auth1.c - platform/external/openssh - Gitiles

 /*
  * 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 1.9 2000/12/27 12:34:49 markus Exp $");

 #ifdef HAVE_OSF_SIA
 # include <sia.h>
 # include <siad.h>
 #endif

 #include "xmalloc.h"
 #include "rsa.h"
 #include "ssh.h"
 #include "packet.h"
 #include "buffer.h"
 #include "mpaux.h"
 #include "servconf.h"
 #include "compat.h"
 #include "auth.h"
 #include "session.h"

 /* import */
 extern ServerOptions options;
 extern char *forced_command;

 #ifdef WITH_AIXAUTHENTICATE
 extern char *aixloginmsg;
 #endif /* WITH_AIXAUTHENTICATE */
 #ifdef HAVE_OSF_SIA
 extern int saved_argc;
 extern char **saved_argv;
 #endif /* HAVE_OSF_SIA */

 /*
  * convert ssh auth msg type into description
  */
 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";
 #ifdef KRB4
 	case SSH_CMSG_AUTH_KERBEROS:
 		return "kerberos";
 #endif
 #ifdef SKEY
 	case SSH_CMSG_AUTH_TIS_RESPONSE:
 		return "s/key";
 #endif
 	}
 	snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
 	return buf;
 }

 /*
  * read packets and try to authenticate local user 'luser'.
  * return if authentication is successful. not that pw == NULL
  * if the user does not exists or is not allowed to login.
  * each auth method has to 'fake' authentication for nonexisting
  * users.
  */
 void
 do_authloop(struct passwd * pw, char *luser)
 {
 	int authenticated = 0;
 	int attempt = 0;
 	u_int bits;
 	RSA *client_host_key;
 	BIGNUM *n;
 	char *client_user, *password;
 	char user[1024];
 	u_int dlen;
 	int plen, nlen, elen;
 	u_int ulen;
 	int type = 0;
 	void (*authlog) (const char *fmt,...) = verbose;

 	/* Indicate that authentication is needed. */
 	packet_start(SSH_SMSG_FAILURE);
 	packet_send();
 	packet_write_wait();

 	client_user = NULL;

 	for (attempt = 1;; attempt++) {
 		/* default to fail */
 		authenticated = 0;

 		strlcpy(user, "", sizeof user);

 		/* Get a packet from the client. */
 		type = packet_read(&plen);

 		/* Process the packet. */
 		switch (type) {
 #ifdef AFS
 		case SSH_CMSG_HAVE_KERBEROS_TGT:
 			if (!options.kerberos_tgt_passing) {
 				verbose("Kerberos tgt passing disabled.");
 				break;
 			} else {
 				/* Accept Kerberos tgt. */
 				char *tgt = packet_get_string(&dlen);
 				packet_integrity_check(plen, 4 + dlen, type);
 				if (!auth_kerberos_tgt(pw, tgt))
 					verbose("Kerberos tgt REFUSED for %.100s", luser);
 				xfree(tgt);
 			}
 			continue;

 		case SSH_CMSG_HAVE_AFS_TOKEN:
 			if (!options.afs_token_passing || !k_hasafs()) {
 				verbose("AFS token passing disabled.");
 				break;
 			} else {
 				/* Accept AFS token. */
 				char *token_string = packet_get_string(&dlen);
 				packet_integrity_check(plen, 4 + dlen, type);
 				if (!auth_afs_token(pw, token_string))
 					verbose("AFS token REFUSED for %.100s", luser);
 				xfree(token_string);
 			}
 			continue;
 #endif /* AFS */
 #ifdef KRB4
 		case SSH_CMSG_AUTH_KERBEROS:
 			if (!options.kerberos_authentication) {
 				/* packet_get_all(); */
 				verbose("Kerberos authentication disabled.");
 				break;
 			} else {
 				/* Try Kerberos v4 authentication. */
 				KTEXT_ST auth;
 				char *tkt_user = NULL;
 				char *kdata = packet_get_string((u_int *) &auth.length);
 				packet_integrity_check(plen, 4 + auth.length, type);

 				if (auth.length < MAX_KTXT_LEN)
 					memcpy(auth.dat, kdata, auth.length);
 				xfree(kdata);

 				if (pw != NULL) {
 					authenticated = auth_krb4(pw->pw_name, &auth, &tkt_user);
 					if (authenticated) {
 						snprintf(user, sizeof user, " tktuser %s", tkt_user);
 						xfree(tkt_user);
 					}
 				}
 			}
 			break;
 #endif /* KRB4 */

