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Damien Millereba71ba2000-04-29 23:57:08 +10001/*
2 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
3 * All rights reserved
Damien Millere4340be2000-09-16 13:29:08 +11004 *
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".
Damien Millereba71ba2000-04-29 23:57:08 +100010 */
11
12#include "includes.h"
Ben Lindstrom95fb2dd2001-01-23 03:12:10 +000013RCSID("$OpenBSD: auth1.c,v 1.14 2001/01/22 23:06:39 markus Exp $");
Damien Millereba71ba2000-04-29 23:57:08 +100014
Damien Millerb8c656e2000-06-28 15:22:41 +100015#ifdef HAVE_OSF_SIA
16# include <sia.h>
17# include <siad.h>
18#endif
19
Damien Miller874d77b2000-10-14 16:23:11 +110020#include "xmalloc.h"
21#include "rsa.h"
Ben Lindstrom226cfa02001-01-22 05:34:40 +000022#include "ssh1.h"
Damien Miller874d77b2000-10-14 16:23:11 +110023#include "packet.h"
24#include "buffer.h"
25#include "mpaux.h"
Ben Lindstrom226cfa02001-01-22 05:34:40 +000026#include "log.h"
Damien Miller874d77b2000-10-14 16:23:11 +110027#include "servconf.h"
28#include "compat.h"
29#include "auth.h"
30#include "session.h"
31
Damien Millereba71ba2000-04-29 23:57:08 +100032/* import */
33extern ServerOptions options;
34extern char *forced_command;
Damien Miller874d77b2000-10-14 16:23:11 +110035
36#ifdef WITH_AIXAUTHENTICATE
37extern char *aixloginmsg;
38#endif /* WITH_AIXAUTHENTICATE */
Damien Millerfe668e42000-07-08 10:44:13 +100039#ifdef HAVE_OSF_SIA
40extern int saved_argc;
41extern char **saved_argv;
42#endif /* HAVE_OSF_SIA */
Damien Millereba71ba2000-04-29 23:57:08 +100043
44/*
45 * convert ssh auth msg type into description
46 */
47char *
48get_authname(int type)
49{
50 static char buf[1024];
51 switch (type) {
52 case SSH_CMSG_AUTH_PASSWORD:
53 return "password";
54 case SSH_CMSG_AUTH_RSA:
55 return "rsa";
56 case SSH_CMSG_AUTH_RHOSTS_RSA:
57 return "rhosts-rsa";
58 case SSH_CMSG_AUTH_RHOSTS:
59 return "rhosts";
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000060 case SSH_CMSG_AUTH_TIS:
61 case SSH_CMSG_AUTH_TIS_RESPONSE:
62 return "challenge-response";
Damien Millereba71ba2000-04-29 23:57:08 +100063#ifdef KRB4
64 case SSH_CMSG_AUTH_KERBEROS:
65 return "kerberos";
66#endif
Damien Millereba71ba2000-04-29 23:57:08 +100067 }
68 snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
69 return buf;
70}
71
72/*
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000073 * read packets, try to authenticate the user and
74 * return only if authentication is successful
Damien Millereba71ba2000-04-29 23:57:08 +100075 */
76void
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000077do_authloop(Authctxt *authctxt)
Damien Millereba71ba2000-04-29 23:57:08 +100078{
Damien Miller874d77b2000-10-14 16:23:11 +110079 int authenticated = 0;
Ben Lindstrom46c16222000-12-22 01:43:59 +000080 u_int bits;
Damien Millereba71ba2000-04-29 23:57:08 +100081 RSA *client_host_key;
82 BIGNUM *n;
Damien Miller874d77b2000-10-14 16:23:11 +110083 char *client_user, *password;
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000084 char info[1024];
Ben Lindstrom46c16222000-12-22 01:43:59 +000085 u_int dlen;
Damien Millereba71ba2000-04-29 23:57:08 +100086 int plen, nlen, elen;
Ben Lindstrom46c16222000-12-22 01:43:59 +000087 u_int ulen;
Damien Millereba71ba2000-04-29 23:57:08 +100088 int type = 0;
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000089 struct passwd *pw = authctxt->pw;
90
91 debug("Attempting authentication for %s%.100s.",
92 authctxt->valid ? "" : "illegal user ", authctxt->user);
93
94 /* If the user has no password, accept authentication immediately. */
95 if (options.password_authentication &&
96#ifdef KRB4
97 (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
