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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"
Damien Millera9fcd3a2003-11-17 21:16:55 +110013RCSID("$OpenBSD: auth1.c,v 1.55 2003/11/08 16:02:40 jakob 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"
Damien Millerc7ef63d2002-02-05 12:21:42 +110025#include "channels.h"
Damien Miller874d77b2000-10-14 16:23:11 +110026#include "session.h"
Ben Lindstromec95ed92001-07-04 04:21:14 +000027#include "uidswap.h"
Ben Lindstrom7a2073c2002-03-22 02:30:41 +000028#include "monitor_wrap.h"
Damien Miller874d77b2000-10-14 16:23:11 +110029
Damien Millereba71ba2000-04-29 23:57:08 +100030/* import */
31extern ServerOptions options;
Damien Miller874d77b2000-10-14 16:23:11 +110032
Damien Millereba71ba2000-04-29 23:57:08 +100033/*
34 * convert ssh auth msg type into description
35 */
Ben Lindstrombba81212001-06-25 05:01:22 +000036static char *
Damien Millereba71ba2000-04-29 23:57:08 +100037get_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";
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000049 case SSH_CMSG_AUTH_TIS:
50 case SSH_CMSG_AUTH_TIS_RESPONSE:
51 return "challenge-response";
Damien Millereba71ba2000-04-29 23:57:08 +100052 }
53 snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
54 return buf;
55}
56
57/*
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000058 * read packets, try to authenticate the user and
59 * return only if authentication is successful
Damien Millereba71ba2000-04-29 23:57:08 +100060 */
Ben Lindstrombba81212001-06-25 05:01:22 +000061static void
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000062do_authloop(Authctxt *authctxt)
Damien Millereba71ba2000-04-29 23:57:08 +100063{
Damien Miller874d77b2000-10-14 16:23:11 +110064 int authenticated = 0;
Ben Lindstrom46c16222000-12-22 01:43:59 +000065 u_int bits;
Damien Millerda755162002-01-22 23:09:22 +110066 Key *client_host_key;
Damien Millereba71ba2000-04-29 23:57:08 +100067 BIGNUM *n;
Damien Miller874d77b2000-10-14 16:23:11 +110068 char *client_user, *password;
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000069 char info[1024];
Ben Lindstrom46c16222000-12-22 01:43:59 +000070 u_int dlen;
Ben Lindstrom46c16222000-12-22 01:43:59 +000071 u_int ulen;
Damien Miller4f9f42a2003-05-10 19:28:02 +100072 int prev, type = 0;
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000073 struct passwd *pw = authctxt->pw;
74
75 debug("Attempting authentication for %s%.100s.",
Damien Miller9f0f5c62001-12-21 14:45:46 +110076 authctxt->valid ? "" : "illegal user ", authctxt->user);
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000077
78 /* If the user has no password, accept authentication immediately. */
79 if (options.password_authentication &&
Darren Tucker6aaa58c2003-08-02 22:24:49 +100080#ifdef KRB5
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000081 (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
82#endif
Ben Lindstrom7a2073c2002-03-22 02:30:41 +000083 PRIVSEP(auth_password(authctxt, ""))) {
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000084 auth_log(authctxt, 1, "without authentication", "");
85 return;
86 }
Damien Millereba71ba2000-04-29 23:57:08 +100087
88 /* Indicate that authentication is needed. */
89 packet_start(SSH_SMSG_FAILURE);
90 packet_send();
91 packet_write_wait();
92
Damien Miller874d77b2000-10-14 16:23:11 +110093 client_user = NULL;
94
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000095 for (;;) {
Damien Miller874d77b2000-10-14 16:23:11 +110096 /* default to fail */
97 authenticated = 0;
98
Ben Lindstromdb65e8f2001-01-19 04:26:52 +000099 info[0] = '\0';
Damien Millereba71ba2000-04-29 23:57:08 +1000100
101 /* Get a packet from the client. */
Damien Miller4f9f42a2003-05-10 19:28:02 +1000102 prev = type;
Damien Millerdff50992002-01-22 23:16:32 +1100103 type = packet_read();
Damien Millereba71ba2000-04-29 23:57:08 +1000104
Damien Miller4f9f42a2003-05-10 19:28:02 +1000105 /*
106 * If we started challenge-response authentication but the
107 * next packet is not a response to our challenge, release
108 * the resources allocated by get_challenge() (which would
109 * normally have been released by verify_response() had we
110 * received such a response)
111 */
112 if (prev == SSH_CMSG_AUTH_TIS &&
113 type != SSH_CMSG_AUTH_TIS_RESPONSE)
114 abandon_challenge_response(authctxt);
115
Damien Millereba71ba2000-04-29 23:57:08 +1000116 /* Process the packet. */
117 switch (type) {
Damien Millereba71ba2000-04-29 23:57:08 +1000118 case SSH_CMSG_AUTH_RHOSTS_RSA:
119 if (!options.rhosts_rsa_authentication) {
120 verbose("Rhosts with RSA authentication disabled.");
121 break;
122 }
123 /*
124 * Get client user name. Note that we just have to
125 * trust the client; root on the client machine can
126 * claim to be any user.
