2 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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".
13 RCSID("$OpenBSD: auth1.c,v 1.59 2004/07/28 09:40:29 markus Exp $");
27 #include "monitor_wrap.h"
31 extern ServerOptions options;
32 extern Buffer loginmsg;
35 * convert ssh auth msg type into description
38 get_authname(int type)
40 static char buf[1024];
42 case SSH_CMSG_AUTH_PASSWORD:
44 case SSH_CMSG_AUTH_RSA:
46 case SSH_CMSG_AUTH_RHOSTS_RSA:
48 case SSH_CMSG_AUTH_RHOSTS:
50 case SSH_CMSG_AUTH_TIS:
51 case SSH_CMSG_AUTH_TIS_RESPONSE:
52 return "challenge-response";
54 snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
59 * read packets, try to authenticate the user and
60 * return only if authentication is successful
63 do_authloop(Authctxt *authctxt)
65 int authenticated = 0;
69 char *client_user, *password;
75 debug("Attempting authentication for %s%.100s.",
76 authctxt->valid ? "" : "invalid user ", authctxt->user);
78 /* If the user has no password, accept authentication immediately. */
79 if (options.password_authentication &&
81 (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
83 PRIVSEP(auth_password(authctxt, ""))) {
85 if (options.use_pam && (PRIVSEP(do_pam_account())))
88 auth_log(authctxt, 1, "without authentication", "");
93 /* Indicate that authentication is needed. */
94 packet_start(SSH_SMSG_FAILURE);
101 /* default to fail */
106 /* Get a packet from the client. */
108 type = packet_read();
111 * If we started challenge-response authentication but the
112 * next packet is not a response to our challenge, release
113 * the resources allocated by get_challenge() (which would
114 * normally have been released by verify_response() had we
115 * received such a response)
117 if (prev == SSH_CMSG_AUTH_TIS &&
118 type != SSH_CMSG_AUTH_TIS_RESPONSE)
119 abandon_challenge_response(authctxt);
121 /* Process the packet. */
123 case SSH_CMSG_AUTH_RHOSTS_RSA:
124 if (!options.rhosts_rsa_authentication) {
125 verbose("Rhosts with RSA authentication disabled.");
129 * Get client user name. Note that we just have to
130 * trust the client; root on the client machine can
131 * claim to be any user.
133 client_user = packet_get_string(&ulen);
135 /* Get the client host key. */
136 client_host_key = key_new(KEY_RSA1);
137 bits = packet_get_int();
138 packet_get_bignum(client_host_key->rsa->e);
139 packet_get_bignum(client_host_key->rsa->n);
141 if (bits != BN_num_bits(client_host_key->rsa->n))
142 verbose("Warning: keysize mismatch for client_host_key: "
143 "actual %d, announced %d",
144 BN_num_bits(client_host_key->rsa->n), bits);
147 authenticated = auth_rhosts_rsa(authctxt, client_user,
149 key_free(client_host_key);
151 snprintf(info, sizeof info, " ruser %.100s", client_user);
154 case SSH_CMSG_AUTH_RSA:
155 if (!options.rsa_authentication) {
156 verbose("RSA authentication disabled.");
159 /* RSA authentication requested. */
160 if ((n = BN_new()) == NULL)
161 fatal("do_authloop: BN_new failed");
162 packet_get_bignum(n);
164 authenticated = auth_rsa(authctxt, n);
168 case SSH_CMSG_AUTH_PASSWORD:
169 if (!options.password_authentication) {
170 verbose("Password authentication disabled.");
174 * Read user password. It is in plain text, but was
175 * transmitted over the encrypted channel so it is
176 * not visible to an outside observer.
178 password = packet_get_string(&dlen);
181 /* Try authentication with the password. */
182 authenticated = PRIVSEP(auth_password(authctxt, password));
184 memset(password, 0, strlen(password));
188 case SSH_CMSG_AUTH_TIS:
189 debug("rcvd SSH_CMSG_AUTH_TIS");
190 if (options.challenge_response_authentication == 1) {
191 char *challenge = get_challenge(authctxt);
192 if (challenge != NULL) {
193 debug("sending challenge '%s'", challenge);
194 packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
195 packet_put_cstring(challenge);
203 case SSH_CMSG_AUTH_TIS_RESPONSE:
204 debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
205 if (options.challenge_response_authentication == 1) {
206 char *response = packet_get_string(&dlen);
208 authenticated = verify_response(authctxt, response);
209 memset(response, 'r', dlen);
216 * Any unknown messages will be ignored (and failure
217 * returned) during authentication.
219 logit("Unknown message during authentication: type %d", type);
224 auth_close(authctxt->as);
228 if (!authctxt->valid && authenticated)
229 fatal("INTERNAL ERROR: authenticated invalid user %s",
233 if (authenticated && cray_access_denied(authctxt->user)) {
235 fatal("Access denied for user %s.",authctxt->user);
241 !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD,
243 packet_disconnect("Authentication rejected for uid %d.",
244 authctxt->pw == NULL ? -1 : authctxt->pw->pw_uid);
248 /* Special handling for root */
249 if (authenticated && authctxt->pw->pw_uid == 0 &&
250 !auth_root_allowed(get_authname(type))) {
252 # ifdef SSH_AUDIT_EVENTS
253 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
259 if (options.use_pam && authenticated &&
260 !PRIVSEP(do_pam_account())) {
264 error("Access denied for user %s by PAM account "
265 "configuration", authctxt->user);
266 len = buffer_len(&loginmsg);
267 buffer_append(&loginmsg, "\0", 1);
268 msg = buffer_ptr(&loginmsg);
269 /* strip trailing newlines */
271 while (len > 0 && msg[--len] == '\n')
274 msg = "Access denied.";
275 packet_disconnect(msg);
279 /* Log before sending the reply */
280 auth_log(authctxt, authenticated, get_authname(type), info);
282 if (client_user != NULL) {
290 if (authctxt->failures++ > options.max_authtries) {
291 #ifdef SSH_AUDIT_EVENTS
292 PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
294 packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
297 packet_start(SSH_SMSG_FAILURE);
304 * Performs authentication of an incoming connection. Session key has already
305 * been exchanged and encryption is enabled.
308 do_authentication(Authctxt *authctxt)
311 char *user, *style = NULL;
313 /* Get the name of the user that we wish to log in as. */
314 packet_read_expect(SSH_CMSG_USER);
316 /* Get the user name. */
317 user = packet_get_string(&ulen);
320 if ((style = strchr(user, ':')) != NULL)
323 authctxt->user = user;
324 authctxt->style = style;
326 /* Verify that the user is a valid user. */
327 if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
330 debug("do_authentication: invalid user %s", user);
331 authctxt->pw = fakepw();
334 setproctitle("%s%s", authctxt->valid ? user : "unknown",
335 use_privsep ? " [net]" : "");
339 PRIVSEP(start_pam(authctxt));
343 * If we are not running as root, the user must have the same uid as
344 * the server. (Unless you are running Windows)
347 if (!use_privsep && getuid() != 0 && authctxt->pw &&
348 authctxt->pw->pw_uid != getuid())
349 packet_disconnect("Cannot change user when server not running as root.");
353 * Loop until the user has been authenticated or the connection is
354 * closed, do_authloop() returns only if authentication is successful
356 do_authloop(authctxt);
358 /* The user has been authenticated and accepted. */
359 packet_start(SSH_SMSG_SUCCESS);