1 /* $OpenBSD: auth2.c,v 1.121 2009/06/22 05:39:28 dtucker Exp $ */
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
26
27 #include <sys/types.h>
28 #include <sys/stat.h>
29 #include <sys/uio.h>
30
31 #include <fcntl.h>
32 #include <pwd.h>
33 #include <stdarg.h>
34 #include <string.h>
35 #include <unistd.h>
36
37 #include "atomicio.h"
38 #include "xmalloc.h"
39 #include "ssh2.h"
40 #include "packet.h"
41 #include "log.h"
42 #include "buffer.h"
43 #include "servconf.h"
44 #include "compat.h"
45 #include "key.h"
46 #include "hostfile.h"
47 #include "auth.h"
48 #include "dispatch.h"
49 #include "pathnames.h"
50 #include "monitor_wrap.h"
51
52 __RCSID("$MirOS: src/usr.bin/ssh/auth2.c,v 1.11 2014/03/28 22:31:55 tg Exp $");
53
54 /* import */
55 extern ServerOptions options;
56 extern u_char *session_id2;
57 extern u_int session_id2_len;
58
59 /* methods */
60
61 extern Authmethod method_none;
62 extern Authmethod method_pubkey;
63 extern Authmethod method_passwd;
64 extern Authmethod method_kbdint;
65 extern Authmethod method_hostbased;
66
67 Authmethod *authmethods[] = {
68 &method_none,
69 &method_pubkey,
70 &method_passwd,
71 &method_kbdint,
72 &method_hostbased,
73 NULL
74 };
75
76 /* protocol */
77
78 static void input_service_request(int, u_int32_t, void *);
79 static void input_userauth_request(int, u_int32_t, void *);
80
81 /* helper */
82 static Authmethod *authmethod_lookup(const char *);
83 static char *authmethods_get(void);
84
85 char *
auth2_read_banner(void)86 auth2_read_banner(void)
87 {
88 struct stat st;
89 char *banner = NULL;
90 size_t len, n;
91 int fd;
92
93 if ((fd = open(options.banner, O_RDONLY)) == -1)
94 return (NULL);
95 if (fstat(fd, &st) == -1) {
96 close(fd);
97 return (NULL);
98 }
99 if (st.st_size > 1*1024*1024) {
100 close(fd);
101 return (NULL);
102 }
103
104 len = (size_t)st.st_size; /* truncate */
105 banner = xmalloc(len + 1);
106 n = atomicio(read, fd, banner, len);
107 close(fd);
108
109 if (n != len) {
110 xfree(banner);
111 return (NULL);
112 }
113 banner[n] = '\0';
114
115 return (banner);
116 }
117
118 static void
userauth_banner(void)119 userauth_banner(void)
120 {
121 char *banner = NULL;
122
123 if (options.banner == NULL ||
124 strcasecmp(options.banner, "none") == 0 ||
125 (datafellows & SSH_BUG_BANNER) != 0)
126 return;
127
128 if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
129 goto done;
130
131 packet_start(SSH2_MSG_USERAUTH_BANNER);
132 packet_put_cstring(banner);
133 packet_put_cstring(""); /* language, unused */
134 packet_send();
135 debug("userauth_banner: sent");
136 done:
137 if (banner)
138 xfree(banner);
139 }
140
141 /*
142 * loop until authctxt->success == TRUE
143 */
144 void
do_authentication2(Authctxt * authctxt)145 do_authentication2(Authctxt *authctxt)
146 {
147 dispatch_init(&dispatch_protocol_error);
148 dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
149 dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
150 }
151
152 /*ARGSUSED*/
153 static void
input_service_request(int type,u_int32_t seq,void * ctxt)154 input_service_request(int type, u_int32_t seq, void *ctxt)
155 {
156 Authctxt *authctxt = ctxt;
157 u_int len;
158 int acceptit = 0;
159 char *service = packet_get_string(&len);
160 packet_check_eom();
161
162 if (authctxt == NULL)
163 fatal("input_service_request: no authctxt");
164
165 if (strcmp(service, "ssh-userauth") == 0) {
166 if (!authctxt->success) {
167 acceptit = 1;
168 /* now we can handle user-auth requests */
169 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
170 }
171 }
172 /* XXX all other service requests are denied */
173
174 if (acceptit) {
175 packet_start(SSH2_MSG_SERVICE_ACCEPT);
176 packet_put_cstring(service);
177 packet_send();
178 packet_write_wait();
179 } else {
180 debug("bad service request %s", service);
181 packet_disconnect("bad service request %s", service);
182 }
183 xfree(service);
184 }
185
186 /*ARGSUSED*/
187 static void
input_userauth_request(int type,u_int32_t seq,void * ctxt)188 input_userauth_request(int type, u_int32_t seq, void *ctxt)
189 {
190 Authctxt *authctxt = ctxt;
191 Authmethod *m = NULL;
192 char *user, *service, *method, *style = NULL;
193 int authenticated = 0;
194
195 if (authctxt == NULL)
196 fatal("input_userauth_request: no authctxt");
