[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 1.57 2004/05/23 23:59:53 dtucker 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"

/* import */
extern ServerOptions options;

/*
 * 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 ? "" : "illegal 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()))
			authenticated = 0;
#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: illegal user %s", user);
		authctxt->pw = fakepw();
	}

	setproctitle("%s%s", authctxt->pw ? 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"
af4bd935	13	RCSID("$OpenBSD: auth1.c,v 1.57 2004/05/23 23:59:53 dtucker 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"
a306f2dd	28
	29	/* import */
	30	extern ServerOptions options;
94ec8c6b	31
a306f2dd	32	/*
	33	* convert ssh auth msg type into description
	34	*/
396c147e	35	static char *
a306f2dd	36	get_authname(int type)
	37	{
	38	static char buf[1024];
	39	switch (type) {
	40	case SSH_CMSG_AUTH_PASSWORD:
	41	return "password";
	42	case SSH_CMSG_AUTH_RSA:
	43	return "rsa";
	44	case SSH_CMSG_AUTH_RHOSTS_RSA:
	45	return "rhosts-rsa";
	46	case SSH_CMSG_AUTH_RHOSTS:
	47	return "rhosts";
59c97189	48	case SSH_CMSG_AUTH_TIS:
	49	case SSH_CMSG_AUTH_TIS_RESPONSE:
	50	return "challenge-response";
a306f2dd	51	}
	52	snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
	53	return buf;
	54	}
	55
	56	/*
59c97189	57	* read packets, try to authenticate the user and
59c97189	58	* return only if authentication is successful
a306f2dd	59	*/
396c147e	60	static void
59c97189	61	do_authloop(Authctxt *authctxt)
a306f2dd	62	{
94ec8c6b	63	int authenticated = 0;
1e3b8b07	64	u_int bits;
b775c6f2	65	Key *client_host_key;
a306f2dd	66	BIGNUM *n;
94ec8c6b	67	char client_user, password;
59c97189	68	char info[1024];
1e3b8b07	69	u_int dlen;
1e3b8b07	70	u_int ulen;
05114c74	71	int prev, type = 0;
59c97189	72
59c97189	73	debug("Attempting authentication for %s%.100s.",
184eed6a	74	authctxt->valid ? "" : "illegal user ", authctxt->user);
59c97189	75
	76	/* If the user has no password, accept authentication immediately. */
	77	if (options.password_authentication &&
1c590258	78	#ifdef KRB5
59c97189	79	(!options.kerberos_authentication \|\| options.kerberos_or_local_passwd) &&
59c97189	80	#endif
1853d1ef	81	PRIVSEP(auth_password(authctxt, ""))) {
ece30983	82	#ifdef USE_PAM
	83	if (options.use_pam && (PRIVSEP(do_pam_account())))
	84	#endif
	85	{
	86	auth_log(authctxt, 1, "without authentication", "");
	87	return;
	88	}
59c97189	89	}
a306f2dd	90
	91	/* Indicate that authentication is needed. */
	92	packet_start(SSH_SMSG_FAILURE);
	93	packet_send();
	94	packet_write_wait();
	95
94ec8c6b	96	client_user = NULL;
94ec8c6b	97
59c97189	98	for (;;) {
94ec8c6b	99	/* default to fail */
	100	authenticated = 0;
	101
59c97189	102	info[0] = '\0';
a306f2dd	103
a306f2dd	104	/* Get a packet from the client. */
05114c74	105	prev = type;
54a5250f	106	type = packet_read();
a306f2dd	107
05114c74	108	/*
	109	* If we started challenge-response authentication but the
	110	* next packet is not a response to our challenge, release
	111	* the resources allocated by get_challenge() (which would
	112	* normally have been released by verify_response() had we
	113	* received such a response)
	114	*/
	115	if (prev == SSH_CMSG_AUTH_TIS &&
	116	type != SSH_CMSG_AUTH_TIS_RESPONSE)
	117	abandon_challenge_response(authctxt);
	118
a306f2dd	119	/* Process the packet. */
a306f2dd	120	switch (type) {
a306f2dd	121	case SSH_CMSG_AUTH_RHOSTS_RSA:
	122	if (!options.rhosts_rsa_authentication) {
	123	verbose("Rhosts with RSA authentication disabled.");
	124	break;
	125	}
	126	/*
	127	* Get client user name. Note that we just have to
	128	* trust the client; root on the client machine can
	129	* claim to be any user.
