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1 | /* | |
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" | |
26 | RCSID("$OpenBSD: auth2.c,v 1.104 2003/11/04 08:54:09 djm Exp $"); | |
27 | ||
28 | #include "ssh2.h" | |
29 | #include "xmalloc.h" | |
30 | #include "packet.h" | |
31 | #include "log.h" | |
32 | #include "servconf.h" | |
33 | #include "compat.h" | |
34 | #include "auth.h" | |
35 | #include "dispatch.h" | |
36 | #include "pathnames.h" | |
37 | #include "monitor_wrap.h" | |
38 | ||
39 | #ifdef GSSAPI | |
40 | #include "ssh-gss.h" | |
41 | #endif | |
42 | ||
43 | /* import */ | |
44 | extern ServerOptions options; | |
45 | extern u_char *session_id2; | |
46 | extern u_int session_id2_len; | |
47 | ||
48 | /* methods */ | |
49 | ||
50 | extern Authmethod method_none; | |
51 | extern Authmethod method_pubkey; | |
52 | extern Authmethod method_passwd; | |
53 | extern Authmethod method_kbdint; | |
54 | extern Authmethod method_hostbased; | |
55 | #ifdef GSSAPI | |
56 | extern Authmethod method_external; | |
57 | extern Authmethod method_gssapi; | |
58 | extern Authmethod method_gssapi_compat; | |
59 | #endif | |
60 | ||
61 | Authmethod *authmethods[] = { | |
62 | &method_none, | |
63 | &method_pubkey, | |
64 | #ifdef GSSAPI | |
65 | &method_external, | |
66 | &method_gssapi, | |
67 | &method_gssapi_compat, | |
68 | #endif | |
69 | &method_passwd, | |
70 | &method_kbdint, | |
71 | &method_hostbased, | |
72 | NULL | |
73 | }; | |
74 | ||
75 | /* protocol */ | |
76 | ||
77 | static void input_service_request(int, u_int32_t, void *); | |
78 | static void input_userauth_request(int, u_int32_t, void *); | |
79 | ||
80 | /* helper */ | |
81 | static Authmethod *authmethod_lookup(const char *); | |
82 | static char *authmethods_get(void); | |
83 | int user_key_allowed(struct passwd *, Key *); | |
84 | ||
85 | /* | |
86 | * loop until authctxt->success == TRUE | |
87 | */ | |
88 | ||
89 | void | |
90 | do_authentication2(Authctxt *authctxt) | |
91 | { | |
92 | /* challenge-response is implemented via keyboard interactive */ | |
93 | if (options.challenge_response_authentication) | |
94 | options.kbd_interactive_authentication = 1; | |
95 | ||
96 | dispatch_init(&dispatch_protocol_error); | |
97 | dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); | |
98 | dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); | |
99 | } | |
100 | ||
101 | static void | |
102 | input_service_request(int type, u_int32_t seq, void *ctxt) | |
103 | { | |
104 | Authctxt *authctxt = ctxt; | |
105 | u_int len; | |
106 | int acceptit = 0; | |
107 | char *service = packet_get_string(&len); | |
108 | packet_check_eom(); | |
109 | ||
110 | if (authctxt == NULL) | |
111 | fatal("input_service_request: no authctxt"); | |
112 | ||
113 | if (strcmp(service, "ssh-userauth") == 0) { | |
114 | if (!authctxt->success) { | |
115 | acceptit = 1; | |
116 | /* now we can handle user-auth requests */ | |
117 | dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); | |
118 | } | |
119 | } | |
120 | /* XXX all other service requests are denied */ | |
121 | ||
122 | if (acceptit) { | |
123 | packet_start(SSH2_MSG_SERVICE_ACCEPT); | |
124 | packet_put_cstring(service); | |
125 | packet_send(); | |
126 | packet_write_wait(); | |
127 | } else { | |
128 | debug("bad service request %s", service); | |
129 | packet_disconnect("bad service request %s", service); | |
130 | } | |
131 | xfree(service); | |
132 | } | |
133 | ||
134 | static void | |
135 | input_userauth_request(int type, u_int32_t seq, void *ctxt) | |
136 | { | |
137 | Authctxt *authctxt = ctxt; | |
138 | Authmethod *m = NULL; | |
