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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 1.19 2001/03/08 18:47:12 stevesk 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 "session.h" | |
26 | #include "misc.h" | |
27 | ||
28 | /* import */ | |
29 | extern ServerOptions options; | |
30 | ||
31 | #ifdef WITH_AIXAUTHENTICATE | |
32 | extern char *aixloginmsg; | |
33 | #endif /* WITH_AIXAUTHENTICATE */ | |
34 | ||
35 | /* | |
36 | * convert ssh auth msg type into description | |
37 | */ | |
38 | char * | |
39 | get_authname(int type) | |
40 | { | |
41 | static char buf[1024]; | |
42 | switch (type) { | |
43 | case SSH_CMSG_AUTH_PASSWORD: | |
44 | return "password"; | |
45 | case SSH_CMSG_AUTH_RSA: | |
46 | return "rsa"; | |
47 | case SSH_CMSG_AUTH_RHOSTS_RSA: | |
48 | return "rhosts-rsa"; | |
49 | case SSH_CMSG_AUTH_RHOSTS: | |
50 | return "rhosts"; | |
51 | case SSH_CMSG_AUTH_TIS: | |
52 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
53 | return "challenge-response"; | |
54 | #ifdef KRB4 | |
55 | case SSH_CMSG_AUTH_KERBEROS: | |
56 | return "kerberos"; | |
57 | #endif | |
58 | } | |
59 | snprintf(buf, sizeof buf, "bad-auth-msg-%d", type); | |
60 | return buf; | |
61 | } | |
62 | ||
63 | /* | |
64 | * read packets, try to authenticate the user and | |
65 | * return only if authentication is successful | |
66 | */ | |
67 | void | |
68 | do_authloop(Authctxt *authctxt) | |
69 | { | |
70 | int authenticated = 0; | |
71 | u_int bits; | |
72 | RSA *client_host_key; | |
73 | BIGNUM *n; | |
74 | char *client_user, *password; | |
75 | char info[1024]; | |
76 | u_int dlen; | |
77 | int plen, nlen, elen; | |
78 | u_int ulen; | |
79 | int type = 0; | |
80 | struct passwd *pw = authctxt->pw; | |
81 | ||
82 | debug("Attempting authentication for %s%.100s.", | |
83 | authctxt->valid ? "" : "illegal user ", authctxt->user); | |
84 | ||
85 | /* If the user has no password, accept authentication immediately. */ | |
86 | if (options.password_authentication && | |
87 | #ifdef KRB4 | |
88 | (!options.kerberos_authentication || options.kerberos_or_local_passwd) && | |
89 | #endif | |
90 | #ifdef USE_PAM | |
91 | auth_pam_password(pw, "")) { | |
92 | #elif defined(HAVE_OSF_SIA) | |
93 | 0) { | |
94 | #else | |
95 | auth_password(authctxt, "")) { | |
96 | #endif | |
97 | auth_log(authctxt, 1, "without authentication", ""); | |
98 | return; | |
99 | } | |
100 | ||
101 | /* Indicate that authentication is needed. */ | |
102 | packet_start(SSH_SMSG_FAILURE); | |
103 | packet_send(); | |
104 | packet_write_wait(); | |
105 | ||
106 | client_user = NULL; | |
107 | ||
108 | for (;;) { | |
109 | /* default to fail */ | |
110 | authenticated = 0; | |
111 | ||
112 | info[0] = '\0'; | |
113 | ||
114 | /* Get a packet from the client. */ | |
115 | type = packet_read(&plen); | |
116 | ||
117 | /* Process the packet. */ | |
118 | switch (type) { | |
119 | #ifdef AFS | |
120 | case SSH_CMSG_HAVE_KERBEROS_TGT: | |
121 | if (!options.kerberos_tgt_passing) { | |
122 | verbose("Kerberos tgt passing disabled."); | |
123 | break; | |
124 | } else { | |
125 | /* Accept Kerberos tgt. */ | |
126 | char *tgt = packet_get_string(&dlen); | |
127 | packet_integrity_check(plen, 4 + dlen, type); | |
128 | if (!auth_kerberos_tgt(pw, tgt)) | |
129 | verbose("Kerberos tgt REFUSED for %.100s", authctxt->user); | |
130 | xfree(tgt); | |
131 | } | |
132 | continue; | |
133 | ||
134 | case SSH_CMSG_HAVE_AFS_TOKEN: | |
135 | if (!options.afs_token_passing || !k_hasafs()) { | |
