Annotation of src/usr.bin/ssh/auth2-hostbased.c, Revision 1.21
1.21 ! djm 1: /* $OpenBSD: auth2-hostbased.c,v 1.20 2014/12/23 22:42:48 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
1.21 ! djm 86: /* XXX provide some way to allow admin to specify key types accepted */
1.1 markus 87: pktype = key_type_from_name(pkalg);
88: if (pktype == KEY_UNSPEC) {
89: /* this is perfectly legal */
1.3 itojun 90: logit("userauth_hostbased: unsupported "
1.1 markus 91: "public key algorithm: %s", pkalg);
92: goto done;
93: }
94: key = key_from_blob(pkblob, blen);
95: if (key == NULL) {
96: error("userauth_hostbased: cannot decode key: %s", pkalg);
97: goto done;
98: }
99: if (key->type != pktype) {
100: error("userauth_hostbased: type mismatch for decoded key "
101: "(received %d, expected %d)", key->type, pktype);
1.17 djm 102: goto done;
103: }
104: if (key_type_plain(key->type) == KEY_RSA &&
105: (datafellows & SSH_BUG_RSASIGMD5) != 0) {
106: error("Refusing RSA key because peer uses unsafe "
107: "signature format");
1.1 markus 108: goto done;
109: }
110: service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
111: authctxt->service;
112: buffer_init(&b);
113: buffer_put_string(&b, session_id2, session_id2_len);
114: /* reconstruct packet */
115: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
116: buffer_put_cstring(&b, authctxt->user);
117: buffer_put_cstring(&b, service);
118: buffer_put_cstring(&b, "hostbased");
119: buffer_put_string(&b, pkalg, alen);
120: buffer_put_string(&b, pkblob, blen);
121: buffer_put_cstring(&b, chost);
122: buffer_put_cstring(&b, cuser);
123: #ifdef DEBUG_PK
124: buffer_dump(&b);
125: #endif
1.16 djm 126:
127: pubkey_auth_info(authctxt, key,
128: "client user \"%.100s\", client host \"%.100s\"", cuser, chost);
129:
1.1 markus 130: /* test for allowed key and correct signature */
131: authenticated = 0;
132: if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&
133: PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
134: buffer_len(&b))) == 1)
135: authenticated = 1;
136:
1.6 markus 137: buffer_free(&b);
1.1 markus 138: done:
139: debug2("userauth_hostbased: authenticated %d", authenticated);
140: if (key != NULL)
141: key_free(key);
1.15 djm 142: free(pkalg);
143: free(pkblob);
144: free(cuser);
145: free(chost);
146: free(sig);
1.1 markus 147: return authenticated;
148: }
149:
150: /* return 1 if given hostkey is allowed */
151: int
152: hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
153: Key *key)
154: {
1.14 djm 155: const char *resolvedname, *ipaddr, *lookup, *reason;
1.1 markus 156: HostStatus host_status;
157: int len;
1.14 djm 158: char *fp;
1.13 djm 159:
160: if (auth_key_is_revoked(key))
161: return 0;
1.1 markus 162:
1.4 markus 163: resolvedname = get_canonical_hostname(options.use_dns);
1.1 markus 164: ipaddr = get_remote_ipaddr();
165:
1.20 djm 166: debug2("%s: chost %s resolvedname %s ipaddr %s", __func__,
1.1 markus 167: chost, resolvedname, ipaddr);
168:
1.12 djm 169: if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
170: debug2("stripping trailing dot from chost %s", chost);
171: chost[len - 1] = '\0';
172: }
173:
1.1 markus 174: if (options.hostbased_uses_name_from_packet_only) {
1.20 djm 175: if (auth_rhosts2(pw, cuser, chost, chost) == 0) {
176: debug2("%s: auth_rhosts2 refused "
177: "user \"%.100s\" host \"%.100s\" (from packet)",
178: __func__, cuser, chost);
1.1 markus 179: return 0;
1.20 djm 180: }
1.1 markus 181: lookup = chost;
182: } else {
183: if (strcasecmp(resolvedname, chost) != 0)
1.3 itojun 184: logit("userauth_hostbased mismatch: "
1.1 markus 185: "client sends %s, but we resolve %s to %s",
186: chost, ipaddr, resolvedname);
1.20 djm 187: if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) {
188: debug2("%s: auth_rhosts2 refused "
189: "user \"%.100s\" host \"%.100s\" addr \"%.100s\"",
190: __func__, cuser, resolvedname, ipaddr);
1.1 markus 191: return 0;
1.20 djm 192: }
1.1 markus 193: lookup = resolvedname;
194: }
1.20 djm 195: debug2("%s: access allowed by auth_rhosts2", __func__);
1.1 markus 196:
1.14 djm 197: if (key_is_cert(key) &&
198: key_cert_check_authority(key, 1, 0, lookup, &reason)) {
199: error("%s", reason);
200: auth_debug_add("%s", reason);
201: return 0;
202: }
203:
1.1 markus 204: host_status = check_key_in_hostfiles(pw, key, lookup,
205: _PATH_SSH_SYSTEM_HOSTFILE,
206: options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
207:
208: /* backward compat if no key has been found. */
1.14 djm 209: if (host_status == HOST_NEW) {
1.1 markus 210: host_status = check_key_in_hostfiles(pw, key, lookup,
211: _PATH_SSH_SYSTEM_HOSTFILE2,
212: options.ignore_user_known_hosts ? NULL :
213: _PATH_SSH_USER_HOSTFILE2);
1.14 djm 214: }
215:
216: if (host_status == HOST_OK) {
217: if (key_is_cert(key)) {
218: fp = key_fingerprint(key->cert->signature_key,
1.19 djm 219: options.fingerprint_hash, SSH_FP_DEFAULT);
1.14 djm 220: verbose("Accepted certificate ID \"%s\" signed by "
221: "%s CA %s from %s@%s", key->cert->key_id,
222: key_type(key->cert->signature_key), fp,
223: cuser, lookup);
224: } else {
1.19 djm 225: fp = key_fingerprint(key, options.fingerprint_hash,
226: SSH_FP_DEFAULT);
1.14 djm 227: verbose("Accepted %s public key %s from %s@%s",
228: key_type(key), fp, cuser, lookup);
229: }
1.15 djm 230: free(fp);
1.14 djm 231: }
1.1 markus 232:
233: return (host_status == HOST_OK);
234: }
1.2 markus 235:
236: Authmethod method_hostbased = {
237: "hostbased",
238: userauth_hostbased,
239: &options.hostbased_authentication
240: };
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