]>
Commit | Line | Data |
---|---|---|
1 | /* | |
2 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
3 | * All rights reserved | |
4 | * | |
5 | * As far as I am concerned, the code I have written for this software | |
6 | * can be used freely for any purpose. Any derived versions of this | |
7 | * software must be clearly marked as such, and if the derived work is | |
8 | * incompatible with the protocol description in the RFC file, it must be | |
9 | * called by a name other than "ssh" or "Secure Shell". | |
10 | */ | |
11 | ||
12 | #include "includes.h" | |
13 | RCSID("$OpenBSD: auth1.c,v 1.59 2004/07/28 09:40:29 markus Exp $"); | |
14 | ||
15 | #include "xmalloc.h" | |
16 | #include "rsa.h" | |
17 | #include "ssh1.h" | |
18 | #include "packet.h" | |
19 | #include "buffer.h" | |
20 | #include "log.h" | |
21 | #include "servconf.h" | |
22 | #include "compat.h" | |
23 | #include "auth.h" | |
24 | #include "channels.h" | |
25 | #include "session.h" | |
26 | #include "uidswap.h" | |
27 | #include "monitor_wrap.h" | |
28 | #include "buffer.h" | |
29 | ||
30 | /* import */ | |
31 | extern ServerOptions options; | |
32 | extern Buffer loginmsg; | |
33 | ||
34 | /* | |
35 | * convert ssh auth msg type into description | |
36 | */ | |
37 | static char * | |
38 | get_authname(int type) | |
39 | { | |
40 | static char buf[1024]; | |
41 | switch (type) { | |
42 | case SSH_CMSG_AUTH_PASSWORD: | |
43 | return "password"; | |
44 | case SSH_CMSG_AUTH_RSA: | |
45 | return "rsa"; | |
46 | case SSH_CMSG_AUTH_RHOSTS_RSA: | |
47 | return "rhosts-rsa"; | |
48 | case SSH_CMSG_AUTH_RHOSTS: | |
49 | return "rhosts"; | |
50 | case SSH_CMSG_AUTH_TIS: | |
51 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
52 | return "challenge-response"; | |
53 | } | |
54 | snprintf(buf, sizeof buf, "bad-auth-msg-%d", type); | |
55 | return buf; | |
56 | } | |
57 | ||
58 | /* | |
59 | * read packets, try to authenticate the user and | |
60 | * return only if authentication is successful | |
61 | */ | |
62 | static void | |
63 | do_authloop(Authctxt *authctxt) | |
64 | { | |
65 | int authenticated = 0; | |
66 | u_int bits; | |
67 | Key *client_host_key; | |
68 | BIGNUM *n; | |
69 | char *client_user, *password; | |
70 | char info[1024]; | |
71 | u_int dlen; | |
72 | u_int ulen; | |
73 | int prev, type = 0; | |
74 | ||
75 | debug("Attempting authentication for %s%.100s.", | |
76 | authctxt->valid ? "" : "invalid user ", authctxt->user); | |
77 | ||
78 | /* If the user has no password, accept authentication immediately. */ | |
79 | if (options.password_authentication && | |
80 | #ifdef KRB5 | |
81 | (!options.kerberos_authentication || options.kerberos_or_local_passwd) && | |
82 | #endif | |
83 | PRIVSEP(auth_password(authctxt, ""))) { | |
84 | #ifdef USE_PAM | |
85 | if (options.use_pam && (PRIVSEP(do_pam_account()))) | |
86 | #endif | |
87 | { | |
88 | auth_log(authctxt, 1, "without authentication", ""); | |
89 | return; | |
90 | } | |
91 | } | |
92 | ||
93 | /* Indicate that authentication is needed. */ | |
94 | packet_start(SSH_SMSG_FAILURE); | |
95 | packet_send(); | |
96 | packet_write_wait(); | |
97 | ||
98 | client_user = NULL; | |
99 | ||
100 | for (;;) { | |
101 | /* default to fail */ | |
102 | authenticated = 0; | |
103 | ||
104 | info[0] = '\0'; | |
105 | ||
106 | /* Get a packet from the client. */ | |
107 | prev = type; | |
108 | type = packet_read(); | |
109 | ||
110 | /* | |
111 | * If we started challenge-response authentication but the | |
112 | * next packet is not a response to our challenge, release | |
113 | * the resources allocated by get_challenge() (which would | |
114 | * normally have been released by verify_response() had we | |
115 | * received such a response) | |
116 | */ | |
117 | if (prev == SSH_CMSG_AUTH_TIS && | |
118 | type != SSH_CMSG_AUTH_TIS_RESPONSE) | |
119 | abandon_challenge_response(authctxt); | |
120 | ||
121 | /* Process the packet. */ | |
122 | switch (type) { | |
123 | case SSH_CMSG_AUTH_RHOSTS_RSA: | |
124 | if (!options.rhosts_rsa_authentication) { | |
