[openssh.git] / auth1.c

/*
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 */

#include "includes.h"
RCSID("$OpenBSD: auth1.c,v 1.59 2004/07/28 09:40:29 markus Exp $");

#include "xmalloc.h"
#include "rsa.h"
#include "ssh1.h"
#include "packet.h"
#include "buffer.h"
#include "log.h"
#include "servconf.h"
#include "compat.h"
#include "auth.h"
#include "channels.h"
#include "session.h"
#include "uidswap.h"
#include "monitor_wrap.h"
#include "buffer.h"

/* import */
extern ServerOptions options;
extern Buffer loginmsg;

/*
 * convert ssh auth msg type into description
 */
static char *
get_authname(int type)
{
	static char buf[1024];
	switch (type) {
	case SSH_CMSG_AUTH_PASSWORD:
		return "password";
	case SSH_CMSG_AUTH_RSA:
		return "rsa";
	case SSH_CMSG_AUTH_RHOSTS_RSA:
		return "rhosts-rsa";
	case SSH_CMSG_AUTH_RHOSTS:
		return "rhosts";
	case SSH_CMSG_AUTH_TIS:
	case SSH_CMSG_AUTH_TIS_RESPONSE:
		return "challenge-response";
	}
	snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
	return buf;
}

/*
 * read packets, try to authenticate the user and
 * return only if authentication is successful
 */
static void
do_authloop(Authctxt *authctxt)
{
	int authenticated = 0;
	u_int bits;
	Key *client_host_key;
	BIGNUM *n;
	char *client_user, *password;
	char info[1024];
	u_int dlen;
	u_int ulen;
	int prev, type = 0;

	debug("Attempting authentication for %s%.100s.",
	    authctxt->valid ? "" : "invalid user ", authctxt->user);

	/* If the user has no password, accept authentication immediately. */
	if (options.password_authentication &&
#ifdef KRB5
	    (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
#endif
	    PRIVSEP(auth_password(authctxt, ""))) {
#ifdef USE_PAM
		if (options.use_pam && (PRIVSEP(do_pam_account())))
#endif
		{
			auth_log(authctxt, 1, "without authentication", "");
			return;
		}
	}

	/* Indicate that authentication is needed. */
	packet_start(SSH_SMSG_FAILURE);
	packet_send();
	packet_write_wait();

	client_user = NULL;

	for (;;) {
		/* default to fail */
		authenticated = 0;

		info[0] = '\0';

		/* Get a packet from the client. */
		prev = type;
		type = packet_read();

		/*
		 * If we started challenge-response authentication but the
		 * next packet is not a response to our challenge, release
		 * the resources allocated by get_challenge() (which would
		 * normally have been released by verify_response() had we
		 * received such a response)
		 */
		if (prev == SSH_CMSG_AUTH_TIS &&
		    type != SSH_CMSG_AUTH_TIS_RESPONSE)
			abandon_challenge_response(authctxt);

		/* Process the packet. */
		switch (type) {
		case SSH_CMSG_AUTH_RHOSTS_RSA:
			if (!options.rhosts_rsa_authentication) {
				verbose("Rhosts with RSA authentication disabled.");
				break;
			}
			/*
			 * Get client user name.  Note that we just have to
			 * trust the client; root on the client machine can
			 * claim to be any user.
			 */
			client_user = packet_get_string(&ulen);