139 | char *user, *service, *method, *style = NULL; | |
140 | int authenticated = 0; | |
141 | ||
142 | if (authctxt == NULL) | |
143 | fatal("input_userauth_request: no authctxt"); | |
144 | ||
145 | user = packet_get_string(NULL); | |
146 | service = packet_get_string(NULL); | |
147 | method = packet_get_string(NULL); | |
148 | ||
149 | #ifdef GSSAPI | |
150 | if (strcmp(user, "") == 0) { | |
151 | debug("received empty username for %s", method); | |
152 | if (strcmp(method, "external-keyx") == 0) { | |
153 | char *lname = NULL; | |
154 | PRIVSEP(ssh_gssapi_localname(&lname)); | |
155 | if (lname && lname[0] != '\0') { | |
156 | xfree(user); | |
157 | user = lname; | |
158 | debug("set username to %s from gssapi context", user); | |
159 | } else { | |
160 | debug("failed to set username from gssapi context"); | |
161 | } | |
162 | } | |
163 | } | |
164 | #endif | |
165 | ||
166 | debug("userauth-request for user %s service %s method %s", | |
167 | (user && user[0]) ? user : "<implicit>", service, method); | |
168 | debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); | |
169 | ||
170 | if ((style = strchr(user, ':')) != NULL) | |
171 | *style++ = 0; | |
172 | ||
173 | /* If first time or username changed or implicit username, | |
174 | setup/reset authentication context. */ | |
175 | if ((authctxt->attempt++ == 0) || | |
176 | (strcmp(user, authctxt->user) != 0) || | |
177 | (strcmp(user, "") == 0)) { | |
178 | /* setup auth context */ | |
179 | if (authctxt->user) { | |
180 | xfree(authctxt->user); | |
181 | authctxt->user = NULL; | |
182 | } | |
183 | if (authctxt->service) { | |
184 | xfree(authctxt->service); | |
185 | authctxt->service = NULL; | |
186 | } | |
187 | if (authctxt->style) { | |
188 | xfree(authctxt->style); | |
189 | authctxt->style = NULL; | |
190 | } | |
191 | authctxt->pw = NULL; | |
192 | authctxt->valid = 0; | |
193 | #ifdef GSSAPI | |
194 | /* If we're going to set the username based on the | |
195 | GSSAPI context later, then wait until then to | |
196 | verify it. */ | |
197 | if ((strcmp(user, "") != 0) || | |
198 | ((strcmp(method, "gssapi") != 0) && | |
199 | (strcmp(method, "gssapi-with-mic") != 0))) { | |
200 | #endif | |
201 | authctxt->pw = PRIVSEP(getpwnamallow(user)); | |
202 | authctxt->user = xstrdup(user); | |
203 | if (authctxt->pw && strcmp(service, "ssh-connection")==0) { | |
204 | authctxt->valid = 1; | |
205 | debug2("input_userauth_request: setting up authctxt for %s", user); | |
206 | #ifdef USE_PAM | |
207 | if (options.use_pam) | |
208 | PRIVSEP(start_pam(authctxt)); | |
209 | #endif | |
210 | } else { | |
211 | logit("input_userauth_request: illegal user %s", user); | |
212 | authctxt->pw = fakepw(); | |
213 | #ifdef USE_PAM | |
214 | if (options.use_pam) | |
215 | PRIVSEP(start_pam(authctxt)); | |
216 | #endif | |
217 | } | |
218 | #ifdef GSSAPI | |
219 | } /* endif for setting username based on GSSAPI context */ | |
220 | #endif | |
221 | setproctitle("%s%s", authctxt->pw ? user : "unknown", | |
222 | use_privsep ? " [net]" : ""); | |
223 | authctxt->service = xstrdup(service); | |
224 | authctxt->style = style ? xstrdup(style) : NULL; | |
225 | if (use_privsep && (authctxt->attempt == 1)) | |
226 | mm_inform_authserv(service, style); | |
227 | } else if (strcmp(service, authctxt->service) != 0) { | |
228 | packet_disconnect("Change of service not allowed: " | |
229 | "(%s,%s) -> (%s,%s)", | |
230 | authctxt->user, authctxt->service, user, service); | |
231 | } | |
232 | /* reset state */ | |
233 | auth2_challenge_stop(authctxt); | |
234 | ||
235 | #ifdef GSSAPI | |
236 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
