1 /* $OpenBSD: auth1.c,v 1.82 2014/07/15 15:54:14 millert Exp $ */
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * As far as I am concerned, the code I have written for this software
7 * can be used freely for any purpose. Any derived versions of this
8 * software must be clearly marked as such, and if the derived work is
9 * incompatible with the protocol description in the RFC file, it must be
10 * called by a name other than "ssh" or "Secure Shell".
17 #include <sys/types.h>
25 #include "openbsd-compat/sys-queue.h"
44 #include "monitor_wrap.h"
48 extern ServerOptions options;
49 extern Buffer loginmsg;
51 static int auth1_process_password(Authctxt *);
52 static int auth1_process_rsa(Authctxt *);
53 static int auth1_process_rhosts_rsa(Authctxt *);
54 static int auth1_process_tis_challenge(Authctxt *);
55 static int auth1_process_tis_response(Authctxt *);
57 static char *client_user = NULL; /* Used to fill in remote user for PAM */
63 int (*method)(Authctxt *);
66 const struct AuthMethod1 auth1_methods[] = {
68 SSH_CMSG_AUTH_PASSWORD, "password",
69 &options.password_authentication, auth1_process_password
72 SSH_CMSG_AUTH_RSA, "rsa",
73 &options.rsa_authentication, auth1_process_rsa
76 SSH_CMSG_AUTH_RHOSTS_RSA, "rhosts-rsa",
77 &options.rhosts_rsa_authentication, auth1_process_rhosts_rsa
80 SSH_CMSG_AUTH_TIS, "challenge-response",
81 &options.challenge_response_authentication,
82 auth1_process_tis_challenge
85 SSH_CMSG_AUTH_TIS_RESPONSE, "challenge-response",
86 &options.challenge_response_authentication,
87 auth1_process_tis_response
89 { -1, NULL, NULL, NULL}
92 static const struct AuthMethod1
93 *lookup_authmethod1(int type)
97 for (i = 0; auth1_methods[i].name != NULL; i++)
98 if (auth1_methods[i].type == type)
99 return (&(auth1_methods[i]));
105 get_authname(int type)
107 const struct AuthMethod1 *a;
110 if ((a = lookup_authmethod1(type)) != NULL)
112 snprintf(buf, sizeof(buf), "bad-auth-msg-%d", type);
118 auth1_process_password(Authctxt *authctxt)
120 int authenticated = 0;
125 * Read user password. It is in plain text, but was
126 * transmitted over the encrypted channel so it is
127 * not visible to an outside observer.
129 password = packet_get_string(&dlen);
132 /* Try authentication with the password. */
133 authenticated = PRIVSEP(auth_password(authctxt, password));
135 explicit_bzero(password, dlen);
138 return (authenticated);
143 auth1_process_rsa(Authctxt *authctxt)
145 int authenticated = 0;
148 /* RSA authentication requested. */
149 if ((n = BN_new()) == NULL)
150 fatal("do_authloop: BN_new failed");
151 packet_get_bignum(n);
153 authenticated = auth_rsa(authctxt, n);
156 return (authenticated);
161 auth1_process_rhosts_rsa(Authctxt *authctxt)
163 int keybits, authenticated = 0;
165 Key *client_host_key;
169 * Get client user name. Note that we just have to
170 * trust the client; root on the client machine can
171 * claim to be any user.
