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3c0ef626 | 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" | |
2ce0bfe4 | 13 | RCSID("$OpenBSD: auth1.c,v 1.62 2005/07/16 01:35:24 djm Exp $"); |
3c0ef626 | 14 | |
15 | #include "xmalloc.h" | |
16 | #include "rsa.h" | |
17 | #include "ssh1.h" | |
18 | #include "packet.h" | |
19 | #include "buffer.h" | |
3c0ef626 | 20 | #include "log.h" |
21 | #include "servconf.h" | |
22 | #include "compat.h" | |
23 | #include "auth.h" | |
1e608e42 | 24 | #include "channels.h" |
3c0ef626 | 25 | #include "session.h" |
3c0ef626 | 26 | #include "uidswap.h" |
510132b6 | 27 | #include "monitor_wrap.h" |
dfddba3d | 28 | #include "buffer.h" |
3c0ef626 | 29 | |
30 | /* import */ | |
31 | extern ServerOptions options; | |
dfddba3d | 32 | extern Buffer loginmsg; |
3c0ef626 | 33 | |
2ce0bfe4 | 34 | static int auth1_process_password(Authctxt *, char *, size_t); |
35 | static int auth1_process_rsa(Authctxt *, char *, size_t); | |
36 | static int auth1_process_rhosts_rsa(Authctxt *, char *, size_t); | |
37 | static int auth1_process_tis_challenge(Authctxt *, char *, size_t); | |
38 | static int auth1_process_tis_response(Authctxt *, char *, size_t); | |
39 | ||
40 | static char *client_user = NULL; /* Used to fill in remote user for PAM */ | |
41 | ||
42 | struct AuthMethod1 { | |
43 | int type; | |
44 | char *name; | |
45 | int *enabled; | |
46 | int (*method)(Authctxt *, char *, size_t); | |
47 | }; | |
48 | ||
49 | const struct AuthMethod1 auth1_methods[] = { | |
50 | { | |
51 | SSH_CMSG_AUTH_PASSWORD, "password", | |
52 | &options.password_authentication, auth1_process_password | |
53 | }, | |
54 | { | |
55 | SSH_CMSG_AUTH_RSA, "rsa", | |
56 | &options.rsa_authentication, auth1_process_rsa | |
57 | }, | |
58 | { | |
59 | SSH_CMSG_AUTH_RHOSTS_RSA, "rhosts-rsa", | |
60 | &options.rhosts_rsa_authentication, auth1_process_rhosts_rsa | |
61 | }, | |
62 | { | |
63 | SSH_CMSG_AUTH_TIS, "challenge-response", | |
64 | &options.challenge_response_authentication, | |
65 | auth1_process_tis_challenge | |
66 | }, | |
67 | { | |
68 | SSH_CMSG_AUTH_TIS_RESPONSE, "challenge-response", | |
69 | &options.challenge_response_authentication, | |
70 | auth1_process_tis_response | |
71 | }, | |
72 | { -1, NULL, NULL, NULL} | |
73 | }; | |
74 | ||
75 | static const struct AuthMethod1 | |
76 | *lookup_authmethod1(int type) | |
77 | { | |
78 | int i; | |
79 | ||
80 | for(i = 0; auth1_methods[i].name != NULL; i++) | |
81 | if (auth1_methods[i].type == type) | |
82 | return (&(auth1_methods[i])); | |
83 | ||
84 | return (NULL); | |
85 | } | |
86 | ||
3c0ef626 | 87 | static char * |
88 | get_authname(int type) | |
89 | { | |
2ce0bfe4 | 90 | const struct AuthMethod1 *a; |
91 | static char buf[64]; | |
92 | ||
93 | if ((a = lookup_authmethod1(type)) != NULL) | |
94 | return (a->name); | |
95 | snprintf(buf, sizeof(buf), "bad-auth-msg-%d", type); | |
96 | return (buf); | |
97 | } | |
98 | ||
99 | static int | |
100 | auth1_process_password(Authctxt *authctxt, char *info, size_t infolen) | |
101 | { | |
102 | int authenticated = 0; | |
103 | char *password; | |
104 | u_int dlen; | |
105 | ||
106 | /* | |
107 | * Read user password. It is in plain text, but was | |
108 | * transmitted over the encrypted channel so it is | |
109 | * not visible to an outside observer. | |
110 | */ | |
111 | password = packet_get_string(&dlen); | |