			/* Get the client host key. */
			client_host_key = key_new(KEY_RSA1);
			bits = packet_get_int();
			packet_get_bignum(client_host_key->rsa->e);
			packet_get_bignum(client_host_key->rsa->n);

			if (bits != BN_num_bits(client_host_key->rsa->n))
				verbose("Warning: keysize mismatch for client_host_key: "
				    "actual %d, announced %d",
				    BN_num_bits(client_host_key->rsa->n), bits);
			packet_check_eom();

			authenticated = auth_rhosts_rsa(authctxt, client_user,
			    client_host_key);
			key_free(client_host_key);

			snprintf(info, sizeof info, " ruser %.100s", client_user);
			break;

		case SSH_CMSG_AUTH_RSA:
			if (!options.rsa_authentication) {
				verbose("RSA authentication disabled.");
				break;
			}
			/* RSA authentication requested. */
			if ((n = BN_new()) == NULL)
				fatal("do_authloop: BN_new failed");
			packet_get_bignum(n);
			packet_check_eom();
			authenticated = auth_rsa(authctxt, n);
			BN_clear_free(n);
			break;

		case SSH_CMSG_AUTH_PASSWORD:
			if (!options.password_authentication) {
				verbose("Password authentication disabled.");
				break;
			}
			/*
			 * Read user password.  It is in plain text, but was
			 * transmitted over the encrypted channel so it is
			 * not visible to an outside observer.
			 */
			password = packet_get_string(&dlen);
			packet_check_eom();

			/* Try authentication with the password. */
			authenticated = PRIVSEP(auth_password(authctxt, password));

			memset(password, 0, strlen(password));
			xfree(password);
			break;

		case SSH_CMSG_AUTH_TIS:
			debug("rcvd SSH_CMSG_AUTH_TIS");
			if (options.challenge_response_authentication == 1) {
				char *challenge = get_challenge(authctxt);
				if (challenge != NULL) {
					debug("sending challenge '%s'", challenge);
					packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
					packet_put_cstring(challenge);
					xfree(challenge);
					packet_send();
					packet_write_wait();
					continue;
				}
			}
			break;
		case SSH_CMSG_AUTH_TIS_RESPONSE:
			debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
			if (options.challenge_response_authentication == 1) {
				char *response = packet_get_string(&dlen);
				packet_check_eom();
				authenticated = verify_response(authctxt, response);
				memset(response, 'r', dlen);
				xfree(response);
			}
			break;

		default:
			/*
			 * Any unknown messages will be ignored (and failure
			 * returned) during authentication.
			 */
			logit("Unknown message during authentication: type %d", type);
			break;
		}
#ifdef BSD_AUTH
		if (authctxt->as) {
			auth_close(authctxt->as);
			authctxt->as = NULL;
		}
#endif
		if (!authctxt->valid && authenticated)
			fatal("INTERNAL ERROR: authenticated invalid user %s",
			    authctxt->user);

#ifdef _UNICOS
		if (authenticated && cray_access_denied(authctxt->user)) {
			authenticated = 0;
			fatal("Access denied for user %s.",authctxt->user);
		}
#endif /* _UNICOS */

#ifdef HAVE_CYGWIN
		if (authenticated &&
		    !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, 
		    authctxt->pw)) {
			packet_disconnect("Authentication rejected for uid %d.",
			    authctxt->pw == NULL ? -1 : authctxt->pw->pw_uid);
			authenticated = 0;
		}
#else
		/* Special handling for root */
		if (authenticated && authctxt->pw->pw_uid == 0 &&
		    !auth_root_allowed(get_authname(type)))
			authenticated = 0;
#endif

#ifdef USE_PAM
		if (options.use_pam && authenticated &&
		    !PRIVSEP(do_pam_account())) {
			char *msg;
			size_t len;

			error("Access denied for user %s by PAM account "
			   "configuration", authctxt->user);
			len = buffer_len(&loginmsg);
			buffer_append(&loginmsg, "\0", 1);
			msg = buffer_ptr(&loginmsg);
			/* strip trailing newlines */
			if (len > 0)
				while (len > 0 && msg[--len] == '\n')
					msg[len] = '\0';
			else
				msg = "Access denied.";
			packet_disconnect(msg);
		}
#endif

