[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 1.55 2003/11/08 16:02:40 jakob Exp $");

#include "xmalloc.h"
#include "rsa.h"
#include "ssh1.h"
#include "packet.h"
#include "buffer.h"
#include "mpaux.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;
	struct passwd *pw = authctxt->pw;

	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, ""))) {
		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, pw)) {
			packet_disconnect("Authentication rejected for uid %d.",
			    pw == NULL ? -1 : 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++ > AUTH_FAIL_MAX)
			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(user));
#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"
dc1759e6	13	RCSID("$OpenBSD: auth1.c,v 1.55 2003/11/08 16:02:40 jakob 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"
a306f2dd	20	#include "mpaux.h"
42f11eb2	21	#include "log.h"
a306f2dd	22	#include "servconf.h"
	23	#include "compat.h"
	24	#include "auth.h"
7899c98f	25	#include "channels.h"
a306f2dd	26	#include "session.h"
ced49be2	27	#include "uidswap.h"
1853d1ef	28	#include "monitor_wrap.h"
a306f2dd	29
	30	/* import */
	31	extern ServerOptions options;
94ec8c6b	32
a306f2dd	33	/*
	34	* convert ssh auth msg type into description
	35	*/
396c147e	36	static char *
a306f2dd	37	get_authname(int type)
	38	{
	39	static char buf[1024];
	40	switch (type) {
	41	case SSH_CMSG_AUTH_PASSWORD:
	42	return "password";
	43	case SSH_CMSG_AUTH_RSA:
	44	return "rsa";
	45	case SSH_CMSG_AUTH_RHOSTS_RSA:
	46	return "rhosts-rsa";
	47	case SSH_CMSG_AUTH_RHOSTS:
	48	return "rhosts";
59c97189	49	case SSH_CMSG_AUTH_TIS:
	50	case SSH_CMSG_AUTH_TIS_RESPONSE:
	51	return "challenge-response";
a306f2dd	52	}
	53	snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
	54	return buf;
	55	}
	56
	57	/*
59c97189	58	* read packets, try to authenticate the user and
59c97189	59	* return only if authentication is successful
a306f2dd	60	*/
396c147e	61	static void
59c97189	62	do_authloop(Authctxt *authctxt)
a306f2dd	63	{
94ec8c6b	64	int authenticated = 0;
1e3b8b07	65	u_int bits;
b775c6f2	66	Key *client_host_key;
a306f2dd	67	BIGNUM *n;
94ec8c6b	68	char client_user, password;
59c97189	69	char info[1024];
1e3b8b07	70	u_int dlen;
1e3b8b07	71	u_int ulen;
05114c74	72	int prev, type = 0;
59c97189	73	struct passwd *pw = authctxt->pw;
	74
	75	debug("Attempting authentication for %s%.100s.",
184eed6a	76	authctxt->valid ? "" : "illegal 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, ""))) {
59c97189	84	auth_log(authctxt, 1, "without authentication", "");
	85	return;
	86	}
a306f2dd	87
	88	/* Indicate that authentication is needed. */
	89	packet_start(SSH_SMSG_FAILURE);
	90	packet_send();
	91	packet_write_wait();
	92
94ec8c6b	93	client_user = NULL;
94ec8c6b	94
59c97189	95	for (;;) {
94ec8c6b	96	/* default to fail */
	97	authenticated = 0;
	98
59c97189	99	info[0] = '\0';
a306f2dd	100
a306f2dd	101	/* Get a packet from the client. */
05114c74	102	prev = type;
54a5250f	103	type = packet_read();
a306f2dd	104
05114c74	105	/*
	106	* If we started challenge-response authentication but the
	107	* next packet is not a response to our challenge, release
	108	* the resources allocated by get_challenge() (which would
	109	* normally have been released by verify_response() had we
	110	* received such a response)
	111	*/
	112	if (prev == SSH_CMSG_AUTH_TIS &&
	113	type != SSH_CMSG_AUTH_TIS_RESPONSE)
	114	abandon_challenge_response(authctxt);
	115
a306f2dd	116	/* Process the packet. */
a306f2dd	117	switch (type) {
a306f2dd	118	case SSH_CMSG_AUTH_RHOSTS_RSA:
	119	if (!options.rhosts_rsa_authentication) {
	120	verbose("Rhosts with RSA authentication disabled.");
	121	break;
	122	}
	123	/*
	124	* Get client user name. Note that we just have to
	125	* trust the client; root on the client machine can
	126	* claim to be any user.
