[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 1.40 2002/04/10 08:21:47 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 "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";
#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
	    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. */
		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();

			/* 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);
				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 (!use_privsep && 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.
 */
Authctxt *
do_authentication(void)
{
	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';

#ifdef KRB5
	/* XXX - SSH.com Kerberos v5 braindeath. */
	if ((datafellows & SSH_BUG_K5USER) &&
	    options.kerberos_authentication) {
		char *p;
		if ((p = strchr(user, '@')) != NULL)
			*p = '\0';
	}
#endif

	authctxt = authctxt_new();
	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);

	setproctitle("%s%s", authctxt->pw ? user : "unknown",
	    use_privsep ? " [net]" : "");

#ifdef USE_PAM
	PRIVSEP(start_pam(authctxt->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 (!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();

	return (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"
700318f3	13	RCSID("$OpenBSD: auth1.c,v 1.40 2002/04/10 08:21:47 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"
3c0ef626	27	#include "uidswap.h"
700318f3	28	#include "monitor_wrap.h"
3c0ef626	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
700318f3	87	PRIVSEP(auth_password(authctxt, ""))) {
3c0ef626	88	auth_log(authctxt, 1, "without authentication", "");
	89	return;
	90	}
	91
	92	/* Indicate that authentication is needed. */
	93	packet_start(SSH_SMSG_FAILURE);
	94	packet_send();
	95	packet_write_wait();
	96
	97	client_user = NULL;
	98
	99	for (;;) {
	100	/* default to fail */
	101	authenticated = 0;
	102
	103	info[0] = '\0';
	104
	105	/* Get a packet from the client. */
e9a17296	106	type = packet_read();
3c0ef626	107
	108	/* Process the packet. */
	109	switch (type) {
	110
	111	#if defined(KRB4) \|\| defined(KRB5)
	112	case SSH_CMSG_AUTH_KERBEROS:
	113	if (!options.kerberos_authentication) {
	114	verbose("Kerberos authentication disabled.");
	115	} else {
	116	char *kdata = packet_get_string(&dlen);
e9a17296	117	packet_check_eom();
e9a17296	118
3c0ef626	119	if (kdata[0] == 4) { /* KRB_PROT_VERSION */
	120	#ifdef KRB4
	121	KTEXT_ST tkt;
e9a17296	122
3c0ef626	123	tkt.length = dlen;
	124	if (tkt.length < MAX_KTXT_LEN)
	125	memcpy(tkt.dat, kdata, tkt.length);
e9a17296	126
3c0ef626	127	if (auth_krb4(authctxt, &tkt, &client_user)) {
	128	authenticated = 1;
	129	snprintf(info, sizeof(info),
	130	" tktuser %.100s",
	131	client_user);
	132	}
	133	#endif /* KRB4 */
	134	} else {
	135	#ifdef KRB5
	136	krb5_data tkt;
	137	tkt.length = dlen;
	138	tkt.data = kdata;
e9a17296	139
3c0ef626	140	if (auth_krb5(authctxt, &tkt, &client_user)) {
	141	authenticated = 1;
	142	snprintf(info, sizeof(info),
	143	" tktuser %.100s",
	144	client_user);
	145	}
	146	#endif /* KRB5 */
	147	}
	148	xfree(kdata);
	149	}
	150	break;
	151	#endif /* KRB4 \|\| KRB5 */
e9a17296	152
3c0ef626	153	#if defined(AFS) \|\| defined(KRB5)
	154	/* XXX - punt on backward compatibility here. */
	155	case SSH_CMSG_HAVE_KERBEROS_TGT:
	156	packet_send_debug("Kerberos TGT passing disabled before authentication.");
	157	break;
	158	#ifdef AFS
	159	case SSH_CMSG_HAVE_AFS_TOKEN:
	160	packet_send_debug("AFS token passing disabled before authentication.");
	161	break;
	162	#endif /* AFS */
	163	#endif /* AFS \|\| KRB5 */
e9a17296	164
3c0ef626	165	case SSH_CMSG_AUTH_RHOSTS:
	166	if (!options.rhosts_authentication) {
	167	verbose("Rhosts authentication disabled.");
	168	break;
	169	}
	170	/*