98#endif
Ben Lindstromb100ec92001-01-19 05:37:32 +000099#ifdef USE_PAM
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000100 auth_pam_password(pw, password)) {
101#else
102 auth_password(pw, "")) {
103#endif
104 auth_log(authctxt, 1, "without authentication", "");
105 return;
106 }
Damien Millereba71ba2000-04-29 23:57:08 +1000107
108 /* Indicate that authentication is needed. */
109 packet_start(SSH_SMSG_FAILURE);
110 packet_send();
111 packet_write_wait();
112
Damien Miller874d77b2000-10-14 16:23:11 +1100113 client_user = NULL;
114
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000115 for (;;) {
Damien Miller874d77b2000-10-14 16:23:11 +1100116 /* default to fail */
117 authenticated = 0;
118
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000119 info[0] = '\0';
Damien Millereba71ba2000-04-29 23:57:08 +1000120
121 /* Get a packet from the client. */
122 type = packet_read(&plen);
123
124 /* Process the packet. */
125 switch (type) {
126#ifdef AFS
127 case SSH_CMSG_HAVE_KERBEROS_TGT:
128 if (!options.kerberos_tgt_passing) {
Damien Millereba71ba2000-04-29 23:57:08 +1000129 verbose("Kerberos tgt passing disabled.");
130 break;
131 } else {
132 /* Accept Kerberos tgt. */
133 char *tgt = packet_get_string(&dlen);
134 packet_integrity_check(plen, 4 + dlen, type);
135 if (!auth_kerberos_tgt(pw, tgt))
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000136 verbose("Kerberos tgt REFUSED for %.100s", authctxt->user);
Damien Millereba71ba2000-04-29 23:57:08 +1000137 xfree(tgt);
138 }
139 continue;
140
141 case SSH_CMSG_HAVE_AFS_TOKEN:
142 if (!options.afs_token_passing || !k_hasafs()) {
Damien Millereba71ba2000-04-29 23:57:08 +1000143 verbose("AFS token passing disabled.");
144 break;
145 } else {
146 /* Accept AFS token. */
147 char *token_string = packet_get_string(&dlen);
148 packet_integrity_check(plen, 4 + dlen, type);
149 if (!auth_afs_token(pw, token_string))
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000150 verbose("AFS token REFUSED for %.100s", authctxt->user);
Damien Millereba71ba2000-04-29 23:57:08 +1000151 xfree(token_string);
152 }
153 continue;
154#endif /* AFS */
155#ifdef KRB4
156 case SSH_CMSG_AUTH_KERBEROS:
157 if (!options.kerberos_authentication) {
Damien Millereba71ba2000-04-29 23:57:08 +1000158 verbose("Kerberos authentication disabled.");
159 break;
160 } else {
161 /* Try Kerberos v4 authentication. */
162 KTEXT_ST auth;
163 char *tkt_user = NULL;
Ben Lindstrom46c16222000-12-22 01:43:59 +0000164 char *kdata = packet_get_string((u_int *) &auth.length);
Damien Millereba71ba2000-04-29 23:57:08 +1000165 packet_integrity_check(plen, 4 + auth.length, type);
166
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000167 if (authctxt->valid) {
168 if (auth.length < MAX_KTXT_LEN)
169 memcpy(auth.dat, kdata, auth.length);
Damien Miller874d77b2000-10-14 16:23:11 +1100170 authenticated = auth_krb4(pw->pw_name, &auth, &tkt_user);
171 if (authenticated) {
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000172 snprintf(info, sizeof info,
173 " tktuser %.100s", tkt_user);
Damien Miller874d77b2000-10-14 16:23:11 +1100174 xfree(tkt_user);
175 }
Damien Millereba71ba2000-04-29 23:57:08 +1000176 }
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000177 xfree(kdata);
Damien Millereba71ba2000-04-29 23:57:08 +1000178 }
179 break;
180#endif /* KRB4 */
181
182 case SSH_CMSG_AUTH_RHOSTS:
183 if (!options.rhosts_authentication) {
184 verbose("Rhosts authentication disabled.");
185 break;
186 }
187 /*
188 * Get client user name. Note that we just have to
189 * trust the client; this is one reason why rhosts
190 * authentication is insecure. (Another is
191 * IP-spoofing on a local network.)
