(key) &&
188: key_cert_check_authority(key, 1, 0, lookup, &reason)) {
189: error("%s", reason);
190: auth_debug_add("%s", reason);
191: return 0;
192: }
193:
1.1 markus 194: host_status = check_key_in_hostfiles(pw, key, lookup,
195: _PATH_SSH_SYSTEM_HOSTFILE,
196: options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
197:
198: /* backward compat if no key has been found. */
1.14 djm 199: if (host_status == HOST_NEW) {
1.1 markus 200: host_status = check_key_in_hostfiles(pw, key, lookup,
201: _PATH_SSH_SYSTEM_HOSTFILE2,
202: options.ignore_user_known_hosts ? NULL :
203: _PATH_SSH_USER_HOSTFILE2);
1.14 djm 204: }
205:
206: if (host_status == HOST_OK) {
207: if (key_is_cert(key)) {
208: fp = key_fingerprint(key->cert->signature_key,
209: SSH_FP_MD5, SSH_FP_HEX);
210: verbose("Accepted certificate ID \"%s\" signed by "
211: "%s CA %s from %s@%s", key->cert->key_id,
212: key_type(key->cert->signature_key), fp,
213: cuser, lookup);
214: } else {
215: fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
216: verbose("Accepted %s public key %s from %s@%s",
217: key_type(key), fp, cuser, lookup);
218: }
1.15 djm 219: free(fp);
1.14 djm 220: }
1.1 markus 221:
222: return (host_status == HOST_OK);
223: }
1.2 markus 224:
225: Authmethod method_hostbased = {
226: "hostbased",
227: userauth_hostbased,
228: &options.hostbased_authentication
229: };
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