blob: 947bfed0bb47e3832e74dde2c3662240dc9471fb [file] [log] [blame]
Ben Lindstrom855bf3a2002-06-06 20:27:55 +00001/*
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"
26RCSID("$OpenBSD: auth2-pubkey.c,v 1.2 2002/05/31 11:35:15 markus Exp $");
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 "pathnames.h"
39#include "uidswap.h"
40#include "auth-options.h"
41#include "canohost.h"
42#include "monitor_wrap.h"
43
44/* import */
45extern ServerOptions options;
46extern u_char *session_id2;
47extern int session_id2_len;
48
49static int
50userauth_pubkey(Authctxt *authctxt)
51{
52 Buffer b;
53 Key *key = NULL;
54 char *pkalg;
55 u_char *pkblob, *sig;
56 u_int alen, blen, slen;
57 int have_sig, pktype;
58 int authenticated = 0;
59
60 if (!authctxt->valid) {
61 debug2("userauth_pubkey: disabled because of invalid user");
62 return 0;
63 }
64 have_sig = packet_get_char();
65 if (datafellows & SSH_BUG_PKAUTH) {
66 debug2("userauth_pubkey: SSH_BUG_PKAUTH");
67 /* no explicit pkalg given */
68 pkblob = packet_get_string(&blen);
69 buffer_init(&b);
70 buffer_append(&b, pkblob, blen);
71 /* so we have to extract the pkalg from the pkblob */
72 pkalg = buffer_get_string(&b, &alen);
73 buffer_free(&b);
74 } else {
75 pkalg = packet_get_string(&alen);
76 pkblob = packet_get_string(&blen);
77 }
78 pktype = key_type_from_name(pkalg);
79 if (pktype == KEY_UNSPEC) {
80 /* this is perfectly legal */
81 log("userauth_pubkey: unsupported public key algorithm: %s",
82 pkalg);
83 goto done;
84 }
85 key = key_from_blob(pkblob, blen);
86 if (key == NULL) {
87 error("userauth_pubkey: cannot decode key: %s", pkalg);
88 goto done;
89 }
90 if (key->type != pktype) {
91 error("userauth_pubkey: type mismatch for decoded key "
92 "(received %d, expected %d)", key->type, pktype);
93 goto done;
94 }
95 if (have_sig) {
96 sig = packet_get_string(&slen);
97 packet_check_eom();
98 buffer_init(&b);
99 if (datafellows & SSH_OLD_SESSIONID) {
100 buffer_append(&b, session_id2, session_id2_len);
101 } else {
102 buffer_put_string(&b, session_id2, session_id2_len);
103 }
104 /* reconstruct packet */
105 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
106 buffer_put_cstring(&b, authctxt->user);
107 buffer_put_cstring(&b,
108 datafellows & SSH_BUG_PKSERVICE ?
