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a306f2dd | 1 | /* |
2 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
3 | * All rights reserved | |
bcbf86ec | 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". | |
a306f2dd | 10 | */ |
11 | ||
12 | #include "includes.h" | |
5d47f1d4 | 13 | RCSID("$OpenBSD: auth1.c,v 1.47 2003/02/06 21:22:42 markus Exp $"); |
94ec8c6b | 14 | |
a306f2dd | 15 | #include "xmalloc.h" |
16 | #include "rsa.h" | |
42f11eb2 | 17 | #include "ssh1.h" |
a306f2dd | 18 | #include "packet.h" |
19 | #include "buffer.h" | |
a306f2dd | 20 | #include "mpaux.h" |
42f11eb2 | 21 | #include "log.h" |
a306f2dd | 22 | #include "servconf.h" |
23 | #include "compat.h" | |
24 | #include "auth.h" | |
7899c98f | 25 | #include "channels.h" |
a306f2dd | 26 | #include "session.h" |
ced49be2 | 27 | #include "uidswap.h" |
1853d1ef | 28 | #include "monitor_wrap.h" |
a306f2dd | 29 | |
30 | /* import */ | |
31 | extern ServerOptions options; | |
94ec8c6b | 32 | |
a306f2dd | 33 | /* |
34 | * convert ssh auth msg type into description | |
35 | */ | |
396c147e | 36 | static char * |
a306f2dd | 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"; | |
59c97189 | 49 | case SSH_CMSG_AUTH_TIS: |
50 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
51 | return "challenge-response"; | |
ced49be2 | 52 | #if defined(KRB4) || defined(KRB5) |
a306f2dd | 53 | case SSH_CMSG_AUTH_KERBEROS: |
54 | return "kerberos"; | |
a306f2dd | 55 | #endif |
56 | } | |
57 | snprintf(buf, sizeof buf, "bad-auth-msg-%d", type); | |
58 | return buf; | |
59 | } | |
60 | ||
61 | /* | |
59c97189 | 62 | * read packets, try to authenticate the user and |
63 | * return only if authentication is successful | |
a306f2dd | 64 | */ |
396c147e | 65 | static void |
59c97189 | 66 | do_authloop(Authctxt *authctxt) |
a306f2dd | 67 | { |
94ec8c6b | 68 | int authenticated = 0; |
1e3b8b07 | 69 | u_int bits; |
b775c6f2 | 70 | Key *client_host_key; |
a306f2dd | 71 | BIGNUM *n; |
94ec8c6b | 72 | char *client_user, *password; |
59c97189 | 73 | char info[1024]; |
1e3b8b07 | 74 | u_int dlen; |
1e3b8b07 | 75 | u_int ulen; |
05114c74 | 76 | int prev, type = 0; |
59c97189 | 77 | struct passwd *pw = authctxt->pw; |
78 | ||
79 | debug("Attempting authentication for %s%.100s.", | |
184eed6a | 80 | authctxt->valid ? "" : "illegal user ", authctxt->user); |
59c97189 | 81 | |
82 | /* If the user has no password, accept authentication immediately. */ | |
83 | if (options.password_authentication && | |
ced49be2 | 84 | #if defined(KRB4) || defined(KRB5) |
59c97189 | 85 | (!options.kerberos_authentication || options.kerberos_or_local_passwd) && |
86 | #endif | |
1853d1ef | 87 | PRIVSEP(auth_password(authctxt, ""))) { |
59c97189 | 88 | auth_log(authctxt, 1, "without authentication", ""); |
89 | return; | |
90 | } | |
a306f2dd | 91 | |
92 | /* Indicate that authentication is needed. */ | |
93 | packet_start(SSH_SMSG_FAILURE); | |
94 | packet_send(); | |
95 | packet_write_wait(); | |
96 | ||
94ec8c6b | 97 | client_user = NULL; |
98 | ||
59c97189 | 99 | for (;;) { |
94ec8c6b | 100 | /* default to fail */ |
101 | authenticated = 0; | |
102 | ||
59c97189 | 103 | info[0] = '\0'; |
a306f2dd | 104 | |
