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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 1.47 2003/02/06 21:22:42 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 "mpaux.h" | |
21 | #include "log.h" | |
22 | #include "servconf.h" | |
23 | #include "compat.h" | |
24 | #include "auth.h" | |
25 | #include "channels.h" | |
26 | #include "session.h" | |
27 | #include "uidswap.h" | |
28 | #include "monitor_wrap.h" | |
29 | ||
30 | /* import */ | |
31 | extern ServerOptions options; | |
32 | ||
33 | /* | |
34 | * convert ssh auth msg type into description | |
35 | */ | |
36 | static char * | |
37 | get_authname(int type) | |
38 | { | |
39 | static char buf[1024]; | |
40 | switch (type) { | |
41 | case SSH_CMSG_AUTH_PASSWORD: | |
42 | return "password"; | |
43 | case SSH_CMSG_AUTH_RSA: | |
44 | return "rsa"; | |
45 | case SSH_CMSG_AUTH_RHOSTS_RSA: | |
46 | return "rhosts-rsa"; | |
47 | case SSH_CMSG_AUTH_RHOSTS: | |
48 | return "rhosts"; | |
49 | case SSH_CMSG_AUTH_TIS: | |
50 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
51 | return "challenge-response"; | |
52 | #if defined(KRB4) || defined(KRB5) | |
53 | case SSH_CMSG_AUTH_KERBEROS: | |
54 | return "kerberos"; | |
55 | #endif | |
56 | } | |
57 | snprintf(buf, sizeof buf, "bad-auth-msg-%d", type); | |
58 | return buf; | |
59 | } | |
60 | ||
61 | /* | |
62 | * read packets, try to authenticate the user and | |
63 | * return only if authentication is successful | |
64 | */ | |
65 | static void | |
66 | do_authloop(Authctxt *authctxt) | |
67 | { | |
68 | int authenticated = 0; | |
69 | u_int bits; | |
70 | Key *client_host_key; | |
71 | BIGNUM *n; | |
72 | char *client_user, *password; | |
73 | char info[1024]; | |
74 | u_int dlen; | |
75 | u_int ulen; | |
76 | int type = 0; | |
77 | struct passwd *pw = authctxt->pw; | |
78 | ||
79 | debug("Attempting authentication for %s%.100s.", | |
80 | authctxt->valid ? "" : "illegal user ", authctxt->user); | |
81 | ||
82 | /* If the user has no password, accept authentication immediately. */ | |
83 | if (options.password_authentication && | |
84 | #if defined(KRB4) || defined(KRB5) | |
85 | (!options.kerberos_authentication || options.kerberos_or_local_passwd) && | |
86 | #endif | |
87 | PRIVSEP(auth_password(authctxt, ""))) { | |
88 | auth_log(authctxt, 1, "without authentication", ""); | |
89 | return; | |
90 | } | |
91 | ||
92 | /* Indicate that authentication is needed. */ | |
93 | packet_start(SSH_SMSG_FAILURE); | |
94 | packet_send(); | |
95 | packet_write_wait(); | |
96 | ||
97 | client_user = NULL; | |
98 | ||
99 | for (;;) { | |
100 | /* default to fail */ | |
101 | authenticated = 0; | |
102 | ||
103 | info[0] = '\0'; | |
104 | ||
105 | /* Get a packet from the client. */ | |
106 | type = packet_read(); | |
107 | ||
108 | /* Process the packet. */ | |
109 | switch (type) { | |
110 | ||
111 | #if defined(KRB4) || defined(KRB5) | |
112 | case SSH_CMSG_AUTH_KERBEROS: | |
113 | if (!options.kerberos_authentication) { | |
114 | verbose("Kerberos authentication disabled."); | |
115 | } else { | |
116 | char *kdata = packet_get_string(&dlen); | |
117 | packet_check_eom(); | |
118 | ||
119 | if (kdata[0] == 4) { /* KRB_PROT_VERSION */ | |
120 | #ifdef KRB4 | |
121 | KTEXT_ST tkt, reply; | |
122 | tkt.length = dlen; | |
123 | if (tkt.length < MAX_KTXT_LEN) | |
124 | memcpy(tkt.dat, kdata, tkt.length); | |
125 | ||
126 | if (PRIVSEP(auth_krb4(authctxt, &tkt, | |