		/* Log before sending the reply */
		auth_log(authctxt, authenticated, get_authname(type), info);

		if (client_user != NULL) {
			xfree(client_user);
			client_user = NULL;
		}

		if (authenticated)
			return;

		if (authctxt->failures++ > options.max_authtries)
			packet_disconnect(AUTH_FAIL_MSG, authctxt->user);

		packet_start(SSH_SMSG_FAILURE);
		packet_send();
		packet_write_wait();
	}
}

/*
 * Performs authentication of an incoming connection.  Session key has already
 * been exchanged and encryption is enabled.
 */
void
do_authentication(Authctxt *authctxt)
{
	u_int ulen;
	char *user, *style = NULL;

	/* Get the name of the user that we wish to log in as. */
	packet_read_expect(SSH_CMSG_USER);

	/* Get the user name. */
	user = packet_get_string(&ulen);
	packet_check_eom();

	if ((style = strchr(user, ':')) != NULL)
		*style++ = '\0';

	authctxt->user = user;
	authctxt->style = style;

	/* Verify that the user is a valid user. */
	if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
		authctxt->valid = 1;
	else {
		debug("do_authentication: invalid user %s", user);
		authctxt->pw = fakepw();
	}

	setproctitle("%s%s", authctxt->valid ? user : "unknown",
	    use_privsep ? " [net]" : "");

#ifdef USE_PAM
	if (options.use_pam)
		PRIVSEP(start_pam(authctxt));
#endif

	/*
	 * If we are not running as root, the user must have the same uid as
	 * the server. (Unless you are running Windows)
	 */
#ifndef HAVE_CYGWIN
	if (!use_privsep && getuid() != 0 && authctxt->pw &&
	    authctxt->pw->pw_uid != getuid())
		packet_disconnect("Cannot change user when server not running as root.");
#endif

	/*
	 * Loop until the user has been authenticated or the connection is
	 * closed, do_authloop() returns only if authentication is successful
	 */
	do_authloop(authctxt);

