1 /* $OpenBSD: auth1.c,v 1.70 2006/08/03 03:34:41 deraadt 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".
15 #include <sys/types.h>
40 #include "monitor_wrap.h"
44 extern ServerOptions options;
45 extern Buffer loginmsg;
47 static int auth1_process_password(Authctxt *, char *, size_t);
48 static int auth1_process_rsa(Authctxt *, char *, size_t);
49 static int auth1_process_rhosts_rsa(Authctxt *, char *, size_t);
50 static int auth1_process_tis_challenge(Authctxt *, char *, size_t);
51 static int auth1_process_tis_response(Authctxt *, char *, size_t);
53 static char *client_user = NULL; /* Used to fill in remote user for PAM */
59 int (*method)(Authctxt *, char *, size_t);
62 const struct AuthMethod1 auth1_methods[] = {
64 SSH_CMSG_AUTH_PASSWORD, "password",
65 &options.password_authentication, auth1_process_password
68 SSH_CMSG_AUTH_RSA, "rsa",
69 &options.rsa_authentication, auth1_process_rsa
72 SSH_CMSG_AUTH_RHOSTS_RSA, "rhosts-rsa",
73 &options.rhosts_rsa_authentication, auth1_process_rhosts_rsa
76 SSH_CMSG_AUTH_TIS, "challenge-response",
77 &options.challenge_response_authentication,
78 auth1_process_tis_challenge
81 SSH_CMSG_AUTH_TIS_RESPONSE, "challenge-response",
82 &options.challenge_response_authentication,
83 auth1_process_tis_response
85 { -1, NULL, NULL, NULL}
88 static const struct AuthMethod1
89 *lookup_authmethod1(int type)
93 for (i = 0; auth1_methods[i].name != NULL; i++)
94 if (auth1_methods[i].type == type)
95 return (&(auth1_methods[i]));
101 get_authname(int type)
103 const struct AuthMethod1 *a;
106 if ((a = lookup_authmethod1(type)) != NULL)
108 snprintf(buf, sizeof(buf), "bad-auth-msg-%d", type);
114 auth1_process_password(Authctxt *authctxt, char *info, size_t infolen)
116 int authenticated = 0;
121 * Read user password. It is in plain text, but was
122 * transmitted over the encrypted channel so it is
123 * not visible to an outside observer.
125 password = packet_get_string(&dlen);
128 /* Try authentication with the password. */
129 authenticated = PRIVSEP(auth_password(authctxt, password));
131 memset(password, 0, dlen);
134 return (authenticated);
139 auth1_process_rsa(Authctxt *authctxt, char *info, size_t infolen)
141 int authenticated = 0;
144 /* RSA authentication requested. */
145 if ((n = BN_new()) == NULL)
146 fatal("do_authloop: BN_new failed");
147 packet_get_bignum(n);
149 authenticated = auth_rsa(authctxt, n);
152 return (authenticated);
157 auth1_process_rhosts_rsa(Authctxt *authctxt, char *info, size_t infolen)
159 int keybits, authenticated = 0;
161 Key *client_host_key;
165 * Get client user name. Note that we just have to
166 * trust the client; root on the client machine can
167 * claim to be any user.