127 | &client_user, &reply))) { | |
128 | authenticated = 1; | |
129 | snprintf(info, sizeof(info), | |
130 | " tktuser %.100s", | |
131 | client_user); | |
132 | ||
133 | packet_start( | |
134 | SSH_SMSG_AUTH_KERBEROS_RESPONSE); | |
135 | packet_put_string((char *) | |
136 | reply.dat, reply.length); | |
137 | packet_send(); | |
138 | packet_write_wait(); | |
139 | } | |
140 | #endif /* KRB4 */ | |
141 | } else { | |
142 | #ifdef KRB5 | |
143 | krb5_data tkt, reply; | |
144 | tkt.length = dlen; | |
145 | tkt.data = kdata; | |
146 | ||
147 | if (PRIVSEP(auth_krb5(authctxt, &tkt, | |
148 | &client_user, &reply))) { | |
149 | authenticated = 1; | |
150 | snprintf(info, sizeof(info), | |
151 | " tktuser %.100s", | |
152 | client_user); | |
153 | ||
154 | /* Send response to client */ | |
155 | packet_start( | |
156 | SSH_SMSG_AUTH_KERBEROS_RESPONSE); | |
157 | packet_put_string((char *) | |
158 | reply.data, reply.length); | |
159 | packet_send(); | |
160 | packet_write_wait(); | |
161 | ||
162 | if (reply.length) | |
163 | xfree(reply.data); | |
164 | } | |
165 | #endif /* KRB5 */ | |
166 | } | |
167 | xfree(kdata); | |
168 | } | |
169 | break; | |
170 | #endif /* KRB4 || KRB5 */ | |
171 | ||
172 | #if defined(AFS) || defined(KRB5) | |
173 | /* XXX - punt on backward compatibility here. */ | |
174 | case SSH_CMSG_HAVE_KERBEROS_TGT: | |
175 | packet_send_debug("Kerberos TGT passing disabled before authentication."); | |
176 | break; | |
177 | #ifdef AFS | |
178 | case SSH_CMSG_HAVE_AFS_TOKEN: | |
179 | packet_send_debug("AFS token passing disabled before authentication."); | |
180 | break; | |
181 | #endif /* AFS */ | |
182 | #endif /* AFS || KRB5 */ | |
183 | ||
184 | case SSH_CMSG_AUTH_RHOSTS: | |
185 | if (!options.rhosts_authentication) { | |
186 | verbose("Rhosts authentication disabled."); | |
187 | break; | |
188 | } | |
189 | /* | |
190 | * Get client user name. Note that we just have to | |
191 | * trust the client; this is one reason why rhosts | |
192 | * authentication is insecure. (Another is | |
193 | * IP-spoofing on a local network.) | |
194 | */ | |
195 | client_user = packet_get_string(&ulen); | |
196 | packet_check_eom(); | |
197 | ||
198 | /* Try to authenticate using /etc/hosts.equiv and .rhosts. */ | |
199 | authenticated = auth_rhosts(pw, client_user); | |
200 | ||
201 | snprintf(info, sizeof info, " ruser %.100s", client_user); | |
202 | break; | |
203 | ||
204 | case SSH_CMSG_AUTH_RHOSTS_RSA: | |
205 | if (!options.rhosts_rsa_authentication) { | |
206 | verbose("Rhosts with RSA authentication disabled."); | |
207 | break; | |
208 | } | |
209 | /* | |
210 | * Get client user name. Note that we just have to | |
211 | * trust the client; root on the client machine can | |
212 | * claim to be any user. | |
213 | */ | |
214 | client_user = packet_get_string(&ulen); | |
215 | ||
216 | /* Get the client host key. */ | |
217 | client_host_key = key_new(KEY_RSA1); | |
218 | bits = packet_get_int(); | |
219 | packet_get_bignum(client_host_key->rsa->e); | |
220 | packet_get_bignum(client_host_key->rsa->n); | |
221 | ||
222 | if (bits != BN_num_bits(client_host_key->rsa->n)) | |
223 | verbose("Warning: keysize mismatch for client_host_key: " | |
224 | "actual %d, announced %d", | |
225 | BN_num_bits(client_host_key->rsa->n), bits); | |
226 | packet_check_eom(); | |
227 | ||
228 | authenticated = auth_rhosts_rsa(pw, client_user, | |
