auth.c - platform/external/openssh - Gitiles

 /* $OpenBSD: auth.c,v 1.83 2010/01/13 23:47:26 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "includes.h"

 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/param.h>

 #include <netinet/in.h>

 #include <errno.h>
 #include <fcntl.h>
 #ifdef HAVE_PATHS_H
 # include <paths.h>
 #endif
 #include <pwd.h>
 #ifdef HAVE_LOGIN_H
 #include <login.h>
 #endif
 #ifdef USE_SHADOW
 #include <shadow.h>
 #endif
 #ifdef HAVE_LIBGEN_H
 #include <libgen.h>
 #endif
 #include <stdarg.h>
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>

 #include "xmalloc.h"
 #include "match.h"
 #include "groupaccess.h"
 #include "log.h"
 #include "buffer.h"
 #include "servconf.h"
 #include "key.h"
 #include "hostfile.h"
 #include "auth.h"
 #include "auth-options.h"
 #include "canohost.h"
 #include "uidswap.h"
 #include "misc.h"
 #include "packet.h"
 #include "loginrec.h"
 #ifdef GSSAPI
 #include "ssh-gss.h"
 #endif
 #include "monitor_wrap.h"

 /* import */
 extern ServerOptions options;
 extern int use_privsep;
 extern Buffer loginmsg;
 extern struct passwd *privsep_pw;

 /* Debugging messages */
 Buffer auth_debug;
 int auth_debug_init;

 /*
  * Check if the user is allowed to log in via ssh. If user is listed
  * in DenyUsers or one of user's groups is listed in DenyGroups, false
  * will be returned. If AllowUsers isn't empty and user isn't listed
  * there, or if AllowGroups isn't empty and one of user's groups isn't
  * listed there, false will be returned.
  * If the user's shell is not executable, false will be returned.
  * Otherwise true is returned.
  */
 int
 allowed_user(struct passwd * pw)
 {
 	struct stat st;
 	const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL;
 	char *shell, *tmp, *chroot_path;
 	u_int i;
 #ifdef USE_SHADOW
 	struct spwd *spw = NULL;
 #endif

 	/* Shouldn't be called if pw is NULL, but better safe than sorry... */
 	if (!pw || !pw->pw_name)
 		return 0;

 #ifdef USE_SHADOW
 	if (!options.use_pam)
 		spw = getspnam(pw->pw_name);
 #ifdef HAS_SHADOW_EXPIRE
 	if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw))
 		return 0;
 #endif /* HAS_SHADOW_EXPIRE */
 #endif /* USE_SHADOW */

 	/* grab passwd field for locked account check */
 	passwd = pw->pw_passwd;
 #ifdef USE_SHADOW
 	if (spw != NULL)
 #ifdef USE_LIBIAF
 		passwd = get_iaf_password(pw);
 #else
 		passwd = spw->sp_pwdp;
 #endif /* USE_LIBIAF */
 #endif

 	/* check for locked account */
 	if (!options.use_pam && passwd && *passwd) {
 		int locked = 0;

 #ifdef LOCKED_PASSWD_STRING
 		if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0)
 			 locked = 1;
 #endif
 #ifdef LOCKED_PASSWD_PREFIX
 		if (strncmp(passwd, LOCKED_PASSWD_PREFIX,
 		    strlen(LOCKED_PASSWD_PREFIX)) == 0)
 			 locked = 1;
 #endif
 #ifdef LOCKED_PASSWD_SUBSTR
 		if (strstr(passwd, LOCKED_PASSWD_SUBSTR))
 			locked = 1;
 #endif
 #ifdef USE_LIBIAF
 		free(passwd);
 #endif /* USE_LIBIAF */
 		if (locked) {
 			logit("User %.100s not allowed because account is locked",
 			    pw->pw_name);
 			return 0;
 		}
 	}

 	/*
 	 * Get the shell from the password data.  An empty shell field is
 	 * legal, and means /bin/sh.
 	 */
 	shell = xstrdup((pw->pw_shell[0] == '\0') ?
 	    _PATH_BSHELL : pw->pw_shell);

 	/*
 	 * Amend shell if chroot is requested.
 	 */
 	if (options.chroot_directory != NULL &&
 	    strcasecmp(options.chroot_directory, "none") != 0) {
 		tmp = tilde_expand_filename(options.chroot_directory,
 		    pw->pw_uid);
 		chroot_path = percent_expand(tmp, "h", pw->pw_dir,
 		    "u", pw->pw_name, (char *)NULL);
 		xfree(tmp);
 		xasprintf(&tmp, "%s/%s", chroot_path, shell);
 		xfree(shell);
 		shell = tmp;
 		free(chroot_path);
 	}