197
198 user = packet_get_string(NULL);
199 service = packet_get_string(NULL);
200 method = packet_get_string(NULL);
201 debug("userauth-request for user %s service %s method %s", user, service, method);
202 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
203
204 if ((style = strchr(user, ':')) != NULL)
205 *style++ = 0;
206
207 if (authctxt->attempt++ == 0) {
208 /* setup auth context */
209 authctxt->pw = PRIVSEP(getpwnamallow(user));
210 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
211 authctxt->valid = 1;
212 debug2("input_userauth_request: setting up authctxt for %s", user);
213 } else {
214 logit("input_userauth_request: invalid user %s", user);
215 authctxt->pw = fakepw();
216 }
217 setproctitle("%s%s", authctxt->valid ? user : "unknown",
218 use_privsep ? " [net]" : "");
219 authctxt->user = xstrdup(user);
220 authctxt->service = xstrdup(service);
221 authctxt->style = style ? xstrdup(style) : NULL;
222 if (use_privsep)
223 mm_inform_authserv(service, style);
224 userauth_banner();
225 } else if (strcmp(user, authctxt->user) != 0 ||
226 strcmp(service, authctxt->service) != 0) {
227 packet_disconnect("Change of username or service not allowed: "
228 "(%s,%s) -> (%s,%s)",
229 authctxt->user, authctxt->service, user, service);
230 }
231 /* reset state */
232 auth2_challenge_stop(authctxt);
233
234 authctxt->postponed = 0;
235
236 /* try to authenticate user */
237 m = authmethod_lookup(method);
238 if (m != NULL && authctxt->failures < options.max_authtries) {
239 debug2("input_userauth_request: try method %s", method);
240 authenticated = m->userauth(authctxt);
241 }
242 userauth_finish(authctxt, authenticated, method);
243
244 xfree(service);
245 xfree(user);
246 xfree(method);
247 }
248
249 void
userauth_finish(Authctxt * authctxt,int authenticated,char * method)250 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
251 {
252 char *methods;
253
254 if (!authctxt->valid && authenticated)
255 fatal("INTERNAL ERROR: authenticated invalid user %s",
256 authctxt->user);
257
258 /* Special handling for root */
259 if (authenticated && authctxt->pw->pw_uid == 0 &&
260 !auth_root_allowed(method))
261 authenticated = 0;
262
263 /* Log before sending the reply */
264 auth_log(authctxt, authenticated, method, " ssh2");
265
266 if (authctxt->postponed)
267 return;
268
269 /* XXX todo: check if multiple auth methods are needed */
270 if (authenticated == 1) {
271 /* turn off userauth */
272 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
273 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
274 packet_send();
275 packet_write_wait();
276 /* now we can break out */
277 authctxt->success = 1;
278 } else {
279 /* Allow initial try of "none" auth without failure penalty */
280 if (authctxt->attempt > 1 || strcmp(method, "none") != 0)
281 authctxt->failures++;
282 if (authctxt->failures >= options.max_authtries)
283 packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
284 methods = authmethods_get();
285 packet_start(SSH2_MSG_USERAUTH_FAILURE);
286 packet_put_cstring(methods);
287 packet_put_char(0); /* XXX partial success, unused */
288 packet_send();
289 packet_write_wait();
290 xfree(methods);
291 }
292 }
293
294 static char *
authmethods_get(void)295 authmethods_get(void)
296 {
297 Buffer b;
298 char *list;
299 int i;
300
301 buffer_init(&b);
302 for (i = 0; authmethods[i] != NULL; i++) {
303 if (strcmp(authmethods[i]->name, "none") == 0)
304 continue;
305 if (authmethods[i]->enabled != NULL &&
306 *(authmethods[i]->enabled) != 0) {
307 if (buffer_len(&b) > 0)
308 buffer_append(&b, ",", 1);
309 buffer_append(&b, authmethods[i]->name,
310 strlen(authmethods[i]->name));
311 }
312 }
313 buffer_append(&b, "\0", 1);
314 list = xstrdup(buffer_ptr(&b));
315 buffer_free(&b);
316 return list;
317 }
318
319 static Authmethod *
authmethod_lookup(const char * name)320 authmethod_lookup(const char *name)
321 {
322 int i;
323
324 if (name != NULL)
325 for (i = 0; authmethods[i] != NULL; i++)
326 if (authmethods[i]->enabled != NULL &&
327 *(authmethods[i]->enabled) != 0 &&
328 strcmp(name, authmethods[i]->name) == 0)
329 return authmethods[i];
330 debug2("Unrecognized authentication method name: %s",
331 name ? name : "NULL");
332 return NULL;
333 }
334
335