[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 1.35 2002/02/03 17:53:25 markus 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 "misc.h"
#include "uidswap.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";
#if defined(KRB4) || defined(KRB5)
	case SSH_CMSG_AUTH_KERBEROS:
		return "kerberos";
#endif
	}
	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 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 &&
#if defined(KRB4) || defined(KRB5)
	    (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
#endif
#ifdef USE_PAM
	    auth_pam_password(pw, "")) {
#elif defined(HAVE_OSF_SIA)
	    0) {
#else
	    auth_password(authctxt, "")) {
#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. */
		type = packet_read();

		/* Process the packet. */
		switch (type) {

#if defined(KRB4) || defined(KRB5)
		case SSH_CMSG_AUTH_KERBEROS:
			if (!options.kerberos_authentication) {
				verbose("Kerberos authentication disabled.");
			} else {
				char *kdata = packet_get_string(&dlen);
				packet_check_eom();

				if (kdata[0] == 4) { /* KRB_PROT_VERSION */
#ifdef KRB4
					KTEXT_ST tkt;

					tkt.length = dlen;
					if (tkt.length < MAX_KTXT_LEN)
						memcpy(tkt.dat, kdata, tkt.length);

					if (auth_krb4(authctxt, &tkt, &client_user)) {
						authenticated = 1;
						snprintf(info, sizeof(info),
						    " tktuser %.100s",
						    client_user);
					}
#endif /* KRB4 */
				} else {
#ifdef KRB5
					krb5_data tkt;
					tkt.length = dlen;
					tkt.data = kdata;

					if (auth_krb5(authctxt, &tkt, &client_user)) {
						authenticated = 1;
						snprintf(info, sizeof(info),
						    " tktuser %.100s",
						    client_user);
					}
#endif /* KRB5 */
				}
				xfree(kdata);
			}
			break;
#endif /* KRB4 || KRB5 */

#if defined(AFS) || defined(KRB5)
			/* XXX - punt on backward compatibility here. */
		case SSH_CMSG_HAVE_KERBEROS_TGT:
			packet_send_debug("Kerberos TGT passing disabled before authentication.");
			break;
#ifdef AFS
		case SSH_CMSG_HAVE_AFS_TOKEN:
			packet_send_debug("AFS token passing disabled before authentication.");
			break;
#endif /* AFS */
#endif /* AFS || KRB5 */

		case SSH_CMSG_AUTH_RHOSTS:
			if (!options.rhosts_authentication) {
				verbose("Rhosts authentication disabled.");
				break;
			}
			/*
			 * Get client user name.  Note that we just have to
			 * trust the client; this is one reason why rhosts
			 * authentication is insecure. (Another is
			 * IP-spoofing on a local network.)
			 */
			client_user = packet_get_string(&ulen);
			packet_check_eom();

			/* Try to authenticate using /etc/hosts.equiv and .rhosts. */
			authenticated = auth_rhosts(pw, client_user);

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

		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(pw, 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(pw, 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();

#ifdef USE_PAM
			/* Do PAM auth with password */
			authenticated = auth_pam_password(pw, password);
#elif defined(HAVE_OSF_SIA)
			/* Do SIA auth with password */
			authenticated = auth_sia_password(authctxt->user, 
			    password);
#else /* !USE_PAM && !HAVE_OSF_SIA */
			/* Try authentication with the password. */
			authenticated = auth_password(authctxt, password);
#endif /* USE_PAM */

			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);
				debug("got response '%s'", response);
				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.
			 */
			log("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 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 (authenticated && !do_pam_account(pw->pw_name, client_user))
			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) {
#ifdef WITH_AIXAUTHENTICATE
			loginfailed(authctxt->user,
			    get_canonical_hostname(options.verify_reverse_mapping),
			    "ssh");
#endif /* WITH_AIXAUTHENTICATE */
			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(void)
{
	Authctxt *authctxt;
	struct passwd *pw;
	u_int ulen;
	char *p, *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';