169 client_user = packet_get_string(&ulen);
171 /* Get the client host key. */
172 client_host_key = key_new(KEY_RSA1);
173 bits = packet_get_int();
174 packet_get_bignum(client_host_key->rsa->e);
175 packet_get_bignum(client_host_key->rsa->n);
177 keybits = BN_num_bits(client_host_key->rsa->n);
178 if (keybits < 0 || bits != (u_int)keybits) {
179 verbose("Warning: keysize mismatch for client_host_key: "
180 "actual %d, announced %d",
181 BN_num_bits(client_host_key->rsa->n), bits);
185 authenticated = auth_rhosts_rsa(authctxt, client_user,
187 key_free(client_host_key);
189 snprintf(info, infolen, " ruser %.100s", client_user);
191 return (authenticated);
196 auth1_process_tis_challenge(Authctxt *authctxt, char *info, size_t infolen)
200 if ((challenge = get_challenge(authctxt)) == NULL)
203 debug("sending challenge '%s'", challenge);
204 packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
205 packet_put_cstring(challenge);
215 auth1_process_tis_response(Authctxt *authctxt, char *info, size_t infolen)
217 int authenticated = 0;
221 response = packet_get_string(&dlen);
223 authenticated = verify_response(authctxt, response);
224 memset(response, 'r', dlen);
227 return (authenticated);
231 * read packets, try to authenticate the user and
232 * return only if authentication is successful
235 do_authloop(Authctxt *authctxt)
237 int authenticated = 0;
239 int prev = 0, type = 0;
240 const struct AuthMethod1 *meth;
242 debug("Attempting authentication for %s%.100s.",
243 authctxt->valid ? "" : "invalid user ", authctxt->user);
245 /* If the user has no password, accept authentication immediately. */
246 if (options.password_authentication &&
248 (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
250 PRIVSEP(auth_password(authctxt, ""))) {
252 if (options.use_pam && (PRIVSEP(do_pam_account())))
255 auth_log(authctxt, 1, "without authentication", "");
260 /* Indicate that authentication is needed. */
261 packet_start(SSH_SMSG_FAILURE);
266 /* default to fail */
271 /* Get a packet from the client. */
273 type = packet_read();
276 * If we started challenge-response authentication but the
277 * next packet is not a response to our challenge, release
278 * the resources allocated by get_challenge() (which would
279 * normally have been released by verify_response() had we
280 * received such a response)
282 if (prev == SSH_CMSG_AUTH_TIS &&
283 type != SSH_CMSG_AUTH_TIS_RESPONSE)
284 abandon_challenge_response(authctxt);
286 if ((meth = lookup_authmethod1(type)) == NULL) {
287 logit("Unknown message during authentication: "
292 if (!*(meth->enabled)) {
293 verbose("%s authentication disabled.", meth->name);
297 authenticated = meth->method(authctxt, info, sizeof(info));
298 if (authenticated == -1)
299 continue; /* "postponed" */
303 auth_close(authctxt->as);
307 if (!authctxt->valid && authenticated)
308 fatal("INTERNAL ERROR: authenticated invalid user %s",
312 if (authenticated && cray_access_denied(authctxt->user)) {
314 fatal("Access denied for user %s.",authctxt->user);
320 !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD,
322 packet_disconnect("Authentication rejected for uid %d.",
323 authctxt->pw == NULL ? -1 : authctxt->pw->pw_uid);
327 /* Special handling for root */
328 if (authenticated && authctxt->pw->pw_uid == 0 &&
329 !auth_root_allowed(meth->name)) {
331 # ifdef SSH_AUDIT_EVENTS
332 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
338 if (options.use_pam && authenticated &&
339 !PRIVSEP(do_pam_account())) {
343 error("Access denied for user %s by PAM account "
344 "configuration", authctxt->user);
345 len = buffer_len(&loginmsg);
346 buffer_append(&loginmsg, "\0", 1);
347 msg = buffer_ptr(&loginmsg);
348 /* strip trailing newlines */
350 while (len > 0 && msg[--len] == '\n')
353 msg = "Access denied.";
354 packet_disconnect(msg);
359 /* Log before sending the reply */
360 auth_log(authctxt, authenticated, get_authname(type), info);
362 if (client_user != NULL) {
370 if (authctxt->failures++ > options.max_authtries) {
371 #ifdef SSH_AUDIT_EVENTS
372 PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
374 packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
377 packet_start(SSH_SMSG_FAILURE);
384 * Performs authentication of an incoming connection. Session key has already
385 * been exchanged and encryption is enabled.
388 do_authentication(Authctxt *authctxt)
391 char *user, *style = NULL;
393 /* Get the name of the user that we wish to log in as. */
394 packet_read_expect(SSH_CMSG_USER);
396 /* Get the user name. */
397 user = packet_get_string(&ulen);
400 if ((style = strchr(user, ':')) != NULL)
403 authctxt->user = user;
404 authctxt->style = style;
406 /* Verify that the user is a valid user. */
407 if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
410 debug("do_authentication: invalid user %s", user);
411 authctxt->pw = fakepw();
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);