	171	* Get client user name. Note that we just have to
	172	* trust the client; this is one reason why rhosts
	173	* authentication is insecure. (Another is
	174	* IP-spoofing on a local network.)
	175	*/
	176	client_user = packet_get_string(&ulen);
e9a17296	177	packet_check_eom();
3c0ef626	178
	179	/* Try to authenticate using /etc/hosts.equiv and .rhosts. */
	180	authenticated = auth_rhosts(pw, client_user);
	181
	182	snprintf(info, sizeof info, " ruser %.100s", client_user);
	183	break;
	184
	185	case SSH_CMSG_AUTH_RHOSTS_RSA:
	186	if (!options.rhosts_rsa_authentication) {
	187	verbose("Rhosts with RSA authentication disabled.");
	188	break;
	189	}
	190	/*
	191	* Get client user name. Note that we just have to
	192	* trust the client; root on the client machine can
	193	* claim to be any user.
	194	*/
	195	client_user = packet_get_string(&ulen);
	196
	197	/* Get the client host key. */
e9a17296	198	client_host_key = key_new(KEY_RSA1);
3c0ef626	199	bits = packet_get_int();
e9a17296	200	packet_get_bignum(client_host_key->rsa->e);
e9a17296	201	packet_get_bignum(client_host_key->rsa->n);
3c0ef626	202
e9a17296	203	if (bits != BN_num_bits(client_host_key->rsa->n))
3c0ef626	204	verbose("Warning: keysize mismatch for client_host_key: "
e9a17296	205	"actual %d, announced %d",
	206	BN_num_bits(client_host_key->rsa->n), bits);
	207	packet_check_eom();
3c0ef626	208
e9a17296	209	authenticated = auth_rhosts_rsa(pw, client_user,
	210	client_host_key);
	211	key_free(client_host_key);
3c0ef626	212
	213	snprintf(info, sizeof info, " ruser %.100s", client_user);
	214	break;
	215
	216	case SSH_CMSG_AUTH_RSA:
	217	if (!options.rsa_authentication) {
	218	verbose("RSA authentication disabled.");
	219	break;
	220	}
	221	/* RSA authentication requested. */
e9a17296	222	if ((n = BN_new()) == NULL)
	223	fatal("do_authloop: BN_new failed");
	224	packet_get_bignum(n);
	225	packet_check_eom();
3c0ef626	226	authenticated = auth_rsa(pw, n);
	227	BN_clear_free(n);
	228	break;
	229
	230	case SSH_CMSG_AUTH_PASSWORD:
	231	if (!options.password_authentication) {
	232	verbose("Password authentication disabled.");
	233	break;
	234	}
	235	/*
	236	* Read user password. It is in plain text, but was
	237	* transmitted over the encrypted channel so it is
	238	* not visible to an outside observer.
	239	*/
	240	password = packet_get_string(&dlen);
e9a17296	241	packet_check_eom();
3c0ef626	242
3c0ef626	243	/* Try authentication with the password. */
700318f3	244	authenticated = PRIVSEP(auth_password(authctxt, password));
3c0ef626	245
	246	memset(password, 0, strlen(password));
	247	xfree(password);
	248	break;
	249
	250	case SSH_CMSG_AUTH_TIS:
	251	debug("rcvd SSH_CMSG_AUTH_TIS");
	252	if (options.challenge_response_authentication == 1) {
	253	char *challenge = get_challenge(authctxt);
	254	if (challenge != NULL) {
	255	debug("sending challenge '%s'", challenge);
	256	packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
	257	packet_put_cstring(challenge);
	258	xfree(challenge);
	259	packet_send();
	260	packet_write_wait();
	261	continue;
	262	}
	263	}
	264	break;
	265	case SSH_CMSG_AUTH_TIS_RESPONSE:
	266	debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
	267	if (options.challenge_response_authentication == 1) {
	268	char *response = packet_get_string(&dlen);
	269	debug("got response '%s'", response);
e9a17296	270	packet_check_eom();
3c0ef626	271	authenticated = verify_response(authctxt, response);
	272	memset(response, 'r', dlen);
	273	xfree(response);
	274	}
	275	break;
	276
	277	default:
	278	/*
	279	* Any unknown messages will be ignored (and failure
	280	* returned) during authentication.
	281	*/
	282	log("Unknown message during authentication: type %d", type);
	283	break;
	284	}
	285	#ifdef BSD_AUTH
	286	if (authctxt->as) {
	287	auth_close(authctxt->as);
