blob: 7962dcef20f99221e975d1b16368eb49253e12e6 [file] [log] [blame]
Damien Miller9f2abc42006-07-10 20:53:08 +10001/* $OpenBSD: auth2-pubkey.c,v 1.13 2006/07/06 16:03:53 stevesk Exp $ */
Ben Lindstrom855bf3a2002-06-06 20:27:55 +00002/*
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
26#include "includes.h"
Damien Millerf17883e2006-03-15 11:45:54 +110027
28#include <sys/types.h>
29#include <sys/stat.h>
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000030
Damien Miller9f2abc42006-07-10 20:53:08 +100031#include <pwd.h>
32
Darren Tucker22cc7412004-12-06 22:47:41 +110033#include "ssh.h"
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000034#include "ssh2.h"
35#include "xmalloc.h"
36#include "packet.h"
37#include "buffer.h"
38#include "log.h"
39#include "servconf.h"
40#include "compat.h"
41#include "bufaux.h"
42#include "auth.h"
43#include "key.h"
44#include "pathnames.h"
45#include "uidswap.h"
46#include "auth-options.h"
47#include "canohost.h"
48#include "monitor_wrap.h"
Darren Tuckerf0f90982004-12-11 13:39:50 +110049#include "misc.h"
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000050
51/* import */
52extern ServerOptions options;
53extern u_char *session_id2;
Darren Tucker502d3842003-06-28 12:38:01 +100054extern u_int session_id2_len;
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000055
56static int
57userauth_pubkey(Authctxt *authctxt)
58{
59 Buffer b;
60 Key *key = NULL;
61 char *pkalg;
62 u_char *pkblob, *sig;
63 u_int alen, blen, slen;
64 int have_sig, pktype;
65 int authenticated = 0;
66
67 if (!authctxt->valid) {
68 debug2("userauth_pubkey: disabled because of invalid user");
69 return 0;
70 }
71 have_sig = packet_get_char();
72 if (datafellows & SSH_BUG_PKAUTH) {
73 debug2("userauth_pubkey: SSH_BUG_PKAUTH");
74 /* no explicit pkalg given */
75 pkblob = packet_get_string(&blen);
76 buffer_init(&b);
77 buffer_append(&b, pkblob, blen);
78 /* so we have to extract the pkalg from the pkblob */
79 pkalg = buffer_get_string(&b, &alen);
80 buffer_free(&b);
81 } else {
82 pkalg = packet_get_string(&alen);
83 pkblob = packet_get_string(&blen);
84 }
85 pktype = key_type_from_name(pkalg);
86 if (pktype == KEY_UNSPEC) {
87 /* this is perfectly legal */
Damien Miller996acd22003-04-09 20:59:48 +100088 logit("userauth_pubkey: unsupported public key algorithm: %s",
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000089 pkalg);
90 goto done;
91 }
92 key = key_from_blob(pkblob, blen);
93 if (key == NULL) {
94 error("userauth_pubkey: cannot decode key: %s", pkalg);
95 goto done;
96 }
97 if (key->type != pktype) {
98 error("userauth_pubkey: type mismatch for decoded key "
99 "(received %d, expected %d)", key->type, pktype);
100 goto done;
101 }
102 if (have_sig) {
103 sig = packet_get_string(&slen);
104 packet_check_eom();
105 buffer_init(&b);
106 if (datafellows & SSH_OLD_SESSIONID) {
107 buffer_append(&b, session_id2, session_id2_len);
108 } else {
109 buffer_put_string(&b, session_id2, session_id2_len);
110 }
111 /* reconstruct packet */
112 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
113 buffer_put_cstring(&b, authctxt->user);
114 buffer_put_cstring(&b,
115 datafellows & SSH_BUG_PKSERVICE ?
