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22616013 1/* $OpenBSD: auth2.c,v 1.119 2008/07/04 23:30:16 djm Exp $ */
3c0ef626 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#include "includes.h"
3c0ef626 27
9108f8d9 28#include <sys/types.h>
22616013 29#include <sys/stat.h>
30#include <sys/uio.h>
9108f8d9 31
22616013 32#include <fcntl.h>
9108f8d9 33#include <pwd.h>
34#include <stdarg.h>
35#include <string.h>
22616013 36#include <unistd.h>
9108f8d9 37
3c0ef626 38#include "xmalloc.h"
22616013 39#include "atomicio.h"
9108f8d9 40#include "ssh2.h"
3c0ef626 41#include "packet.h"
3c0ef626 42#include "log.h"
9108f8d9 43#include "buffer.h"
3c0ef626 44#include "servconf.h"
45#include "compat.h"
9108f8d9 46#include "key.h"
47#include "hostfile.h"
3c0ef626 48#include "auth.h"
3c0ef626 49#include "dispatch.h"
3c0ef626 50#include "pathnames.h"
996d5e62 51#include "buffer.h"
3c0ef626 52
0fff78ff 53#ifdef GSSAPI
54#include "ssh-gss.h"
55#endif
9108f8d9 56#include "monitor_wrap.h"
0fff78ff 57
3c0ef626 58/* import */
59extern ServerOptions options;
60extern u_char *session_id2;
0fff78ff 61extern u_int session_id2_len;
996d5e62 62extern Buffer loginmsg;
3c0ef626 63
f5799ae1 64/* methods */
65
66extern Authmethod method_none;
67extern Authmethod method_pubkey;
68extern Authmethod method_passwd;
69extern Authmethod method_kbdint;
70extern Authmethod method_hostbased;
0fff78ff 71#ifdef GSSAPI
72extern Authmethod method_gssapi;
73#endif
f5799ae1 74
75Authmethod *authmethods[] = {
76 &method_none,
77 &method_pubkey,
0fff78ff 78#ifdef GSSAPI
79 &method_gssapi,
80#endif
f5799ae1 81 &method_passwd,
82 &method_kbdint,
83 &method_hostbased,
84 NULL
3c0ef626 85};
86
87/* protocol */
88
e9a17296 89static void input_service_request(int, u_int32_t, void *);
90static void input_userauth_request(int, u_int32_t, void *);
3c0ef626 91
92/* helper */
93static Authmethod *authmethod_lookup(const char *);
94static char *authmethods_get(void);
3c0ef626 95
22616013 96char *
97auth2_read_banner(void)
98{
99 struct stat st;
100 char *banner = NULL;
101 size_t len, n;
102 int fd;
103
104 if ((fd = open(options.banner, O_RDONLY)) == -1)
105 return (NULL);
106 if (fstat(fd, &st) == -1) {
107 close(fd);
108 return (NULL);
109 }
110 if (st.st_size > 1*1024*1024) {
111 close(fd);
112 return (NULL);
113 }
114
115 len = (size_t)st.st_size; /* truncate */
116 banner = xmalloc(len + 1);
117 n = atomicio(read, fd, banner, len);
118 close(fd);
119
120 if (n != len) {
121 xfree(banner);
122 return (NULL);
123 }
124 banner[n] = '\0';
125
126 return (banner);
127}
128
129void
130userauth_send_banner(const char *msg)
131{
132 if (datafellows & SSH_BUG_BANNER)
133 return;
134
135 packet_start(SSH2_MSG_USERAUTH_BANNER);
136 packet_put_cstring(msg);
137 packet_put_cstring(""); /* language, unused */
138 packet_send();
139 debug("%s: sent", __func__);
140}
141
142static void
143userauth_banner(void)
144{
145 char *banner = NULL;
146
147 if (options.banner == NULL ||
148 strcasecmp(options.banner, "none") == 0 ||
149 (datafellows & SSH_BUG_BANNER) != 0)
150 return;
151
152 if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
153 goto done;
154 userauth_send_banner(banner);
155
156done:
157 if (banner)
158 xfree(banner);
159}
160
3c0ef626 161/*
162 * loop until authctxt->success == TRUE
163 */
cdd66111 164void
165do_authentication2(Authctxt *authctxt)
3c0ef626 166{
e9a17296 167 dispatch_init(&dispatch_protocol_error);
3c0ef626 168 dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
169 dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
3c0ef626 170}
171
9108f8d9 172/*ARGSUSED*/