127 */
128 client_user = packet_get_string(&ulen);
129
130 /* Get the client host key. */
Damien Millerda755162002-01-22 23:09:22 +1100131 client_host_key = key_new(KEY_RSA1);
Damien Millereba71ba2000-04-29 23:57:08 +1000132 bits = packet_get_int();
Damien Millerd432ccf2002-01-22 23:14:44 +1100133 packet_get_bignum(client_host_key->rsa->e);
134 packet_get_bignum(client_host_key->rsa->n);
Damien Millereba71ba2000-04-29 23:57:08 +1000135
Damien Millerda755162002-01-22 23:09:22 +1100136 if (bits != BN_num_bits(client_host_key->rsa->n))
Damien Miller874d77b2000-10-14 16:23:11 +1100137 verbose("Warning: keysize mismatch for client_host_key: "
Damien Millerda755162002-01-22 23:09:22 +1100138 "actual %d, announced %d",
Ben Lindstromcb72e4f2002-06-21 00:41:51 +0000139 BN_num_bits(client_host_key->rsa->n), bits);
Damien Miller48b03fc2002-01-22 23:11:40 +1100140 packet_check_eom();
Damien Millereba71ba2000-04-29 23:57:08 +1000141
Damien Miller3e3b5142003-11-17 21:13:40 +1100142 authenticated = auth_rhosts_rsa(authctxt, client_user,
Damien Millerd221ca62002-01-22 23:11:00 +1100143 client_host_key);
Damien Millerda755162002-01-22 23:09:22 +1100144 key_free(client_host_key);
Damien Millereba71ba2000-04-29 23:57:08 +1000145
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000146 snprintf(info, sizeof info, " ruser %.100s", client_user);
Damien Millereba71ba2000-04-29 23:57:08 +1000147 break;
148
149 case SSH_CMSG_AUTH_RSA:
150 if (!options.rsa_authentication) {
151 verbose("RSA authentication disabled.");
152 break;
153 }
154 /* RSA authentication requested. */
Damien Millerda755162002-01-22 23:09:22 +1100155 if ((n = BN_new()) == NULL)
156 fatal("do_authloop: BN_new failed");
Damien Millerd432ccf2002-01-22 23:14:44 +1100157 packet_get_bignum(n);
Damien Miller48b03fc2002-01-22 23:11:40 +1100158 packet_check_eom();
Damien Miller3e3b5142003-11-17 21:13:40 +1100159 authenticated = auth_rsa(authctxt, n);
Damien Millereba71ba2000-04-29 23:57:08 +1000160 BN_clear_free(n);
161 break;
162
163 case SSH_CMSG_AUTH_PASSWORD:
164 if (!options.password_authentication) {
165 verbose("Password authentication disabled.");
166 break;
167 }
168 /*
169 * Read user password. It is in plain text, but was
170 * transmitted over the encrypted channel so it is
171 * not visible to an outside observer.
