1/*
2 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
3 *                    All rights reserved
4 *
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".
10 */
11/*
12 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
13 * Use is subject to license terms.
14 */
15
16#include "includes.h"
17RCSID("$OpenBSD: auth1.c,v 1.44 2002/09/26 11:38:43 markus Exp $");
18
19#include "xmalloc.h"
20#include "rsa.h"
21#include "ssh1.h"
22#include "packet.h"
23#include "buffer.h"
24#include "mpaux.h"
25#include "log.h"
26#include "servconf.h"
27#include "compat.h"
28#include "auth.h"
29#include "channels.h"
30#include "session.h"
31#include "uidswap.h"
32
33#ifdef HAVE_BSM
34#include "bsmaudit.h"
35extern adt_session_data_t *ah;
36#endif /* HAVE_BSM */
37
38/* import */
39extern ServerOptions options;
40
41/*
42 * convert ssh auth msg type into description
43 */
44static char *
45get_authname(int type)
46{
47	static char buf[1024];
48	switch (type) {
49	case SSH_CMSG_AUTH_PASSWORD:
50		return "password";
51	case SSH_CMSG_AUTH_RSA:
52		return "rsa";
53	case SSH_CMSG_AUTH_RHOSTS_RSA:
54		return "rhosts-rsa";
55	case SSH_CMSG_AUTH_RHOSTS:
56		return "rhosts";
57	case SSH_CMSG_AUTH_TIS:
58	case SSH_CMSG_AUTH_TIS_RESPONSE:
59		return "challenge-response";
60#if defined(KRB4) || defined(KRB5)
61	case SSH_CMSG_AUTH_KERBEROS:
62		return "kerberos";
63#endif
64	}
65	snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
66	return buf;
67}
68
69/*
70 * read packets, try to authenticate the user and
71 * return only if authentication is successful
72 */
73static void
74do_authloop(Authctxt *authctxt)
75{
76	int authenticated = 0;
77	u_int bits;
78	Key *client_host_key;
79	BIGNUM *n;
80	char *client_user, *password;
81	char info[1024];
82	u_int dlen;
83	u_int ulen;
84	int type = 0;
85	struct passwd *pw = authctxt->pw;
86
87	debug("Attempting authentication for %s%.100s.",
88	    authctxt->valid ? "" : "illegal user ", authctxt->user);
89
90	/* If the user has no password, accept authentication immediately. */
91	if (options.password_authentication &&
92#if defined(KRB4) || defined(KRB5)
93	    (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
94#endif
95	    auth_password(authctxt, "")) {
96		auth_log(authctxt, 1, "without authentication", "");
97		return;
98	}
99
100	/* Indicate that authentication is needed. */
101	packet_start(SSH_SMSG_FAILURE);
102	packet_send();
103	packet_write_wait();
104
105	client_user = NULL;
106
107	for ( ;; ) {
108		/* default to fail */
109		authenticated = 0;
110
111		info[0] = '\0';
112
113		/* Get a packet from the client. */
114		authctxt->v1_auth_type = type = packet_read();
115		authctxt->v1_auth_name = get_authname(type);
116
117		authctxt->attempt++;
118
119		/* Process the packet. */
120		switch (type) {
121
122#if defined(KRB4) || defined(KRB5)
123		case SSH_CMSG_AUTH_KERBEROS:
124			if (!options.kerberos_authentication) {
125				verbose("Kerberos authentication disabled.");
126			} else {
127				char *kdata = packet_get_string(&dlen);
128				packet_check_eom();
129
130				if (kdata[0] == 4) { /* KRB_PROT_VERSION */
131#ifdef KRB4
132					KTEXT_ST tkt, reply;
133					tkt.length = dlen;
134					if (tkt.length < MAX_KTXT_LEN)
135						memcpy(tkt.dat, kdata, tkt.length);
136
137					if (auth_krb4(authctxt, &tkt,
138					    &client_user, &reply)) {
139						authenticated = 1;
140						snprintf(info, sizeof(info),
141						    " tktuser %.100s",
142						    client_user);
143
144						packet_start(
145						    SSH_SMSG_AUTH_KERBEROS_RESPONSE);
146						packet_put_string((char *)
147						    reply.dat, reply.length);
148						packet_send();
149						packet_write_wait();
150					}
151#endif /* KRB4 */
152				} else {
153#ifdef KRB5
154					krb5_data tkt, reply;
155					tkt.length = dlen;
156					tkt.data = kdata;
157
158					if (auth_krb5(authctxt, &tkt,
159					    &client_user, &reply)) {
160						authenticated = 1;
161						snprintf(info, sizeof(info),
162						    " tktuser %.100s",
163						    client_user);
164
165 						/* Send response to client */
166 						packet_start(
167						    SSH_SMSG_AUTH_KERBEROS_RESPONSE);
168 						packet_put_string((char *)
169						    reply.data, reply.length);
170 						packet_send();
171 						packet_write_wait();
172
173 						if (reply.length)
174 							xfree(reply.data);
175					}
176#endif /* KRB5 */
177				}
178				xfree(kdata);
179			}
180			break;
181#endif /* KRB4 || KRB5 */
182
183#if defined(AFS) || defined(KRB5)
184			/* XXX - punt on backward compatibility here. */
185		case SSH_CMSG_HAVE_KERBEROS_TGT:
186			packet_send_debug("Kerberos TGT passing disabled before authentication.");
187			break;
188#ifdef AFS
189		case SSH_CMSG_HAVE_AFS_TOKEN:
190			packet_send_debug("AFS token passing disabled before authentication.");
191			break;
192#endif /* AFS */
193#endif /* AFS || KRB5 */
194
195		case SSH_CMSG_AUTH_RHOSTS:
196			if (!options.rhosts_authentication) {
197				verbose("Rhosts authentication disabled.");
198				break;
199			}
200			/*
201			 * Get client user name.  Note that we just have to
202			 * trust the client; this is one reason why rhosts
203			 * authentication is insecure. (Another is
204			 * IP-spoofing on a local network.)