229 | client_host_key); | |
230 | key_free(client_host_key); | |
231 | ||
232 | snprintf(info, sizeof info, " ruser %.100s", client_user); | |
233 | break; | |
234 | ||
235 | case SSH_CMSG_AUTH_RSA: | |
236 | if (!options.rsa_authentication) { | |
237 | verbose("RSA authentication disabled."); | |
238 | break; | |
239 | } | |
240 | /* RSA authentication requested. */ | |
241 | if ((n = BN_new()) == NULL) | |
242 | fatal("do_authloop: BN_new failed"); | |
243 | packet_get_bignum(n); | |
244 | packet_check_eom(); | |
245 | authenticated = auth_rsa(pw, n); | |
246 | BN_clear_free(n); | |
247 | break; | |
248 | ||
249 | case SSH_CMSG_AUTH_PASSWORD: | |
250 | if (!options.password_authentication) { | |
251 | verbose("Password authentication disabled."); | |
252 | break; | |
253 | } | |
254 | /* | |
255 | * Read user password. It is in plain text, but was | |
256 | * transmitted over the encrypted channel so it is | |
257 | * not visible to an outside observer. | |
258 | */ | |
259 | password = packet_get_string(&dlen); | |
260 | packet_check_eom(); | |
261 | ||
262 | /* Try authentication with the password. */ | |
263 | authenticated = PRIVSEP(auth_password(authctxt, password)); | |
264 | ||
265 | memset(password, 0, strlen(password)); | |
266 | xfree(password); | |
267 | break; | |
268 | ||
269 | case SSH_CMSG_AUTH_TIS: | |
270 | debug("rcvd SSH_CMSG_AUTH_TIS"); | |
271 | if (options.challenge_response_authentication == 1) { | |
272 | char *challenge = get_challenge(authctxt); | |
273 | if (challenge != NULL) { | |
274 | debug("sending challenge '%s'", challenge); | |
275 | packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); | |
276 | packet_put_cstring(challenge); | |
277 | xfree(challenge); | |
278 | packet_send(); | |
279 | packet_write_wait(); | |
280 | continue; | |
281 | } | |
282 | } | |
283 | break; | |
284 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
285 | debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE"); | |
286 | if (options.challenge_response_authentication == 1) { | |
287 | char *response = packet_get_string(&dlen); | |
288 | packet_check_eom(); | |
289 | authenticated = verify_response(authctxt, response); | |
290 | memset(response, 'r', dlen); | |
291 | xfree(response); | |
292 | } | |
293 | break; | |
294 | ||
295 | default: | |
296 | /* | |
297 | * Any unknown messages will be ignored (and failure | |
298 | * returned) during authentication. | |
299 | */ | |
300 | log("Unknown message during authentication: type %d", type); | |
301 | break; | |
302 | } | |
303 | #ifdef BSD_AUTH | |
304 | if (authctxt->as) { | |
305 | auth_close(authctxt->as); | |
306 | authctxt->as = NULL; | |
307 | } | |
308 | #endif | |
309 | if (!authctxt->valid && authenticated) | |
310 | fatal("INTERNAL ERROR: authenticated invalid user %s", | |
311 | authctxt->user); | |
312 | ||
313 | #ifdef _UNICOS | |
314 | if (type == SSH_CMSG_AUTH_PASSWORD && !authenticated) | |
315 | cray_login_failure(authctxt->user, IA_UDBERR); | |
316 | if (authenticated && cray_access_denied(authctxt->user)) { | |
317 | authenticated = 0; | |
318 | fatal("Access denied for user %s.",authctxt->user); | |
319 | } | |
320 | #endif /* _UNICOS */ | |
321 | ||
322 | #ifdef HAVE_CYGWIN | |
323 | if (authenticated && | |
324 | !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) { | |
325 | packet_disconnect("Authentication rejected for uid %d.", | |