172 */
173 password = packet_get_string(&dlen);
Damien Miller48b03fc2002-01-22 23:11:40 +1100174 packet_check_eom();
Damien Millereba71ba2000-04-29 23:57:08 +1000175
Kevin Steves12aaa042001-01-24 21:23:39 +0000176 /* Try authentication with the password. */
Ben Lindstrom7a2073c2002-03-22 02:30:41 +0000177 authenticated = PRIVSEP(auth_password(authctxt, password));
Damien Millereba71ba2000-04-29 23:57:08 +1000178
179 memset(password, 0, strlen(password));
180 xfree(password);
181 break;
182
Damien Millereba71ba2000-04-29 23:57:08 +1000183 case SSH_CMSG_AUTH_TIS:
184 debug("rcvd SSH_CMSG_AUTH_TIS");
Ben Lindstrom551ea372001-06-05 18:56:16 +0000185 if (options.challenge_response_authentication == 1) {
186 char *challenge = get_challenge(authctxt);
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000187 if (challenge != NULL) {
188 debug("sending challenge '%s'", challenge);
Damien Millereba71ba2000-04-29 23:57:08 +1000189 packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000190 packet_put_cstring(challenge);
Ben Lindstrom551ea372001-06-05 18:56:16 +0000191 xfree(challenge);
Damien Millereba71ba2000-04-29 23:57:08 +1000192 packet_send();
193 packet_write_wait();
194 continue;
195 }
196 }
197 break;
198 case SSH_CMSG_AUTH_TIS_RESPONSE:
199 debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
Ben Lindstrom551ea372001-06-05 18:56:16 +0000200 if (options.challenge_response_authentication == 1) {
Damien Millereba71ba2000-04-29 23:57:08 +1000201 char *response = packet_get_string(&dlen);
Damien Miller48b03fc2002-01-22 23:11:40 +1100202 packet_check_eom();
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000203 authenticated = verify_response(authctxt, response);
204 memset(response, 'r', dlen);
Damien Millereba71ba2000-04-29 23:57:08 +1000205 xfree(response);
206 }
207 break;
Damien Millereba71ba2000-04-29 23:57:08 +1000208
209 default:
210 /*
211 * Any unknown messages will be ignored (and failure
212 * returned) during authentication.
213 */
Damien Miller996acd22003-04-09 20:59:48 +1000214 logit("Unknown message during authentication: type %d", type);
Damien Millereba71ba2000-04-29 23:57:08 +1000215 break;
216 }
Damien Miller60396b02001-02-18 17:01:00 +1100217#ifdef BSD_AUTH
218 if (authctxt->as) {
219 auth_close(authctxt->as);
220 authctxt->as = NULL;
221 }
222#endif
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000223 if (!authctxt->valid && authenticated)
224 fatal("INTERNAL ERROR: authenticated invalid user %s",
225 authctxt->user);
Damien Millereba71ba2000-04-29 23:57:08 +1000226
Tim Rice81ed5182002-09-25 17:38:46 -0700227#ifdef _UNICOS
Tim Rice81ed5182002-09-25 17:38:46 -0700228 if (authenticated && cray_access_denied(authctxt->user)) {
229 authenticated = 0;
230 fatal("Access denied for user %s.",authctxt->user);
231 }
232#endif /* _UNICOS */
233
Kevin Stevesef4eea92001-02-05 12:42:17 +0000234#ifdef HAVE_CYGWIN
235 if (authenticated &&
Damien Miller0dea79d2001-12-29 14:08:28 +1100236 !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) {
Damien Millerbac2d8a2000-09-05 16:13:06 +1100237 packet_disconnect("Authentication rejected for uid %d.",
Damien Miller0eae4422003-11-22 14:15:30 +1100238 pw == NULL ? -1 : pw->pw_uid);
Damien Millerbac2d8a2000-09-05 16:13:06 +1100239 authenticated = 0;
240 }
Ben Lindstrom5dc81502001-01-19 06:10:29 +0000241#else
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000242 /* Special handling for root */
Damien Miller556f9312003-02-24 11:59:26 +1100243 if (authenticated && authctxt->pw->pw_uid == 0 &&
Ben Lindstromd8a90212001-02-15 03:08:27 +0000244 !auth_root_allowed(get_authname(type)))
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000245 authenticated = 0;
Ben Lindstrom5dc81502001-01-19 06:10:29 +0000246#endif
Damien Millereba71ba2000-04-29 23:57:08 +1000247
Damien Miller1f499fd2003-08-25 13:08:49 +1000248#ifdef USE_PAM
Damien Millera8e06ce2003-11-21 23:48:55 +1100249 if (options.use_pam && authenticated &&
Damien Miller1f499fd2003-08-25 13:08:49 +1000250 !PRIVSEP(do_pam_account()))
251 authenticated = 0;
252#endif
253
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000254 /* Log before sending the reply */
255 auth_log(authctxt, authenticated, get_authname(type), info);
256
Damien Millereba71ba2000-04-29 23:57:08 +1000257 if (client_user != NULL) {
258 xfree(client_user);
259 client_user = NULL;
260 }
261
Damien Miller874d77b2000-10-14 16:23:11 +1100262 if (authenticated)
263 return;
264
Ben Lindstrom683036e2003-04-27 18:41:30 +0000265 if (authctxt->failures++ > AUTH_FAIL_MAX)
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000266 packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
Damien Millereba71ba2000-04-29 23:57:08 +1000267
Damien Millereba71ba2000-04-29 23:57:08 +1000268 packet_start(SSH_SMSG_FAILURE);
269 packet_send();
270 packet_write_wait();
271 }
272}
273
274/*
275 * Performs authentication of an incoming connection. Session key has already
276 * been exchanged and encryption is enabled.