125 | verbose("Rhosts with RSA authentication disabled."); | |
126 | break; | |
127 | } | |
128 | /* | |
129 | * Get client user name. Note that we just have to | |
130 | * trust the client; root on the client machine can | |
131 | * claim to be any user. | |
132 | */ | |
133 | client_user = packet_get_string(&ulen); | |
134 | ||
135 | /* Get the client host key. */ | |
136 | client_host_key = key_new(KEY_RSA1); | |
137 | bits = packet_get_int(); | |
138 | packet_get_bignum(client_host_key->rsa->e); | |
139 | packet_get_bignum(client_host_key->rsa->n); | |
140 | ||
141 | if (bits != BN_num_bits(client_host_key->rsa->n)) | |
142 | verbose("Warning: keysize mismatch for client_host_key: " | |
143 | "actual %d, announced %d", | |
144 | BN_num_bits(client_host_key->rsa->n), bits); | |
145 | packet_check_eom(); | |
146 | ||
147 | authenticated = auth_rhosts_rsa(authctxt, client_user, | |
148 | client_host_key); | |
149 | key_free(client_host_key); | |
150 | ||
151 | snprintf(info, sizeof info, " ruser %.100s", client_user); | |
152 | break; | |
153 | ||
154 | case SSH_CMSG_AUTH_RSA: | |
155 | if (!options.rsa_authentication) { | |
156 | verbose("RSA authentication disabled."); | |
157 | break; | |
158 | } | |
159 | /* RSA authentication requested. */ | |
160 | if ((n = BN_new()) == NULL) | |
161 | fatal("do_authloop: BN_new failed"); | |
162 | packet_get_bignum(n); | |
163 | packet_check_eom(); | |
164 | authenticated = auth_rsa(authctxt, n); | |
165 | BN_clear_free(n); | |
166 | break; | |
167 | ||
168 | case SSH_CMSG_AUTH_PASSWORD: | |
169 | if (!options.password_authentication) { | |
170 | verbose("Password authentication disabled."); | |
171 | break; | |
172 | } | |
173 | /* | |
174 | * Read user password. It is in plain text, but was | |
175 | * transmitted over the encrypted channel so it is | |
176 | * not visible to an outside observer. | |
177 | */ | |
178 | password = packet_get_string(&dlen); | |
179 | packet_check_eom(); | |
180 | ||
181 | /* Try authentication with the password. */ | |
182 | authenticated = PRIVSEP(auth_password(authctxt, password)); | |
183 | ||
184 | memset(password, 0, strlen(password)); | |
185 | xfree(password); | |
186 | break; | |
187 | ||
188 | case SSH_CMSG_AUTH_TIS: | |
189 | debug("rcvd SSH_CMSG_AUTH_TIS"); | |
190 | if (options.challenge_response_authentication == 1) { | |
191 | char *challenge = get_challenge(authctxt); | |
192 | if (challenge != NULL) { | |
193 | debug("sending challenge '%s'", challenge); | |
194 | packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); | |
195 | packet_put_cstring(challenge); | |
196 | xfree(challenge); | |
197 | packet_send(); | |
198 | packet_write_wait(); | |
199 | continue; | |
200 | } | |
201 | } | |
202 | break; | |
203 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
204 | debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE"); | |
205 | if (options.challenge_response_authentication == 1) { | |
206 | char *response = packet_get_string(&dlen); | |
207 | packet_check_eom(); | |
208 | authenticated = verify_response(authctxt, response); | |
209 | memset(response, 'r', dlen); | |
210 | xfree(response); | |
211 | } | |
212 | break; | |
213 | ||
214 | default: | |
215 | /* | |
216 | * Any unknown messages will be ignored (and failure | |
217 | * returned) during authentication. | |
218 | */ | |
219 | logit("Unknown message during authentication: type %d", type); | |
220 | break; | |
221 | } | |
222 | #ifdef BSD_AUTH | |
223 | if (authctxt->as) { | |
224 | auth_close(authctxt->as); | |
225 | authctxt->as = NULL; | |
226 | } | |
227 | #endif | |
228 | if (!authctxt->valid && authenticated) | |
229 | fatal("INTERNAL ERROR: authenticated invalid user %s", | |
230 | authctxt->user); | |
231 | ||
232 | #ifdef _UNICOS | |
233 | if (authenticated && cray_access_denied(authctxt->user)) { | |
234 | authenticated = 0; | |
235 | fatal("Access denied for user %s.",authctxt->user); | |
236 | } | |
237 | #endif /* _UNICOS */ | |
238 | ||
239 | #ifdef HAVE_CYGWIN | |