 	/* deny if shell does not exists or is not executable */
 	if (stat(shell, &st) != 0) {
 		logit("User %.100s not allowed because shell %.100s does not exist",
 		    pw->pw_name, shell);
 		xfree(shell);
 		return 0;
 	}
 	if (S_ISREG(st.st_mode) == 0 ||
 	    (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
 		logit("User %.100s not allowed because shell %.100s is not executable",
 		    pw->pw_name, shell);
 		xfree(shell);
 		return 0;
 	}
 	xfree(shell);

 	if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
 	    options.num_deny_groups > 0 || options.num_allow_groups > 0) {
 		hostname = get_canonical_hostname(options.use_dns);
 		ipaddr = get_remote_ipaddr();
 	}

 	/* Return false if user is listed in DenyUsers */
 	if (options.num_deny_users > 0) {
 		for (i = 0; i < options.num_deny_users; i++)
 			if (match_user(pw->pw_name, hostname, ipaddr,
 			    options.deny_users[i])) {
 				logit("User %.100s from %.100s not allowed "
 				    "because listed in DenyUsers",
 				    pw->pw_name, hostname);
 				return 0;
 			}
 	}
 	/* Return false if AllowUsers isn't empty and user isn't listed there */
 	if (options.num_allow_users > 0) {
 		for (i = 0; i < options.num_allow_users; i++)
 			if (match_user(pw->pw_name, hostname, ipaddr,
 			    options.allow_users[i]))
 				break;
 		/* i < options.num_allow_users iff we break for loop */
 		if (i >= options.num_allow_users) {
 			logit("User %.100s from %.100s not allowed because "
 			    "not listed in AllowUsers", pw->pw_name, hostname);
 			return 0;
 		}
 	}
 	if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
 		/* Get the user's group access list (primary and supplementary) */
 		if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
 			logit("User %.100s from %.100s not allowed because "
 			    "not in any group", pw->pw_name, hostname);
 			return 0;
 		}

 		/* Return false if one of user's groups is listed in DenyGroups */
 		if (options.num_deny_groups > 0)
 			if (ga_match(options.deny_groups,
 			    options.num_deny_groups)) {
 				ga_free();
 				logit("User %.100s from %.100s not allowed "
 				    "because a group is listed in DenyGroups",
 				    pw->pw_name, hostname);
 				return 0;
 			}
 		/*
 		 * Return false if AllowGroups isn't empty and one of user's groups
 		 * isn't listed there
 		 */
 		if (options.num_allow_groups > 0)
 			if (!ga_match(options.allow_groups,
 			    options.num_allow_groups)) {
 				ga_free();
 				logit("User %.100s from %.100s not allowed "
 				    "because none of user's groups are listed "
 				    "in AllowGroups", pw->pw_name, hostname);
 				return 0;
 			}
 		ga_free();
 	}

 #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER
 	if (!sys_auth_allowed_user(pw, &loginmsg))
 		return 0;
 #endif

 	/* We found no reason not to let this user try to log on... */
 	return 1;
 }

 void
 auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
 {
 	void (*authlog) (const char *fmt,...) = verbose;
 	char *authmsg;

 	if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
 		return;

 	/* Raise logging level */
 	if (authenticated == 1 ||
 	    !authctxt->valid ||
 	    authctxt->failures >= options.max_authtries / 2 ||
 	    strcmp(method, "password") == 0)
 		authlog = logit;

 	if (authctxt->postponed)
 		authmsg = "Postponed";
 	else
 		authmsg = authenticated ? "Accepted" : "Failed";

 	authlog("%s %s for %s%.100s from %.200s port %d%s",
 	    authmsg,
 	    method,
 	    authctxt->valid ? "" : "invalid user ",
 	    authctxt->user,
 	    get_remote_ipaddr(),
 	    get_remote_port(),
 	    info);

 #ifdef CUSTOM_FAILED_LOGIN
 	if (authenticated == 0 && !authctxt->postponed &&
 	    (strcmp(method, "password") == 0 ||
 	    strncmp(method, "keyboard-interactive", 20) == 0 ||
 	    strcmp(method, "challenge-response") == 0))
 		record_failed_login(authctxt->user,
 		    get_canonical_hostname(options.use_dns), "ssh");
 # ifdef WITH_AIXAUTHENTICATE
 	if (authenticated)
 		sys_auth_record_login(authctxt->user,
 		    get_canonical_hostname(options.use_dns), "ssh", &loginmsg);
 # endif
 #endif
 #ifdef SSH_AUDIT_EVENTS
 	if (authenticated == 0 && !authctxt->postponed)
 		audit_event(audit_classify_auth(method));
 #endif
 }

