blob: 4d623717f8badcb4e0bb182cea9f0216c16f6f8c [file] [log] [blame]
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 Lindstrom086cf212001-03-05 05:56:40 +000013RCSID("$OpenBSD: auth1.c,v 1.18 2001/02/22 21:59:43 markus Exp $");
Damien Millereba71ba2000-04-29 23:57:08 +100014
Damien Miller874d77b2000-10-14 16:23:11 +110015#include "xmalloc.h"
16#include "rsa.h"
Ben Lindstrom226cfa02001-01-22 05:34:40 +000017#include "ssh1.h"
Damien Miller874d77b2000-10-14 16:23:11 +110018#include "packet.h"
19#include "buffer.h"
20#include "mpaux.h"
Ben Lindstrom226cfa02001-01-22 05:34:40 +000021#include "log.h"
Damien Miller874d77b2000-10-14 16:23:11 +110022#include "servconf.h"
23#include "compat.h"
24#include "auth.h"
25#include "session.h"
Ben Lindstrom086cf212001-03-05 05:56:40 +000026#include "misc.h"
Damien Miller874d77b2000-10-14 16:23:11 +110027
Damien Millereba71ba2000-04-29 23:57:08 +100028/* import */
29extern ServerOptions options;
30extern char *forced_command;
Damien Miller874d77b2000-10-14 16:23:11 +110031
32#ifdef WITH_AIXAUTHENTICATE
33extern char *aixloginmsg;
34#endif /* WITH_AIXAUTHENTICATE */
Damien Millereba71ba2000-04-29 23:57:08 +100035
36/*
37 * convert ssh auth msg type into description
38 */
39char *
40get_authname(int type)
41{
42 static char buf[1024];
43 switch (type) {
44 case SSH_CMSG_AUTH_PASSWORD:
45 return "password";
46 case SSH_CMSG_AUTH_RSA:
47 return "rsa";
48 case SSH_CMSG_AUTH_RHOSTS_RSA:
49 return "rhosts-rsa";
50 case SSH_CMSG_AUTH_RHOSTS:
51 return "rhosts";
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000052 case SSH_CMSG_AUTH_TIS:
53 case SSH_CMSG_AUTH_TIS_RESPONSE:
54 return "challenge-response";
Damien Millereba71ba2000-04-29 23:57:08 +100055#ifdef KRB4
56 case SSH_CMSG_AUTH_KERBEROS:
57 return "kerberos";
58#endif
Damien Millereba71ba2000-04-29 23:57:08 +100059 }
60 snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
61 return buf;
62}
63
64/*
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000065 * read packets, try to authenticate the user and
66 * return only if authentication is successful
Damien Millereba71ba2000-04-29 23:57:08 +100067 */
68void
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000069do_authloop(Authctxt *authctxt)
Damien Millereba71ba2000-04-29 23:57:08 +100070{
Damien Miller874d77b2000-10-14 16:23:11 +110071 int authenticated = 0;
Ben Lindstrom46c16222000-12-22 01:43:59 +000072 u_int bits;
Damien Millereba71ba2000-04-29 23:57:08 +100073 RSA *client_host_key;
74 BIGNUM *n;
Damien Miller874d77b2000-10-14 16:23:11 +110075 char *client_user, *password;
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000076 char info[1024];
Ben Lindstrom46c16222000-12-22 01:43:59 +000077 u_int dlen;
Damien Millereba71ba2000-04-29 23:57:08 +100078 int plen, nlen, elen;
Ben Lindstrom46c16222000-12-22 01:43:59 +000079 u_int ulen;
Damien Millereba71ba2000-04-29 23:57:08 +100080 int type = 0;
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000081 struct passwd *pw = authctxt->pw;
82
83 debug("Attempting authentication for %s%.100s.",
84 authctxt->valid ? "" : "illegal user ", authctxt->user);
85
86 /* If the user has no password, accept authentication immediately. */
87 if (options.password_authentication &&
88#ifdef KRB4
89 (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
90#endif
Ben Lindstromb100ec92001-01-19 05:37:32 +000091#ifdef USE_PAM
Kevin Stevesbca8c8f2001-02-13 11:26:21 +000092 auth_pam_password(pw, "")) {
Damien Miller92ddb7d2001-02-14 01:25:23 +110093#elif defined(HAVE_OSF_SIA)
94 0) {
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000095#else