	130	*/
	131	client_user = packet_get_string(&ulen);
	132
	133	/* Get the client host key. */
b775c6f2	134	client_host_key = key_new(KEY_RSA1);
a306f2dd	135	bits = packet_get_int();
20b279e6	136	packet_get_bignum(client_host_key->rsa->e);
20b279e6	137	packet_get_bignum(client_host_key->rsa->n);
a306f2dd	138
b775c6f2	139	if (bits != BN_num_bits(client_host_key->rsa->n))
94ec8c6b	140	verbose("Warning: keysize mismatch for client_host_key: "
b775c6f2	141	"actual %d, announced %d",
7203d6bb	142	BN_num_bits(client_host_key->rsa->n), bits);
95500969	143	packet_check_eom();
a306f2dd	144
fdaef11e	145	authenticated = auth_rhosts_rsa(authctxt, client_user,
dc421aa3	146	client_host_key);
b775c6f2	147	key_free(client_host_key);
a306f2dd	148
59c97189	149	snprintf(info, sizeof info, " ruser %.100s", client_user);
a306f2dd	150	break;
	151
	152	case SSH_CMSG_AUTH_RSA:
	153	if (!options.rsa_authentication) {
	154	verbose("RSA authentication disabled.");
	155	break;
	156	}
	157	/* RSA authentication requested. */
b775c6f2	158	if ((n = BN_new()) == NULL)
b775c6f2	159	fatal("do_authloop: BN_new failed");
20b279e6	160	packet_get_bignum(n);
95500969	161	packet_check_eom();
fdaef11e	162	authenticated = auth_rsa(authctxt, n);
a306f2dd	163	BN_clear_free(n);
	164	break;
	165
	166	case SSH_CMSG_AUTH_PASSWORD:
	167	if (!options.password_authentication) {
	168	verbose("Password authentication disabled.");
	169	break;
	170	}
	171	/*
	172	* Read user password. It is in plain text, but was
	173	* transmitted over the encrypted channel so it is
	174	* not visible to an outside observer.
	175	*/
	176	password = packet_get_string(&dlen);
95500969	177	packet_check_eom();
a306f2dd	178
b4b5d644	179	/* Try authentication with the password. */
1853d1ef	180	authenticated = PRIVSEP(auth_password(authctxt, password));
a306f2dd	181
	182	memset(password, 0, strlen(password));
	183	xfree(password);
	184	break;
	185
a306f2dd	186	case SSH_CMSG_AUTH_TIS:
a306f2dd	187	debug("rcvd SSH_CMSG_AUTH_TIS");
5ba55ada	188	if (options.challenge_response_authentication == 1) {
5ba55ada	189	char *challenge = get_challenge(authctxt);
59c97189	190	if (challenge != NULL) {
59c97189	191	debug("sending challenge '%s'", challenge);
a306f2dd	192	packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
59c97189	193	packet_put_cstring(challenge);
5ba55ada	194	xfree(challenge);
a306f2dd	195	packet_send();
	196	packet_write_wait();
	197	continue;
	198	}
	199	}
	200	break;
	201	case SSH_CMSG_AUTH_TIS_RESPONSE:
	202	debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
5ba55ada	203	if (options.challenge_response_authentication == 1) {
a306f2dd	204	char *response = packet_get_string(&dlen);
95500969	205	packet_check_eom();
59c97189	206	authenticated = verify_response(authctxt, response);
59c97189	207	memset(response, 'r', dlen);
a306f2dd	208	xfree(response);
	209	}
	210	break;
a306f2dd	211
	212	default:
	213	/*
	214	* Any unknown messages will be ignored (and failure
	215	* returned) during authentication.