3c0ef626 173static void
e9a17296 174input_service_request(int type, u_int32_t seq, void *ctxt)
3c0ef626 175{
176 Authctxt *authctxt = ctxt;
177 u_int len;
41b2f314 178 int acceptit = 0;
3c0ef626 179 char *service = packet_get_string(&len);
e9a17296 180 packet_check_eom();
3c0ef626 181
182 if (authctxt == NULL)
183 fatal("input_service_request: no authctxt");
184
185 if (strcmp(service, "ssh-userauth") == 0) {
186 if (!authctxt->success) {
41b2f314 187 acceptit = 1;
3c0ef626 188 /* now we can handle user-auth requests */
189 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
190 }
191 }
192 /* XXX all other service requests are denied */
193
41b2f314 194 if (acceptit) {
3c0ef626 195 packet_start(SSH2_MSG_SERVICE_ACCEPT);
196 packet_put_cstring(service);
197 packet_send();
198 packet_write_wait();
199 } else {
200 debug("bad service request %s", service);
201 packet_disconnect("bad service request %s", service);
202 }
203 xfree(service);
204}
205
9108f8d9 206/*ARGSUSED*/
3c0ef626 207static void
e9a17296 208input_userauth_request(int type, u_int32_t seq, void *ctxt)
3c0ef626 209{
210 Authctxt *authctxt = ctxt;
211 Authmethod *m = NULL;
212 char *user, *service, *method, *style = NULL;
213 int authenticated = 0;
214
215 if (authctxt == NULL)
216 fatal("input_userauth_request: no authctxt");
217
218 user = packet_get_string(NULL);
219 service = packet_get_string(NULL);
220 method = packet_get_string(NULL);
221 debug("userauth-request for user %s service %s method %s", user, service, method);
222 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
223
224 if ((style = strchr(user, ':')) != NULL)
225 *style++ = 0;
226
227 if (authctxt->attempt++ == 0) {
228 /* setup auth context */
700318f3 229 authctxt->pw = PRIVSEP(getpwnamallow(user));
99be0775 230 authctxt->user = xstrdup(user);
700318f3 231 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
3c0ef626 232 authctxt->valid = 1;
233 debug2("input_userauth_request: setting up authctxt for %s", user);
3c0ef626 234 } else {
c9f39d2c 235 logit("input_userauth_request: invalid user %s", user);
0fff78ff 236 authctxt->pw = fakepw();
996d5e62 237#ifdef SSH_AUDIT_EVENTS
238 PRIVSEP(audit_event(SSH_INVALID_USER));
3c0ef626 239#endif
240 }
2c06c99b 241#ifdef USE_PAM
242 if (options.use_pam)
243 PRIVSEP(start_pam(authctxt));
244#endif
c9f39d2c 245 setproctitle("%s%s", authctxt->valid ? user : "unknown",
700318f3 246 use_privsep ? " [net]" : "");
3c0ef626 247 authctxt->service = xstrdup(service);
248 authctxt->style = style ? xstrdup(style) : NULL;
700318f3 249 if (use_privsep)
250 mm_inform_authserv(service, style);
22616013 251 userauth_banner();
3c0ef626 252 } else if (strcmp(user, authctxt->user) != 0 ||
253 strcmp(service, authctxt->service) != 0) {
254 packet_disconnect("Change of username or service not allowed: "
255 "(%s,%s) -> (%s,%s)",
256 authctxt->user, authctxt->service, user, service);
257 }
258 /* reset state */
e9a17296 259 auth2_challenge_stop(authctxt);
0fff78ff 260
261#ifdef GSSAPI
262 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
263 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
264#endif
265
3c0ef626 266 authctxt->postponed = 0;
3c0ef626 267
268 /* try to authenticate user */
269 m = authmethod_lookup(method);
22616013 270 if (m != NULL && authctxt->failures < options.max_authtries) {
3c0ef626 271 debug2("input_userauth_request: try method %s", method);
272 authenticated = m->userauth(authctxt);
273 }
274 userauth_finish(authctxt, authenticated, method);
275
276 xfree(service);
277 xfree(user);
278 xfree(method);
279}
280
281void