 /*
  * Check whether root logins are disallowed.
  */
 int
 auth_root_allowed(char *method)
 {
 	switch (options.permit_root_login) {
 	case PERMIT_YES:
 		return 1;
 	case PERMIT_NO_PASSWD:
 		if (strcmp(method, "password") != 0)
 			return 1;
 		break;
 	case PERMIT_FORCED_ONLY:
 		if (forced_command) {
 			logit("Root login accepted for forced command.");
 			return 1;
 		}
 		break;
 	}
 	logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
 	return 0;
 }


 /*
  * Given a template and a passwd structure, build a filename
  * by substituting % tokenised options. Currently, %% becomes '%',
  * %h becomes the home directory and %u the username.
  *
  * This returns a buffer allocated by xmalloc.
  */
 static char *
 expand_authorized_keys(const char *filename, struct passwd *pw)
 {
 	char *file, ret[MAXPATHLEN];
 	int i;

 	file = percent_expand(filename, "h", pw->pw_dir,
 	    "u", pw->pw_name, (char *)NULL);

 	/*
 	 * Ensure that filename starts anchored. If not, be backward
 	 * compatible and prepend the '%h/'
 	 */
 	if (*file == '/')
 		return (file);

 	i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
 	if (i < 0 || (size_t)i >= sizeof(ret))
 		fatal("expand_authorized_keys: path too long");
 	xfree(file);
 	return (xstrdup(ret));
 }

 char *
 authorized_keys_file(struct passwd *pw)
 {
 	return expand_authorized_keys(options.authorized_keys_file, pw);
 }

 char *
 authorized_keys_file2(struct passwd *pw)
 {
 	return expand_authorized_keys(options.authorized_keys_file2, pw);
 }

 /* return ok if key exists in sysfile or userfile */
 HostStatus
 check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
     const char *sysfile, const char *userfile)
 {
 	Key *found;
 	char *user_hostfile;
 	struct stat st;
 	HostStatus host_status;

 	/* Check if we know the host and its host key. */
 	found = key_new(key->type);
 	host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);

 	if (host_status != HOST_OK && userfile != NULL) {
 		user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
 		if (options.strict_modes &&
 		    (stat(user_hostfile, &st) == 0) &&
 		    ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
 		    (st.st_mode & 022) != 0)) {
 			logit("Authentication refused for %.100s: "
 			    "bad owner or modes for %.200s",
 			    pw->pw_name, user_hostfile);
 		} else {
 			temporarily_use_uid(pw);
 			host_status = check_host_in_hostfile(user_hostfile,
 			    host, key, found, NULL);
 			restore_uid();
 		}
 		xfree(user_hostfile);
 	}
 	key_free(found);

 	debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
 	    "ok" : "not found", host);
 	return host_status;
 }


 /*
  * Check a given file for security. This is defined as all components
  * of the path to the file must be owned by either the owner of
  * of the file or root and no directories must be group or world writable.
  *
  * XXX Should any specific check be done for sym links ?
  *
  * Takes an open file descriptor, the file name, a uid and and
  * error buffer plus max size as arguments.
  *
  * Returns 0 on success and -1 on failure
  */
 static int
 secure_filename(FILE *f, const char *file, struct passwd *pw,
     char *err, size_t errlen)
 {
 	uid_t uid = pw->pw_uid;
 	char buf[MAXPATHLEN], homedir[MAXPATHLEN];
 	char *cp;
 	int comparehome = 0;
 	struct stat st;

 	if (realpath(file, buf) == NULL) {
 		snprintf(err, errlen, "realpath %s failed: %s", file,
 		    strerror(errno));
 		return -1;
 	}
 	if (realpath(pw->pw_dir, homedir) != NULL)
 		comparehome = 1;

 	/* check the open file to avoid races */
 	if (fstat(fileno(f), &st) < 0 ||
 	    (st.st_uid != 0 && st.st_uid != uid) ||
 	    (st.st_mode & 022) != 0) {
 		snprintf(err, errlen, "bad ownership or modes for file %s",
 		    buf);
 		return -1;
 	}

 	/* for each component of the canonical path, walking upwards */
 	for (;;) {
 		if ((cp = dirname(buf)) == NULL) {
 			snprintf(err, errlen, "dirname() failed");
 			return -1;
 		}
 		strlcpy(buf, cp, sizeof(buf));

 		debug3("secure_filename: checking '%s'", buf);
 		if (stat(buf, &st) < 0 ||
 		    (st.st_uid != 0 && st.st_uid != uid) ||
 		    (st.st_mode & 022) != 0) {
 			snprintf(err, errlen,
 			    "bad ownership or modes for directory %s", buf);
 			return -1;
 		}