205			 */
206			client_user = packet_get_string(&ulen);
207			packet_check_eom();
208
209			/* Try to authenticate using /etc/hosts.equiv and .rhosts. */
210			authenticated = auth_rhosts(pw, client_user);
211
212			snprintf(info, sizeof info, " ruser %.100s", client_user);
213			break;
214
215		case SSH_CMSG_AUTH_RHOSTS_RSA:
216			if (!options.rhosts_rsa_authentication) {
217				verbose("Rhosts with RSA authentication disabled.");
218				break;
219			}
220			/*
221			 * Get client user name.  Note that we just have to
222			 * trust the client; root on the client machine can
223			 * claim to be any user.
224			 */
225			client_user = packet_get_string(&ulen);
226
227			/* Get the client host key. */
228			client_host_key = key_new(KEY_RSA1);
229			bits = packet_get_int();
230			packet_get_bignum(client_host_key->rsa->e);
231			packet_get_bignum(client_host_key->rsa->n);
232
233			if (bits != BN_num_bits(client_host_key->rsa->n))
234				verbose("Warning: keysize mismatch for client_host_key: "
235				    "actual %d, announced %d",
236				    BN_num_bits(client_host_key->rsa->n), bits);
237			packet_check_eom();
238
239			authenticated = auth_rhosts_rsa(pw, client_user,
240			    client_host_key);
241			key_free(client_host_key);
242
243			snprintf(info, sizeof info, " ruser %.100s", client_user);
244			break;
245
246		case SSH_CMSG_AUTH_RSA:
247			if (!options.rsa_authentication) {
248				verbose("RSA authentication disabled.");
249				break;
250			}
251			/* RSA authentication requested. */
252			if ((n = BN_new()) == NULL)
253				fatal("do_authloop: BN_new failed");
254			packet_get_bignum(n);
255			packet_check_eom();
256			authenticated = auth_rsa(pw, n);
257			BN_clear_free(n);
258			break;
259
260		case SSH_CMSG_AUTH_PASSWORD:
261			authctxt->init_attempt++;
262
263			if (!options.password_authentication) {
264				verbose("Password authentication disabled.");
265				break;
266			}
267			/*
268			 * Read user password.  It is in plain text, but was
269			 * transmitted over the encrypted channel so it is
270			 * not visible to an outside observer.
271			 */
272			password = packet_get_string(&dlen);
273			packet_check_eom();
274
275			/* Try authentication with the password. */
276			if (authctxt->init_failures <
277				options.max_init_auth_tries)
278				authenticated =
279				    auth_password(authctxt, password);
280
281			memset(password, 0, strlen(password));
282			xfree(password);
283			break;
284
285		case SSH_CMSG_AUTH_TIS:
286			debug("rcvd SSH_CMSG_AUTH_TIS");
287			if (options.challenge_response_authentication == 1) {
288				char *challenge = get_challenge(authctxt);
289				if (challenge != NULL) {
290					debug("sending challenge '%s'", challenge);
291					packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
292					packet_put_cstring(challenge);
293					xfree(challenge);
294					packet_send();
295					packet_write_wait();
296					continue;
297				}
298			}
299			break;
300		case SSH_CMSG_AUTH_TIS_RESPONSE:
301			debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
302			if (options.challenge_response_authentication == 1) {
303				char *response = packet_get_string(&dlen);
304				debug("got response '%s'", response);
305				packet_check_eom();
306				authenticated = verify_response(authctxt, response);
307				memset(response, 'r', dlen);
308				xfree(response);
309			}
310			break;
311
312		default:
313			/*
314			 * Any unknown messages will be ignored (and failure
315			 * returned) during authentication.