Damien Miller60396b02001-02-18 17:01:00 +110096 auth_password(authctxt, "")) {
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000097#endif
98 auth_log(authctxt, 1, "without authentication", "");
99 return;
100 }
Damien Millereba71ba2000-04-29 23:57:08 +1000101
102 /* Indicate that authentication is needed. */
103 packet_start(SSH_SMSG_FAILURE);
104 packet_send();
105 packet_write_wait();
106
Damien Miller874d77b2000-10-14 16:23:11 +1100107 client_user = NULL;
108
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000109 for (;;) {
Damien Miller874d77b2000-10-14 16:23:11 +1100110 /* default to fail */
111 authenticated = 0;
112
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000113 info[0] = '\0';
Damien Millereba71ba2000-04-29 23:57:08 +1000114
115 /* Get a packet from the client. */
116 type = packet_read(&plen);
117
118 /* Process the packet. */
119 switch (type) {
120#ifdef AFS
121 case SSH_CMSG_HAVE_KERBEROS_TGT:
122 if (!options.kerberos_tgt_passing) {
Damien Millereba71ba2000-04-29 23:57:08 +1000123 verbose("Kerberos tgt passing disabled.");
124 break;
125 } else {
126 /* Accept Kerberos tgt. */
127 char *tgt = packet_get_string(&dlen);
128 packet_integrity_check(plen, 4 + dlen, type);
129 if (!auth_kerberos_tgt(pw, tgt))
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000130 verbose("Kerberos tgt REFUSED for %.100s", authctxt->user);
Damien Millereba71ba2000-04-29 23:57:08 +1000131 xfree(tgt);
132 }
133 continue;
134
135 case SSH_CMSG_HAVE_AFS_TOKEN:
136 if (!options.afs_token_passing || !k_hasafs()) {
Damien Millereba71ba2000-04-29 23:57:08 +1000137 verbose("AFS token passing disabled.");
138 break;
139 } else {
140 /* Accept AFS token. */
141 char *token_string = packet_get_string(&dlen);
142 packet_integrity_check(plen, 4 + dlen, type);
143 if (!auth_afs_token(pw, token_string))
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000144 verbose("AFS token REFUSED for %.100s", authctxt->user);
Damien Millereba71ba2000-04-29 23:57:08 +1000145 xfree(token_string);
146 }
147 continue;
148#endif /* AFS */
149#ifdef KRB4
150 case SSH_CMSG_AUTH_KERBEROS:
151 if (!options.kerberos_authentication) {
Damien Millereba71ba2000-04-29 23:57:08 +1000152 verbose("Kerberos authentication disabled.");
153 break;
154 } else {
155 /* Try Kerberos v4 authentication. */
156 KTEXT_ST auth;
157 char *tkt_user = NULL;
Ben Lindstrom46c16222000-12-22 01:43:59 +0000158 char *kdata = packet_get_string((u_int *) &auth.length);
Damien Millereba71ba2000-04-29 23:57:08 +1000159 packet_integrity_check(plen, 4 + auth.length, type);
160
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000161 if (authctxt->valid) {
162 if (auth.length < MAX_KTXT_LEN)
163 memcpy(auth.dat, kdata, auth.length);
Damien Miller874d77b2000-10-14 16:23:11 +1100164 authenticated = auth_krb4(pw->pw_name, &auth, &tkt_user);
165 if (authenticated) {
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000166 snprintf(info, sizeof info,
167 " tktuser %.100s", tkt_user);
Damien Miller874d77b2000-10-14 16:23:11 +1100168 xfree(tkt_user);
169 }
Damien Millereba71ba2000-04-29 23:57:08 +1000170 }
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000171 xfree(kdata);
Damien Millereba71ba2000-04-29 23:57:08 +1000172 }
173 break;
174#endif /* KRB4 */
175
176 case SSH_CMSG_AUTH_RHOSTS:
177 if (!options.rhosts_authentication) {
178 verbose("Rhosts authentication disabled.");
179 break;
180 }
181 /*
182 * Get client user name. Note that we just have to
183 * trust the client; this is one reason why rhosts
184 * authentication is insecure. (Another is
185 * IP-spoofing on a local network.)