	/* XXX - SSH.com Kerberos v5 braindeath. */
	if ((p = strchr(user, '@')) != NULL)
		*p = '\0';

	authctxt = authctxt_new();
	authctxt->user = user;
	authctxt->style = style;

	/* Verify that the user is a valid user. */
	pw = getpwnam(user);
	if (pw && allowed_user(pw)) {
		authctxt->valid = 1;
		pw = pwcopy(pw);
	} else {
		debug("do_authentication: illegal user %s", user);
		pw = NULL;
	}
	authctxt->pw = pw;

	setproctitle("%s", pw ? user : "unknown");

#ifdef USE_PAM
	start_pam(pw == NULL ? "NOUSER" : 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 (getuid() != 0 && pw && 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();

	/* Perform session preparation. */
	do_authenticated(authctxt);
}
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"
e9a17296	13	RCSID("$OpenBSD: auth1.c,v 1.35 2002/02/03 17:53:25 markus Exp $");
3c0ef626	14
	15	#include "xmalloc.h"
	16	#include "rsa.h"
	17	#include "ssh1.h"
	18	#include "packet.h"
	19	#include "buffer.h"
	20	#include "mpaux.h"
	21	#include "log.h"
	22	#include "servconf.h"
	23	#include "compat.h"
	24	#include "auth.h"
e9a17296	25	#include "channels.h"
3c0ef626	26	#include "session.h"
	27	#include "misc.h"
	28	#include "uidswap.h"
	29
	30	/* import */
	31	extern ServerOptions options;
	32
	33	/*
	34	* convert ssh auth msg type into description
	35	*/
	36	static char *
	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";
	49	case SSH_CMSG_AUTH_TIS:
	50	case SSH_CMSG_AUTH_TIS_RESPONSE:
	51	return "challenge-response";
	52	#if defined(KRB4) \|\| defined(KRB5)
	53	case SSH_CMSG_AUTH_KERBEROS:
	54	return "kerberos";
	55	#endif
	56	}
	57	snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
	58	return buf;
	59	}
	60
	61	/*
	62	* read packets, try to authenticate the user and
	63	* return only if authentication is successful
	64	*/
	65	static void
	66	do_authloop(Authctxt *authctxt)
	67	{
	68	int authenticated = 0;
	69	u_int bits;
e9a17296	70	Key *client_host_key;
3c0ef626	71	BIGNUM *n;
	72	char client_user, password;
	73	char info[1024];
	74	u_int dlen;
3c0ef626	75	u_int ulen;
	76	int type = 0;
	77	struct passwd *pw = authctxt->pw;
	78
	79	debug("Attempting authentication for %s%.100s.",
e9a17296	80	authctxt->valid ? "" : "illegal user ", authctxt->user);
3c0ef626	81
	82	/* If the user has no password, accept authentication immediately. */
	83	if (options.password_authentication &&
	84	#if defined(KRB4) \|\| defined(KRB5)
	85	(!options.kerberos_authentication \|\| options.kerberos_or_local_passwd) &&
	86	#endif
	87	#ifdef USE_PAM
	88	auth_pam_password(pw, "")) {
	89	#elif defined(HAVE_OSF_SIA)
	90	0) {
	91	#else
	92	auth_password(authctxt, "")) {
	93	#endif
	94	auth_log(authctxt, 1, "without authentication", "");
	95	return;
	96	}
	97
	98	/* Indicate that authentication is needed. */
	99	packet_start(SSH_SMSG_FAILURE);
	100	packet_send();
	101	packet_write_wait();
	102
	103	client_user = NULL;
	104
	105	for (;;) {
	106	/* default to fail */
	107	authenticated = 0;
	108
	109	info[0] = '\0';
	110
	111	/* Get a packet from the client. */
e9a17296	112	type = packet_read();
3c0ef626	113