 		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_integrity_check(plen, 4 + ulen, type);

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

 			snprintf(user, sizeof user, " ruser %s", 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 = RSA_new();
 			if (client_host_key == NULL)
 				fatal("RSA_new failed");
 			client_host_key->e = BN_new();
 			client_host_key->n = BN_new();
 			if (client_host_key->e == NULL || client_host_key->n == NULL)
 				fatal("BN_new failed");
 			bits = packet_get_int();
 			packet_get_bignum(client_host_key->e, &elen);
 			packet_get_bignum(client_host_key->n, &nlen);

 			if (bits != BN_num_bits(client_host_key->n))
 				verbose("Warning: keysize mismatch for client_host_key: "
 				    "actual %d, announced %d", BN_num_bits(client_host_key->n), bits);
 			packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type);

 			authenticated = auth_rhosts_rsa(pw, client_user, client_host_key);
 			RSA_free(client_host_key);

 			snprintf(user, sizeof user, " ruser %s", client_user);
 			break;

 		case SSH_CMSG_AUTH_RSA:
 			if (!options.rsa_authentication) {
 				verbose("RSA authentication disabled.");
 				break;
 			}
 			/* RSA authentication requested. */
 			n = BN_new();
 			packet_get_bignum(n, &nlen);
 			packet_integrity_check(plen, nlen, type);
 			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_integrity_check(plen, 4 + dlen, type);

 #ifdef USE_PAM
 			/* Do PAM auth with password */
 			authenticated = auth_pam_password(pw, password);
 #elif defined(HAVE_OSF_SIA)
 			/* Do SIA auth with password */
 			if (sia_validate_user(NULL, saved_argc, saved_argv,
 				get_canonical_hostname(), pw->pw_name, NULL, 0,
 				NULL, password) == SIASUCCESS) {
 				authenticated = 1;
 			}
 #else /* !USE_PAM && !HAVE_OSF_SIA */
  			/* Try authentication with the password. */
 			authenticated = auth_password(pw, password);
 #endif /* USE_PAM */

 			memset(password, 0, strlen(password));
 			xfree(password);
 			break;

 #ifdef SKEY
 		case SSH_CMSG_AUTH_TIS:
 			debug("rcvd SSH_CMSG_AUTH_TIS");
 			if (options.skey_authentication == 1) {
 				char *skeyinfo = NULL;
 				if (pw != NULL)
 					skeyinfo = skey_keyinfo(pw->pw_name);
 				if (skeyinfo == NULL) {
 					debug("generating fake skeyinfo for %.100s.", luser);
 					skeyinfo = skey_fake_keyinfo(luser);
 				}
 				if (skeyinfo != NULL) {
 					/* we send our s/key- in tis-challenge messages */
 					debug("sending challenge '%s'", skeyinfo);
 					packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
 					packet_put_cstring(skeyinfo);
 					packet_send();
 					packet_write_wait();
 					continue;
 				}
 			}
 			break;
 		case SSH_CMSG_AUTH_TIS_RESPONSE:
 			debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
 			if (options.skey_authentication == 1) {
 				char *response = packet_get_string(&dlen);
 				debug("skey response == '%s'", response);
 				packet_integrity_check(plen, 4 + dlen, type);
 				authenticated = (pw != NULL &&
 				    skey_haskey(pw->pw_name) == 0 &&
 				    skey_passcheck(pw->pw_name, response) != -1);
 				xfree(response);
 			}
 			break;
 #else
 		case SSH_CMSG_AUTH_TIS:
 			/* TIS Authentication is unsupported */
 			log("TIS authentication unsupported.");
 			break;
 #endif

 		default:
 			/*
 			 * Any unknown messages will be ignored (and failure
 			 * returned) during authentication.
 			 */
 			log("Unknown message during authentication: type %d", type);
 			break;
 		}
 		if (authenticated && pw == NULL)
 			fatal("internal error: authenticated for pw == NULL");

 #ifdef HAVE_CYGWIN
 		if (authenticated &&
 		    !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD,pw->pw_uid)) {
 			packet_disconnect("Authentication rejected for uid %d.",
 			(int)pw->pw_uid);
 			authenticated = 0;
 		}
 #endif

 		/*
 		 * Check if the user is logging in as root and root logins
 		 * are disallowed.
 		 * Note that root login is allowed for forced commands.
 		 */
 		if (authenticated && pw && pw->pw_uid == 0 && !options.permit_root_login) {
 			if (forced_command) {
 				log("Root login accepted for forced command.");
 			} else {
 				authenticated = 0;
 				log("ROOT LOGIN REFUSED FROM %.200s",
 				    get_canonical_hostname());
 			}
 		}