186 */
187 client_user = packet_get_string(&ulen);
188 packet_integrity_check(plen, 4 + ulen, type);
189
Damien Miller874d77b2000-10-14 16:23:11 +1100190 /* Try to authenticate using /etc/hosts.equiv and .rhosts. */
Damien Millereba71ba2000-04-29 23:57:08 +1000191 authenticated = auth_rhosts(pw, client_user);
192
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000193 snprintf(info, sizeof info, " ruser %.100s", client_user);
Damien Millereba71ba2000-04-29 23:57:08 +1000194 break;
195
196 case SSH_CMSG_AUTH_RHOSTS_RSA:
197 if (!options.rhosts_rsa_authentication) {
198 verbose("Rhosts with RSA authentication disabled.");
199 break;
200 }
201 /*
202 * Get client user name. Note that we just have to
203 * trust the client; root on the client machine can
204 * claim to be any user.
205 */
206 client_user = packet_get_string(&ulen);
207
208 /* Get the client host key. */
209 client_host_key = RSA_new();
210 if (client_host_key == NULL)
211 fatal("RSA_new failed");
212 client_host_key->e = BN_new();
213 client_host_key->n = BN_new();
214 if (client_host_key->e == NULL || client_host_key->n == NULL)
215 fatal("BN_new failed");
216 bits = packet_get_int();
217 packet_get_bignum(client_host_key->e, &elen);
218 packet_get_bignum(client_host_key->n, &nlen);
219
220 if (bits != BN_num_bits(client_host_key->n))
Damien Miller874d77b2000-10-14 16:23:11 +1100221 verbose("Warning: keysize mismatch for client_host_key: "
Damien Millerbd483e72000-04-30 10:00:53 +1000222 "actual %d, announced %d", BN_num_bits(client_host_key->n), bits);
Damien Millereba71ba2000-04-29 23:57:08 +1000223 packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type);
224
225 authenticated = auth_rhosts_rsa(pw, client_user, client_host_key);
226 RSA_free(client_host_key);
227
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000228 snprintf(info, sizeof info, " ruser %.100s", client_user);
Damien Millereba71ba2000-04-29 23:57:08 +1000229 break;
230
231 case SSH_CMSG_AUTH_RSA:
232 if (!options.rsa_authentication) {
233 verbose("RSA authentication disabled.");
234 break;
235 }
236 /* RSA authentication requested. */
237 n = BN_new();
238 packet_get_bignum(n, &nlen);
239 packet_integrity_check(plen, nlen, type);
240 authenticated = auth_rsa(pw, n);
241 BN_clear_free(n);
242 break;
243
244 case SSH_CMSG_AUTH_PASSWORD:
245 if (!options.password_authentication) {
246 verbose("Password authentication disabled.");
247 break;
248 }
249 /*
250 * Read user password. It is in plain text, but was
251 * transmitted over the encrypted channel so it is
252 * not visible to an outside observer.
253 */
254 password = packet_get_string(&dlen);
255 packet_integrity_check(plen, 4 + dlen, type);
256
257#ifdef USE_PAM
258 /* Do PAM auth with password */
259 authenticated = auth_pam_password(pw, password);
Damien Millerb8c656e2000-06-28 15:22:41 +1000260#elif defined(HAVE_OSF_SIA)
261 /* Do SIA auth with password */
Damien Miller92ddb7d2001-02-14 01:25:23 +1100262 authenticated = auth_sia_password(authctxt->user,
263 password);
Damien Millerb8c656e2000-06-28 15:22:41 +1000264#else /* !USE_PAM && !HAVE_OSF_SIA */
Kevin Steves12aaa042001-01-24 21:23:39 +0000265 /* Try authentication with the password. */
Damien Miller60396b02001-02-18 17:01:00 +1100266 authenticated = auth_password(authctxt, password);
Damien Millereba71ba2000-04-29 23:57:08 +1000267#endif /* USE_PAM */
268
269 memset(password, 0, strlen(password));
270 xfree(password);
271 break;
272
Damien Millereba71ba2000-04-29 23:57:08 +1000273 case SSH_CMSG_AUTH_TIS:
274 debug("rcvd SSH_CMSG_AUTH_TIS");
Ben Lindstrom95fb2dd2001-01-23 03:12:10 +0000275 if (options.challenge_reponse_authentication == 1) {
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000276 char *challenge = get_challenge(authctxt, authctxt->style);
277 if (challenge != NULL) {
278 debug("sending challenge '%s'", challenge);
Damien Millereba71ba2000-04-29 23:57:08 +1000279 packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000280 packet_put_cstring(challenge);
Damien Millereba71ba2000-04-29 23:57:08 +1000281 packet_send();
282 packet_write_wait();
283 continue;
284 }
285 }
286 break;
287 case SSH_CMSG_AUTH_TIS_RESPONSE:
288 debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
Ben Lindstrom95fb2dd2001-01-23 03:12:10 +0000289 if (options.challenge_reponse_authentication == 1) {
Damien Millereba71ba2000-04-29 23:57:08 +1000290 char *response = packet_get_string(&dlen);
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000291 debug("got response '%s'", response);
Damien Millereba71ba2000-04-29 23:57:08 +1000292 packet_integrity_check(plen, 4 + dlen, type);
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000293 authenticated = verify_response(authctxt, response);
294 memset(response, 'r', dlen);
Damien Millereba71ba2000-04-29 23:57:08 +1000295 xfree(response);
296 }
297 break;
Damien Millereba71ba2000-04-29 23:57:08 +1000298
299 default:
300 /*
301 * Any unknown messages will be ignored (and failure
302 * returned) during authentication.