	114	/* Process the packet. */
	115	switch (type) {
	116
	117	#if defined(KRB4) \|\| defined(KRB5)
	118	case SSH_CMSG_AUTH_KERBEROS:
	119	if (!options.kerberos_authentication) {
	120	verbose("Kerberos authentication disabled.");
	121	} else {
	122	char *kdata = packet_get_string(&dlen);
e9a17296	123	packet_check_eom();
e9a17296	124
3c0ef626	125	if (kdata[0] == 4) { /* KRB_PROT_VERSION */
	126	#ifdef KRB4
	127	KTEXT_ST tkt;
e9a17296	128
3c0ef626	129	tkt.length = dlen;
	130	if (tkt.length < MAX_KTXT_LEN)
	131	memcpy(tkt.dat, kdata, tkt.length);
e9a17296	132
3c0ef626	133	if (auth_krb4(authctxt, &tkt, &client_user)) {
	134	authenticated = 1;
	135	snprintf(info, sizeof(info),
	136	" tktuser %.100s",
	137	client_user);
	138	}
	139	#endif /* KRB4 */
	140	} else {
	141	#ifdef KRB5
	142	krb5_data tkt;
	143	tkt.length = dlen;
	144	tkt.data = kdata;
e9a17296	145
3c0ef626	146	if (auth_krb5(authctxt, &tkt, &client_user)) {
	147	authenticated = 1;
	148	snprintf(info, sizeof(info),
	149	" tktuser %.100s",
	150	client_user);
	151	}
	152	#endif /* KRB5 */
	153	}
	154	xfree(kdata);
	155	}
	156	break;
	157	#endif /* KRB4 \|\| KRB5 */
e9a17296	158
3c0ef626	159	#if defined(AFS) \|\| defined(KRB5)
	160	/* XXX - punt on backward compatibility here. */
	161	case SSH_CMSG_HAVE_KERBEROS_TGT:
	162	packet_send_debug("Kerberos TGT passing disabled before authentication.");
	163	break;
	164	#ifdef AFS
	165	case SSH_CMSG_HAVE_AFS_TOKEN:
	166	packet_send_debug("AFS token passing disabled before authentication.");
	167	break;
	168	#endif /* AFS */
	169	#endif /* AFS \|\| KRB5 */
e9a17296	170
3c0ef626	171	case SSH_CMSG_AUTH_RHOSTS:
	172	if (!options.rhosts_authentication) {
	173	verbose("Rhosts authentication disabled.");
	174	break;
	175	}
	176	/*
	177	* Get client user name. Note that we just have to
	178	* trust the client; this is one reason why rhosts
	179	* authentication is insecure. (Another is
	180	* IP-spoofing on a local network.)
	181	*/
	182	client_user = packet_get_string(&ulen);
e9a17296	183	packet_check_eom();
3c0ef626	184
	185	/* Try to authenticate using /etc/hosts.equiv and .rhosts. */
	186	authenticated = auth_rhosts(pw, client_user);
	187
	188	snprintf(info, sizeof info, " ruser %.100s", client_user);
	189	break;
	190
	191	case SSH_CMSG_AUTH_RHOSTS_RSA:
	192	if (!options.rhosts_rsa_authentication) {
	193	verbose("Rhosts with RSA authentication disabled.");
	194	break;
	195	}
	196	/*
	197	* Get client user name. Note that we just have to
	198	* trust the client; root on the client machine can
	199	* claim to be any user.
	200	*/
	201	client_user = packet_get_string(&ulen);
	202
	203	/* Get the client host key. */
e9a17296	204	client_host_key = key_new(KEY_RSA1);
3c0ef626	205	bits = packet_get_int();
e9a17296	206	packet_get_bignum(client_host_key->rsa->e);
e9a17296	207	packet_get_bignum(client_host_key->rsa->n);
3c0ef626	208
e9a17296	209	if (bits != BN_num_bits(client_host_key->rsa->n))
3c0ef626	210	verbose("Warning: keysize mismatch for client_host_key: "
e9a17296	211	"actual %d, announced %d",
	212	BN_num_bits(client_host_key->rsa->n), bits);
	213	packet_check_eom();