 		/* If are past the homedir then we can stop */
 		if (comparehome && strcmp(homedir, buf) == 0) {
 			debug3("secure_filename: terminating check at '%s'",
 			    buf);
 			break;
 		}
 		/*
 		 * dirname should always complete with a "/" path,
 		 * but we can be paranoid and check for "." too
 		 */
 		if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
 			break;
 	}
 	return 0;
 }

 FILE *
 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
 {
 	char line[1024];
 	struct stat st;
 	int fd;
 	FILE *f;

 	/*
 	 * Open the file containing the authorized keys
 	 * Fail quietly if file does not exist
 	 */
 	if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) {
 		if (errno != ENOENT)
 			debug("Could not open keyfile '%s': %s", file,
 			   strerror(errno));
 		return NULL;
 	}

 	if (fstat(fd, &st) < 0) {
 		close(fd);
 		return NULL;
 	}
 	if (!S_ISREG(st.st_mode)) {
 		logit("User %s authorized keys %s is not a regular file",
 		    pw->pw_name, file);
 		close(fd);
 		return NULL;
 	}
 	unset_nonblock(fd);
 	if ((f = fdopen(fd, "r")) == NULL) {
 		close(fd);
 		return NULL;
 	}
 	if (options.strict_modes &&
 	    secure_filename(f, file, pw, line, sizeof(line)) != 0) {
 		fclose(f);
 		logit("Authentication refused: %s", line);
 		return NULL;
 	}

 	return f;
 }

 struct passwd *
 getpwnamallow(const char *user)
 {
 #ifdef HAVE_LOGIN_CAP
 	extern login_cap_t *lc;
 #ifdef BSD_AUTH
 	auth_session_t *as;
 #endif
 #endif
 	struct passwd *pw;

 	parse_server_match_config(&options, user,
 	    get_canonical_hostname(options.use_dns), get_remote_ipaddr());

 	pw = getpwnam(user);
 	if (pw == NULL) {
 		logit("Invalid user %.100s from %.100s",
 		    user, get_remote_ipaddr());
 #ifdef CUSTOM_FAILED_LOGIN
 		record_failed_login(user,
 		    get_canonical_hostname(options.use_dns), "ssh");
 #endif
 #ifdef SSH_AUDIT_EVENTS
 		audit_event(SSH_INVALID_USER);
 #endif /* SSH_AUDIT_EVENTS */
 		return (NULL);
 	}
 	if (!allowed_user(pw))
 		return (NULL);
 #ifdef HAVE_LOGIN_CAP
 	if ((lc = login_getclass(pw->pw_class)) == NULL) {
 		debug("unable to get login class: %s", user);
 		return (NULL);
 	}
 #ifdef BSD_AUTH
 	if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
 	    auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
 		debug("Approval failure for %s", user);
 		pw = NULL;
 	}
 	if (as != NULL)
 		auth_close(as);
 #endif
 #endif
 	if (pw != NULL)
 		return (pwcopy(pw));
 	return (NULL);
 }

 void
 auth_debug_add(const char *fmt,...)
 {
 	char buf[1024];
 	va_list args;

 	if (!auth_debug_init)
 		return;

 	va_start(args, fmt);
 	vsnprintf(buf, sizeof(buf), fmt, args);
 	va_end(args);
 	buffer_put_cstring(&auth_debug, buf);
 }

 void
 auth_debug_send(void)
 {
 	char *msg;

 	if (!auth_debug_init)
 		return;
 	while (buffer_len(&auth_debug)) {
 		msg = buffer_get_string(&auth_debug, NULL);
 		packet_send_debug("%s", msg);
 		xfree(msg);
 	}
 }

 void
 auth_debug_reset(void)
 {
 	if (auth_debug_init)
 		buffer_clear(&auth_debug);
 	else {
 		buffer_init(&auth_debug);
 		auth_debug_init = 1;
 	}
 }

 struct passwd *
 fakepw(void)
 {
 	static struct passwd fake;

 	memset(&fake, 0, sizeof(fake));
 	fake.pw_name = "NOUSER";
 	fake.pw_passwd =
 	    "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
 	fake.pw_gecos = "NOUSER";
 	fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid;
 	fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid;
 #ifdef HAVE_PW_CLASS_IN_PASSWD
 	fake.pw_class = "";
 #endif
 	fake.pw_dir = "/nonexist";
 	fake.pw_shell = "/nonexist";

 	return (&fake);
 }
	/* $OpenBSD: auth.c,v 1.83 2010/01/13 23:47:26 djm Exp $ */
	/*
	* Copyright (c) 2000 Markus Friedl. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "includes.h"