	/* The user has been authenticated and accepted. */
	packet_start(SSH_SMSG_SUCCESS);
	packet_send();
	packet_write_wait();
}
Commit	Line	Data
a306f2dd	1	/*
	2	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
	3	* All rights reserved
bcbf86ec	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".
a306f2dd	10	*/
	11
	12	#include "includes.h"
d77347cc	13	RCSID("$OpenBSD: auth1.c,v 1.59 2004/07/28 09:40:29 markus Exp $");
94ec8c6b	14
a306f2dd	15	#include "xmalloc.h"
a306f2dd	16	#include "rsa.h"
42f11eb2	17	#include "ssh1.h"
a306f2dd	18	#include "packet.h"
a306f2dd	19	#include "buffer.h"
42f11eb2	20	#include "log.h"
a306f2dd	21	#include "servconf.h"
	22	#include "compat.h"
	23	#include "auth.h"
7899c98f	24	#include "channels.h"
a306f2dd	25	#include "session.h"
ced49be2	26	#include "uidswap.h"
1853d1ef	27	#include "monitor_wrap.h"
9aab0af7	28	#include "buffer.h"
a306f2dd	29
	30	/* import */
	31	extern ServerOptions options;
9aab0af7	32	extern Buffer loginmsg;
94ec8c6b	33
a306f2dd	34	/*
	35	* convert ssh auth msg type into description
	36	*/
396c147e	37	static char *
a306f2dd	38	get_authname(int type)
	39	{
	40	static char buf[1024];
	41	switch (type) {
	42	case SSH_CMSG_AUTH_PASSWORD:
	43	return "password";
	44	case SSH_CMSG_AUTH_RSA:
	45	return "rsa";
	46	case SSH_CMSG_AUTH_RHOSTS_RSA:
	47	return "rhosts-rsa";
	48	case SSH_CMSG_AUTH_RHOSTS:
	49	return "rhosts";
59c97189	50	case SSH_CMSG_AUTH_TIS:
	51	case SSH_CMSG_AUTH_TIS_RESPONSE:
	52	return "challenge-response";
a306f2dd	53	}
	54	snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
	55	return buf;
	56	}
	57
	58	/*
59c97189	59	* read packets, try to authenticate the user and
59c97189	60	* return only if authentication is successful
a306f2dd	61	*/
396c147e	62	static void
59c97189	63	do_authloop(Authctxt *authctxt)
a306f2dd	64	{
94ec8c6b	65	int authenticated = 0;
1e3b8b07	66	u_int bits;
b775c6f2	67	Key *client_host_key;
a306f2dd	68	BIGNUM *n;
94ec8c6b	69	char client_user, password;
59c97189	70	char info[1024];
1e3b8b07	71	u_int dlen;
1e3b8b07	72	u_int ulen;
05114c74	73	int prev, type = 0;
59c97189	74
59c97189	75	debug("Attempting authentication for %s%.100s.",
d77347cc	76	authctxt->valid ? "" : "invalid user ", authctxt->user);
59c97189	77
	78	/* If the user has no password, accept authentication immediately. */
	79	if (options.password_authentication &&
1c590258	80	#ifdef KRB5
59c97189	81	(!options.kerberos_authentication \|\| options.kerberos_or_local_passwd) &&
59c97189	82	#endif
1853d1ef	83	PRIVSEP(auth_password(authctxt, ""))) {
ece30983	84	#ifdef USE_PAM
	85	if (options.use_pam && (PRIVSEP(do_pam_account())))
	86	#endif
	87	{
	88	auth_log(authctxt, 1, "without authentication", "");
	89	return;
	90	}
59c97189	91	}
a306f2dd	92
	93	/* Indicate that authentication is needed. */
	94	packet_start(SSH_SMSG_FAILURE);
	95	packet_send();
	96	packet_write_wait();
	97
94ec8c6b	98	client_user = NULL;
94ec8c6b	99
59c97189	100	for (;;) {
94ec8c6b	101	/* default to fail */
	102	authenticated = 0;
	103
59c97189	104	info[0] = '\0';
a306f2dd	105
a306f2dd	106	/* Get a packet from the client. */
05114c74	107	prev = type;
54a5250f	108	type = packet_read();
a306f2dd	109
05114c74	110	/*
	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)
	116	*/
	117	if (prev == SSH_CMSG_AUTH_TIS &&
	118	type != SSH_CMSG_AUTH_TIS_RESPONSE)
	119	abandon_challenge_response(authctxt);
	120
a306f2dd	121	/* Process the packet. */
a306f2dd	122	switch (type) {
a306f2dd	123	case SSH_CMSG_AUTH_RHOSTS_RSA:
	124	if (!options.rhosts_rsa_authentication) {
	125	verbose("Rhosts with RSA authentication disabled.");
	126	break;
	127	}
	128	/*
	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.