	127	*/
	128	client_user = packet_get_string(&ulen);
	129
	130	/* Get the client host key. */
b775c6f2	131	client_host_key = key_new(KEY_RSA1);
a306f2dd	132	bits = packet_get_int();
20b279e6	133	packet_get_bignum(client_host_key->rsa->e);
20b279e6	134	packet_get_bignum(client_host_key->rsa->n);
a306f2dd	135
b775c6f2	136	if (bits != BN_num_bits(client_host_key->rsa->n))
94ec8c6b	137	verbose("Warning: keysize mismatch for client_host_key: "
b775c6f2	138	"actual %d, announced %d",
7203d6bb	139	BN_num_bits(client_host_key->rsa->n), bits);
95500969	140	packet_check_eom();
a306f2dd	141
fdaef11e	142	authenticated = auth_rhosts_rsa(authctxt, client_user,
dc421aa3	143	client_host_key);
b775c6f2	144	key_free(client_host_key);
a306f2dd	145
59c97189	146	snprintf(info, sizeof info, " ruser %.100s", client_user);
a306f2dd	147	break;
	148
	149	case SSH_CMSG_AUTH_RSA:
	150	if (!options.rsa_authentication) {
	151	verbose("RSA authentication disabled.");
	152	break;
	153	}
	154	/* RSA authentication requested. */
b775c6f2	155	if ((n = BN_new()) == NULL)
b775c6f2	156	fatal("do_authloop: BN_new failed");
20b279e6	157	packet_get_bignum(n);
95500969	158	packet_check_eom();
fdaef11e	159	authenticated = auth_rsa(authctxt, n);
a306f2dd	160	BN_clear_free(n);
	161	break;
	162
	163	case SSH_CMSG_AUTH_PASSWORD:
	164	if (!options.password_authentication) {
	165	verbose("Password authentication disabled.");
	166	break;
	167	}
	168	/*
	169	* Read user password. It is in plain text, but was
	170	* transmitted over the encrypted channel so it is
	171	* not visible to an outside observer.
	172	*/
	173	password = packet_get_string(&dlen);
95500969	174	packet_check_eom();
a306f2dd	175
b4b5d644	176	/* Try authentication with the password. */
1853d1ef	177	authenticated = PRIVSEP(auth_password(authctxt, password));
a306f2dd	178
	179	memset(password, 0, strlen(password));
	180	xfree(password);
	181	break;
	182
a306f2dd	183	case SSH_CMSG_AUTH_TIS:
a306f2dd	184	debug("rcvd SSH_CMSG_AUTH_TIS");
5ba55ada	185	if (options.challenge_response_authentication == 1) {
5ba55ada	186	char *challenge = get_challenge(authctxt);
59c97189	187	if (challenge != NULL) {
59c97189	188	debug("sending challenge '%s'", challenge);
a306f2dd	189	packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
59c97189	190	packet_put_cstring(challenge);
5ba55ada	191	xfree(challenge);
a306f2dd	192	packet_send();
	193	packet_write_wait();
	194	continue;
	195	}
	196	}
	197	break;
	198	case SSH_CMSG_AUTH_TIS_RESPONSE:
	199	debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
5ba55ada	200	if (options.challenge_response_authentication == 1) {
a306f2dd	201	char *response = packet_get_string(&dlen);
95500969	202	packet_check_eom();
59c97189	203	authenticated = verify_response(authctxt, response);
59c97189	204	memset(response, 'r', dlen);
a306f2dd	205	xfree(response);
	206	}
	207	break;
a306f2dd	208
	209	default:
	210	/*
	211	* Any unknown messages will be ignored (and failure
	212	* returned) during authentication.