303 */
304 log("Unknown message during authentication: type %d", type);
305 break;
306 }
Damien Miller60396b02001-02-18 17:01:00 +1100307#ifdef BSD_AUTH
308 if (authctxt->as) {
309 auth_close(authctxt->as);
310 authctxt->as = NULL;
311 }
312#endif
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000313 if (!authctxt->valid && authenticated)
314 fatal("INTERNAL ERROR: authenticated invalid user %s",
315 authctxt->user);
Damien Millereba71ba2000-04-29 23:57:08 +1000316
Kevin Stevesef4eea92001-02-05 12:42:17 +0000317#ifdef HAVE_CYGWIN
318 if (authenticated &&
Damien Millerb70b61f2000-09-16 16:25:12 +1100319 !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD,pw->pw_uid)) {
Damien Millerbac2d8a2000-09-05 16:13:06 +1100320 packet_disconnect("Authentication rejected for uid %d.",
Damien Miller874d77b2000-10-14 16:23:11 +1100321 (int)pw->pw_uid);
Damien Millerbac2d8a2000-09-05 16:13:06 +1100322 authenticated = 0;
323 }
Ben Lindstrom5dc81502001-01-19 06:10:29 +0000324#else
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000325 /* Special handling for root */
Ben Lindstromd8a90212001-02-15 03:08:27 +0000326 if (authenticated && authctxt->pw->pw_uid == 0 &&
327 !auth_root_allowed(get_authname(type)))
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000328 authenticated = 0;
Ben Lindstrom5dc81502001-01-19 06:10:29 +0000329#endif
Kevin Stevesef4eea92001-02-05 12:42:17 +0000330#ifdef USE_PAM
Damien Miller874d77b2000-10-14 16:23:11 +1100331 if (authenticated && !do_pam_account(pw->pw_name, client_user))
332 authenticated = 0;
333#endif
Damien Millereba71ba2000-04-29 23:57:08 +1000334
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000335 /* Log before sending the reply */
336 auth_log(authctxt, authenticated, get_authname(type), info);
337
Damien Millereba71ba2000-04-29 23:57:08 +1000338 if (client_user != NULL) {
339 xfree(client_user);
340 client_user = NULL;
341 }
342
Damien Miller874d77b2000-10-14 16:23:11 +1100343 if (authenticated)
344 return;
345
Kevin Steves12aaa042001-01-24 21:23:39 +0000346 if (authctxt->failures++ > AUTH_FAIL_MAX) {
Kevin Stevesef4eea92001-02-05 12:42:17 +0000347#ifdef WITH_AIXAUTHENTICATE
348 loginfailed(authctxt->user,
349 get_canonical_hostname(options.reverse_mapping_check),
Damien Miller33804262001-02-04 23:20:18 +1100350 "ssh");
Damien Millerd2c208a2000-05-17 22:00:02 +1000351#endif /* WITH_AIXAUTHENTICATE */
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000352 packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
Damien Millerd2c208a2000-05-17 22:00:02 +1000353 }
Damien Millereba71ba2000-04-29 23:57:08 +1000354
Damien Millereba71ba2000-04-29 23:57:08 +1000355 packet_start(SSH_SMSG_FAILURE);
356 packet_send();
357 packet_write_wait();
358 }
359}
360
361/*
362 * Performs authentication of an incoming connection. Session key has already
363 * been exchanged and encryption is enabled.