	132	*/
	133	client_user = packet_get_string(&ulen);
	134
	135	/* Get the client host key. */
b775c6f2	136	client_host_key = key_new(KEY_RSA1);
a306f2dd	137	bits = packet_get_int();
20b279e6	138	packet_get_bignum(client_host_key->rsa->e);
20b279e6	139	packet_get_bignum(client_host_key->rsa->n);
a306f2dd	140
b775c6f2	141	if (bits != BN_num_bits(client_host_key->rsa->n))
94ec8c6b	142	verbose("Warning: keysize mismatch for client_host_key: "
b775c6f2	143	"actual %d, announced %d",
7203d6bb	144	BN_num_bits(client_host_key->rsa->n), bits);
95500969	145	packet_check_eom();
a306f2dd	146
fdaef11e	147	authenticated = auth_rhosts_rsa(authctxt, client_user,
dc421aa3	148	client_host_key);
b775c6f2	149	key_free(client_host_key);
a306f2dd	150
59c97189	151	snprintf(info, sizeof info, " ruser %.100s", client_user);
a306f2dd	152	break;
	153
	154	case SSH_CMSG_AUTH_RSA:
	155	if (!options.rsa_authentication) {
	156	verbose("RSA authentication disabled.");
	157	break;
	158	}
	159	/* RSA authentication requested. */
b775c6f2	160	if ((n = BN_new()) == NULL)
b775c6f2	161	fatal("do_authloop: BN_new failed");
20b279e6	162	packet_get_bignum(n);
95500969	163	packet_check_eom();
fdaef11e	164	authenticated = auth_rsa(authctxt, n);
a306f2dd	165	BN_clear_free(n);
	166	break;
	167
	168	case SSH_CMSG_AUTH_PASSWORD:
	169	if (!options.password_authentication) {
	170	verbose("Password authentication disabled.");
	171	break;
	172	}
	173	/*
	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.
	177	*/
	178	password = packet_get_string(&dlen);
95500969	179	packet_check_eom();
a306f2dd	180
b4b5d644	181	/* Try authentication with the password. */
1853d1ef	182	authenticated = PRIVSEP(auth_password(authctxt, password));
a306f2dd	183
	184	memset(password, 0, strlen(password));
	185	xfree(password);
	186	break;
	187
a306f2dd	188	case SSH_CMSG_AUTH_TIS:
a306f2dd	189	debug("rcvd SSH_CMSG_AUTH_TIS");
5ba55ada	190	if (options.challenge_response_authentication == 1) {
5ba55ada	191	char *challenge = get_challenge(authctxt);
59c97189	192	if (challenge != NULL) {
59c97189	193	debug("sending challenge '%s'", challenge);
a306f2dd	194	packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
59c97189	195	packet_put_cstring(challenge);
5ba55ada	196	xfree(challenge);
a306f2dd	197	packet_send();
	198	packet_write_wait();
	199	continue;
	200	}
	201	}
	202	break;
	203	case SSH_CMSG_AUTH_TIS_RESPONSE:
	204	debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
5ba55ada	205	if (options.challenge_response_authentication == 1) {
a306f2dd	206	char *response = packet_get_string(&dlen);
95500969	207	packet_check_eom();
59c97189	208	authenticated = verify_response(authctxt, response);
59c97189	209	memset(response, 'r', dlen);
a306f2dd	210	xfree(response);
	211	}
	212	break;
a306f2dd	213
	214	default:
	215	/*
	216	* Any unknown messages will be ignored (and failure
	217	* returned) during authentication.
	218	*/
bbe88b6d	219	logit("Unknown message during authentication: type %d", type);
a306f2dd	220	break;
a306f2dd	221	}
af774732	222	#ifdef BSD_AUTH
	223	if (authctxt->as) {
	224	auth_close(authctxt->as);
	225	authctxt->as = NULL;
	226	}
	227	#endif
59c97189	228	if (!authctxt->valid && authenticated)
	229	fatal("INTERNAL ERROR: authenticated invalid user %s",
	230	authctxt->user);
a306f2dd	231
ef51930f	232	#ifdef _UNICOS
ef51930f	233	if (authenticated && cray_access_denied(authctxt->user)) {
	234	authenticated = 0;
	235	fatal("Access denied for user %s.",authctxt->user);
	236	}
	237	#endif /* _UNICOS */
	238
2b87da3b	239	#ifdef HAVE_CYGWIN
2b87da3b	240	if (authenticated &&
02a57950	241	!check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD,