 		/* Raise logging level */
 		if (authenticated ||
 		    attempt == AUTH_FAIL_LOG ||
 		    type == SSH_CMSG_AUTH_PASSWORD)
 			authlog = log;

 		authlog("%s %s for %s%.100s from %.200s port %d%s",
 			authenticated ? "Accepted" : "Failed",
 			get_authname(type),
 			pw ? "" : "illegal user ",
 			pw && pw->pw_uid == 0 ? "ROOT" : luser,
 			get_remote_ipaddr(),
 			get_remote_port(),
 			user);

 #ifdef USE_PAM
 		if (authenticated && !do_pam_account(pw->pw_name, client_user))
 			authenticated = 0;
 #endif

 		if (client_user != NULL) {
 			xfree(client_user);
 			client_user = NULL;
 		}

 		if (authenticated)
 			return;

 		if (attempt > AUTH_FAIL_MAX) {
 #ifdef WITH_AIXAUTHENTICATE
 			loginfailed(user,get_canonical_hostname(),"ssh");
 #endif /* WITH_AIXAUTHENTICATE */
 			packet_disconnect(AUTH_FAIL_MSG, luser);
 		}

 		/* Send a message indicating that the authentication attempt failed. */
 		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()
 {
 	struct passwd *pw, pwcopy;
 	int plen;
 	u_int ulen;
 	char *user;

 	/* Get the name of the user that we wish to log in as. */
 	packet_read_expect(&plen, SSH_CMSG_USER);

 	/* Get the user name. */
 	user = packet_get_string(&ulen);
 	packet_integrity_check(plen, (4 + ulen), SSH_CMSG_USER);

 	setproctitle("%s", user);

 #ifdef AFS
 	/* If machine has AFS, set process authentication group. */
 	if (k_hasafs()) {
 		k_setpag();
 		k_unlog();
 	}
 #endif /* AFS */

 	/* Verify that the user is a valid user. */
 	pw = getpwnam(user);
 	if (pw && allowed_user(pw)) {
 		/* Take a copy of the returned structure. */
 		memset(&pwcopy, 0, sizeof(pwcopy));
 		pwcopy.pw_name = xstrdup(pw->pw_name);
 		pwcopy.pw_passwd = xstrdup(pw->pw_passwd);
 		pwcopy.pw_uid = pw->pw_uid;
 		pwcopy.pw_gid = pw->pw_gid;
 #ifdef HAVE_PW_CLASS_IN_PASSWD
 		pwcopy.pw_class = xstrdup(pw->pw_class);
 #endif
 		pwcopy.pw_dir = xstrdup(pw->pw_dir);
 		pwcopy.pw_shell = xstrdup(pw->pw_shell);
 		pw = &pwcopy;
 	} else {
 		pw = NULL;
 	}

 #ifdef USE_PAM
 	if (pw)
 		start_pam(pw);
 #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

 	debug("Attempting authentication for %s%.100s.", pw ? "" : "illegal user ", user);

 	/* If the user has no password, accept authentication immediately. */
 	if (options.password_authentication &&
 #ifdef KRB4
 	    (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
 #endif /* KRB4 */
 #ifdef USE_PAM
 	    auth_pam_password(pw, "")) {
 #elif defined(HAVE_OSF_SIA)
 	    (sia_validate_user(NULL, saved_argc, saved_argv,
 	    get_canonical_hostname(), pw->pw_name, NULL, 0,
 		 NULL, "") == SIASUCCESS)) {
 #else /* !HAVE_OSF_SIA && !USE_PAM */
  	    auth_password(pw, "")) {
 #endif /* USE_PAM */
 		/* Authentication with empty password succeeded. */
 		log("Login for user %s from %.100s, accepted without authentication.",
 		    user, get_remote_ipaddr());
 	} else {
 		/* Loop until the user has been authenticated or the
 		   connection is closed, do_authloop() returns only if
 		   authentication is successful */
 		do_authloop(pw, user);
 	}
 	if (pw == NULL)
 		fatal("internal error, authentication successful for user '%.100s'", user);

 	/* The user has been authenticated and accepted. */
 	packet_start(SSH_SMSG_SUCCESS);
 	packet_send();
 	packet_write_wait();