3c0ef626	214
e9a17296	215	authenticated = auth_rhosts_rsa(pw, client_user,
	216	client_host_key);
	217	key_free(client_host_key);
3c0ef626	218
	219	snprintf(info, sizeof info, " ruser %.100s", client_user);
	220	break;
	221
	222	case SSH_CMSG_AUTH_RSA:
	223	if (!options.rsa_authentication) {
	224	verbose("RSA authentication disabled.");
	225	break;
	226	}
	227	/* RSA authentication requested. */
e9a17296	228	if ((n = BN_new()) == NULL)
	229	fatal("do_authloop: BN_new failed");
	230	packet_get_bignum(n);
	231	packet_check_eom();
3c0ef626	232	authenticated = auth_rsa(pw, n);
	233	BN_clear_free(n);
	234	break;
	235
	236	case SSH_CMSG_AUTH_PASSWORD:
	237	if (!options.password_authentication) {
	238	verbose("Password authentication disabled.");
	239	break;
	240	}
	241	/*
	242	* Read user password. It is in plain text, but was
	243	* transmitted over the encrypted channel so it is
	244	* not visible to an outside observer.
	245	*/
	246	password = packet_get_string(&dlen);
e9a17296	247	packet_check_eom();
3c0ef626	248
	249	#ifdef USE_PAM
	250	/* Do PAM auth with password */
	251	authenticated = auth_pam_password(pw, password);
	252	#elif defined(HAVE_OSF_SIA)
	253	/* Do SIA auth with password */
	254	authenticated = auth_sia_password(authctxt->user,
	255	password);
	256	#else /* !USE_PAM && !HAVE_OSF_SIA */
	257	/* Try authentication with the password. */
	258	authenticated = auth_password(authctxt, password);
	259	#endif /* USE_PAM */
	260
	261	memset(password, 0, strlen(password));
	262	xfree(password);
	263	break;
	264
	265	case SSH_CMSG_AUTH_TIS:
	266	debug("rcvd SSH_CMSG_AUTH_TIS");
	267	if (options.challenge_response_authentication == 1) {
	268	char *challenge = get_challenge(authctxt);
	269	if (challenge != NULL) {
	270	debug("sending challenge '%s'", challenge);
	271	packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
	272	packet_put_cstring(challenge);
	273	xfree(challenge);
	274	packet_send();
	275	packet_write_wait();
	276	continue;
	277	}
	278	}
	279	break;
	280	case SSH_CMSG_AUTH_TIS_RESPONSE:
	281	debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
	282	if (options.challenge_response_authentication == 1) {
	283	char *response = packet_get_string(&dlen);
	284	debug("got response '%s'", response);
e9a17296	285	packet_check_eom();
3c0ef626	286	authenticated = verify_response(authctxt, response);
	287	memset(response, 'r', dlen);
	288	xfree(response);
	289	}
	290	break;
	291
	292	default:
	293	/*
	294	* Any unknown messages will be ignored (and failure
	295	* returned) during authentication.
	296	*/
	297	log("Unknown message during authentication: type %d", type);
	298	break;
	299	}
	300	#ifdef BSD_AUTH
	301	if (authctxt->as) {
	302	auth_close(authctxt->as);
	303	authctxt->as = NULL;
	304	}
	305	#endif
	306	if (!authctxt->valid && authenticated)
	307	fatal("INTERNAL ERROR: authenticated invalid user %s",
	308	authctxt->user);
	309
	310	#ifdef HAVE_CYGWIN
	311	if (authenticated &&
e9a17296	312	!check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) {
3c0ef626	313	packet_disconnect("Authentication rejected for uid %d.",