136 | verbose("AFS token passing disabled."); | |
137 | break; | |
138 | } else { | |
139 | /* Accept AFS token. */ | |
140 | char *token_string = packet_get_string(&dlen); | |
141 | packet_integrity_check(plen, 4 + dlen, type); | |
142 | if (!auth_afs_token(pw, token_string)) | |
143 | verbose("AFS token REFUSED for %.100s", authctxt->user); | |
144 | xfree(token_string); | |
145 | } | |
146 | continue; | |
147 | #endif /* AFS */ | |
148 | #ifdef KRB4 | |
149 | case SSH_CMSG_AUTH_KERBEROS: | |
150 | if (!options.kerberos_authentication) { | |
151 | verbose("Kerberos authentication disabled."); | |
152 | break; | |
153 | } else { | |
154 | /* Try Kerberos v4 authentication. */ | |
155 | KTEXT_ST auth; | |
156 | char *tkt_user = NULL; | |
157 | char *kdata = packet_get_string((u_int *) &auth.length); | |
158 | packet_integrity_check(plen, 4 + auth.length, type); | |
159 | ||
160 | if (authctxt->valid) { | |
161 | if (auth.length < MAX_KTXT_LEN) | |
162 | memcpy(auth.dat, kdata, auth.length); | |
163 | authenticated = auth_krb4(pw->pw_name, &auth, &tkt_user); | |
164 | if (authenticated) { | |
165 | snprintf(info, sizeof info, | |
166 | " tktuser %.100s", tkt_user); | |
167 | xfree(tkt_user); | |
168 | } | |
169 | } | |
170 | xfree(kdata); | |
171 | } | |
172 | break; | |
173 | #endif /* KRB4 */ | |
174 | ||
175 | case SSH_CMSG_AUTH_RHOSTS: | |
176 | if (!options.rhosts_authentication) { | |
177 | verbose("Rhosts authentication disabled."); | |
178 | break; | |
179 | } | |
180 | /* | |
181 | * Get client user name. Note that we just have to | |
182 | * trust the client; this is one reason why rhosts | |
183 | * authentication is insecure. (Another is | |
184 | * IP-spoofing on a local network.) | |
185 | */ | |
186 | client_user = packet_get_string(&ulen); | |
187 | packet_integrity_check(plen, 4 + ulen, type); | |
188 | ||
189 | /* Try to authenticate using /etc/hosts.equiv and .rhosts. */ | |
190 | authenticated = auth_rhosts(pw, client_user); | |
191 | ||
192 | snprintf(info, sizeof info, " ruser %.100s", client_user); | |
193 | break; | |
194 | ||
195 | case SSH_CMSG_AUTH_RHOSTS_RSA: | |
196 | if (!options.rhosts_rsa_authentication) { | |
197 | verbose("Rhosts with RSA authentication disabled."); | |
198 | break; | |
199 | } | |
200 | /* | |
201 | * Get client user name. Note that we just have to | |
202 | * trust the client; root on the client machine can | |
203 | * claim to be any user. | |
204 | */ | |
205 | client_user = packet_get_string(&ulen); | |
206 | ||
207 | /* Get the client host key. */ | |
208 | client_host_key = RSA_new(); | |
209 | if (client_host_key == NULL) | |
210 | fatal("RSA_new failed"); | |
211 | client_host_key->e = BN_new(); | |
212 | client_host_key->n = BN_new(); | |
213 | if (client_host_key->e == NULL || client_host_key->n == NULL) | |
214 | fatal("BN_new failed"); | |
215 | bits = packet_get_int(); | |
216 | packet_get_bignum(client_host_key->e, &elen); | |
217 | packet_get_bignum(client_host_key->n, &nlen); | |
218 | ||
219 | if (bits != BN_num_bits(client_host_key->n)) | |
220 | verbose("Warning: keysize mismatch for client_host_key: " | |
221 | "actual %d, announced %d", BN_num_bits(client_host_key->n), bits); | |
222 | packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type); | |
223 | ||
224 | authenticated = auth_rhosts_rsa(pw, client_user, client_host_key); | |
225 | RSA_free(client_host_key); | |
226 | ||
227 | snprintf(info, sizeof info, " ruser %.100s", client_user); | |
228 | break; | |