 #ifdef WITH_AIXAUTHENTICATE
 	/* We don't have a pty yet, so just label the line as "ssh" */
 	if (loginsuccess(user,get_canonical_hostname(),"ssh",&aixloginmsg) < 0)
 		aixloginmsg = NULL;
 #endif /* WITH_AIXAUTHENTICATE */

 	/* Perform session preparation. */
 	do_authenticated(pw);
 }
	/*
	* 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 1.9 2000/12/27 12:34:49 markus Exp $");

	#ifdef HAVE_OSF_SIA
	# include <sia.h>
	# include <siad.h>
	#endif

	#include "xmalloc.h"
	#include "rsa.h"
	#include "ssh.h"
	#include "packet.h"
	#include "buffer.h"
	#include "mpaux.h"
	#include "servconf.h"
	#include "compat.h"
	#include "auth.h"
	#include "session.h"

	/* import */
	extern ServerOptions options;
	extern char *forced_command;

	#ifdef WITH_AIXAUTHENTICATE
	extern char *aixloginmsg;
	#endif /* WITH_AIXAUTHENTICATE */
	#ifdef HAVE_OSF_SIA
	extern int saved_argc;
	extern char **saved_argv;
	#endif /* HAVE_OSF_SIA */

	/*
	* convert ssh auth msg type into description
	*/
	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";
	#ifdef KRB4
	case SSH_CMSG_AUTH_KERBEROS:
	return "kerberos";
	#endif
	#ifdef SKEY
	case SSH_CMSG_AUTH_TIS_RESPONSE:
	return "s/key";
	#endif
	}
	snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
	return buf;
	}

	/*
	* read packets and try to authenticate local user 'luser'.
	* return if authentication is successful. not that pw == NULL
	* if the user does not exists or is not allowed to login.
	* each auth method has to 'fake' authentication for nonexisting
	* users.
	*/
	void
	do_authloop(struct passwd * pw, char *luser)
	{
	int authenticated = 0;
	int attempt = 0;
	u_int bits;
	RSA *client_host_key;
	BIGNUM *n;
	char client_user, password;
	char user[1024];
	u_int dlen;
	int plen, nlen, elen;
	u_int ulen;
	int type = 0;
	void (authlog) (const char fmt,...) = verbose;

	/* Indicate that authentication is needed. */
	packet_start(SSH_SMSG_FAILURE);
	packet_send();
	packet_write_wait();

	client_user = NULL;

	for (attempt = 1;; attempt++) {
	/* default to fail */
	authenticated = 0;

	strlcpy(user, "", sizeof user);

	/* Get a packet from the client. */
	type = packet_read(&plen);

	/* Process the packet. */
	switch (type) {
	#ifdef AFS
	case SSH_CMSG_HAVE_KERBEROS_TGT:
	if (!options.kerberos_tgt_passing) {
	verbose("Kerberos tgt passing disabled.");
	break;
	} else {
	/* Accept Kerberos tgt. */
	char *tgt = packet_get_string(&dlen);
	packet_integrity_check(plen, 4 + dlen, type);
	if (!auth_kerberos_tgt(pw, tgt))
	verbose("Kerberos tgt REFUSED for %.100s", luser);
	xfree(tgt);
	}
	continue;

	case SSH_CMSG_HAVE_AFS_TOKEN:
	if (!options.afs_token_passing \|\| !k_hasafs()) {
	verbose("AFS token passing disabled.");
	break;
	} else {
	/* Accept AFS token. */
	char *token_string = packet_get_string(&dlen);
	packet_integrity_check(plen, 4 + dlen, type);
	if (!auth_afs_token(pw, token_string))
	verbose("AFS token REFUSED for %.100s", luser);
	xfree(token_string);
	}
	continue;
	#endif /* AFS */
	#ifdef KRB4
	case SSH_CMSG_AUTH_KERBEROS:
	if (!options.kerberos_authentication) {
	/* packet_get_all(); */
	verbose("Kerberos authentication disabled.");
	break;
	} else {
	/* Try Kerberos v4 authentication. */
	KTEXT_ST auth;
	char *tkt_user = NULL;
	char kdata = packet_get_string((u_int ) &auth.length);
	packet_integrity_check(plen, 4 + auth.length, type);

	if (auth.length < MAX_KTXT_LEN)
	memcpy(auth.dat, kdata, auth.length);
	xfree(kdata);

	if (pw != NULL) {
	authenticated = auth_krb4(pw->pw_name, &auth, &tkt_user);
	if (authenticated) {
	snprintf(user, sizeof user, " tktuser %s", tkt_user);
	xfree(tkt_user);
	}
	}
	}
	break;
	#endif /* KRB4 */