e9a17296	314	pw == NULL ? -1 : pw->pw_uid);
3c0ef626	315	authenticated = 0;
	316	}
	317	#else
	318	/* Special handling for root */
	319	if (authenticated && authctxt->pw->pw_uid == 0 &&
	320	!auth_root_allowed(get_authname(type)))
	321	authenticated = 0;
	322	#endif
	323	#ifdef USE_PAM
	324	if (authenticated && !do_pam_account(pw->pw_name, client_user))
	325	authenticated = 0;
	326	#endif
	327
	328	/* Log before sending the reply */
	329	auth_log(authctxt, authenticated, get_authname(type), info);
	330
	331	if (client_user != NULL) {
	332	xfree(client_user);
	333	client_user = NULL;
	334	}
	335
	336	if (authenticated)
	337	return;
	338
	339	if (authctxt->failures++ > AUTH_FAIL_MAX) {
	340	#ifdef WITH_AIXAUTHENTICATE
	341	loginfailed(authctxt->user,
e9a17296	342	get_canonical_hostname(options.verify_reverse_mapping),
3c0ef626	343	"ssh");
	344	#endif /* WITH_AIXAUTHENTICATE */
	345	packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
	346	}
	347
	348	packet_start(SSH_SMSG_FAILURE);
	349	packet_send();
	350	packet_write_wait();
	351	}
	352	}
	353
	354	/*
	355	* Performs authentication of an incoming connection. Session key has already
	356	* been exchanged and encryption is enabled.
	357	*/
	358	void
e9a17296	359	do_authentication(void)
3c0ef626	360	{
	361	Authctxt *authctxt;
	362	struct passwd *pw;
3c0ef626	363	u_int ulen;
	364	char p, user, *style = NULL;
	365
	366	/* Get the name of the user that we wish to log in as. */
e9a17296	367	packet_read_expect(SSH_CMSG_USER);
3c0ef626	368
	369	/* Get the user name. */
	370	user = packet_get_string(&ulen);
e9a17296	371	packet_check_eom();
3c0ef626	372
	373	if ((style = strchr(user, ':')) != NULL)
	374	*style++ = '\0';
	375
	376	/* XXX - SSH.com Kerberos v5 braindeath. */
	377	if ((p = strchr(user, '@')) != NULL)
	378	*p = '\0';
e9a17296	379
3c0ef626	380	authctxt = authctxt_new();
	381	authctxt->user = user;
	382	authctxt->style = style;
	383
	384	/* Verify that the user is a valid user. */
	385	pw = getpwnam(user);
	386	if (pw && allowed_user(pw)) {
	387	authctxt->valid = 1;
	388	pw = pwcopy(pw);
	389	} else {
	390	debug("do_authentication: illegal user %s", user);
	391	pw = NULL;
	392	}
	393	authctxt->pw = pw;
	394
	395	setproctitle("%s", pw ? user : "unknown");
	396
	397	#ifdef USE_PAM
e9a17296	398	start_pam(pw == NULL ? "NOUSER" : user);
3c0ef626	399	#endif
	400
	401	/*
	402	* If we are not running as root, the user must have the same uid as
	403	* the server. (Unless you are running Windows)
	404	*/
	405	#ifndef HAVE_CYGWIN
	406	if (getuid() != 0 && pw && pw->pw_uid != getuid())
	407	packet_disconnect("Cannot change user when server not running as root.");
	408	#endif
	409
	410	/*
	411	* Loop until the user has been authenticated or the connection is
	412	* closed, do_authloop() returns only if authentication is successful
	413	*/
	414	do_authloop(authctxt);
	415
	416	/* The user has been authenticated and accepted. */
	417	packet_start(SSH_SMSG_SUCCESS);
	418	packet_send();
	419	packet_write_wait();
	420
	421	/* Perform session preparation. */
	422	do_authenticated(authctxt);
	423	}