	213	*/
bbe88b6d	214	logit("Unknown message during authentication: type %d", type);
a306f2dd	215	break;
a306f2dd	216	}
af774732	217	#ifdef BSD_AUTH
	218	if (authctxt->as) {
	219	auth_close(authctxt->as);
	220	authctxt->as = NULL;
	221	}
	222	#endif
59c97189	223	if (!authctxt->valid && authenticated)
	224	fatal("INTERNAL ERROR: authenticated invalid user %s",
	225	authctxt->user);
a306f2dd	226
ef51930f	227	#ifdef _UNICOS
ef51930f	228	if (authenticated && cray_access_denied(authctxt->user)) {
	229	authenticated = 0;
	230	fatal("Access denied for user %s.",authctxt->user);
	231	}
	232	#endif /* _UNICOS */
	233
2b87da3b	234	#ifdef HAVE_CYGWIN
2b87da3b	235	if (authenticated &&
e9571a2c	236	!check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) {
3c62e7eb	237	packet_disconnect("Authentication rejected for uid %d.",
6ae852fd	238	pw == NULL ? -1 : pw->pw_uid);
3c62e7eb	239	authenticated = 0;
3c62e7eb	240	}
3c418020	241	#else
59c97189	242	/* Special handling for root */
5d47f1d4	243	if (authenticated && authctxt->pw->pw_uid == 0 &&
15853e93	244	!auth_root_allowed(get_authname(type)))
59c97189	245	authenticated = 0;
3c418020	246	#endif
a306f2dd	247
5b9e2464	248	#ifdef USE_PAM
aff51935	249	if (options.use_pam && authenticated &&
5b9e2464	250	!PRIVSEP(do_pam_account()))
	251	authenticated = 0;
	252	#endif
	253
59c97189	254	/* Log before sending the reply */
	255	auth_log(authctxt, authenticated, get_authname(type), info);
	256
a306f2dd	257	if (client_user != NULL) {
	258	xfree(client_user);
	259	client_user = NULL;
	260	}
	261
94ec8c6b	262	if (authenticated)
	263	return;
	264
9a6fee8b	265	if (authctxt->failures++ > AUTH_FAIL_MAX)
59c97189	266	packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
a306f2dd	267
a306f2dd	268	packet_start(SSH_SMSG_FAILURE);
	269	packet_send();
	270	packet_write_wait();
	271	}
	272	}
	273
	274	/*
	275	* Performs authentication of an incoming connection. Session key has already
	276	* been exchanged and encryption is enabled.
	277	*/
2362db19	278	void
2362db19	279	do_authentication(Authctxt *authctxt)
a306f2dd	280	{
1e3b8b07	281	u_int ulen;
f8d99a32	282	char user, style = NULL;
a306f2dd	283
a306f2dd	284	/* Get the name of the user that we wish to log in as. */
54a5250f	285	packet_read_expect(SSH_CMSG_USER);
a306f2dd	286
	287	/* Get the user name. */
	288	user = packet_get_string(&ulen);
95500969	289	packet_check_eom();
a306f2dd	290
59c97189	291	if ((style = strchr(user, ':')) != NULL)
ced49be2	292	*style++ = '\0';
59c97189	293
59c97189	294	authctxt->user = user;
	295	authctxt->style = style;
	296
a306f2dd	297	/* Verify that the user is a valid user. */
5f1f36b5	298	if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
59c97189	299	authctxt->valid = 1;
96d0bf74	300	else {
59c97189	301	debug("do_authentication: illegal user %s", user);
96d0bf74	302	authctxt->pw = fakepw();
96d0bf74	303	}
a306f2dd	304
5f1f36b5	305	setproctitle("%s%s", authctxt->pw ? user : "unknown",
1853d1ef	306	use_privsep ? " [net]" : "");
6172e290	307
a306f2dd	308	#ifdef USE_PAM
7fceb20d	309	if (options.use_pam)
7fceb20d	310	PRIVSEP(start_pam(user));
a306f2dd	311	#endif
	312
	313	/*
	314	* If we are not running as root, the user must have the same uid as
94ec8c6b	315	* the server. (Unless you are running Windows)
a306f2dd	316	*/
94ec8c6b	317	#ifndef HAVE_CYGWIN
5f1f36b5	318	if (!use_privsep && getuid() != 0 && authctxt->pw &&
5f1f36b5	319	authctxt->pw->pw_uid != getuid())
a306f2dd	320	packet_disconnect("Cannot change user when server not running as root.");
3c62e7eb	321	#endif
a306f2dd	322
59c97189	323	/*
b4b5d644	324	* Loop until the user has been authenticated or the connection is
	325	* closed, do_authloop() returns only if authentication is successful
	326	*/
59c97189	327	do_authloop(authctxt);
a306f2dd	328
a306f2dd	329	/* The user has been authenticated and accepted. */
94ec8c6b	330	packet_start(SSH_SMSG_SUCCESS);
	331	packet_send();
	332	packet_write_wait();
a306f2dd	333	}