192 */
193 client_user = packet_get_string(&ulen);
194 packet_integrity_check(plen, 4 + ulen, type);
195
Damien Miller874d77b2000-10-14 16:23:11 +1100196 /* Try to authenticate using /etc/hosts.equiv and .rhosts. */
Damien Millereba71ba2000-04-29 23:57:08 +1000197 authenticated = auth_rhosts(pw, client_user);
198
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000199 snprintf(info, sizeof info, " ruser %.100s", client_user);
Damien Millereba71ba2000-04-29 23:57:08 +1000200 break;
201
202 case SSH_CMSG_AUTH_RHOSTS_RSA:
203 if (!options.rhosts_rsa_authentication) {
204 verbose("Rhosts with RSA authentication disabled.");
205 break;
206 }
207 /*
208 * Get client user name. Note that we just have to
209 * trust the client; root on the client machine can
210 * claim to be any user.
211 */
212 client_user = packet_get_string(&ulen);
213
214 /* Get the client host key. */
215 client_host_key = RSA_new();
216 if (client_host_key == NULL)
217 fatal("RSA_new failed");
218 client_host_key->e = BN_new();
219 client_host_key->n = BN_new();
220 if (client_host_key->e == NULL || client_host_key->n == NULL)
221 fatal("BN_new failed");
222 bits = packet_get_int();
223 packet_get_bignum(client_host_key->e, &elen);
224 packet_get_bignum(client_host_key->n, &nlen);
225
226 if (bits != BN_num_bits(client_host_key->n))
Damien Miller874d77b2000-10-14 16:23:11 +1100227 verbose("Warning: keysize mismatch for client_host_key: "
Damien Millerbd483e72000-04-30 10:00:53 +1000228 "actual %d, announced %d", BN_num_bits(client_host_key->n), bits);
Damien Millereba71ba2000-04-29 23:57:08 +1000229 packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type);
230
231 authenticated = auth_rhosts_rsa(pw, client_user, client_host_key);
232 RSA_free(client_host_key);
233
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000234 snprintf(info, sizeof info, " ruser %.100s", client_user);
Damien Millereba71ba2000-04-29 23:57:08 +1000235 break;
236
237 case SSH_CMSG_AUTH_RSA:
238 if (!options.rsa_authentication) {
239 verbose("RSA authentication disabled.");
240 break;
241 }
242 /* RSA authentication requested. */
243 n = BN_new();
244 packet_get_bignum(n, &nlen);
245 packet_integrity_check(plen, nlen, type);
246 authenticated = auth_rsa(pw, n);
247 BN_clear_free(n);
248 break;
249
250 case SSH_CMSG_AUTH_PASSWORD:
251 if (!options.password_authentication) {
252 verbose("Password authentication disabled.");
253 break;
254 }
255 /*
256 * Read user password. It is in plain text, but was
257 * transmitted over the encrypted channel so it is
258 * not visible to an outside observer.
259 */
260 password = packet_get_string(&dlen);
261 packet_integrity_check(plen, 4 + dlen, type);
262
263#ifdef USE_PAM
264 /* Do PAM auth with password */
265 authenticated = auth_pam_password(pw, password);
Damien Millerb8c656e2000-06-28 15:22:41 +1000266#elif defined(HAVE_OSF_SIA)
267 /* Do SIA auth with password */
Kevin Stevesef4eea92001-02-05 12:42:17 +0000268 if (sia_validate_user(NULL, saved_argc, saved_argv,
269 get_canonical_hostname(options.reverse_mapping_check),
Damien Miller33804262001-02-04 23:20:18 +1100270 pw->pw_name, NULL, 0, NULL, password) == SIASUCCESS) {
Damien Millerb8c656e2000-06-28 15:22:41 +1000271 authenticated = 1;
272 }
273#else /* !USE_PAM && !HAVE_OSF_SIA */
Kevin Steves12aaa042001-01-24 21:23:39 +0000274 /* Try authentication with the password. */
Damien Millereba71ba2000-04-29 23:57:08 +1000275 authenticated = auth_password(pw, password);
276#endif /* USE_PAM */
277
278 memset(password, 0, strlen(password));
279 xfree(password);
280 break;
281
Damien Millereba71ba2000-04-29 23:57:08 +1000282 case SSH_CMSG_AUTH_TIS:
283 debug("rcvd SSH_CMSG_AUTH_TIS");
Ben Lindstrom95fb2dd2001-01-23 03:12:10 +0000284 if (options.challenge_reponse_authentication == 1) {
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000285 char *challenge = get_challenge(authctxt, authctxt->style);
286 if (challenge != NULL) {
287 debug("sending challenge '%s'", challenge);
Damien Millereba71ba2000-04-29 23:57:08 +1000288 packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000289 packet_put_cstring(challenge);
Damien Millereba71ba2000-04-29 23:57:08 +1000290 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");
Ben Lindstrom95fb2dd2001-01-23 03:12:10 +0000298 if (options.challenge_reponse_authentication == 1) {
Damien Millereba71ba2000-04-29 23:57:08 +1000299 char *response = packet_get_string(&dlen);
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000300 debug("got response '%s'", response);
Damien Millereba71ba2000-04-29 23:57:08 +1000301 packet_integrity_check(plen, 4 + dlen, type);
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000302 authenticated = verify_response(authctxt, response);
303 memset(response, 'r', dlen);
Damien Millereba71ba2000-04-29 23:57:08 +1000304 xfree(response);
305 }
306 break;
Damien Millereba71ba2000-04-29 23:57:08 +1000307
308 default:
309 /*
310 * Any unknown messages will be ignored (and failure
311 * returned) during authentication.