	216	*/
bbe88b6d	217	logit("Unknown message during authentication: type %d", type);
a306f2dd	218	break;
a306f2dd	219	}
af774732	220	#ifdef BSD_AUTH
	221	if (authctxt->as) {
	222	auth_close(authctxt->as);
	223	authctxt->as = NULL;
	224	}
	225	#endif
59c97189	226	if (!authctxt->valid && authenticated)
	227	fatal("INTERNAL ERROR: authenticated invalid user %s",
	228	authctxt->user);
a306f2dd	229
ef51930f	230	#ifdef _UNICOS
ef51930f	231	if (authenticated && cray_access_denied(authctxt->user)) {
	232	authenticated = 0;
	233	fatal("Access denied for user %s.",authctxt->user);
	234	}
	235	#endif /* _UNICOS */
	236
2b87da3b	237	#ifdef HAVE_CYGWIN
2b87da3b	238	if (authenticated &&
02a57950	239	!check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD,
02a57950	240	authctxt->pw)) {
3c62e7eb	241	packet_disconnect("Authentication rejected for uid %d.",
02a57950	242	authctxt->pw == NULL ? -1 : authctxt->pw->pw_uid);
3c62e7eb	243	authenticated = 0;
3c62e7eb	244	}
3c418020	245	#else
59c97189	246	/* Special handling for root */
5d47f1d4	247	if (authenticated && authctxt->pw->pw_uid == 0 &&
15853e93	248	!auth_root_allowed(get_authname(type)))
59c97189	249	authenticated = 0;
3c418020	250	#endif
a306f2dd	251
5b9e2464	252	#ifdef USE_PAM
aff51935	253	if (options.use_pam && authenticated &&
5b9e2464	254	!PRIVSEP(do_pam_account()))
	255	authenticated = 0;
	256	#endif
	257
59c97189	258	/* Log before sending the reply */
	259	auth_log(authctxt, authenticated, get_authname(type), info);
	260
a306f2dd	261	if (client_user != NULL) {
	262	xfree(client_user);
	263	client_user = NULL;
	264	}
	265
94ec8c6b	266	if (authenticated)
	267	return;
	268
af4bd935	269	if (authctxt->failures++ > options.max_authtries)
59c97189	270	packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
a306f2dd	271
a306f2dd	272	packet_start(SSH_SMSG_FAILURE);
	273	packet_send();
	274	packet_write_wait();
	275	}
	276	}
	277
	278	/*
	279	* Performs authentication of an incoming connection. Session key has already
	280	* been exchanged and encryption is enabled.
	281	*/
2362db19	282	void
2362db19	283	do_authentication(Authctxt *authctxt)
a306f2dd	284	{
1e3b8b07	285	u_int ulen;
f8d99a32	286	char user, style = NULL;
a306f2dd	287
a306f2dd	288	/* Get the name of the user that we wish to log in as. */
54a5250f	289	packet_read_expect(SSH_CMSG_USER);
a306f2dd	290
	291	/* Get the user name. */
	292	user = packet_get_string(&ulen);
95500969	293	packet_check_eom();
a306f2dd	294
59c97189	295	if ((style = strchr(user, ':')) != NULL)
ced49be2	296	*style++ = '\0';
59c97189	297
59c97189	298	authctxt->user = user;
	299	authctxt->style = style;
	300
a306f2dd	301	/* Verify that the user is a valid user. */
5f1f36b5	302	if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
59c97189	303	authctxt->valid = 1;
96d0bf74	304	else {
59c97189	305	debug("do_authentication: illegal user %s", user);
96d0bf74	306	authctxt->pw = fakepw();
96d0bf74	307	}
a306f2dd	308
5f1f36b5	309	setproctitle("%s%s", authctxt->pw ? user : "unknown",
1853d1ef	310	use_privsep ? " [net]" : "");
6172e290	311
a306f2dd	312	#ifdef USE_PAM
7fceb20d	313	if (options.use_pam)
529d73ab	314	PRIVSEP(start_pam(authctxt));
a306f2dd	315	#endif
	316
	317	/*
	318	* If we are not running as root, the user must have the same uid as
94ec8c6b	319	* the server. (Unless you are running Windows)
a306f2dd	320	*/
94ec8c6b	321	#ifndef HAVE_CYGWIN
5f1f36b5	322	if (!use_privsep && getuid() != 0 && authctxt->pw &&
5f1f36b5	323	authctxt->pw->pw_uid != getuid())
a306f2dd	324	packet_disconnect("Cannot change user when server not running as root.");
3c62e7eb	325	#endif
a306f2dd	326
59c97189	327	/*
b4b5d644	328	* Loop until the user has been authenticated or the connection is
	329	* closed, do_authloop() returns only if authentication is successful
	330	*/
59c97189	331	do_authloop(authctxt);
a306f2dd	332
a306f2dd	333	/* The user has been authenticated and accepted. */
94ec8c6b	334	packet_start(SSH_SMSG_SUCCESS);
	335	packet_send();
	336	packet_write_wait();
a306f2dd	337	}