	#include <sys/types.h>
	#include <sys/stat.h>
	#include <sys/param.h>

	#include <netinet/in.h>

	#include <errno.h>
	#include <fcntl.h>
	#ifdef HAVE_PATHS_H
	# include <paths.h>
	#endif
	#include <pwd.h>
	#ifdef HAVE_LOGIN_H
	#include <login.h>
	#endif
	#ifdef USE_SHADOW
	#include <shadow.h>
	#endif
	#ifdef HAVE_LIBGEN_H
	#include <libgen.h>
	#endif
	#include <stdarg.h>
	#include <stdio.h>
	#include <string.h>
	#include <unistd.h>

	#include "xmalloc.h"
	#include "match.h"
	#include "groupaccess.h"
	#include "log.h"
	#include "buffer.h"
	#include "servconf.h"
	#include "key.h"
	#include "hostfile.h"
	#include "auth.h"
	#include "auth-options.h"
	#include "canohost.h"
	#include "uidswap.h"
	#include "misc.h"
	#include "packet.h"
	#include "loginrec.h"
	#ifdef GSSAPI
	#include "ssh-gss.h"
	#endif
	#include "monitor_wrap.h"

	/* import */
	extern ServerOptions options;
	extern int use_privsep;
	extern Buffer loginmsg;
	extern struct passwd *privsep_pw;

	/* Debugging messages */
	Buffer auth_debug;
	int auth_debug_init;

	/*
	* Check if the user is allowed to log in via ssh. If user is listed
	* in DenyUsers or one of user's groups is listed in DenyGroups, false
	* will be returned. If AllowUsers isn't empty and user isn't listed
	* there, or if AllowGroups isn't empty and one of user's groups isn't
	* listed there, false will be returned.
	* If the user's shell is not executable, false will be returned.
	* Otherwise true is returned.
	*/
	int
	allowed_user(struct passwd * pw)
	{
	struct stat st;
	const char hostname = NULL, ipaddr = NULL, *passwd = NULL;
	char shell, tmp, *chroot_path;
	u_int i;
	#ifdef USE_SHADOW
	struct spwd *spw = NULL;
	#endif

	/* Shouldn't be called if pw is NULL, but better safe than sorry... */
	if (!pw \|\| !pw->pw_name)
	return 0;

	#ifdef USE_SHADOW
	if (!options.use_pam)
	spw = getspnam(pw->pw_name);
	#ifdef HAS_SHADOW_EXPIRE
	if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw))
	return 0;
	#endif /* HAS_SHADOW_EXPIRE */
	#endif /* USE_SHADOW */

	/* grab passwd field for locked account check */
	passwd = pw->pw_passwd;
	#ifdef USE_SHADOW
	if (spw != NULL)
	#ifdef USE_LIBIAF
	passwd = get_iaf_password(pw);
	#else
	passwd = spw->sp_pwdp;
	#endif /* USE_LIBIAF */
	#endif

	/* check for locked account */
	if (!options.use_pam && passwd && *passwd) {
	int locked = 0;

	#ifdef LOCKED_PASSWD_STRING
	if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0)
	locked = 1;
	#endif
	#ifdef LOCKED_PASSWD_PREFIX
	if (strncmp(passwd, LOCKED_PASSWD_PREFIX,
	strlen(LOCKED_PASSWD_PREFIX)) == 0)
	locked = 1;
	#endif
	#ifdef LOCKED_PASSWD_SUBSTR
	if (strstr(passwd, LOCKED_PASSWD_SUBSTR))
	locked = 1;
	#endif
	#ifdef USE_LIBIAF
	free(passwd);
	#endif /* USE_LIBIAF */
	if (locked) {
	logit("User %.100s not allowed because account is locked",
	pw->pw_name);
	return 0;
	}
	}

	/*
	* Get the shell from the password data. An empty shell field is
	* legal, and means /bin/sh.
	*/
	shell = xstrdup((pw->pw_shell[0] == '\0') ?
	_PATH_BSHELL : pw->pw_shell);

	/*
	* Amend shell if chroot is requested.
	*/
	if (options.chroot_directory != NULL &&
	strcasecmp(options.chroot_directory, "none") != 0) {
	tmp = tilde_expand_filename(options.chroot_directory,
	pw->pw_uid);
	chroot_path = percent_expand(tmp, "h", pw->pw_dir,
	"u", pw->pw_name, (char *)NULL);
	xfree(tmp);
	xasprintf(&tmp, "%s/%s", chroot_path, shell);
	xfree(shell);
	shell = tmp;
	free(chroot_path);
	}

