[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;
	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++ > 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	struct passwd *pw = authctxt->pw;
	73
	74	debug("Attempting authentication for %s%.100s.",
184eed6a	75	authctxt->valid ? "" : "illegal user ", authctxt->user);
59c97189	76
	77	/* If the user has no password, accept authentication immediately. */
	78	if (options.password_authentication &&
1c590258	79	#ifdef KRB5
59c97189	80	(!options.kerberos_authentication \|\| options.kerberos_or_local_passwd) &&
59c97189	81	#endif
1853d1ef	82	PRIVSEP(auth_password(authctxt, ""))) {
59c97189	83	auth_log(authctxt, 1, "without authentication", "");
	84	return;
	85	}
a306f2dd	86
	87	/* Indicate that authentication is needed. */
	88	packet_start(SSH_SMSG_FAILURE);
	89	packet_send();
	90	packet_write_wait();
	91
94ec8c6b	92	client_user = NULL;
94ec8c6b	93
59c97189	94	for (;;) {
94ec8c6b	95	/* default to fail */
	96	authenticated = 0;
	97
59c97189	98	info[0] = '\0';
a306f2dd	99
a306f2dd	100	/* Get a packet from the client. */
05114c74	101	prev = type;
54a5250f	102	type = packet_read();
a306f2dd	103
05114c74	104	/*
	105	* If we started challenge-response authentication but the
	106	* next packet is not a response to our challenge, release
	107	* the resources allocated by get_challenge() (which would
	108	* normally have been released by verify_response() had we
	109	* received such a response)
	110	*/
	111	if (prev == SSH_CMSG_AUTH_TIS &&
	112	type != SSH_CMSG_AUTH_TIS_RESPONSE)
	113	abandon_challenge_response(authctxt);
	114
a306f2dd	115	/* Process the packet. */
a306f2dd	116	switch (type) {
a306f2dd	117	case SSH_CMSG_AUTH_RHOSTS_RSA:
	118	if (!options.rhosts_rsa_authentication) {
	119	verbose("Rhosts with RSA authentication disabled.");
	120	break;
	121	}
	122	/*
	123	* Get client user name. Note that we just have to
	124	* trust the client; root on the client machine can
	125	* claim to be any user.
	126	*/
	127	client_user = packet_get_string(&ulen);
	128
	129	/* Get the client host key. */
b775c6f2	130	client_host_key = key_new(KEY_RSA1);
a306f2dd	131	bits = packet_get_int();
20b279e6	132	packet_get_bignum(client_host_key->rsa->e);
20b279e6	133	packet_get_bignum(client_host_key->rsa->n);
a306f2dd	134
b775c6f2	135	if (bits != BN_num_bits(client_host_key->rsa->n))
94ec8c6b	136	verbose("Warning: keysize mismatch for client_host_key: "
b775c6f2	137	"actual %d, announced %d",
7203d6bb	138	BN_num_bits(client_host_key->rsa->n), bits);
95500969	139	packet_check_eom();
a306f2dd	140
fdaef11e	141	authenticated = auth_rhosts_rsa(authctxt, client_user,
dc421aa3	142	client_host_key);
b775c6f2	143	key_free(client_host_key);
a306f2dd	144
59c97189	145	snprintf(info, sizeof info, " ruser %.100s", client_user);
a306f2dd	146	break;
	147
	148	case SSH_CMSG_AUTH_RSA:
	149	if (!options.rsa_authentication) {
	150	verbose("RSA authentication disabled.");
	151	break;
	152	}
	153	/* RSA authentication requested. */
b775c6f2	154	if ((n = BN_new()) == NULL)
b775c6f2	155	fatal("do_authloop: BN_new failed");
20b279e6	156	packet_get_bignum(n);
95500969	157	packet_check_eom();
fdaef11e	158	authenticated = auth_rsa(authctxt, n);
a306f2dd	159	BN_clear_free(n);
	160	break;
	161
	162	case SSH_CMSG_AUTH_PASSWORD:
	163	if (!options.password_authentication) {
	164	verbose("Password authentication disabled.");
	165	break;
	166	}
	167	/*
	168	* Read user password. It is in plain text, but was
	169	* transmitted over the encrypted channel so it is
	170	* not visible to an outside observer.
	171	*/
	172	password = packet_get_string(&dlen);
95500969	173	packet_check_eom();
a306f2dd	174
b4b5d644	175	/* Try authentication with the password. */
1853d1ef	176	authenticated = PRIVSEP(auth_password(authctxt, password));
a306f2dd	177
	178	memset(password, 0, strlen(password));
	179	xfree(password);
	180	break;
	181
a306f2dd	182	case SSH_CMSG_AUTH_TIS:
a306f2dd	183	debug("rcvd SSH_CMSG_AUTH_TIS");
5ba55ada	184	if (options.challenge_response_authentication == 1) {
5ba55ada	185	char *challenge = get_challenge(authctxt);
59c97189	186	if (challenge != NULL) {
59c97189	187	debug("sending challenge '%s'", challenge);
a306f2dd	188	packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
59c97189	189	packet_put_cstring(challenge);
5ba55ada	190	xfree(challenge);
a306f2dd	191	packet_send();
	192	packet_write_wait();
	193	continue;
	194	}
	195	}
	196	break;
	197	case SSH_CMSG_AUTH_TIS_RESPONSE:
	198	debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
5ba55ada	199	if (options.challenge_response_authentication == 1) {
a306f2dd	200	char *response = packet_get_string(&dlen);
95500969	201	packet_check_eom();
59c97189	202	authenticated = verify_response(authctxt, response);
59c97189	203	memset(response, 'r', dlen);
a306f2dd	204	xfree(response);
	205	}
	206	break;
a306f2dd	207
	208	default:
	209	/*
	210	* Any unknown messages will be ignored (and failure
	211	* returned) during authentication.