02a57950	242	authctxt->pw)) {
3c62e7eb	243	packet_disconnect("Authentication rejected for uid %d.",
02a57950	244	authctxt->pw == NULL ? -1 : authctxt->pw->pw_uid);
3c62e7eb	245	authenticated = 0;
3c62e7eb	246	}
3c418020	247	#else
59c97189	248	/* Special handling for root */
5d47f1d4	249	if (authenticated && authctxt->pw->pw_uid == 0 &&
15853e93	250	!auth_root_allowed(get_authname(type)))
59c97189	251	authenticated = 0;
3c418020	252	#endif
a306f2dd	253
5b9e2464	254	#ifdef USE_PAM
aff51935	255	if (options.use_pam && authenticated &&
9aab0af7	256	!PRIVSEP(do_pam_account())) {
	257	char *msg;
	258	size_t len;
	259
	260	error("Access denied for user %s by PAM account "
	261	"configuration", authctxt->user);
	262	len = buffer_len(&loginmsg);
	263	buffer_append(&loginmsg, "\0", 1);
	264	msg = buffer_ptr(&loginmsg);
	265	/* strip trailing newlines */
	266	if (len > 0)
	267	while (len > 0 && msg[--len] == '\n')
	268	msg[len] = '\0';
	269	else
	270	msg = "Access denied.";
	271	packet_disconnect(msg);
	272	}
5b9e2464	273	#endif
5b9e2464	274
59c97189	275	/* Log before sending the reply */
	276	auth_log(authctxt, authenticated, get_authname(type), info);
	277
a306f2dd	278	if (client_user != NULL) {
	279	xfree(client_user);
	280	client_user = NULL;
	281	}
	282
94ec8c6b	283	if (authenticated)
	284	return;
	285
af4bd935	286	if (authctxt->failures++ > options.max_authtries)
59c97189	287	packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
a306f2dd	288
a306f2dd	289	packet_start(SSH_SMSG_FAILURE);
	290	packet_send();
	291	packet_write_wait();
	292	}
	293	}
	294
	295	/*
	296	* Performs authentication of an incoming connection. Session key has already
	297	* been exchanged and encryption is enabled.
	298	*/
2362db19	299	void
2362db19	300	do_authentication(Authctxt *authctxt)
a306f2dd	301	{
1e3b8b07	302	u_int ulen;
f8d99a32	303	char user, style = NULL;
a306f2dd	304
a306f2dd	305	/* Get the name of the user that we wish to log in as. */
54a5250f	306	packet_read_expect(SSH_CMSG_USER);
a306f2dd	307
	308	/* Get the user name. */
	309	user = packet_get_string(&ulen);
95500969	310	packet_check_eom();
a306f2dd	311
59c97189	312	if ((style = strchr(user, ':')) != NULL)
ced49be2	313	*style++ = '\0';
59c97189	314
59c97189	315	authctxt->user = user;
	316	authctxt->style = style;
	317
a306f2dd	318	/* Verify that the user is a valid user. */
5f1f36b5	319	if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
59c97189	320	authctxt->valid = 1;
96d0bf74	321	else {
d77347cc	322	debug("do_authentication: invalid user %s", user);
96d0bf74	323	authctxt->pw = fakepw();
96d0bf74	324	}
a306f2dd	325
bd5c0694	326	setproctitle("%s%s", authctxt->valid ? user : "unknown",
1853d1ef	327	use_privsep ? " [net]" : "");
6172e290	328
a306f2dd	329	#ifdef USE_PAM
7fceb20d	330	if (options.use_pam)
529d73ab	331	PRIVSEP(start_pam(authctxt));
a306f2dd	332	#endif
	333
	334	/*
	335	* If we are not running as root, the user must have the same uid as
94ec8c6b	336	* the server. (Unless you are running Windows)
a306f2dd	337	*/
94ec8c6b	338	#ifndef HAVE_CYGWIN
5f1f36b5	339	if (!use_privsep && getuid() != 0 && authctxt->pw &&
5f1f36b5	340	authctxt->pw->pw_uid != getuid())
a306f2dd	341	packet_disconnect("Cannot change user when server not running as root.");
3c62e7eb	342	#endif
a306f2dd	343
59c97189	344	/*
b4b5d644	345	* Loop until the user has been authenticated or the connection is
	346	* closed, do_authloop() returns only if authentication is successful
	347	*/
59c97189	348	do_authloop(authctxt);
a306f2dd	349
a306f2dd	350	/* The user has been authenticated and accepted. */
94ec8c6b	351	packet_start(SSH_SMSG_SUCCESS);
	352	packet_send();
	353	packet_write_wait();
a306f2dd	354	}