[gssapi-openssh.git] / openssh / 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;
# ifdef SSH_AUDIT_EVENTS
			PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
# endif
		}
#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) {
#ifdef SSH_AUDIT_EVENTS
			PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
#endif
			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
3c0ef626	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	#include "includes.h"
c9f39d2c	13	RCSID("$OpenBSD: auth1.c,v 1.59 2004/07/28 09:40:29 markus Exp $");
3c0ef626	14
	15	#include "xmalloc.h"
	16	#include "rsa.h"
	17	#include "ssh1.h"
	18	#include "packet.h"
	19	#include "buffer.h"
3c0ef626	20	#include "log.h"
	21	#include "servconf.h"
	22	#include "compat.h"
	23	#include "auth.h"
e9a17296	24	#include "channels.h"
3c0ef626	25	#include "session.h"
3c0ef626	26	#include "uidswap.h"
700318f3	27	#include "monitor_wrap.h"
996d5e62	28	#include "buffer.h"
3c0ef626	29
	30	/* import */
	31	extern ServerOptions options;
996d5e62	32	extern Buffer loginmsg;
3c0ef626	33
	34	/*
	35	* convert ssh auth msg type into description
	36	*/
	37	static char *
	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";
	50	case SSH_CMSG_AUTH_TIS:
	51	case SSH_CMSG_AUTH_TIS_RESPONSE:
	52	return "challenge-response";
3c0ef626	53	}
	54	snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
	55	return buf;
	56	}
	57
	58	/*
	59	* read packets, try to authenticate the user and
	60	* return only if authentication is successful
	61	*/
	62	static void
	63	do_authloop(Authctxt *authctxt)
	64	{
	65	int authenticated = 0;
	66	u_int bits;
e9a17296	67	Key *client_host_key;
3c0ef626	68	BIGNUM *n;
	69	char client_user, password;
	70	char info[1024];
	71	u_int dlen;
3c0ef626	72	u_int ulen;
0fff78ff	73	int prev, type = 0;
3c0ef626	74
3c0ef626	75	debug("Attempting authentication for %s%.100s.",
c9f39d2c	76	authctxt->valid ? "" : "invalid user ", authctxt->user);
3c0ef626	77
	78	/* If the user has no password, accept authentication immediately. */
	79	if (options.password_authentication &&
0fff78ff	80	#ifdef KRB5
3c0ef626	81	(!options.kerberos_authentication \|\| options.kerberos_or_local_passwd) &&
3c0ef626	82	#endif
700318f3	83	PRIVSEP(auth_password(authctxt, ""))) {
c9f39d2c	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	}
3c0ef626	91	}
	92
	93	/* Indicate that authentication is needed. */
	94	packet_start(SSH_SMSG_FAILURE);
	95	packet_send();
	96	packet_write_wait();
	97
	98	client_user = NULL;
	99
	100	for (;;) {
	101	/* default to fail */
	102	authenticated = 0;
	103
	104	info[0] = '\0';
	105
	106	/* Get a packet from the client. */
0fff78ff	107	prev = type;
e9a17296	108	type = packet_read();
3c0ef626	109
0fff78ff	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
3c0ef626	121	/* Process the packet. */
3c0ef626	122	switch (type) {
3c0ef626	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. */
e9a17296	136	client_host_key = key_new(KEY_RSA1);
3c0ef626	137	bits = packet_get_int();
e9a17296	138	packet_get_bignum(client_host_key->rsa->e);
e9a17296	139	packet_get_bignum(client_host_key->rsa->n);
3c0ef626	140
e9a17296	141	if (bits != BN_num_bits(client_host_key->rsa->n))
3c0ef626	142	verbose("Warning: keysize mismatch for client_host_key: "
e9a17296	143	"actual %d, announced %d",
f5799ae1	144	BN_num_bits(client_host_key->rsa->n), bits);
e9a17296	145	packet_check_eom();
3c0ef626	146
cdd66111	147	authenticated = auth_rhosts_rsa(authctxt, client_user,
e9a17296	148	client_host_key);
e9a17296	149	key_free(client_host_key);
3c0ef626	150
	151	snprintf(info, sizeof info, " ruser %.100s", client_user);
	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. */
e9a17296	160	if ((n = BN_new()) == NULL)
	161	fatal("do_authloop: BN_new failed");
	162	packet_get_bignum(n);
	163	packet_check_eom();
cdd66111	164	authenticated = auth_rsa(authctxt, n);
3c0ef626	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);
e9a17296	179	packet_check_eom();
3c0ef626	180
3c0ef626	181	/* Try authentication with the password. */
700318f3	182	authenticated = PRIVSEP(auth_password(authctxt, password));
3c0ef626	183
	184	memset(password, 0, strlen(password));
	185	xfree(password);
	186	break;
	187
	188	case SSH_CMSG_AUTH_TIS:
	189	debug("rcvd SSH_CMSG_AUTH_TIS");
	190	if (options.challenge_response_authentication == 1) {
	191	char *challenge = get_challenge(authctxt);
	192	if (challenge != NULL) {
	193	debug("sending challenge '%s'", challenge);
	194	packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
	195	packet_put_cstring(challenge);
	196	xfree(challenge);
	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");
	205	if (options.challenge_response_authentication == 1) {
	206	char *response = packet_get_string(&dlen);
e9a17296	207	packet_check_eom();
3c0ef626	208	authenticated = verify_response(authctxt, response);
	209	memset(response, 'r', dlen);
	210	xfree(response);
	211	}
	212	break;
	213
	214	default:
	215	/*
	216	* Any unknown messages will be ignored (and failure
	217	* returned) during authentication.