	288	authctxt->as = NULL;
	289	}
	290	#endif
	291	if (!authctxt->valid && authenticated)
	292	fatal("INTERNAL ERROR: authenticated invalid user %s",
	293	authctxt->user);
	294
	295	#ifdef HAVE_CYGWIN
	296	if (authenticated &&
e9a17296	297	!check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) {
3c0ef626	298	packet_disconnect("Authentication rejected for uid %d.",
e9a17296	299	pw == NULL ? -1 : pw->pw_uid);
3c0ef626	300	authenticated = 0;
	301	}
	302	#else
	303	/* Special handling for root */
	304	if (authenticated && authctxt->pw->pw_uid == 0 &&
	305	!auth_root_allowed(get_authname(type)))
	306	authenticated = 0;
	307	#endif
	308	#ifdef USE_PAM
700318f3	309	if (!use_privsep && authenticated &&
700318f3	310	!do_pam_account(pw->pw_name, client_user))
3c0ef626	311	authenticated = 0;
	312	#endif
	313
	314	/* Log before sending the reply */
	315	auth_log(authctxt, authenticated, get_authname(type), info);
	316
	317	if (client_user != NULL) {
	318	xfree(client_user);
	319	client_user = NULL;
	320	}
	321
	322	if (authenticated)
	323	return;
	324
	325	if (authctxt->failures++ > AUTH_FAIL_MAX) {
	326	#ifdef WITH_AIXAUTHENTICATE
	327	loginfailed(authctxt->user,
e9a17296	328	get_canonical_hostname(options.verify_reverse_mapping),
3c0ef626	329	"ssh");
	330	#endif /* WITH_AIXAUTHENTICATE */
	331	packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
	332	}
	333
	334	packet_start(SSH_SMSG_FAILURE);
	335	packet_send();
	336	packet_write_wait();
	337	}
	338	}
	339
	340	/*
	341	* Performs authentication of an incoming connection. Session key has already
	342	* been exchanged and encryption is enabled.
	343	*/
700318f3	344	Authctxt *
e9a17296	345	do_authentication(void)
3c0ef626	346	{
3c0ef626	347	Authctxt *authctxt;
3c0ef626	348	u_int ulen;
700318f3	349	char user, style = NULL;
3c0ef626	350
3c0ef626	351	/* Get the name of the user that we wish to log in as. */
e9a17296	352	packet_read_expect(SSH_CMSG_USER);
3c0ef626	353
	354	/* Get the user name. */
	355	user = packet_get_string(&ulen);
e9a17296	356	packet_check_eom();
3c0ef626	357
	358	if ((style = strchr(user, ':')) != NULL)
	359	*style++ = '\0';
	360
700318f3	361	#ifdef KRB5
3c0ef626	362	/* XXX - SSH.com Kerberos v5 braindeath. */
700318f3	363	if ((datafellows & SSH_BUG_K5USER) &&
	364	options.kerberos_authentication) {
	365	char *p;
	366	if ((p = strchr(user, '@')) != NULL)
	367	*p = '\0';
	368	}
	369	#endif
e9a17296	370
3c0ef626	371	authctxt = authctxt_new();
	372	authctxt->user = user;
	373	authctxt->style = style;
	374
	375	/* Verify that the user is a valid user. */
700318f3	376	if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
3c0ef626	377	authctxt->valid = 1;
700318f3	378	else
3c0ef626	379	debug("do_authentication: illegal user %s", user);
3c0ef626	380
700318f3	381	setproctitle("%s%s", authctxt->pw ? user : "unknown",
700318f3	382	use_privsep ? " [net]" : "");
3c0ef626	383
3c0ef626	384	#ifdef USE_PAM
700318f3	385	PRIVSEP(start_pam(authctxt->pw == NULL ? "NOUSER" : user));
3c0ef626	386	#endif
	387
	388	/*
	389	* If we are not running as root, the user must have the same uid as
	390	* the server. (Unless you are running Windows)
	391	*/
	392	#ifndef HAVE_CYGWIN
700318f3	393	if (!use_privsep && getuid() != 0 && authctxt->pw &&
700318f3	394	authctxt->pw->pw_uid != getuid())
3c0ef626	395	packet_disconnect("Cannot change user when server not running as root.");
	396	#endif
	397
	398	/*
	399	* Loop until the user has been authenticated or the connection is
	400	* closed, do_authloop() returns only if authentication is successful
	401	*/
	402	do_authloop(authctxt);
	403
	404	/* The user has been authenticated and accepted. */
	405	packet_start(SSH_SMSG_SUCCESS);
	406	packet_send();
	407	packet_write_wait();
	408
700318f3	409	return (authctxt);
3c0ef626	410	}