105 | /* Get a packet from the client. */ | |
05114c74 | 106 | prev = type; |
54a5250f | 107 | type = packet_read(); |
a306f2dd | 108 | |
05114c74 | 109 | /* |
110 | * If we started challenge-response authentication but the | |
111 | * next packet is not a response to our challenge, release | |
112 | * the resources allocated by get_challenge() (which would | |
113 | * normally have been released by verify_response() had we | |
114 | * received such a response) | |
115 | */ | |
116 | if (prev == SSH_CMSG_AUTH_TIS && | |
117 | type != SSH_CMSG_AUTH_TIS_RESPONSE) | |
118 | abandon_challenge_response(authctxt); | |
119 | ||
a306f2dd | 120 | /* Process the packet. */ |
121 | switch (type) { | |
a306f2dd | 122 | |
ced49be2 | 123 | #if defined(KRB4) || defined(KRB5) |
a306f2dd | 124 | case SSH_CMSG_AUTH_KERBEROS: |
125 | if (!options.kerberos_authentication) { | |
a306f2dd | 126 | verbose("Kerberos authentication disabled."); |
a306f2dd | 127 | } else { |
ced49be2 | 128 | char *kdata = packet_get_string(&dlen); |
95500969 | 129 | packet_check_eom(); |
184eed6a | 130 | |
ced49be2 | 131 | if (kdata[0] == 4) { /* KRB_PROT_VERSION */ |
132 | #ifdef KRB4 | |
2db9d8aa | 133 | KTEXT_ST tkt, reply; |
ced49be2 | 134 | tkt.length = dlen; |
135 | if (tkt.length < MAX_KTXT_LEN) | |
136 | memcpy(tkt.dat, kdata, tkt.length); | |
184eed6a | 137 | |
2db9d8aa | 138 | if (PRIVSEP(auth_krb4(authctxt, &tkt, |
139 | &client_user, &reply))) { | |
ced49be2 | 140 | authenticated = 1; |
141 | snprintf(info, sizeof(info), | |
142 | " tktuser %.100s", | |
143 | client_user); | |
2db9d8aa | 144 | |
145 | packet_start( | |
146 | SSH_SMSG_AUTH_KERBEROS_RESPONSE); | |
147 | packet_put_string((char *) | |
148 | reply.dat, reply.length); | |
149 | packet_send(); | |
150 | packet_write_wait(); | |
94ec8c6b | 151 | } |
ced49be2 | 152 | #endif /* KRB4 */ |
153 | } else { | |
154 | #ifdef KRB5 | |
696f6bef | 155 | krb5_data tkt, reply; |
ced49be2 | 156 | tkt.length = dlen; |
157 | tkt.data = kdata; | |
184eed6a | 158 | |
696f6bef | 159 | if (PRIVSEP(auth_krb5(authctxt, &tkt, |
160 | &client_user, &reply))) { | |
ced49be2 | 161 | authenticated = 1; |
162 | snprintf(info, sizeof(info), | |
163 | " tktuser %.100s", | |
164 | client_user); | |
b77a87e5 | 165 | |
696f6bef | 166 | /* Send response to client */ |
167 | packet_start( | |
168 | SSH_SMSG_AUTH_KERBEROS_RESPONSE); | |
169 | packet_put_string((char *) | |
170 | reply.data, reply.length); | |
171 | packet_send(); | |
172 | packet_write_wait(); | |
173 | ||
174 | if (reply.length) | |
175 | xfree(reply.data); | |
ced49be2 | 176 | } |
177 | #endif /* KRB5 */ | |
a306f2dd | 178 | } |
59c97189 | 179 | xfree(kdata); |
a306f2dd | 180 | } |
181 | break; | |
ced49be2 | 182 | #endif /* KRB4 || KRB5 */ |
184eed6a | 183 | |
ced49be2 | 184 | #if defined(AFS) || defined(KRB5) |
185 | /* XXX - punt on backward compatibility here. */ | |
186 | case SSH_CMSG_HAVE_KERBEROS_TGT: | |
187 | packet_send_debug("Kerberos TGT passing disabled before authentication."); | |
188 | break; | |
189 | #ifdef AFS | |
190 | case SSH_CMSG_HAVE_AFS_TOKEN: | |
191 | packet_send_debug("AFS token passing disabled before authentication."); | |
192 | break; | |