	/* deny if shell does not exists or is not executable */
	if (stat(shell, &st) != 0) {
	logit("User %.100s not allowed because shell %.100s does not exist",
	pw->pw_name, shell);
	xfree(shell);
	return 0;
	}
	if (S_ISREG(st.st_mode) == 0 \|\|
	(st.st_mode & (S_IXOTH\|S_IXUSR\|S_IXGRP)) == 0) {
	logit("User %.100s not allowed because shell %.100s is not executable",
	pw->pw_name, shell);
	xfree(shell);
	return 0;
	}
	xfree(shell);

	if (options.num_deny_users > 0 \|\| options.num_allow_users > 0 \|\|
	options.num_deny_groups > 0 \|\| options.num_allow_groups > 0) {
	hostname = get_canonical_hostname(options.use_dns);
	ipaddr = get_remote_ipaddr();
	}

	/* Return false if user is listed in DenyUsers */
	if (options.num_deny_users > 0) {
	for (i = 0; i < options.num_deny_users; i++)
	if (match_user(pw->pw_name, hostname, ipaddr,
	options.deny_users[i])) {
	logit("User %.100s from %.100s not allowed "
	"because listed in DenyUsers",
	pw->pw_name, hostname);
	return 0;
	}
	}
	/* Return false if AllowUsers isn't empty and user isn't listed there */
	if (options.num_allow_users > 0) {
	for (i = 0; i < options.num_allow_users; i++)
	if (match_user(pw->pw_name, hostname, ipaddr,
	options.allow_users[i]))
	break;
	/* i < options.num_allow_users iff we break for loop */
	if (i >= options.num_allow_users) {
	logit("User %.100s from %.100s not allowed because "
	"not listed in AllowUsers", pw->pw_name, hostname);
	return 0;
	}
	}
	if (options.num_deny_groups > 0 \|\| options.num_allow_groups > 0) {
	/* Get the user's group access list (primary and supplementary) */
	if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
	logit("User %.100s from %.100s not allowed because "
	"not in any group", pw->pw_name, hostname);
	return 0;
	}

	/* Return false if one of user's groups is listed in DenyGroups */
	if (options.num_deny_groups > 0)
	if (ga_match(options.deny_groups,
	options.num_deny_groups)) {
	ga_free();
	logit("User %.100s from %.100s not allowed "
	"because a group is listed in DenyGroups",
	pw->pw_name, hostname);
	return 0;
	}
	/*
	* Return false if AllowGroups isn't empty and one of user's groups
	* isn't listed there
	*/
	if (options.num_allow_groups > 0)
	if (!ga_match(options.allow_groups,
	options.num_allow_groups)) {
	ga_free();
	logit("User %.100s from %.100s not allowed "
	"because none of user's groups are listed "
	"in AllowGroups", pw->pw_name, hostname);
	return 0;
	}
	ga_free();
	}

	#ifdef CUSTOM_SYS_AUTH_ALLOWED_USER
	if (!sys_auth_allowed_user(pw, &loginmsg))
	return 0;
	#endif

	/* We found no reason not to let this user try to log on... */
	return 1;
	}

	void
	auth_log(Authctxt authctxt, int authenticated, char method, char *info)
	{
	void (authlog) (const char fmt,...) = verbose;
	char *authmsg;

	if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
	return;

	/* Raise logging level */
	if (authenticated == 1 \|\|
	!authctxt->valid \|\|
	authctxt->failures >= options.max_authtries / 2 \|\|
	strcmp(method, "password") == 0)
	authlog = logit;

	if (authctxt->postponed)
	authmsg = "Postponed";
	else
	authmsg = authenticated ? "Accepted" : "Failed";

	authlog("%s %s for %s%.100s from %.200s port %d%s",
	authmsg,
	method,
	authctxt->valid ? "" : "invalid user ",
	authctxt->user,
	get_remote_ipaddr(),
	get_remote_port(),
	info);

	#ifdef CUSTOM_FAILED_LOGIN
	if (authenticated == 0 && !authctxt->postponed &&
	(strcmp(method, "password") == 0 \|\|
	strncmp(method, "keyboard-interactive", 20) == 0 \|\|
	strcmp(method, "challenge-response") == 0))
	record_failed_login(authctxt->user,
	get_canonical_hostname(options.use_dns), "ssh");
	# ifdef WITH_AIXAUTHENTICATE
	if (authenticated)
	sys_auth_record_login(authctxt->user,
	get_canonical_hostname(options.use_dns), "ssh", &loginmsg);
	# endif
	#endif
	#ifdef SSH_AUDIT_EVENTS
	if (authenticated == 0 && !authctxt->postponed)
	audit_event(audit_classify_auth(method));
	#endif
	}