112 | packet_check_eom(); | |
113 | ||
114 | /* Try authentication with the password. */ | |
115 | authenticated = PRIVSEP(auth_password(authctxt, password)); | |
116 | ||
117 | memset(password, 0, dlen); | |
118 | xfree(password); | |
119 | ||
120 | return (authenticated); | |
121 | } | |
122 | ||
123 | static int | |
124 | auth1_process_rsa(Authctxt *authctxt, char *info, size_t infolen) | |
125 | { | |
126 | int authenticated = 0; | |
127 | BIGNUM *n; | |
128 | ||
129 | /* RSA authentication requested. */ | |
130 | if ((n = BN_new()) == NULL) | |
131 | fatal("do_authloop: BN_new failed"); | |
132 | packet_get_bignum(n); | |
133 | packet_check_eom(); | |
134 | authenticated = auth_rsa(authctxt, n); | |
135 | BN_clear_free(n); | |
136 | ||
137 | return (authenticated); | |
138 | } | |
139 | ||
140 | static int | |
141 | auth1_process_rhosts_rsa(Authctxt *authctxt, char *info, size_t infolen) | |
142 | { | |
143 | int keybits, authenticated = 0; | |
144 | u_int bits; | |
145 | Key *client_host_key; | |
146 | u_int ulen; | |
147 | ||
148 | /* | |
149 | * Get client user name. Note that we just have to | |
150 | * trust the client; root on the client machine can | |
151 | * claim to be any user. | |
152 | */ | |
153 | client_user = packet_get_string(&ulen); | |
154 | ||
155 | /* Get the client host key. */ | |
156 | client_host_key = key_new(KEY_RSA1); | |
157 | bits = packet_get_int(); | |
158 | packet_get_bignum(client_host_key->rsa->e); | |
159 | packet_get_bignum(client_host_key->rsa->n); | |
160 | ||
161 | keybits = BN_num_bits(client_host_key->rsa->n); | |
162 | if (keybits < 0 || bits != (u_int)keybits) { | |
163 | verbose("Warning: keysize mismatch for client_host_key: " | |
164 | "actual %d, announced %d", | |
165 | BN_num_bits(client_host_key->rsa->n), bits); | |
3c0ef626 | 166 | } |
2ce0bfe4 | 167 | packet_check_eom(); |
168 | ||
169 | authenticated = auth_rhosts_rsa(authctxt, client_user, | |
170 | client_host_key); | |
171 | key_free(client_host_key); | |
172 | ||
173 | snprintf(info, infolen, " ruser %.100s", client_user); | |
174 | ||
175 | return (authenticated); | |
176 | } | |
177 | ||
178 | static int | |
179 | auth1_process_tis_challenge(Authctxt *authctxt, char *info, size_t infolen) | |
180 | { | |
181 | char *challenge; | |
182 | ||
183 | if ((challenge = get_challenge(authctxt)) == NULL) | |
184 | return (0); | |
185 | ||
186 | debug("sending challenge '%s'", challenge); | |
187 | packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); | |
188 | packet_put_cstring(challenge); | |
189 | xfree(challenge); | |
190 | packet_send(); | |
191 | packet_write_wait(); | |
192 | ||
193 | return (-1); | |
194 | } | |
195 | ||
196 | static int | |
197 | auth1_process_tis_response(Authctxt *authctxt, char *info, size_t infolen) | |
198 | { | |
199 | int authenticated = 0; | |
200 | char *response; | |
201 | u_int dlen; | |
202 | ||
203 | response = packet_get_string(&dlen); | |
204 | packet_check_eom(); | |
205 | authenticated = verify_response(authctxt, response); | |
206 | memset(response, 'r', dlen); | |
207 | xfree(response); | |
208 | ||
209 | return (authenticated); | |
3c0ef626 | 210 | } |
211 | ||
212 | /* | |
213 | * read packets, try to authenticate the user and | |
214 | * return only if authentication is successful | |
215 | */ | |
216 | static void | |
217 | do_authloop(Authctxt *authctxt) | |