	212	*/
bbe88b6d	213	logit("Unknown message during authentication: type %d", type);
a306f2dd	214	break;
a306f2dd	215	}
af774732	216	#ifdef BSD_AUTH
	217	if (authctxt->as) {
	218	auth_close(authctxt->as);
	219	authctxt->as = NULL;
	220	}
	221	#endif
59c97189	222	if (!authctxt->valid && authenticated)
	223	fatal("INTERNAL ERROR: authenticated invalid user %s",
	224	authctxt->user);
a306f2dd	225
ef51930f	226	#ifdef _UNICOS
ef51930f	227	if (authenticated && cray_access_denied(authctxt->user)) {
	228	authenticated = 0;
	229	fatal("Access denied for user %s.",authctxt->user);
	230	}
	231	#endif /* _UNICOS */
	232
2b87da3b	233	#ifdef HAVE_CYGWIN
2b87da3b	234	if (authenticated &&
e9571a2c	235	!check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) {
3c62e7eb	236	packet_disconnect("Authentication rejected for uid %d.",
6ae852fd	237	pw == NULL ? -1 : pw->pw_uid);
3c62e7eb	238	authenticated = 0;
3c62e7eb	239	}
3c418020	240	#else
59c97189	241	/* Special handling for root */
5d47f1d4	242	if (authenticated && authctxt->pw->pw_uid == 0 &&
15853e93	243	!auth_root_allowed(get_authname(type)))
59c97189	244	authenticated = 0;
3c418020	245	#endif
a306f2dd	246
5b9e2464	247	#ifdef USE_PAM
aff51935	248	if (options.use_pam && authenticated &&
5b9e2464	249	!PRIVSEP(do_pam_account()))
	250	authenticated = 0;
	251	#endif
	252
59c97189	253	/* Log before sending the reply */
	254	auth_log(authctxt, authenticated, get_authname(type), info);
	255
a306f2dd	256	if (client_user != NULL) {
	257	xfree(client_user);
	258	client_user = NULL;
	259	}
	260
94ec8c6b	261	if (authenticated)
	262	return;
	263
af4bd935	264	if (authctxt->failures++ > options.max_authtries)
59c97189	265	packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
a306f2dd	266
a306f2dd	267	packet_start(SSH_SMSG_FAILURE);
	268	packet_send();
	269	packet_write_wait();
	270	}
	271	}
	272
	273	/*
	274	* Performs authentication of an incoming connection. Session key has already
	275	* been exchanged and encryption is enabled.
	276	*/
2362db19	277	void
2362db19	278	do_authentication(Authctxt *authctxt)
a306f2dd	279	{
1e3b8b07	280	u_int ulen;
f8d99a32	281	char user, style = NULL;
a306f2dd	282
a306f2dd	283	/* Get the name of the user that we wish to log in as. */
54a5250f	284	packet_read_expect(SSH_CMSG_USER);
a306f2dd	285
	286	/* Get the user name. */
	287	user = packet_get_string(&ulen);
95500969	288	packet_check_eom();
a306f2dd	289
59c97189	290	if ((style = strchr(user, ':')) != NULL)
ced49be2	291	*style++ = '\0';
59c97189	292
59c97189	293	authctxt->user = user;
	294	authctxt->style = style;
	295
a306f2dd	296	/* Verify that the user is a valid user. */
5f1f36b5	297	if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
59c97189	298	authctxt->valid = 1;
96d0bf74	299	else {
59c97189	300	debug("do_authentication: illegal user %s", user);
96d0bf74	301	authctxt->pw = fakepw();
96d0bf74	302	}
a306f2dd	303
5f1f36b5	304	setproctitle("%s%s", authctxt->pw ? user : "unknown",
1853d1ef	305	use_privsep ? " [net]" : "");
6172e290	306
a306f2dd	307	#ifdef USE_PAM
7fceb20d	308	if (options.use_pam)
529d73ab	309	PRIVSEP(start_pam(authctxt));
a306f2dd	310	#endif
	311
	312	/*
	313	* If we are not running as root, the user must have the same uid as
94ec8c6b	314	* the server. (Unless you are running Windows)
a306f2dd	315	*/
94ec8c6b	316	#ifndef HAVE_CYGWIN
5f1f36b5	317	if (!use_privsep && getuid() != 0 && authctxt->pw &&
5f1f36b5	318	authctxt->pw->pw_uid != getuid())
a306f2dd	319	packet_disconnect("Cannot change user when server not running as root.");
3c62e7eb	320	#endif
a306f2dd	321
59c97189	322	/*
b4b5d644	323	* Loop until the user has been authenticated or the connection is
	324	* closed, do_authloop() returns only if authentication is successful
	325	*/
59c97189	326	do_authloop(authctxt);
a306f2dd	327
a306f2dd	328	/* The user has been authenticated and accepted. */
94ec8c6b	329	packet_start(SSH_SMSG_SUCCESS);
	330	packet_send();
	331	packet_write_wait();
a306f2dd	332	}