193 | #endif /* AFS */ | |
194 | #endif /* AFS || KRB5 */ | |
184eed6a | 195 | |
a306f2dd | 196 | case SSH_CMSG_AUTH_RHOSTS: |
197 | if (!options.rhosts_authentication) { | |
198 | verbose("Rhosts authentication disabled."); | |
199 | break; | |
200 | } | |
201 | /* | |
202 | * Get client user name. Note that we just have to | |
203 | * trust the client; this is one reason why rhosts | |
204 | * authentication is insecure. (Another is | |
205 | * IP-spoofing on a local network.) | |
206 | */ | |
207 | client_user = packet_get_string(&ulen); | |
95500969 | 208 | packet_check_eom(); |
a306f2dd | 209 | |
94ec8c6b | 210 | /* Try to authenticate using /etc/hosts.equiv and .rhosts. */ |
a306f2dd | 211 | authenticated = auth_rhosts(pw, client_user); |
212 | ||
59c97189 | 213 | snprintf(info, sizeof info, " ruser %.100s", client_user); |
a306f2dd | 214 | break; |
215 | ||
216 | case SSH_CMSG_AUTH_RHOSTS_RSA: | |
217 | if (!options.rhosts_rsa_authentication) { | |
218 | verbose("Rhosts with RSA authentication disabled."); | |
219 | break; | |
220 | } | |
221 | /* | |
222 | * Get client user name. Note that we just have to | |
223 | * trust the client; root on the client machine can | |
224 | * claim to be any user. | |
225 | */ | |
226 | client_user = packet_get_string(&ulen); | |
227 | ||
228 | /* Get the client host key. */ | |
b775c6f2 | 229 | client_host_key = key_new(KEY_RSA1); |
a306f2dd | 230 | bits = packet_get_int(); |
20b279e6 | 231 | packet_get_bignum(client_host_key->rsa->e); |
232 | packet_get_bignum(client_host_key->rsa->n); | |
a306f2dd | 233 | |
b775c6f2 | 234 | if (bits != BN_num_bits(client_host_key->rsa->n)) |
94ec8c6b | 235 | verbose("Warning: keysize mismatch for client_host_key: " |
b775c6f2 | 236 | "actual %d, announced %d", |
7203d6bb | 237 | BN_num_bits(client_host_key->rsa->n), bits); |
95500969 | 238 | packet_check_eom(); |
a306f2dd | 239 | |
b775c6f2 | 240 | authenticated = auth_rhosts_rsa(pw, client_user, |
dc421aa3 | 241 | client_host_key); |
b775c6f2 | 242 | key_free(client_host_key); |
a306f2dd | 243 | |
59c97189 | 244 | snprintf(info, sizeof info, " ruser %.100s", client_user); |
a306f2dd | 245 | break; |
246 | ||
247 | case SSH_CMSG_AUTH_RSA: | |
248 | if (!options.rsa_authentication) { | |
249 | verbose("RSA authentication disabled."); | |
250 | break; | |
251 | } | |
252 | /* RSA authentication requested. */ | |
b775c6f2 | 253 | if ((n = BN_new()) == NULL) |
254 | fatal("do_authloop: BN_new failed"); | |
20b279e6 | 255 | packet_get_bignum(n); |
95500969 | 256 | packet_check_eom(); |
a306f2dd | 257 | authenticated = auth_rsa(pw, n); |
258 | BN_clear_free(n); | |
259 | break; | |
260 | ||
261 | case SSH_CMSG_AUTH_PASSWORD: | |
262 | if (!options.password_authentication) { | |
263 | verbose("Password authentication disabled."); | |
264 | break; | |
265 | } | |
266 | /* | |
267 | * Read user password. It is in plain text, but was | |
268 | * transmitted over the encrypted channel so it is | |
269 | * not visible to an outside observer. | |
270 | */ | |
271 | password = packet_get_string(&dlen); | |
95500969 | 272 | packet_check_eom(); |
a306f2dd | 273 | |
b4b5d644 | 274 | /* Try authentication with the password. */ |