	/*
	* Check whether root logins are disallowed.
	*/
	int
	auth_root_allowed(char *method)
	{
	switch (options.permit_root_login) {
	case PERMIT_YES:
	return 1;
	case PERMIT_NO_PASSWD:
	if (strcmp(method, "password") != 0)
	return 1;
	break;
	case PERMIT_FORCED_ONLY:
	if (forced_command) {
	logit("Root login accepted for forced command.");
	return 1;
	}
	break;
	}
	logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
	return 0;
	}


	/*
	* Given a template and a passwd structure, build a filename
	* by substituting % tokenised options. Currently, %% becomes '%',
	* %h becomes the home directory and %u the username.
	*
	* This returns a buffer allocated by xmalloc.
	*/
	static char *
	expand_authorized_keys(const char filename, struct passwd pw)
	{
	char *file, ret[MAXPATHLEN];
	int i;

	file = percent_expand(filename, "h", pw->pw_dir,
	"u", pw->pw_name, (char *)NULL);

	/*
	* Ensure that filename starts anchored. If not, be backward
	* compatible and prepend the '%h/'
	*/
	if (*file == '/')
	return (file);

	i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
	if (i < 0 \|\| (size_t)i >= sizeof(ret))
	fatal("expand_authorized_keys: path too long");
	xfree(file);
	return (xstrdup(ret));
	}

	char *
	authorized_keys_file(struct passwd *pw)
	{
	return expand_authorized_keys(options.authorized_keys_file, pw);
	}

	char *
	authorized_keys_file2(struct passwd *pw)
	{
	return expand_authorized_keys(options.authorized_keys_file2, pw);
	}

	/* return ok if key exists in sysfile or userfile */
	HostStatus
	check_key_in_hostfiles(struct passwd pw, Key key, const char *host,
	const char sysfile, const char userfile)
	{
	Key *found;
	char *user_hostfile;
	struct stat st;
	HostStatus host_status;

	/* Check if we know the host and its host key. */
	found = key_new(key->type);
	host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);

	if (host_status != HOST_OK && userfile != NULL) {
	user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
	if (options.strict_modes &&
	(stat(user_hostfile, &st) == 0) &&
	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
	(st.st_mode & 022) != 0)) {
	logit("Authentication refused for %.100s: "
	"bad owner or modes for %.200s",
	pw->pw_name, user_hostfile);
	} else {
	temporarily_use_uid(pw);
	host_status = check_host_in_hostfile(user_hostfile,
	host, key, found, NULL);
	restore_uid();
	}
	xfree(user_hostfile);
	}
	key_free(found);

	debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
	"ok" : "not found", host);
	return host_status;
	}


	/*
	* Check a given file for security. This is defined as all components
	* of the path to the file must be owned by either the owner of
	* of the file or root and no directories must be group or world writable.
	*
	* XXX Should any specific check be done for sym links ?
	*
	* Takes an open file descriptor, the file name, a uid and and
	* error buffer plus max size as arguments.
	*
	* Returns 0 on success and -1 on failure
	*/
	static int
	secure_filename(FILE f, const char file, struct passwd *pw,
	char *err, size_t errlen)
	{
	uid_t uid = pw->pw_uid;
	char buf[MAXPATHLEN], homedir[MAXPATHLEN];
	char *cp;
	int comparehome = 0;
	struct stat st;

	if (realpath(file, buf) == NULL) {
	snprintf(err, errlen, "realpath %s failed: %s", file,
	strerror(errno));
	return -1;
	}
	if (realpath(pw->pw_dir, homedir) != NULL)
	comparehome = 1;

	/* check the open file to avoid races */
	if (fstat(fileno(f), &st) < 0 \|\|
	(st.st_uid != 0 && st.st_uid != uid) \|\|
	(st.st_mode & 022) != 0) {
	snprintf(err, errlen, "bad ownership or modes for file %s",
	buf);
	return -1;
	}

	/* for each component of the canonical path, walking upwards */
	for (;;) {
	if ((cp = dirname(buf)) == NULL) {
	snprintf(err, errlen, "dirname() failed");
	return -1;
	}
	strlcpy(buf, cp, sizeof(buf));

	debug3("secure_filename: checking '%s'", buf);
	if (stat(buf, &st) < 0 \|\|
	(st.st_uid != 0 && st.st_uid != uid) \|\|
	(st.st_mode & 022) != 0) {
	snprintf(err, errlen,
	"bad ownership or modes for directory %s", buf);
	return -1;
	}