312 */
313 log("Unknown message during authentication: type %d", type);
314 break;
315 }
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000316 if (!authctxt->valid && authenticated)
317 fatal("INTERNAL ERROR: authenticated invalid user %s",
318 authctxt->user);
Damien Millereba71ba2000-04-29 23:57:08 +1000319
Kevin Stevesef4eea92001-02-05 12:42:17 +0000320#ifdef HAVE_CYGWIN
321 if (authenticated &&
Damien Millerb70b61f2000-09-16 16:25:12 +1100322 !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD,pw->pw_uid)) {
Damien Millerbac2d8a2000-09-05 16:13:06 +1100323 packet_disconnect("Authentication rejected for uid %d.",
Damien Miller874d77b2000-10-14 16:23:11 +1100324 (int)pw->pw_uid);
Damien Millerbac2d8a2000-09-05 16:13:06 +1100325 authenticated = 0;
326 }
Ben Lindstrom5dc81502001-01-19 06:10:29 +0000327#else
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000328 /* Special handling for root */
329 if (authenticated && authctxt->pw->pw_uid == 0 && !auth_root_allowed())
330 authenticated = 0;
Ben Lindstrom5dc81502001-01-19 06:10:29 +0000331#endif
Kevin Stevesef4eea92001-02-05 12:42:17 +0000332#ifdef USE_PAM
Damien Miller874d77b2000-10-14 16:23:11 +1100333 if (authenticated && !do_pam_account(pw->pw_name, client_user))
334 authenticated = 0;
335#endif
Damien Millereba71ba2000-04-29 23:57:08 +1000336
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000337 /* Log before sending the reply */
338 auth_log(authctxt, authenticated, get_authname(type), info);
339
Damien Millereba71ba2000-04-29 23:57:08 +1000340 if (client_user != NULL) {
341 xfree(client_user);
342 client_user = NULL;
343 }
344
Damien Miller874d77b2000-10-14 16:23:11 +1100345 if (authenticated)
346 return;
347
Kevin Steves12aaa042001-01-24 21:23:39 +0000348 if (authctxt->failures++ > AUTH_FAIL_MAX) {
Kevin Stevesef4eea92001-02-05 12:42:17 +0000349#ifdef WITH_AIXAUTHENTICATE
350 loginfailed(authctxt->user,
351 get_canonical_hostname(options.reverse_mapping_check),
Damien Miller33804262001-02-04 23:20:18 +1100352 "ssh");
Damien Millerd2c208a2000-05-17 22:00:02 +1000353#endif /* WITH_AIXAUTHENTICATE */
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000354 packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
Damien Millerd2c208a2000-05-17 22:00:02 +1000355 }
Damien Millereba71ba2000-04-29 23:57:08 +1000356
Damien Millereba71ba2000-04-29 23:57:08 +1000357 packet_start(SSH_SMSG_FAILURE);
358 packet_send();
359 packet_write_wait();
360 }
361}
362
363/*
364 * Performs authentication of an incoming connection. Session key has already
365 * been exchanged and encryption is enabled.