218 | { | |
219 | int authenticated = 0; | |
3c0ef626 | 220 | char info[1024]; |
2ce0bfe4 | 221 | int prev = 0, type = 0; |
222 | const struct AuthMethod1 *meth; | |
3c0ef626 | 223 | |
224 | debug("Attempting authentication for %s%.100s.", | |
7e82606e | 225 | authctxt->valid ? "" : "invalid user ", authctxt->user); |
3c0ef626 | 226 | |
227 | /* If the user has no password, accept authentication immediately. */ | |
228 | if (options.password_authentication && | |
7cac2b65 | 229 | #ifdef KRB5 |
3c0ef626 | 230 | (!options.kerberos_authentication || options.kerberos_or_local_passwd) && |
231 | #endif | |
510132b6 | 232 | PRIVSEP(auth_password(authctxt, ""))) { |
7e82606e | 233 | #ifdef USE_PAM |
234 | if (options.use_pam && (PRIVSEP(do_pam_account()))) | |
235 | #endif | |
236 | { | |
237 | auth_log(authctxt, 1, "without authentication", ""); | |
238 | return; | |
239 | } | |
3c0ef626 | 240 | } |
241 | ||
242 | /* Indicate that authentication is needed. */ | |
243 | packet_start(SSH_SMSG_FAILURE); | |
244 | packet_send(); | |
245 | packet_write_wait(); | |
246 | ||
3c0ef626 | 247 | for (;;) { |
248 | /* default to fail */ | |
249 | authenticated = 0; | |
250 | ||
251 | info[0] = '\0'; | |
252 | ||
253 | /* Get a packet from the client. */ | |
7cac2b65 | 254 | prev = type; |
1e608e42 | 255 | type = packet_read(); |
3c0ef626 | 256 | |
7cac2b65 | 257 | /* |
258 | * If we started challenge-response authentication but the | |
259 | * next packet is not a response to our challenge, release | |
260 | * the resources allocated by get_challenge() (which would | |
261 | * normally have been released by verify_response() had we | |
262 | * received such a response) | |
263 | */ | |
264 | if (prev == SSH_CMSG_AUTH_TIS && | |
265 | type != SSH_CMSG_AUTH_TIS_RESPONSE) | |
266 | abandon_challenge_response(authctxt); | |
267 | ||
2ce0bfe4 | 268 | if ((meth = lookup_authmethod1(type)) == NULL) { |
269 | logit("Unknown message during authentication: " | |
270 | "type %d", type); | |
271 | goto skip; | |
272 | } | |
273 | ||
274 | if (!*(meth->enabled)) { | |
275 | verbose("%s authentication disabled.", meth->name); | |
276 | goto skip; | |
3c0ef626 | 277 | } |
2ce0bfe4 | 278 | |
279 | authenticated = meth->method(authctxt, info, sizeof(info)); | |
280 | if (authenticated == -1) | |
281 | continue; /* "postponed" */ | |
282 | ||
3c0ef626 | 283 | #ifdef BSD_AUTH |
284 | if (authctxt->as) { | |
285 | auth_close(authctxt->as); | |
286 | authctxt->as = NULL; | |
287 | } | |
288 | #endif | |
289 | if (!authctxt->valid && authenticated) | |
290 | fatal("INTERNAL ERROR: authenticated invalid user %s", | |
291 | authctxt->user); | |
292 | ||
d03f4262 | 293 | #ifdef _UNICOS |
d03f4262 | 294 | if (authenticated && cray_access_denied(authctxt->user)) { |
295 | authenticated = 0; | |
296 | fatal("Access denied for user %s.",authctxt->user); | |
297 | } | |
298 | #endif /* _UNICOS */ | |
299 | ||
3c0ef626 | 300 | #ifdef HAVE_CYGWIN |
301 | if (authenticated && | |
2ce0bfe4 | 302 | !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, |
7e82606e | 303 | authctxt->pw)) { |
3c0ef626 | 304 | packet_disconnect("Authentication rejected for uid %d.", |
7e82606e | 305 | authctxt->pw == NULL ? -1 : authctxt->pw->pw_uid); |
3c0ef626 | 306 | authenticated = 0; |
307 | } | |
308 | #else | |
309 | /* Special handling for root */ | |