1853d1ef | 275 | authenticated = PRIVSEP(auth_password(authctxt, password)); |
a306f2dd | 276 | |
277 | memset(password, 0, strlen(password)); | |
278 | xfree(password); | |
279 | break; | |
280 | ||
a306f2dd | 281 | case SSH_CMSG_AUTH_TIS: |
282 | debug("rcvd SSH_CMSG_AUTH_TIS"); | |
5ba55ada | 283 | if (options.challenge_response_authentication == 1) { |
284 | char *challenge = get_challenge(authctxt); | |
59c97189 | 285 | if (challenge != NULL) { |
286 | debug("sending challenge '%s'", challenge); | |
a306f2dd | 287 | packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); |
59c97189 | 288 | packet_put_cstring(challenge); |
5ba55ada | 289 | xfree(challenge); |
a306f2dd | 290 | packet_send(); |
291 | packet_write_wait(); | |
292 | continue; | |
293 | } | |
294 | } | |
295 | break; | |
296 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
297 | debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE"); | |
5ba55ada | 298 | if (options.challenge_response_authentication == 1) { |
a306f2dd | 299 | char *response = packet_get_string(&dlen); |
95500969 | 300 | packet_check_eom(); |
59c97189 | 301 | authenticated = verify_response(authctxt, response); |
302 | memset(response, 'r', dlen); | |
a306f2dd | 303 | xfree(response); |
304 | } | |
305 | break; | |
a306f2dd | 306 | |
307 | default: | |
308 | /* | |
309 | * Any unknown messages will be ignored (and failure | |
310 | * returned) during authentication. | |
311 | */ | |
bbe88b6d | 312 | logit("Unknown message during authentication: type %d", type); |
a306f2dd | 313 | break; |
314 | } | |
af774732 | 315 | #ifdef BSD_AUTH |
316 | if (authctxt->as) { | |
317 | auth_close(authctxt->as); | |
318 | authctxt->as = NULL; | |
319 | } | |
320 | #endif | |
59c97189 | 321 | if (!authctxt->valid && authenticated) |
322 | fatal("INTERNAL ERROR: authenticated invalid user %s", | |
323 | authctxt->user); | |
a306f2dd | 324 | |
ef51930f | 325 | #ifdef _UNICOS |
ef51930f | 326 | if (authenticated && cray_access_denied(authctxt->user)) { |
327 | authenticated = 0; | |
328 | fatal("Access denied for user %s.",authctxt->user); | |
329 | } | |
330 | #endif /* _UNICOS */ | |
331 | ||
2b87da3b | 332 | #ifdef HAVE_CYGWIN |
333 | if (authenticated && | |
e9571a2c | 334 | !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) { |
3c62e7eb | 335 | packet_disconnect("Authentication rejected for uid %d.", |
e9571a2c | 336 | pw == NULL ? -1 : pw->pw_uid); |
3c62e7eb | 337 | authenticated = 0; |
338 | } | |
3c418020 | 339 | #else |
59c97189 | 340 | /* Special handling for root */ |
5d47f1d4 | 341 | if (authenticated && authctxt->pw->pw_uid == 0 && |
15853e93 | 342 | !auth_root_allowed(get_authname(type))) |
59c97189 | 343 | authenticated = 0; |
3c418020 | 344 | #endif |
2b87da3b | 345 | #ifdef USE_PAM |
ad200abb | 346 | if (!use_privsep && authenticated && |
347 | !do_pam_account(pw->pw_name, client_user)) | |
94ec8c6b | 348 | authenticated = 0; |
349 | #endif | |
a306f2dd | 350 | |
59c97189 | 351 | /* Log before sending the reply */ |
352 | auth_log(authctxt, authenticated, get_authname(type), info); | |
353 | ||
a306f2dd | 354 | if (client_user != NULL) { |
355 | xfree(client_user); | |