366 */
367void
368do_authentication()
369{
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000370 Authctxt *authctxt;
371 struct passwd *pw;
Damien Millereba71ba2000-04-29 23:57:08 +1000372 int plen;
Ben Lindstrom46c16222000-12-22 01:43:59 +0000373 u_int ulen;
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000374 char *user, *style = NULL;
Damien Millereba71ba2000-04-29 23:57:08 +1000375
376 /* Get the name of the user that we wish to log in as. */
377 packet_read_expect(&plen, SSH_CMSG_USER);
378
379 /* Get the user name. */
380 user = packet_get_string(&ulen);
381 packet_integrity_check(plen, (4 + ulen), SSH_CMSG_USER);
382
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000383 if ((style = strchr(user, ':')) != NULL)
384 *style++ = 0;
385
386 authctxt = authctxt_new();
387 authctxt->user = user;
388 authctxt->style = style;
389
Damien Millereba71ba2000-04-29 23:57:08 +1000390 setproctitle("%s", user);
391
392#ifdef AFS
393 /* If machine has AFS, set process authentication group. */
394 if (k_hasafs()) {
395 k_setpag();
396 k_unlog();
397 }
398#endif /* AFS */
399
400 /* Verify that the user is a valid user. */
401 pw = getpwnam(user);
Damien Miller874d77b2000-10-14 16:23:11 +1100402 if (pw && allowed_user(pw)) {
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000403 authctxt->valid = 1;
404 pw = pwcopy(pw);
Damien Miller874d77b2000-10-14 16:23:11 +1100405 } else {
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000406 debug("do_authentication: illegal user %s", user);
Damien Miller874d77b2000-10-14 16:23:11 +1100407 pw = NULL;
408 }
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000409 authctxt->pw = pw;
Damien Millereba71ba2000-04-29 23:57:08 +1000410
411#ifdef USE_PAM
Damien Miller874d77b2000-10-14 16:23:11 +1100412 if (pw)
Damien Miller22e22bf2001-01-19 15:46:38 +1100413 start_pam(user);
Damien Millereba71ba2000-04-29 23:57:08 +1000414#endif
415
416 /*
417 * If we are not running as root, the user must have the same uid as
Damien Miller874d77b2000-10-14 16:23:11 +1100418 * the server. (Unless you are running Windows)
Damien Millereba71ba2000-04-29 23:57:08 +1000419 */
Damien Miller874d77b2000-10-14 16:23:11 +1100420#ifndef HAVE_CYGWIN
421 if (getuid() != 0 && pw && pw->pw_uid != getuid())
Damien Millereba71ba2000-04-29 23:57:08 +1000422 packet_disconnect("Cannot change user when server not running as root.");
Damien Millerbac2d8a2000-09-05 16:13:06 +1100423#endif
Damien Millereba71ba2000-04-29 23:57:08 +1000424
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000425 /*
Kevin Steves12aaa042001-01-24 21:23:39 +0000426 * Loop until the user has been authenticated or the connection is
427 * closed, do_authloop() returns only if authentication is successful
428 */
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000429 do_authloop(authctxt);
Damien Millereba71ba2000-04-29 23:57:08 +1000430
431 /* The user has been authenticated and accepted. */
Damien Miller874d77b2000-10-14 16:23:11 +1100432 packet_start(SSH_SMSG_SUCCESS);
433 packet_send();
434 packet_write_wait();
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000435
Damien Millereba71ba2000-04-29 23:57:08 +1000436#ifdef WITH_AIXAUTHENTICATE
Damien Millerd2c208a2000-05-17 22:00:02 +1000437 /* We don't have a pty yet, so just label the line as "ssh" */
Kevin Stevesef4eea92001-02-05 12:42:17 +0000438 if (loginsuccess(authctxt->user,
Damien Miller33804262001-02-04 23:20:18 +1100439 get_canonical_hostname(options.reverse_mapping_check),
440 "ssh", &aixloginmsg) < 0)
Damien Millerd2c208a2000-05-17 22:00:02 +1000441 aixloginmsg = NULL;
Damien Millereba71ba2000-04-29 23:57:08 +1000442#endif /* WITH_AIXAUTHENTICATE */
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000443
444 xfree(authctxt->user);
445 xfree(authctxt);
Damien Millereba71ba2000-04-29 23:57:08 +1000446
447 /* Perform session preparation. */
448 do_authenticated(pw);
449}