bfe49944 | 310 | if (authenticated && authctxt->pw->pw_uid == 0 && |
2ce0bfe4 | 311 | !auth_root_allowed(meth->name)) { |
312 | authenticated = 0; | |
dfddba3d | 313 | # ifdef SSH_AUDIT_EVENTS |
314 | PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); | |
315 | # endif | |
316 | } | |
3c0ef626 | 317 | #endif |
7cac2b65 | 318 | |
3c0ef626 | 319 | #ifdef USE_PAM |
540d72c3 | 320 | if (options.use_pam && authenticated && |
dfddba3d | 321 | !PRIVSEP(do_pam_account())) { |
322 | char *msg; | |
323 | size_t len; | |
324 | ||
325 | error("Access denied for user %s by PAM account " | |
2ce0bfe4 | 326 | "configuration", authctxt->user); |
dfddba3d | 327 | len = buffer_len(&loginmsg); |
328 | buffer_append(&loginmsg, "\0", 1); | |
329 | msg = buffer_ptr(&loginmsg); | |
330 | /* strip trailing newlines */ | |
331 | if (len > 0) | |
332 | while (len > 0 && msg[--len] == '\n') | |
333 | msg[len] = '\0'; | |
334 | else | |
335 | msg = "Access denied."; | |
336 | packet_disconnect(msg); | |
337 | } | |
3c0ef626 | 338 | #endif |
339 | ||
2ce0bfe4 | 340 | skip: |
3c0ef626 | 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 | ||
dfddba3d | 352 | if (authctxt->failures++ > options.max_authtries) { |
353 | #ifdef SSH_AUDIT_EVENTS | |
354 | PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES)); | |
355 | #endif | |
3c0ef626 | 356 | packet_disconnect(AUTH_FAIL_MSG, authctxt->user); |
dfddba3d | 357 | } |
3c0ef626 | 358 | |
359 | packet_start(SSH_SMSG_FAILURE); | |
360 | packet_send(); | |
361 | packet_write_wait(); | |
362 | } | |
363 | } | |
364 | ||
365 | /* | |
366 | * Performs authentication of an incoming connection. Session key has already | |
367 | * been exchanged and encryption is enabled. | |
368 | */ | |
540d72c3 | 369 | void |
370 | do_authentication(Authctxt *authctxt) | |
3c0ef626 | 371 | { |
3c0ef626 | 372 | u_int ulen; |
510132b6 | 373 | char *user, *style = NULL; |
3c0ef626 | 374 | |
375 | /* Get the name of the user that we wish to log in as. */ | |
1e608e42 | 376 | packet_read_expect(SSH_CMSG_USER); |
3c0ef626 | 377 | |
378 | /* Get the user name. */ | |
379 | user = packet_get_string(&ulen); | |
1e608e42 | 380 | packet_check_eom(); |
3c0ef626 | 381 | |
382 | if ((style = strchr(user, ':')) != NULL) | |
383 | *style++ = '\0'; | |
384 | ||
3c0ef626 | 385 | authctxt->user = user; |
386 | authctxt->style = style; | |
387 | ||
388 | /* Verify that the user is a valid user. */ | |
510132b6 | 389 | if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL) |
3c0ef626 | 390 | authctxt->valid = 1; |
7cac2b65 | 391 | else { |
7e82606e | 392 | debug("do_authentication: invalid user %s", user); |
7cac2b65 | 393 | authctxt->pw = fakepw(); |
394 | } | |
3c0ef626 | 395 | |
7e82606e | 396 | setproctitle("%s%s", authctxt->valid ? user : "unknown", |
510132b6 | 397 | use_privsep ? " [net]" : ""); |
3c0ef626 | 398 | |
399 | #ifdef USE_PAM | |
7cac2b65 | 400 | if (options.use_pam) |
12a403af | 401 | PRIVSEP(start_pam(authctxt)); |
3c0ef626 | 402 | #endif |
403 | ||
404 | /* | |
405 | * If we are not running as root, the user must have the same uid as | |
2ce0bfe4 | 406 | * the server. |
3c0ef626 | 407 | */ |
408 | #ifndef HAVE_CYGWIN | |
510132b6 | 409 | if (!use_privsep && getuid() != 0 && authctxt->pw && |
410 | authctxt->pw->pw_uid != getuid()) | |
3c0ef626 | 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(); | |
3c0ef626 | 424 | } |