240 | if (authenticated && | |
241 | !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, | |
242 | authctxt->pw)) { | |
243 | packet_disconnect("Authentication rejected for uid %d.", | |
244 | authctxt->pw == NULL ? -1 : authctxt->pw->pw_uid); | |
245 | authenticated = 0; | |
246 | } | |
247 | #else | |
248 | /* Special handling for root */ | |
249 | if (authenticated && authctxt->pw->pw_uid == 0 && | |
250 | !auth_root_allowed(get_authname(type))) { | |
251 | authenticated = 0; | |
252 | # ifdef SSH_AUDIT_EVENTS | |
253 | PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); | |
254 | # endif | |
255 | } | |
256 | #endif | |
257 | ||
258 | #ifdef USE_PAM | |
259 | if (options.use_pam && authenticated && | |
260 | !PRIVSEP(do_pam_account())) { | |
261 | char *msg; | |
262 | size_t len; | |
263 | ||
264 | error("Access denied for user %s by PAM account " | |
265 | "configuration", authctxt->user); | |
266 | len = buffer_len(&loginmsg); | |
267 | buffer_append(&loginmsg, "\0", 1); | |
268 | msg = buffer_ptr(&loginmsg); | |
269 | /* strip trailing newlines */ | |
270 | if (len > 0) | |
271 | while (len > 0 && msg[--len] == '\n') | |
272 | msg[len] = '\0'; | |
273 | else | |
274 | msg = "Access denied."; | |
275 | packet_disconnect(msg); | |
276 | } | |
277 | #endif | |
278 | ||
279 | /* Log before sending the reply */ | |
280 | auth_log(authctxt, authenticated, get_authname(type), info); | |
281 | ||
282 | if (client_user != NULL) { | |
283 | xfree(client_user); | |
284 | client_user = NULL; | |
285 | } | |
286 | ||
287 | if (authenticated) | |
288 | return; | |
289 | ||
290 | if (authctxt->failures++ > options.max_authtries) { | |
291 | #ifdef SSH_AUDIT_EVENTS | |
292 | PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES)); | |
293 | #endif | |
294 | packet_disconnect(AUTH_FAIL_MSG, authctxt->user); | |
295 | } | |
296 | ||
297 | packet_start(SSH_SMSG_FAILURE); | |
298 | packet_send(); | |
299 | packet_write_wait(); | |
300 | } | |
301 | } | |
302 | ||
303 | /* | |
304 | * Performs authentication of an incoming connection. Session key has already | |
305 | * been exchanged and encryption is enabled. | |
306 | */ | |
307 | void | |
308 | do_authentication(Authctxt *authctxt) | |
309 | { | |
310 | u_int ulen; | |
311 | char *user, *style = NULL; | |
312 | ||
313 | /* Get the name of the user that we wish to log in as. */ | |
314 | packet_read_expect(SSH_CMSG_USER); | |
315 | ||
316 | /* Get the user name. */ | |
317 | user = packet_get_string(&ulen); | |
318 | packet_check_eom(); | |
319 | ||
320 | if ((style = strchr(user, ':')) != NULL) | |
321 | *style++ = '\0'; | |
322 | ||
323 | authctxt->user = user; | |
324 | authctxt->style = style; | |
325 | ||
326 | /* Verify that the user is a valid user. */ | |
327 | if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL) | |
328 | authctxt->valid = 1; | |
329 | else { | |
330 | debug("do_authentication: invalid user %s", user); | |
331 | authctxt->pw = fakepw(); | |
332 | } | |
333 | ||
334 | setproctitle("%s%s", authctxt->valid ? user : "unknown", | |
335 | use_privsep ? " [net]" : ""); | |
336 | ||
337 | #ifdef USE_PAM | |
338 | if (options.use_pam) | |
339 | PRIVSEP(start_pam(authctxt)); | |
340 | #endif | |
341 | ||
342 | /* | |
343 | * If we are not running as root, the user must have the same uid as | |
344 | * the server. (Unless you are running Windows) | |
345 | */ | |
346 | #ifndef HAVE_CYGWIN | |
347 | if (!use_privsep && getuid() != 0 && authctxt->pw && | |
348 | authctxt->pw->pw_uid != getuid()) | |
349 | packet_disconnect("Cannot change user when server not running as root."); | |
350 | #endif | |
351 | ||
352 | /* | |
353 | * Loop until the user has been authenticated or the connection is | |
354 | * closed, do_authloop() returns only if authentication is successful | |
355 | */ | |
356 | do_authloop(authctxt); | |
357 | ||
358 | /* The user has been authenticated and accepted. */ | |
359 | packet_start(SSH_SMSG_SUCCESS); | |
360 | packet_send(); | |
361 | packet_write_wait(); | |
362 | } |