229 | ||
230 | case SSH_CMSG_AUTH_RSA: | |
231 | if (!options.rsa_authentication) { | |
232 | verbose("RSA authentication disabled."); | |
233 | break; | |
234 | } | |
235 | /* RSA authentication requested. */ | |
236 | n = BN_new(); | |
237 | packet_get_bignum(n, &nlen); | |
238 | packet_integrity_check(plen, nlen, type); | |
239 | authenticated = auth_rsa(pw, n); | |
240 | BN_clear_free(n); | |
241 | break; | |
242 | ||
243 | case SSH_CMSG_AUTH_PASSWORD: | |
244 | if (!options.password_authentication) { | |
245 | verbose("Password authentication disabled."); | |
246 | break; | |
247 | } | |
248 | /* | |
249 | * Read user password. It is in plain text, but was | |
250 | * transmitted over the encrypted channel so it is | |
251 | * not visible to an outside observer. | |
252 | */ | |
253 | password = packet_get_string(&dlen); | |
254 | packet_integrity_check(plen, 4 + dlen, type); | |
255 | ||
256 | #ifdef USE_PAM | |
257 | /* Do PAM auth with password */ | |
258 | authenticated = auth_pam_password(pw, password); | |
259 | #elif defined(HAVE_OSF_SIA) | |
260 | /* Do SIA auth with password */ | |
261 | authenticated = auth_sia_password(authctxt->user, | |
262 | password); | |
263 | #else /* !USE_PAM && !HAVE_OSF_SIA */ | |
264 | /* Try authentication with the password. */ | |
265 | authenticated = auth_password(authctxt, password); | |
266 | #endif /* USE_PAM */ | |
267 | ||
268 | memset(password, 0, strlen(password)); | |
269 | xfree(password); | |
270 | break; | |
271 | ||
272 | case SSH_CMSG_AUTH_TIS: | |
273 | debug("rcvd SSH_CMSG_AUTH_TIS"); | |
274 | if (options.challenge_reponse_authentication == 1) { | |
275 | char *challenge = get_challenge(authctxt, authctxt->style); | |
276 | if (challenge != NULL) { | |
277 | debug("sending challenge '%s'", challenge); | |
278 | packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); | |
279 | packet_put_cstring(challenge); | |
280 | packet_send(); | |
281 | packet_write_wait(); | |
282 | continue; | |
283 | } | |
284 | } | |
285 | break; | |
286 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
287 | debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE"); | |
288 | if (options.challenge_reponse_authentication == 1) { | |
289 | char *response = packet_get_string(&dlen); | |
290 | debug("got response '%s'", response); | |
291 | packet_integrity_check(plen, 4 + dlen, type); | |
292 | authenticated = verify_response(authctxt, response); | |
293 | memset(response, 'r', dlen); | |
294 | xfree(response); | |
295 | } | |
296 | break; | |
297 | ||
298 | default: | |
299 | /* | |
300 | * Any unknown messages will be ignored (and failure | |
301 | * returned) during authentication. | |
302 | */ | |
303 | log("Unknown message during authentication: type %d", type); | |
304 | break; | |
305 | } | |
306 | #ifdef BSD_AUTH | |
307 | if (authctxt->as) { | |
308 | auth_close(authctxt->as); | |
309 | authctxt->as = NULL; | |
310 | } | |
311 | #endif | |
312 | if (!authctxt->valid && authenticated) | |
313 | fatal("INTERNAL ERROR: authenticated invalid user %s", | |
314 | authctxt->user); | |
315 | ||
316 | #ifdef HAVE_CYGWIN | |
317 | if (authenticated && | |
318 | !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD,pw->pw_uid)) { | |
319 | packet_disconnect("Authentication rejected for uid %d.", | |
320 | (int)pw->pw_uid); | |
321 | authenticated = 0; | |
322 | } | |
323 | #else | |
324 | /* Special handling for root */ | |
325 | if (authenticated && authctxt->pw->pw_uid == 0 && | |