364 */
365void
366do_authentication()
367{
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000368 Authctxt *authctxt;
369 struct passwd *pw;
Damien Millereba71ba2000-04-29 23:57:08 +1000370 int plen;
Ben Lindstrom46c16222000-12-22 01:43:59 +0000371 u_int ulen;
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000372 char *user, *style = NULL;
Damien Millereba71ba2000-04-29 23:57:08 +1000373
374 /* Get the name of the user that we wish to log in as. */
375 packet_read_expect(&plen, SSH_CMSG_USER);
376
377 /* Get the user name. */
378 user = packet_get_string(&ulen);
379 packet_integrity_check(plen, (4 + ulen), SSH_CMSG_USER);
380
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000381 if ((style = strchr(user, ':')) != NULL)
382 *style++ = 0;
383
384 authctxt = authctxt_new();
385 authctxt->user = user;
386 authctxt->style = style;
387
Damien Millereba71ba2000-04-29 23:57:08 +1000388 /* Verify that the user is a valid user. */
389 pw = getpwnam(user);
Damien Miller874d77b2000-10-14 16:23:11 +1100390 if (pw && allowed_user(pw)) {
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000391 authctxt->valid = 1;
392 pw = pwcopy(pw);
Damien Miller874d77b2000-10-14 16:23:11 +1100393 } else {
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000394 debug("do_authentication: illegal user %s", user);
Damien Miller874d77b2000-10-14 16:23:11 +1100395 pw = NULL;
396 }
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000397 authctxt->pw = pw;
Damien Millereba71ba2000-04-29 23:57:08 +1000398
Ben Lindstromc1ba31f2001-02-15 03:14:11 +0000399 setproctitle("%s", pw ? user : "unknown");
400
Damien Millereba71ba2000-04-29 23:57:08 +1000401#ifdef USE_PAM
Damien Miller874d77b2000-10-14 16:23:11 +1100402 if (pw)
Damien Miller22e22bf2001-01-19 15:46:38 +1100403 start_pam(user);
Damien Millereba71ba2000-04-29 23:57:08 +1000404#endif
405
406 /*
407 * If we are not running as root, the user must have the same uid as
Damien Miller874d77b2000-10-14 16:23:11 +1100408 * the server. (Unless you are running Windows)
Damien Millereba71ba2000-04-29 23:57:08 +1000409 */
Damien Miller874d77b2000-10-14 16:23:11 +1100410#ifndef HAVE_CYGWIN
411 if (getuid() != 0 && pw && pw->pw_uid != getuid())
Damien Millereba71ba2000-04-29 23:57:08 +1000412 packet_disconnect("Cannot change user when server not running as root.");
Damien Millerbac2d8a2000-09-05 16:13:06 +1100413#endif
Damien Millereba71ba2000-04-29 23:57:08 +1000414
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000415 /*
Kevin Steves12aaa042001-01-24 21:23:39 +0000416 * Loop until the user has been authenticated or the connection is
417 * closed, do_authloop() returns only if authentication is successful
418 */
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000419 do_authloop(authctxt);
Damien Millereba71ba2000-04-29 23:57:08 +1000420
421 /* The user has been authenticated and accepted. */
Damien Miller874d77b2000-10-14 16:23:11 +1100422 packet_start(SSH_SMSG_SUCCESS);
423 packet_send();
424 packet_write_wait();
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000425
Damien Millereba71ba2000-04-29 23:57:08 +1000426#ifdef WITH_AIXAUTHENTICATE
Damien Millerd2c208a2000-05-17 22:00:02 +1000427 /* We don't have a pty yet, so just label the line as "ssh" */
Kevin Stevesef4eea92001-02-05 12:42:17 +0000428 if (loginsuccess(authctxt->user,
Damien Miller33804262001-02-04 23:20:18 +1100429 get_canonical_hostname(options.reverse_mapping_check),
430 "ssh", &aixloginmsg) < 0)
Damien Millerd2c208a2000-05-17 22:00:02 +1000431 aixloginmsg = NULL;
Damien Millereba71ba2000-04-29 23:57:08 +1000432#endif /* WITH_AIXAUTHENTICATE */
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000433
434 xfree(authctxt->user);
435 xfree(authctxt);
Damien Millereba71ba2000-04-29 23:57:08 +1000436
437 /* Perform session preparation. */
438 do_authenticated(pw);
439}