	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_integrity_check(plen, 4 + ulen, type);

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

	snprintf(user, sizeof user, " ruser %s", 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 = RSA_new();
	if (client_host_key == NULL)
	fatal("RSA_new failed");
	client_host_key->e = BN_new();
	client_host_key->n = BN_new();
	if (client_host_key->e == NULL \|\| client_host_key->n == NULL)
	fatal("BN_new failed");
	bits = packet_get_int();
	packet_get_bignum(client_host_key->e, &elen);
	packet_get_bignum(client_host_key->n, &nlen);

	if (bits != BN_num_bits(client_host_key->n))
	verbose("Warning: keysize mismatch for client_host_key: "
	"actual %d, announced %d", BN_num_bits(client_host_key->n), bits);
	packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type);

	authenticated = auth_rhosts_rsa(pw, client_user, client_host_key);
	RSA_free(client_host_key);

	snprintf(user, sizeof user, " ruser %s", client_user);
	break;

	case SSH_CMSG_AUTH_RSA:
	if (!options.rsa_authentication) {
	verbose("RSA authentication disabled.");
	break;
	}
	/* RSA authentication requested. */
	n = BN_new();
	packet_get_bignum(n, &nlen);
	packet_integrity_check(plen, nlen, type);
	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_integrity_check(plen, 4 + dlen, type);

	#ifdef USE_PAM
	/* Do PAM auth with password */
	authenticated = auth_pam_password(pw, password);
	#elif defined(HAVE_OSF_SIA)
	/* Do SIA auth with password */
	if (sia_validate_user(NULL, saved_argc, saved_argv,
	get_canonical_hostname(), pw->pw_name, NULL, 0,
	NULL, password) == SIASUCCESS) {
	authenticated = 1;
	}
	#else /* !USE_PAM && !HAVE_OSF_SIA */
	/* Try authentication with the password. */
	authenticated = auth_password(pw, password);
	#endif /* USE_PAM */

	memset(password, 0, strlen(password));
	xfree(password);
	break;

	#ifdef SKEY
	case SSH_CMSG_AUTH_TIS:
	debug("rcvd SSH_CMSG_AUTH_TIS");
	if (options.skey_authentication == 1) {
	char *skeyinfo = NULL;
	if (pw != NULL)
	skeyinfo = skey_keyinfo(pw->pw_name);
	if (skeyinfo == NULL) {
	debug("generating fake skeyinfo for %.100s.", luser);
	skeyinfo = skey_fake_keyinfo(luser);
	}
	if (skeyinfo != NULL) {
	/* we send our s/key- in tis-challenge messages */
	debug("sending challenge '%s'", skeyinfo);
	packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
	packet_put_cstring(skeyinfo);
	packet_send();
	packet_write_wait();
	continue;
	}
	}
	break;
	case SSH_CMSG_AUTH_TIS_RESPONSE:
	debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
	if (options.skey_authentication == 1) {
	char *response = packet_get_string(&dlen);
	debug("skey response == '%s'", response);
	packet_integrity_check(plen, 4 + dlen, type);
	authenticated = (pw != NULL &&
	skey_haskey(pw->pw_name) == 0 &&
	skey_passcheck(pw->pw_name, response) != -1);
	xfree(response);
	}
	break;
	#else
	case SSH_CMSG_AUTH_TIS:
	/* TIS Authentication is unsupported */
	log("TIS authentication unsupported.");
	break;
	#endif

	default:
	/*
	* Any unknown messages will be ignored (and failure
	* returned) during authentication.
	*/
	log("Unknown message during authentication: type %d", type);
	break;
	}
	if (authenticated && pw == NULL)
	fatal("internal error: authenticated for pw == NULL");

	#ifdef HAVE_CYGWIN
	if (authenticated &&
	!check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD,pw->pw_uid)) {
	packet_disconnect("Authentication rejected for uid %d.",
	(int)pw->pw_uid);
	authenticated = 0;
	}
	#endif

	/*
	* Check if the user is logging in as root and root logins
	* are disallowed.
	* Note that root login is allowed for forced commands.
	*/
	if (authenticated && pw && pw->pw_uid == 0 && !options.permit_root_login) {
	if (forced_command) {
	log("Root login accepted for forced command.");
	} else {
	authenticated = 0;
	log("ROOT LOGIN REFUSED FROM %.200s",
	get_canonical_hostname());
	}
	}