326 | !auth_root_allowed(get_authname(type))) | |
327 | authenticated = 0; | |
328 | #endif | |
329 | #ifdef USE_PAM | |
330 | if (authenticated && !do_pam_account(pw->pw_name, client_user)) | |
331 | authenticated = 0; | |
332 | #endif | |
333 | ||
334 | /* Log before sending the reply */ | |
335 | auth_log(authctxt, authenticated, get_authname(type), info); | |
336 | ||
337 | if (client_user != NULL) { | |
338 | xfree(client_user); | |
339 | client_user = NULL; | |
340 | } | |
341 | ||
342 | if (authenticated) | |
343 | return; | |
344 | ||
345 | if (authctxt->failures++ > AUTH_FAIL_MAX) { | |
346 | #ifdef WITH_AIXAUTHENTICATE | |
347 | loginfailed(authctxt->user, | |
348 | get_canonical_hostname(options.reverse_mapping_check), | |
349 | "ssh"); | |
350 | #endif /* WITH_AIXAUTHENTICATE */ | |
351 | packet_disconnect(AUTH_FAIL_MSG, authctxt->user); | |
352 | } | |
353 | ||
354 | packet_start(SSH_SMSG_FAILURE); | |
355 | packet_send(); | |
356 | packet_write_wait(); | |
357 | } | |
358 | } | |
359 | ||
360 | /* | |
361 | * Performs authentication of an incoming connection. Session key has already | |
362 | * been exchanged and encryption is enabled. | |
363 | */ | |
364 | void | |
365 | do_authentication() | |
366 | { | |
367 | Authctxt *authctxt; | |
368 | struct passwd *pw; | |
369 | int plen; | |
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(&plen, SSH_CMSG_USER); | |
375 | ||
376 | /* Get the user name. */ | |
377 | user = packet_get_string(&ulen); | |
378 | packet_integrity_check(plen, (4 + ulen), SSH_CMSG_USER); | |
379 | ||
380 | if ((style = strchr(user, ':')) != NULL) | |
381 | *style++ = 0; | |
382 | ||
383 | authctxt = authctxt_new(); | |
384 | authctxt->user = user; | |
385 | authctxt->style = style; | |
386 | ||
387 | /* Verify that the user is a valid user. */ | |
388 | pw = getpwnam(user); | |
389 | if (pw && allowed_user(pw)) { | |
390 | authctxt->valid = 1; | |
391 | pw = pwcopy(pw); | |
392 | } else { | |
393 | debug("do_authentication: illegal user %s", user); | |
394 | pw = NULL; | |
395 | } | |
396 | authctxt->pw = pw; | |
397 | ||
398 | setproctitle("%s", pw ? user : "unknown"); | |
399 | ||
400 | #ifdef USE_PAM | |
401 | if (pw) | |
402 | start_pam(user); | |
403 | #endif | |
404 | ||
405 | /* | |
406 | * If we are not running as root, the user must have the same uid as | |
407 | * the server. (Unless you are running Windows) | |
408 | */ | |
409 | #ifndef HAVE_CYGWIN | |
410 | if (getuid() != 0 && pw && pw->pw_uid != getuid()) | |
411 | packet_disconnect("Cannot change user when server not running as root."); | |
412 | #endif | |
413 | ||
414 | /* | |
415 | * Loop until the user has been authenticated or the connection is | |
416 | * closed, do_authloop() returns only if authentication is successful | |
417 | */ | |
418 | do_authloop(authctxt); | |
419 | ||
420 | /* The user has been authenticated and accepted. */ | |
421 | packet_start(SSH_SMSG_SUCCESS); | |
422 | packet_send(); | |
423 | packet_write_wait(); | |
424 | ||
425 | #ifdef WITH_AIXAUTHENTICATE | |
426 | /* We don't have a pty yet, so just label the line as "ssh" */ | |
427 | if (loginsuccess(authctxt->user, | |
428 | get_canonical_hostname(options.reverse_mapping_check), | |
429 | "ssh", &aixloginmsg) < 0) | |
430 | aixloginmsg = NULL; | |
431 | #endif /* WITH_AIXAUTHENTICATE */ | |
432 | ||
433 | xfree(authctxt->user); | |
434 | xfree(authctxt); | |
435 | ||
436 | /* Perform session preparation. */ | |
437 | do_authenticated(pw); | |
438 | } |