316			 */
317			log("Unknown message during authentication: type %d", type);
318			break;
319		}
320#ifdef BSD_AUTH
321		if (authctxt->as) {
322			auth_close(authctxt->as);
323			authctxt->as = NULL;
324		}
325#endif
326		if (!authctxt->valid && authenticated) {
327			authenticated = 0;
328			log("Ignoring authenticated invalid user %s",
329			    authctxt->user);
330		}
331
332#ifdef _UNICOS
333		if (type == SSH_CMSG_AUTH_PASSWORD && !authenticated)
334			cray_login_failure(authctxt->user, IA_UDBERR);
335		if (authenticated && cray_access_denied(authctxt->user)) {
336			authenticated = 0;
337			fatal("Access denied for user %s.",authctxt->user);
338		}
339#endif /* _UNICOS */
340
341#ifdef HAVE_CYGWIN
342		if (authenticated &&
343		    !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) {
344			packet_disconnect("Authentication rejected for uid %d.",
345			pw == NULL ? -1 : pw->pw_uid);
346			authenticated = 0;
347		}
348#else
349		/* Special handling for root */
350		if (authenticated && authctxt->pw->pw_uid == 0 &&
351		    !auth_root_allowed(get_authname(type)))
352			authenticated = 0;
353#endif
354#ifdef USE_PAM
355		if (authenticated && type != SSH_CMSG_AUTH_PASSWORD)
356			authenticated = do_pam_non_initial_userauth(authctxt);
357		else if (authenticated && !AUTHPAM_DONE(authctxt))
358			authenticated = 0;
359
360		if (!authenticated)
361			authctxt->pam_retval = AUTHPAM_ERROR(authctxt,
362				PAM_PERM_DENIED);
363#endif /* USE_PAM */
364
365		/* Log before sending the reply */
366		auth_log(authctxt, authenticated, get_authname(type), info);
367
368		if (client_user != NULL) {
369			xfree(client_user);
370			client_user = NULL;
371		}
372
373		if (authenticated)
374			return;
375
376		if (type == SSH_CMSG_AUTH_PASSWORD)
377			authctxt->init_failures++;
378
379		if (authctxt->failures++ > options.max_auth_tries) {
380#ifdef HAVE_BSM
381			fatal_remove_cleanup(audit_failed_login_cleanup,
382				authctxt);
383			audit_sshd_login_failure(&ah, PAM_MAXTRIES,
384			    authctxt->user);
385#endif /* HAVE_BSM */
386			packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
387		}
388
389		packet_start(SSH_SMSG_FAILURE);
390		packet_send();
391		packet_write_wait();
392	}
393}
394
395/*
396 * Performs authentication of an incoming connection.  Session key has already
397 * been exchanged and encryption is enabled.
398 */
399Authctxt *
400do_authentication(void)
401{
402	Authctxt *authctxt;
403	u_int ulen;
404	char *user, *style = NULL;
405
406	/* Get the name of the user that we wish to log in as. */
407	packet_read_expect(SSH_CMSG_USER);
408
409	/* Get the user name. */
410	user = packet_get_string(&ulen);
411	packet_check_eom();
412
413	if ((style = strchr(user, ':')) != NULL)
414		*style++ = '\0';
415
416#ifdef KRB5
417	/* XXX - SSH.com Kerberos v5 braindeath. */
418	if ((datafellows & SSH_BUG_K5USER) &&
419	    options.kerberos_authentication) {
420		char *p;
421		if ((p = strchr(user, '@')) != NULL)
422			*p = '\0';
423	}
424#endif
425
426	authctxt = authctxt_new();
427	authctxt->user = user;
428	authctxt->style = style;
429
430#ifdef HAVE_BSM
431	fatal_add_cleanup(audit_failed_login_cleanup, authctxt);
432#endif /* HAVE_BSM */
433
434	/* Verify that the user is a valid user. */
435	if ((authctxt->pw = getpwnamallow(user)) != NULL) {
436		authctxt->valid = 1;
437	} else {
438		authctxt->valid = 0;
439		debug("do_authentication: illegal user %s", user);
440	}
441
442	setproctitle("%s", authctxt->pw ? user : "unknown");
443
444	/*
445	 * If we are not running as root, the user must have the same uid as
446	 * the server. (Unless you are running Windows)
447	 */
448#ifndef HAVE_CYGWIN
449	if (getuid() != 0 && authctxt->pw &&
450	    authctxt->pw->pw_uid != getuid())
451		packet_disconnect("Cannot change user when server not running as root.");
452#endif
453
454	/*
455	 * Loop until the user has been authenticated or the connection is
456	 * closed, do_authloop() returns only if authentication is successful
457	 */
458	do_authloop(authctxt);
459
460	/* The user has been authenticated and accepted. */
461	packet_start(SSH_SMSG_SUCCESS);
462	packet_send();
463	packet_write_wait();
464
465	return (authctxt);
466}
467