109 "ssh-userauth" :
110 authctxt->service);
111 if (datafellows & SSH_BUG_PKAUTH) {
112 buffer_put_char(&b, have_sig);
113 } else {
114 buffer_put_cstring(&b, "publickey");
115 buffer_put_char(&b, have_sig);
116 buffer_put_cstring(&b, pkalg);
117 }
118 buffer_put_string(&b, pkblob, blen);
119#ifdef DEBUG_PK
120 buffer_dump(&b);
121#endif
122 /* test for correct signature */
123 authenticated = 0;
124 if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
125 PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
126 buffer_len(&b))) == 1)
127 authenticated = 1;
128 buffer_clear(&b);
129 xfree(sig);
130 } else {
131 debug("test whether pkalg/pkblob are acceptable");
132 packet_check_eom();
133
134 /* XXX fake reply and always send PK_OK ? */
135 /*
136 * XXX this allows testing whether a user is allowed
137 * to login: if you happen to have a valid pubkey this
138 * message is sent. the message is NEVER sent at all
139 * if a user is not allowed to login. is this an
140 * issue? -markus
141 */
142 if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
143 packet_start(SSH2_MSG_USERAUTH_PK_OK);
144 packet_put_string(pkalg, alen);
145 packet_put_string(pkblob, blen);
146 packet_send();
147 packet_write_wait();
148 authctxt->postponed = 1;
149 }
150 }
151 if (authenticated != 1)
152 auth_clear_options();
153done:
154 debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
155 if (key != NULL)
156 key_free(key);
157 xfree(pkalg);
158 xfree(pkblob);
159#ifdef HAVE_CYGWIN
160 if (check_nt_auth(0, authctxt->pw) == 0)
161 return(0);
162#endif
163 return authenticated;
164}
165
166/* return 1 if user allows given key */
167static int
168user_key_allowed2(struct passwd *pw, Key *key, char *file)
169{
170 char line[8192];
171 int found_key = 0;
172 FILE *f;
173 u_long linenum = 0;
174 struct stat st;
175 Key *found;
176 char *fp;
177
178 if (pw == NULL)
179 return 0;
180
181 /* Temporarily use the user's uid. */
182 temporarily_use_uid(pw);
183
184 debug("trying public key file %s", file);
185
186 /* Fail quietly if file does not exist */
187 if (stat(file, &st) < 0) {
188 /* Restore the privileged uid. */
189 restore_uid();
190 return 0;
191 }
192 /* Open the file containing the authorized keys. */
193 f = fopen(file, "r");
194 if (!f) {
195 /* Restore the privileged uid. */
196 restore_uid();
197 return 0;
198 }
199 if (options.strict_modes &&
200 secure_filename(f, file, pw, line, sizeof(line)) != 0) {
201 fclose(f);
202 log("Authentication refused: %s", line);
203 restore_uid();
204 return 0;
205 }
206
207 found_key = 0;
208 found = key_new(key->type);
209
210 while (fgets(line, sizeof(line), f)) {
211 char *cp, *options = NULL;
212 linenum++;
213 /* Skip leading whitespace, empty and comment lines. */
214 for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
215 ;
216 if (!*cp || *cp == '\n' || *cp == '#')
217 continue;
218
219 if (key_read(found, &cp) != 1) {
220 /* no key? check if there are options for this key */
221 int quoted = 0;
222 debug2("user_key_allowed: check options: '%s'", cp);
223 options = cp;
224 for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
225 if (*cp == '\\' && cp[1] == '"')
226 cp++; /* Skip both */
227 else if (*cp == '"')
228 quoted = !quoted;
229 }
230 /* Skip remaining whitespace. */
231 for (; *cp == ' ' || *cp == '\t'; cp++)
232 ;
233 if (key_read(found, &cp) != 1) {
234 debug2("user_key_allowed: advance: '%s'", cp);
235 /* still no key? advance to next line*/
236 continue;
237 }
238 }
239 if (key_equal(found, key) &&
240 auth_parse_options(pw, options, file, linenum) == 1) {
241 found_key = 1;
242 debug("matching key found: file %s, line %lu",
243 file, linenum);
244 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
245 verbose("Found matching %s key: %s",
246 key_type(found), fp);
247 xfree(fp);
248 break;
249 }
250 }
251 restore_uid();
252 fclose(f);
253 key_free(found);
254 if (!found_key)
255 debug2("key not found");
256 return found_key;
257}
258
259/* check whether given key is in .ssh/authorized_keys* */
260int
261user_key_allowed(struct passwd *pw, Key *key)
262{
263 int success;
264 char *file;
265
266 file = authorized_keys_file(pw);
267 success = user_key_allowed2(pw, key, file);
268 xfree(file);
269 if (success)
270 return success;
271
272 /* try suffix "2" for backward compat, too */
273 file = authorized_keys_file2(pw);
274 success = user_key_allowed2(pw, key, file);
275 xfree(file);
276 return success;
277}
278
279Authmethod method_pubkey = {
280 "publickey",
281 userauth_pubkey,
282 &options.pubkey_authentication
283};