173 client_user = packet_get_cstring(&ulen);
175 /* Get the client host key. */
176 client_host_key = key_new(KEY_RSA1);
177 bits = packet_get_int();
178 packet_get_bignum(client_host_key->rsa->e);
179 packet_get_bignum(client_host_key->rsa->n);
181 keybits = BN_num_bits(client_host_key->rsa->n);
182 if (keybits < 0 || bits != (u_int)keybits) {
183 verbose("Warning: keysize mismatch for client_host_key: "
184 "actual %d, announced %d",
185 BN_num_bits(client_host_key->rsa->n), bits);
189 authenticated = auth_rhosts_rsa(authctxt, client_user,
191 key_free(client_host_key);
193 auth_info(authctxt, "ruser %.100s", client_user);
195 return (authenticated);
200 auth1_process_tis_challenge(Authctxt *authctxt)
204 if ((challenge = get_challenge(authctxt)) == NULL)
207 debug("sending challenge '%s'", challenge);
208 packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
209 packet_put_cstring(challenge);
219 auth1_process_tis_response(Authctxt *authctxt)
221 int authenticated = 0;
225 response = packet_get_string(&dlen);
227 authenticated = verify_response(authctxt, response);
228 explicit_bzero(response, dlen);
231 return (authenticated);
235 * read packets, try to authenticate the user and
236 * return only if authentication is successful
239 do_authloop(Authctxt *authctxt)
241 int authenticated = 0;
242 int prev = 0, type = 0;
243 const struct AuthMethod1 *meth;
245 debug("Attempting authentication for %s%.100s.",
246 authctxt->valid ? "" : "invalid user ", authctxt->user);
248 /* If the user has no password, accept authentication immediately. */
249 if (options.permit_empty_passwd && options.password_authentication &&
251 (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
253 PRIVSEP(auth_password(authctxt, ""))) {
255 if (options.use_pam && (PRIVSEP(do_pam_account())))
258 auth_log(authctxt, 1, 0, "without authentication",
264 /* Indicate that authentication is needed. */
265 packet_start(SSH_SMSG_FAILURE);
270 /* default to fail */
274 /* Get a packet from the client. */
276 type = packet_read();
279 * If we started challenge-response authentication but the
280 * next packet is not a response to our challenge, release
281 * the resources allocated by get_challenge() (which would
282 * normally have been released by verify_response() had we
283 * received such a response)
285 if (prev == SSH_CMSG_AUTH_TIS &&
286 type != SSH_CMSG_AUTH_TIS_RESPONSE)
287 abandon_challenge_response(authctxt);
289 if (authctxt->failures >= options.max_authtries)
291 if ((meth = lookup_authmethod1(type)) == NULL) {
292 logit("Unknown message during authentication: "
297 if (!*(meth->enabled)) {
298 verbose("%s authentication disabled.", meth->name);
302 authenticated = meth->method(authctxt);
303 if (authenticated == -1)
304 continue; /* "postponed" */
308 auth_close(authctxt->as);
312 if (!authctxt->valid && authenticated)
313 fatal("INTERNAL ERROR: authenticated invalid user %s",
317 if (authenticated && cray_access_denied(authctxt->user)) {
319 fatal("Access denied for user %s.",authctxt->user);
324 /* Special handling for root */
325 if (authenticated && authctxt->pw->pw_uid == 0 &&
326 !auth_root_allowed(meth->name)) {
328 # ifdef SSH_AUDIT_EVENTS
329 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
335 if (options.use_pam && authenticated &&
336 !PRIVSEP(do_pam_account())) {
340 error("Access denied for user %s by PAM account "
341 "configuration", authctxt->user);
342 len = buffer_len(&loginmsg);
343 buffer_append(&loginmsg, "\0", 1);
344 msg = buffer_ptr(&loginmsg);
345 /* strip trailing newlines */
347 while (len > 0 && msg[--len] == '\n')
350 msg = "Access denied.";
351 packet_disconnect("%s", msg);
356 /* Log before sending the reply */
357 auth_log(authctxt, authenticated, 0, get_authname(type), NULL);
365 if (++authctxt->failures >= options.max_authtries) {
366 #ifdef SSH_AUDIT_EVENTS
367 PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
369 auth_maxtries_exceeded(authctxt);
372 packet_start(SSH_SMSG_FAILURE);
379 * Performs authentication of an incoming connection. Session key has already
380 * been exchanged and encryption is enabled.
383 do_authentication(Authctxt *authctxt)
386 char *user, *style = NULL;
388 /* Get the name of the user that we wish to log in as. */
389 packet_read_expect(SSH_CMSG_USER);
391 /* Get the user name. */
392 user = packet_get_cstring(&ulen);
395 if ((style = strchr(user, ':')) != NULL)
398 authctxt->user = user;
399 authctxt->style = style;
401 /* Verify that the user is a valid user. */
402 if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
405 debug("do_authentication: invalid user %s", user);
406 authctxt->pw = fakepw();
409 /* Configuration may have changed as a result of Match */
410 if (options.num_auth_methods != 0)
411 fatal("AuthenticationMethods is not supported with SSH "
414 setproctitle("%s%s", authctxt->valid ? user : "unknown",
415 use_privsep ? " [net]" : "");
419 PRIVSEP(start_pam(authctxt));
423 * If we are not running as root, the user must have the same uid as
427 if (!use_privsep && getuid() != 0 && authctxt->pw &&
428 authctxt->pw->pw_uid != getuid())
429 packet_disconnect("Cannot change user when server not running as root.");
433 * Loop until the user has been authenticated or the connection is
434 * closed, do_authloop() returns only if authentication is successful
436 do_authloop(authctxt);
438 /* The user has been authenticated and accepted. */
439 packet_start(SSH_SMSG_SUCCESS);
444 #endif /* WITH_SSH1 */