326 | pw == NULL ? -1 : pw->pw_uid); | |
327 | authenticated = 0; | |
328 | } | |
329 | #else | |
330 | /* Special handling for root */ | |
331 | if (authenticated && authctxt->pw->pw_uid == 0 && | |
332 | !auth_root_allowed(get_authname(type))) | |
333 | authenticated = 0; | |
334 | #endif | |
335 | #ifdef USE_PAM | |
336 | if (!use_privsep && authenticated && | |
337 | !do_pam_account(pw->pw_name, client_user)) | |
338 | authenticated = 0; | |
339 | #endif | |
340 | ||
341 | /* Log before sending the reply */ | |
342 | auth_log(authctxt, authenticated, get_authname(type), info); | |
343 | ||
344 | if (client_user != NULL) { | |
345 | xfree(client_user); | |
346 | client_user = NULL; | |
347 | } | |
348 | ||
349 | if (authenticated) | |
350 | return; | |
351 | ||
352 | if (authctxt->failures++ > AUTH_FAIL_MAX) { | |
353 | packet_disconnect(AUTH_FAIL_MSG, authctxt->user); | |
354 | } | |
355 | ||
356 | packet_start(SSH_SMSG_FAILURE); | |
357 | packet_send(); | |
358 | packet_write_wait(); | |
359 | } | |
360 | } | |
361 | ||
362 | /* | |
363 | * Performs authentication of an incoming connection. Session key has already | |
364 | * been exchanged and encryption is enabled. | |
365 | */ | |
366 | Authctxt * | |
367 | do_authentication(void) | |
368 | { | |
369 | Authctxt *authctxt; | |
370 | u_int ulen; | |
371 | char *user, *style = NULL; | |
372 | ||
373 | /* Get the name of the user that we wish to log in as. */ | |
374 | packet_read_expect(SSH_CMSG_USER); | |
375 | ||
376 | /* Get the user name. */ | |
377 | user = packet_get_string(&ulen); | |
378 | packet_check_eom(); | |
379 | ||
380 | if ((style = strchr(user, ':')) != NULL) | |
381 | *style++ = '\0'; | |
382 | ||
383 | #ifdef KRB5 | |
384 | /* XXX - SSH.com Kerberos v5 braindeath. */ | |
385 | if ((datafellows & SSH_BUG_K5USER) && | |
386 | options.kerberos_authentication) { | |
387 | char *p; | |
388 | if ((p = strchr(user, '@')) != NULL) | |
389 | *p = '\0'; | |
390 | } | |
391 | #endif | |
392 | ||
393 | authctxt = authctxt_new(); | |
394 | authctxt->user = user; | |
395 | authctxt->style = style; | |
396 | ||
397 | /* Verify that the user is a valid user. */ | |
398 | if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL) | |
399 | authctxt->valid = 1; | |
400 | else | |
401 | debug("do_authentication: illegal user %s", user); | |
402 | ||
403 | setproctitle("%s%s", authctxt->pw ? user : "unknown", | |
404 | use_privsep ? " [net]" : ""); | |
405 | ||
406 | #ifdef USE_PAM | |
407 | PRIVSEP(start_pam(authctxt->pw == NULL ? "NOUSER" : user)); | |
408 | #endif | |
409 | ||
410 | /* | |
411 | * If we are not running as root, the user must have the same uid as | |
412 | * the server. (Unless you are running Windows) | |
413 | */ | |
414 | #ifndef HAVE_CYGWIN | |
415 | if (!use_privsep && getuid() != 0 && authctxt->pw && | |
416 | authctxt->pw->pw_uid != getuid()) | |
417 | packet_disconnect("Cannot change user when server not running as root."); | |
418 | #endif | |
419 | ||
420 | /* | |
421 | * Loop until the user has been authenticated or the connection is | |
422 | * closed, do_authloop() returns only if authentication is successful | |
423 | */ | |
424 | do_authloop(authctxt); | |
425 | ||
426 | /* The user has been authenticated and accepted. */ | |
427 | packet_start(SSH_SMSG_SUCCESS); | |
428 | packet_send(); | |
429 | packet_write_wait(); | |
430 | ||
431 | return (authctxt); | |
432 | } |