356 | client_user = NULL; | |
357 | } | |
358 | ||
94ec8c6b | 359 | if (authenticated) |
360 | return; | |
361 | ||
9a6fee8b | 362 | if (authctxt->failures++ > AUTH_FAIL_MAX) |
59c97189 | 363 | packet_disconnect(AUTH_FAIL_MSG, authctxt->user); |
a306f2dd | 364 | |
a306f2dd | 365 | packet_start(SSH_SMSG_FAILURE); |
366 | packet_send(); | |
367 | packet_write_wait(); | |
368 | } | |
369 | } | |
370 | ||
371 | /* | |
372 | * Performs authentication of an incoming connection. Session key has already | |
373 | * been exchanged and encryption is enabled. | |
374 | */ | |
1b34c1b3 | 375 | Authctxt * |
d5bb9418 | 376 | do_authentication(void) |
a306f2dd | 377 | { |
59c97189 | 378 | Authctxt *authctxt; |
1e3b8b07 | 379 | u_int ulen; |
f8d99a32 | 380 | char *user, *style = NULL; |
a306f2dd | 381 | |
382 | /* Get the name of the user that we wish to log in as. */ | |
54a5250f | 383 | packet_read_expect(SSH_CMSG_USER); |
a306f2dd | 384 | |
385 | /* Get the user name. */ | |
386 | user = packet_get_string(&ulen); | |
95500969 | 387 | packet_check_eom(); |
a306f2dd | 388 | |
59c97189 | 389 | if ((style = strchr(user, ':')) != NULL) |
ced49be2 | 390 | *style++ = '\0'; |
59c97189 | 391 | |
f8d99a32 | 392 | #ifdef KRB5 |
ced49be2 | 393 | /* XXX - SSH.com Kerberos v5 braindeath. */ |
f8d99a32 | 394 | if ((datafellows & SSH_BUG_K5USER) && |
395 | options.kerberos_authentication) { | |
396 | char *p; | |
397 | if ((p = strchr(user, '@')) != NULL) | |
398 | *p = '\0'; | |
399 | } | |
400 | #endif | |
184eed6a | 401 | |
59c97189 | 402 | authctxt = authctxt_new(); |
403 | authctxt->user = user; | |
404 | authctxt->style = style; | |
405 | ||
a306f2dd | 406 | /* Verify that the user is a valid user. */ |
5f1f36b5 | 407 | if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL) |
59c97189 | 408 | authctxt->valid = 1; |
5f1f36b5 | 409 | else |
59c97189 | 410 | debug("do_authentication: illegal user %s", user); |
a306f2dd | 411 | |
5f1f36b5 | 412 | setproctitle("%s%s", authctxt->pw ? user : "unknown", |
1853d1ef | 413 | use_privsep ? " [net]" : ""); |
6172e290 | 414 | |
a306f2dd | 415 | #ifdef USE_PAM |
ad200abb | 416 | PRIVSEP(start_pam(authctxt->pw == NULL ? "NOUSER" : user)); |
a306f2dd | 417 | #endif |
418 | ||
419 | /* | |
420 | * If we are not running as root, the user must have the same uid as | |
94ec8c6b | 421 | * the server. (Unless you are running Windows) |
a306f2dd | 422 | */ |
94ec8c6b | 423 | #ifndef HAVE_CYGWIN |
5f1f36b5 | 424 | if (!use_privsep && getuid() != 0 && authctxt->pw && |
425 | authctxt->pw->pw_uid != getuid()) | |
a306f2dd | 426 | packet_disconnect("Cannot change user when server not running as root."); |
3c62e7eb | 427 | #endif |
a306f2dd | 428 | |
59c97189 | 429 | /* |
b4b5d644 | 430 | * Loop until the user has been authenticated or the connection is |
431 | * closed, do_authloop() returns only if authentication is successful | |
432 | */ | |
59c97189 | 433 | do_authloop(authctxt); |
a306f2dd | 434 | |
435 | /* The user has been authenticated and accepted. */ | |
94ec8c6b | 436 | packet_start(SSH_SMSG_SUCCESS); |
437 | packet_send(); | |
438 | packet_write_wait(); | |
59c97189 | 439 | |
1b34c1b3 | 440 | return (authctxt); |
a306f2dd | 441 | } |