	/* Raise logging level */
	if (authenticated \|\|
	attempt == AUTH_FAIL_LOG \|\|
	type == SSH_CMSG_AUTH_PASSWORD)
	authlog = log;

	authlog("%s %s for %s%.100s from %.200s port %d%s",
	authenticated ? "Accepted" : "Failed",
	get_authname(type),
	pw ? "" : "illegal user ",
	pw && pw->pw_uid == 0 ? "ROOT" : luser,
	get_remote_ipaddr(),
	get_remote_port(),
	user);

	#ifdef USE_PAM
	if (authenticated && !do_pam_account(pw->pw_name, client_user))
	authenticated = 0;
	#endif

	if (client_user != NULL) {
	xfree(client_user);
	client_user = NULL;
	}

	if (authenticated)
	return;

	if (attempt > AUTH_FAIL_MAX) {
	#ifdef WITH_AIXAUTHENTICATE
	loginfailed(user,get_canonical_hostname(),"ssh");
	#endif /* WITH_AIXAUTHENTICATE */
	packet_disconnect(AUTH_FAIL_MSG, luser);
	}

	/* Send a message indicating that the authentication attempt failed. */
	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()
	{
	struct passwd *pw, pwcopy;
	int plen;
	u_int ulen;
	char *user;

	/* Get the name of the user that we wish to log in as. */
	packet_read_expect(&plen, SSH_CMSG_USER);

	/* Get the user name. */
	user = packet_get_string(&ulen);
	packet_integrity_check(plen, (4 + ulen), SSH_CMSG_USER);

	setproctitle("%s", user);

	#ifdef AFS
	/* If machine has AFS, set process authentication group. */
	if (k_hasafs()) {
	k_setpag();
	k_unlog();
	}
	#endif /* AFS */

	/* Verify that the user is a valid user. */
	pw = getpwnam(user);
	if (pw && allowed_user(pw)) {
	/* Take a copy of the returned structure. */
	memset(&pwcopy, 0, sizeof(pwcopy));
	pwcopy.pw_name = xstrdup(pw->pw_name);
	pwcopy.pw_passwd = xstrdup(pw->pw_passwd);
	pwcopy.pw_uid = pw->pw_uid;
	pwcopy.pw_gid = pw->pw_gid;
	#ifdef HAVE_PW_CLASS_IN_PASSWD
	pwcopy.pw_class = xstrdup(pw->pw_class);
	#endif
	pwcopy.pw_dir = xstrdup(pw->pw_dir);
	pwcopy.pw_shell = xstrdup(pw->pw_shell);
	pw = &pwcopy;
	} else {
	pw = NULL;
	}

	#ifdef USE_PAM
	if (pw)
	start_pam(pw);
	#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

	debug("Attempting authentication for %s%.100s.", pw ? "" : "illegal user ", user);

	/* If the user has no password, accept authentication immediately. */
	if (options.password_authentication &&
	#ifdef KRB4
	(!options.kerberos_authentication \|\| options.kerberos_or_local_passwd) &&
	#endif /* KRB4 */
	#ifdef USE_PAM
	auth_pam_password(pw, "")) {
	#elif defined(HAVE_OSF_SIA)
	(sia_validate_user(NULL, saved_argc, saved_argv,
	get_canonical_hostname(), pw->pw_name, NULL, 0,
	NULL, "") == SIASUCCESS)) {
	#else /* !HAVE_OSF_SIA && !USE_PAM */
	auth_password(pw, "")) {
	#endif /* USE_PAM */
	/* Authentication with empty password succeeded. */
	log("Login for user %s from %.100s, accepted without authentication.",
	user, get_remote_ipaddr());
	} else {
	/* Loop until the user has been authenticated or the
	connection is closed, do_authloop() returns only if
	authentication is successful */
	do_authloop(pw, user);
	}
	if (pw == NULL)
	fatal("internal error, authentication successful for user '%.100s'", user);

	/* The user has been authenticated and accepted. */
	packet_start(SSH_SMSG_SUCCESS);
	packet_send();
	packet_write_wait();

	#ifdef WITH_AIXAUTHENTICATE
	/* We don't have a pty yet, so just label the line as "ssh" */
	if (loginsuccess(user,get_canonical_hostname(),"ssh",&aixloginmsg) < 0)
	aixloginmsg = NULL;
	#endif /* WITH_AIXAUTHENTICATE */

	/* Perform session preparation. */
	do_authenticated(pw);
	}