237 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); | |
238 | #endif | |
239 | ||
240 | authctxt->postponed = 0; | |
241 | ||
242 | /* try to authenticate user */ | |
243 | m = authmethod_lookup(method); | |
244 | if (m != NULL) { | |
245 | debug2("input_userauth_request: try method %s", method); | |
246 | authenticated = m->userauth(authctxt); | |
247 | } | |
248 | userauth_finish(authctxt, authenticated, method); | |
249 | ||
250 | xfree(service); | |
251 | xfree(user); | |
252 | xfree(method); | |
253 | } | |
254 | ||
255 | void | |
256 | userauth_finish(Authctxt *authctxt, int authenticated, char *method) | |
257 | { | |
258 | char *methods; | |
259 | ||
260 | if (!authctxt->valid && authenticated) | |
261 | fatal("INTERNAL ERROR: authenticated invalid user %s", | |
262 | authctxt->user); | |
263 | ||
264 | /* Special handling for root */ | |
265 | if (authenticated && authctxt->pw->pw_uid == 0 && | |
266 | !auth_root_allowed(method)) | |
267 | authenticated = 0; | |
268 | ||
269 | #ifdef USE_PAM | |
270 | if (options.use_pam && authenticated && !PRIVSEP(do_pam_account())) | |
271 | authenticated = 0; | |
272 | #endif | |
273 | ||
274 | #ifdef _UNICOS | |
275 | if (authenticated && cray_access_denied(authctxt->user)) { | |
276 | authenticated = 0; | |
277 | fatal("Access denied for user %s.",authctxt->user); | |
278 | } | |
279 | #endif /* _UNICOS */ | |
280 | ||
281 | /* Log before sending the reply */ | |
282 | auth_log(authctxt, authenticated, method, " ssh2"); | |
283 | ||
284 | if (authctxt->postponed) | |
285 | return; | |
286 | ||
287 | /* XXX todo: check if multiple auth methods are needed */ | |
288 | if (authenticated == 1) { | |
289 | /* turn off userauth */ | |
290 | dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); | |
291 | packet_start(SSH2_MSG_USERAUTH_SUCCESS); | |
292 | packet_send(); | |
293 | packet_write_wait(); | |
294 | /* now we can break out */ | |
295 | authctxt->success = 1; | |
296 | } else { | |
297 | if (authctxt->failures++ > AUTH_FAIL_MAX) | |
298 | packet_disconnect(AUTH_FAIL_MSG, authctxt->user); | |
299 | methods = authmethods_get(); | |
300 | packet_start(SSH2_MSG_USERAUTH_FAILURE); | |
301 | packet_put_cstring(methods); | |
302 | packet_put_char(0); /* XXX partial success, unused */ | |
303 | packet_send(); | |
304 | packet_write_wait(); | |
305 | xfree(methods); | |
306 | } | |
307 | } | |
308 | ||
309 | #define DELIM "," | |
310 | ||
311 | static char * | |
312 | authmethods_get(void) | |
313 | { | |
314 | Buffer b; | |
315 | char *list; | |
316 | int i; | |
317 | ||
318 | buffer_init(&b); | |
319 | for (i = 0; authmethods[i] != NULL; i++) { | |
320 | if (strcmp(authmethods[i]->name, "none") == 0) | |
321 | continue; | |
322 | if (authmethods[i]->enabled != NULL && | |
323 | *(authmethods[i]->enabled) != 0) { | |
324 | if (buffer_len(&b) > 0) | |
325 | buffer_append(&b, ",", 1); | |
326 | buffer_append(&b, authmethods[i]->name, | |
327 | strlen(authmethods[i]->name)); | |
328 | } | |
329 | } | |
330 | buffer_append(&b, "\0", 1); | |
331 | list = xstrdup(buffer_ptr(&b)); | |
332 | buffer_free(&b); | |
333 | return list; | |
334 | } | |
335 | ||
336 | static Authmethod * | |
337 | authmethod_lookup(const char *name) | |
338 | { | |
339 | int i; | |
340 | ||
341 | if (name != NULL) | |
342 | for (i = 0; authmethods[i] != NULL; i++) | |
343 | if (authmethods[i]->enabled != NULL && | |
344 | *(authmethods[i]->enabled) != 0 && | |
345 | strcmp(name, authmethods[i]->name) == 0) | |
346 | return authmethods[i]; | |
347 | debug2("Unrecognized authentication method name: %s", | |
348 | name ? name : "NULL"); | |
349 | return NULL; | |
350 | } |