	/* If are past the homedir then we can stop */
	if (comparehome && strcmp(homedir, buf) == 0) {
	debug3("secure_filename: terminating check at '%s'",
	buf);
	break;
	}
	/*
	* dirname should always complete with a "/" path,
	* but we can be paranoid and check for "." too
	*/
	if ((strcmp("/", buf) == 0) \|\| (strcmp(".", buf) == 0))
	break;
	}
	return 0;
	}

	FILE *
	auth_openkeyfile(const char file, struct passwd pw, int strict_modes)
	{
	char line[1024];
	struct stat st;
	int fd;
	FILE *f;

	/*
	* Open the file containing the authorized keys
	* Fail quietly if file does not exist
	*/
	if ((fd = open(file, O_RDONLY\|O_NONBLOCK)) == -1) {
	if (errno != ENOENT)
	debug("Could not open keyfile '%s': %s", file,
	strerror(errno));
	return NULL;
	}

	if (fstat(fd, &st) < 0) {
	close(fd);
	return NULL;
	}
	if (!S_ISREG(st.st_mode)) {
	logit("User %s authorized keys %s is not a regular file",
	pw->pw_name, file);
	close(fd);
	return NULL;
	}
	unset_nonblock(fd);
	if ((f = fdopen(fd, "r")) == NULL) {
	close(fd);
	return NULL;
	}
	if (options.strict_modes &&
	secure_filename(f, file, pw, line, sizeof(line)) != 0) {
	fclose(f);
	logit("Authentication refused: %s", line);
	return NULL;
	}

	return f;
	}

	struct passwd *
	getpwnamallow(const char *user)
	{
	#ifdef HAVE_LOGIN_CAP
	extern login_cap_t *lc;
	#ifdef BSD_AUTH
	auth_session_t *as;
	#endif
	#endif
	struct passwd *pw;

	parse_server_match_config(&options, user,
	get_canonical_hostname(options.use_dns), get_remote_ipaddr());

	pw = getpwnam(user);
	if (pw == NULL) {
	logit("Invalid user %.100s from %.100s",
	user, get_remote_ipaddr());
	#ifdef CUSTOM_FAILED_LOGIN
	record_failed_login(user,
	get_canonical_hostname(options.use_dns), "ssh");
	#endif
	#ifdef SSH_AUDIT_EVENTS
	audit_event(SSH_INVALID_USER);
	#endif /* SSH_AUDIT_EVENTS */
	return (NULL);
	}
	if (!allowed_user(pw))
	return (NULL);
	#ifdef HAVE_LOGIN_CAP
	if ((lc = login_getclass(pw->pw_class)) == NULL) {
	debug("unable to get login class: %s", user);
	return (NULL);
	}
	#ifdef BSD_AUTH
	if ((as = auth_open()) == NULL \|\| auth_setpwd(as, pw) != 0 \|\|
	auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
	debug("Approval failure for %s", user);
	pw = NULL;
	}
	if (as != NULL)
	auth_close(as);
	#endif
	#endif
	if (pw != NULL)
	return (pwcopy(pw));
	return (NULL);
	}

	void
	auth_debug_add(const char *fmt,...)
	{
	char buf[1024];
	va_list args;

	if (!auth_debug_init)
	return;

	va_start(args, fmt);
	vsnprintf(buf, sizeof(buf), fmt, args);
	va_end(args);
	buffer_put_cstring(&auth_debug, buf);
	}

	void
	auth_debug_send(void)
	{
	char *msg;

	if (!auth_debug_init)
	return;
	while (buffer_len(&auth_debug)) {
	msg = buffer_get_string(&auth_debug, NULL);
	packet_send_debug("%s", msg);
	xfree(msg);
	}
	}

	void
	auth_debug_reset(void)
	{
	if (auth_debug_init)
	buffer_clear(&auth_debug);
	else {
	buffer_init(&auth_debug);
	auth_debug_init = 1;
	}
	}

	struct passwd *
	fakepw(void)
	{
	static struct passwd fake;

	memset(&fake, 0, sizeof(fake));
	fake.pw_name = "NOUSER";
	fake.pw_passwd =
	"$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
	fake.pw_gecos = "NOUSER";
	fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid;
	fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid;
	#ifdef HAVE_PW_CLASS_IN_PASSWD
	fake.pw_class = "";
	#endif
	fake.pw_dir = "/nonexist";
	fake.pw_shell = "/nonexist";

	return (&fake);
	}