277 */
Darren Tucker3e33cec2003-10-02 16:12:36 +1000278void
279do_authentication(Authctxt *authctxt)
Damien Millereba71ba2000-04-29 23:57:08 +1000280{
Ben Lindstrom46c16222000-12-22 01:43:59 +0000281 u_int ulen;
Ben Lindstromc8226382002-04-10 16:22:09 +0000282 char *user, *style = NULL;
Damien Millereba71ba2000-04-29 23:57:08 +1000283
284 /* Get the name of the user that we wish to log in as. */
Damien Millerdff50992002-01-22 23:16:32 +1100285 packet_read_expect(SSH_CMSG_USER);
Damien Millereba71ba2000-04-29 23:57:08 +1000286
287 /* Get the user name. */
288 user = packet_get_string(&ulen);
Damien Miller48b03fc2002-01-22 23:11:40 +1100289 packet_check_eom();
Damien Millereba71ba2000-04-29 23:57:08 +1000290
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000291 if ((style = strchr(user, ':')) != NULL)
Ben Lindstromec95ed92001-07-04 04:21:14 +0000292 *style++ = '\0';
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000293
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000294 authctxt->user = user;
295 authctxt->style = style;
296
Damien Millereba71ba2000-04-29 23:57:08 +1000297 /* Verify that the user is a valid user. */
Ben Lindstrom7ebb6352002-03-22 03:04:08 +0000298 if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000299 authctxt->valid = 1;
Damien Miller856f0be2003-09-03 07:32:45 +1000300 else {
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000301 debug("do_authentication: illegal user %s", user);
Damien Miller856f0be2003-09-03 07:32:45 +1000302 authctxt->pw = fakepw();
303 }
Ben Lindstrom7a2073c2002-03-22 02:30:41 +0000304
Ben Lindstrom7ebb6352002-03-22 03:04:08 +0000305 setproctitle("%s%s", authctxt->pw ? user : "unknown",
Ben Lindstrom7a2073c2002-03-22 02:30:41 +0000306 use_privsep ? " [net]" : "");
Ben Lindstromc1ba31f2001-02-15 03:14:11 +0000307
Damien Millereba71ba2000-04-29 23:57:08 +1000308#ifdef USE_PAM
Damien Miller4e448a32003-05-14 15:11:48 +1000309 if (options.use_pam)
Darren Tuckerdbf7a742004-03-08 23:04:06 +1100310 PRIVSEP(start_pam(authctxt));
Damien Millereba71ba2000-04-29 23:57:08 +1000311#endif
312
313 /*
314 * If we are not running as root, the user must have the same uid as
Damien Miller874d77b2000-10-14 16:23:11 +1100315 * the server. (Unless you are running Windows)
Damien Millereba71ba2000-04-29 23:57:08 +1000316 */
Damien Miller874d77b2000-10-14 16:23:11 +1100317#ifndef HAVE_CYGWIN
Ben Lindstrom7ebb6352002-03-22 03:04:08 +0000318 if (!use_privsep && getuid() != 0 && authctxt->pw &&
319 authctxt->pw->pw_uid != getuid())
Damien Millereba71ba2000-04-29 23:57:08 +1000320 packet_disconnect("Cannot change user when server not running as root.");
Damien Millerbac2d8a2000-09-05 16:13:06 +1100321#endif
Damien Millereba71ba2000-04-29 23:57:08 +1000322
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000323 /*
Kevin Steves12aaa042001-01-24 21:23:39 +0000324 * Loop until the user has been authenticated or the connection is
325 * closed, do_authloop() returns only if authentication is successful
326 */
Ben Lindstromdb65e8f2001-01-19 04:26:52 +0000327 do_authloop(authctxt);
Damien Millereba71ba2000-04-29 23:57:08 +1000328
329 /* The user has been authenticated and accepted. */
Damien Miller874d77b2000-10-14 16:23:11 +1100330 packet_start(SSH_SMSG_SUCCESS);
331 packet_send();
332 packet_write_wait();
Damien Millereba71ba2000-04-29 23:57:08 +1000333}