282userauth_finish(Authctxt *authctxt, int authenticated, char *method)
283{
284 char *methods;
285
286 if (!authctxt->valid && authenticated)
287 fatal("INTERNAL ERROR: authenticated invalid user %s",
288 authctxt->user);
289
290 /* Special handling for root */
6a9b3198 291 if (authenticated && authctxt->pw->pw_uid == 0 &&
996d5e62 292 !auth_root_allowed(method)) {
3c0ef626 293 authenticated = 0;
996d5e62 294#ifdef SSH_AUDIT_EVENTS
295 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
296#endif
297 }
3c0ef626 298
299#ifdef USE_PAM
996d5e62 300 if (options.use_pam && authenticated) {
301 if (!PRIVSEP(do_pam_account())) {
302 /* if PAM returned a message, send it to the user */
303 if (buffer_len(&loginmsg) > 0) {
304 buffer_append(&loginmsg, "\0", 1);
305 userauth_send_banner(buffer_ptr(&loginmsg));
306 packet_write_wait();
307 }
308 fatal("Access denied for user %s by PAM account "
665a873d 309 "configuration", authctxt->user);
996d5e62 310 }
311 }
0fff78ff 312#endif
3c0ef626 313
41b2f314 314#ifdef _UNICOS
315 if (authenticated && cray_access_denied(authctxt->user)) {
316 authenticated = 0;
317 fatal("Access denied for user %s.",authctxt->user);
318 }
319#endif /* _UNICOS */
320
3c0ef626 321 /* Log before sending the reply */
322 auth_log(authctxt, authenticated, method, " ssh2");
323
324 if (authctxt->postponed)
325 return;
326
327 /* XXX todo: check if multiple auth methods are needed */
328 if (authenticated == 1) {
329 /* turn off userauth */
e9a17296 330 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
3c0ef626 331 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
332 packet_send();
333 packet_write_wait();
334 /* now we can break out */
335 authctxt->success = 1;
336 } else {
22616013 337
338 /* Allow initial try of "none" auth without failure penalty */
339 if (authctxt->attempt > 1 || strcmp(method, "none") != 0)
340 authctxt->failures++;
341 if (authctxt->failures >= options.max_authtries) {
996d5e62 342#ifdef SSH_AUDIT_EVENTS
343 PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
344#endif
3c0ef626 345 packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
996d5e62 346 }
3c0ef626 347 methods = authmethods_get();
348 packet_start(SSH2_MSG_USERAUTH_FAILURE);
349 packet_put_cstring(methods);
350 packet_put_char(0); /* XXX partial success, unused */
351 packet_send();
352 packet_write_wait();
353 xfree(methods);
354 }
355}
356
3c0ef626 357static char *
358authmethods_get(void)
359{
e9a17296 360 Buffer b;
3c0ef626 361 char *list;
f5799ae1 362 int i;
3c0ef626 363
e9a17296 364 buffer_init(&b);
f5799ae1 365 for (i = 0; authmethods[i] != NULL; i++) {
366 if (strcmp(authmethods[i]->name, "none") == 0)
3c0ef626 367 continue;
f5799ae1 368 if (authmethods[i]->enabled != NULL &&
369 *(authmethods[i]->enabled) != 0) {
e9a17296 370 if (buffer_len(&b) > 0)
371 buffer_append(&b, ",", 1);
f5799ae1 372 buffer_append(&b, authmethods[i]->name,
373 strlen(authmethods[i]->name));
3c0ef626 374 }
375 }
e9a17296 376 buffer_append(&b, "\0", 1);
377 list = xstrdup(buffer_ptr(&b));
378 buffer_free(&b);
3c0ef626 379 return list;
380}
381
382static Authmethod *
383authmethod_lookup(const char *name)
384{
f5799ae1 385 int i;
386
3c0ef626 387 if (name != NULL)
f5799ae1 388 for (i = 0; authmethods[i] != NULL; i++)
389 if (authmethods[i]->enabled != NULL &&
390 *(authmethods[i]->enabled) != 0 &&
391 strcmp(name, authmethods[i]->name) == 0)
392 return authmethods[i];
393 debug2("Unrecognized authentication method name: %s",
394 name ? name : "NULL");
3c0ef626 395 return NULL;
396}
22616013 397
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