116 "ssh-userauth" :
117 authctxt->service);
118 if (datafellows & SSH_BUG_PKAUTH) {
119 buffer_put_char(&b, have_sig);
120 } else {
121 buffer_put_cstring(&b, "publickey");
122 buffer_put_char(&b, have_sig);
123 buffer_put_cstring(&b, pkalg);
124 }
125 buffer_put_string(&b, pkblob, blen);
126#ifdef DEBUG_PK
127 buffer_dump(&b);
128#endif
129 /* test for correct signature */
130 authenticated = 0;
131 if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
132 PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
Damien Millerfb1310e2004-01-21 11:02:50 +1100133 buffer_len(&b))) == 1)
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000134 authenticated = 1;
Damien Millerfb1310e2004-01-21 11:02:50 +1100135 buffer_free(&b);
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000136 xfree(sig);
137 } else {
138 debug("test whether pkalg/pkblob are acceptable");
139 packet_check_eom();
140
141 /* XXX fake reply and always send PK_OK ? */
142 /*
143 * XXX this allows testing whether a user is allowed
144 * to login: if you happen to have a valid pubkey this
145 * message is sent. the message is NEVER sent at all
146 * if a user is not allowed to login. is this an
147 * issue? -markus
148 */
149 if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
150 packet_start(SSH2_MSG_USERAUTH_PK_OK);
151 packet_put_string(pkalg, alen);
152 packet_put_string(pkblob, blen);
153 packet_send();
154 packet_write_wait();
155 authctxt->postponed = 1;
156 }
157 }
158 if (authenticated != 1)
159 auth_clear_options();
160done:
161 debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
162 if (key != NULL)
163 key_free(key);
164 xfree(pkalg);
165 xfree(pkblob);
166#ifdef HAVE_CYGWIN
167 if (check_nt_auth(0, authctxt->pw) == 0)
Damien Miller47656792004-09-11 22:42:09 +1000168 authenticated = 0;
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000169#endif
170 return authenticated;
171}
172
173/* return 1 if user allows given key */
174static int
175user_key_allowed2(struct passwd *pw, Key *key, char *file)
176{
Darren Tucker22cc7412004-12-06 22:47:41 +1100177 char line[SSH_MAX_PUBKEY_BYTES];
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000178 int found_key = 0;
179 FILE *f;
180 u_long linenum = 0;
181 struct stat st;
182 Key *found;
183 char *fp;
184
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000185 /* Temporarily use the user's uid. */
186 temporarily_use_uid(pw);
187
188 debug("trying public key file %s", file);
189
190 /* Fail quietly if file does not exist */
191 if (stat(file, &st) < 0) {
192 /* Restore the privileged uid. */
193 restore_uid();
194 return 0;
195 }
196 /* Open the file containing the authorized keys. */
197 f = fopen(file, "r");
198 if (!f) {
199 /* Restore the privileged uid. */
200 restore_uid();
201 return 0;
202 }
203 if (options.strict_modes &&
204 secure_filename(f, file, pw, line, sizeof(line)) != 0) {
205 fclose(f);
Damien Miller996acd22003-04-09 20:59:48 +1000206 logit("Authentication refused: %s", line);
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000207 restore_uid();
208 return 0;
209 }
210
211 found_key = 0;
212 found = key_new(key->type);
213
Darren Tucker22cc7412004-12-06 22:47:41 +1100214 while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
Darren Tucker3f9fdc72004-06-22 12:56:01 +1000215 char *cp, *key_options = NULL;
Darren Tucker22cc7412004-12-06 22:47:41 +1100216
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000217 /* Skip leading whitespace, empty and comment lines. */
218 for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
219 ;
220 if (!*cp || *cp == '\n' || *cp == '#')
221 continue;
222
223 if (key_read(found, &cp) != 1) {
224 /* no key? check if there are options for this key */
225 int quoted = 0;
226 debug2("user_key_allowed: check options: '%s'", cp);
Darren Tucker3f9fdc72004-06-22 12:56:01 +1000227 key_options = cp;
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000228 for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
229 if (*cp == '\\' && cp[1] == '"')
230 cp++; /* Skip both */
231 else if (*cp == '"')
232 quoted = !quoted;
233 }
234 /* Skip remaining whitespace. */
235 for (; *cp == ' ' || *cp == '\t'; cp++)
236 ;
237 if (key_read(found, &cp) != 1) {
238 debug2("user_key_allowed: advance: '%s'", cp);
239 /* still no key? advance to next line*/
240 continue;
241 }
242 }
243 if (key_equal(found, key) &&
Darren Tucker3f9fdc72004-06-22 12:56:01 +1000244 auth_parse_options(pw, key_options, file, linenum) == 1) {
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000245 found_key = 1;
246 debug("matching key found: file %s, line %lu",
247 file, linenum);
248 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
249 verbose("Found matching %s key: %s",
250 key_type(found), fp);
251 xfree(fp);
252 break;
253 }
254 }
255 restore_uid();
256 fclose(f);
257 key_free(found);
258 if (!found_key)
259 debug2("key not found");
260 return found_key;
261}
262
263/* check whether given key is in .ssh/authorized_keys* */
264int
265user_key_allowed(struct passwd *pw, Key *key)
266{
267 int success;
268 char *file;
269
270 file = authorized_keys_file(pw);
271 success = user_key_allowed2(pw, key, file);
272 xfree(file);
273 if (success)
274 return success;
275
276 /* try suffix "2" for backward compat, too */
277 file = authorized_keys_file2(pw);
278 success = user_key_allowed2(pw, key, file);
279 xfree(file);
280 return success;
281}
282
283Authmethod method_pubkey = {
284 "publickey",
285 userauth_pubkey,
286 &options.pubkey_authentication
287};