	218	*/
0fff78ff	219	logit("Unknown message during authentication: type %d", type);
3c0ef626	220	break;
	221	}
	222	#ifdef BSD_AUTH
	223	if (authctxt->as) {
	224	auth_close(authctxt->as);
	225	authctxt->as = NULL;
	226	}
	227	#endif
	228	if (!authctxt->valid && authenticated)
	229	fatal("INTERNAL ERROR: authenticated invalid user %s",
	230	authctxt->user);
	231
41b2f314	232	#ifdef _UNICOS
41b2f314	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
3c0ef626	239	#ifdef HAVE_CYGWIN
3c0ef626	240	if (authenticated &&
c9f39d2c	241	!check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD,
c9f39d2c	242	authctxt->pw)) {
3c0ef626	243	packet_disconnect("Authentication rejected for uid %d.",
c9f39d2c	244	authctxt->pw == NULL ? -1 : authctxt->pw->pw_uid);
3c0ef626	245	authenticated = 0;
	246	}
	247	#else
	248	/* Special handling for root */
6a9b3198	249	if (authenticated && authctxt->pw->pw_uid == 0 &&
996d5e62	250	!auth_root_allowed(get_authname(type))) {
3c0ef626	251	authenticated = 0;
996d5e62	252	# ifdef SSH_AUDIT_EVENTS
	253	PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
	254	# endif
	255	}
3c0ef626	256	#endif
0fff78ff	257
3c0ef626	258	#ifdef USE_PAM
cdd66111	259	if (options.use_pam && authenticated &&
996d5e62	260	!PRIVSEP(do_pam_account())) {
	261	char *msg;
	262	size_t len;
	263
	264	error("Access denied for user %s by PAM account "
	265	"configuration", authctxt->user);
	266	len = buffer_len(&loginmsg);
	267	buffer_append(&loginmsg, "\0", 1);
	268	msg = buffer_ptr(&loginmsg);
	269	/* strip trailing newlines */
	270	if (len > 0)
	271	while (len > 0 && msg[--len] == '\n')
	272	msg[len] = '\0';
	273	else
	274	msg = "Access denied.";
	275	packet_disconnect(msg);
	276	}
3c0ef626	277	#endif
	278
	279	/* Log before sending the reply */
	280	auth_log(authctxt, authenticated, get_authname(type), info);
	281
	282	if (client_user != NULL) {
	283	xfree(client_user);
	284	client_user = NULL;
	285	}
	286
	287	if (authenticated)
	288	return;
	289
996d5e62	290	if (authctxt->failures++ > options.max_authtries) {
	291	#ifdef SSH_AUDIT_EVENTS
	292	PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
	293	#endif
3c0ef626	294	packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
996d5e62	295	}
3c0ef626	296
	297	packet_start(SSH_SMSG_FAILURE);
	298	packet_send();
	299	packet_write_wait();
	300	}
	301	}
	302
	303	/*
	304	* Performs authentication of an incoming connection. Session key has already
	305	* been exchanged and encryption is enabled.
	306	*/
cdd66111	307	void
cdd66111	308	do_authentication(Authctxt *authctxt)
3c0ef626	309	{
3c0ef626	310	u_int ulen;
700318f3	311	char user, style = NULL;
3c0ef626	312
3c0ef626	313	/* Get the name of the user that we wish to log in as. */
e9a17296	314	packet_read_expect(SSH_CMSG_USER);
3c0ef626	315
	316	/* Get the user name. */
	317	user = packet_get_string(&ulen);
e9a17296	318	packet_check_eom();
3c0ef626	319
	320	if ((style = strchr(user, ':')) != NULL)
	321	*style++ = '\0';
	322
3c0ef626	323	authctxt->user = user;
	324	authctxt->style = style;
	325
	326	/* Verify that the user is a valid user. */
700318f3	327	if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
3c0ef626	328	authctxt->valid = 1;
0fff78ff	329	else {
c9f39d2c	330	debug("do_authentication: invalid user %s", user);
0fff78ff	331	authctxt->pw = fakepw();
0fff78ff	332	}
3c0ef626	333
c9f39d2c	334	setproctitle("%s%s", authctxt->valid ? user : "unknown",
700318f3	335	use_privsep ? " [net]" : "");
3c0ef626	336
3c0ef626	337	#ifdef USE_PAM
0fff78ff	338	if (options.use_pam)
99be0775	339	PRIVSEP(start_pam(authctxt));
3c0ef626	340	#endif
	341
	342	/*
	343	* If we are not running as root, the user must have the same uid as
	344	* the server. (Unless you are running Windows)
	345	*/
	346	#ifndef HAVE_CYGWIN
700318f3	347	if (!use_privsep && getuid() != 0 && authctxt->pw &&
700318f3	348	authctxt->pw->pw_uid != getuid())
3c0ef626	349	packet_disconnect("Cannot change user when server not running as root.");
	350	#endif
	351
	352	/*
	353	* Loop until the user has been authenticated or the connection is
	354	* closed, do_authloop() returns only if authentication is successful
	355	*/
	356	do_authloop(authctxt);
	357
	358	/* The user has been authenticated and accepted. */
	359	packet_start(SSH_SMSG_SUCCESS);
	360	packet_send();
	361	packet_write_wait();
3c0ef626	362	}