auth.c - security/openssh-library - Rivoreo Source Code Repositories

 /*
  * 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"
 RCSID("$OpenBSD: auth.c,v 1.48 2003/06/02 09:17:34 markus Exp $");

 #ifdef HAVE_LOGIN_H
 #include <login.h>
 #endif
 #if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW)
 #include <shadow.h>
 #endif /* defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) */

 #ifdef HAVE_LIBGEN_H
 #include <libgen.h>
 #endif

 #include "xmalloc.h"
 #include "match.h"
 #include "groupaccess.h"
 #include "log.h"
 #include "servconf.h"
 #include "auth.h"
 #include "auth-options.h"
 #include "canohost.h"
 #include "buffer.h"
 #include "bufaux.h"
 #include "uidswap.h"
 #include "tildexpand.h"
 #include "misc.h"
 #include "bufaux.h"
 #include "packet.h"

 /* import */
 extern ServerOptions options;
 extern Buffer loginmsg;

 /* 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;
 	char *shell;
 	int i;
 #if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) && \
     defined(HAS_SHADOW_EXPIRE)
 	struct spwd *spw;
 	time_t today;
 #endif

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

 #if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) && \
     defined(HAS_SHADOW_EXPIRE)
 #define	DAY		(24L * 60 * 60) /* 1 day in seconds */
 	if (!options.use_pam && (spw = getspnam(pw->pw_name)) != NULL) {
 		today = time(NULL) / DAY;
 		debug3("allowed_user: today %d sp_expire %d sp_lstchg %d"
 		    " sp_max %d", (int)today, (int)spw->sp_expire,
 		    (int)spw->sp_lstchg, (int)spw->sp_max);

 		/*
 		 * We assume account and password expiration occurs the
 		 * day after the day specified.
 		 */
 		if (spw->sp_expire != -1 && today > spw->sp_expire) {
 			logit("Account %.100s has expired", pw->pw_name);
 			return 0;
 		}

 		if (spw->sp_lstchg == 0) {
 			logit("User %.100s password has expired (root forced)",
 			    pw->pw_name);
 			return 0;
 		}

 		if (spw->sp_max != -1 &&
 		    today > spw->sp_lstchg + spw->sp_max) {
 			logit("User %.100s password has expired (password aged)",
 			    pw->pw_name);
 			return 0;
 		}
 	}
 #endif

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

 	/* 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);
 		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);
 		return 0;
 	}

 	if (options.num_deny_users > 0 || options.num_allow_users > 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 not allowed because listed in DenyUsers",
 				    pw->pw_name);
 				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 not allowed because not listed in AllowUsers",
 			    pw->pw_name);
 			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 not allowed because not in any group",
 			    pw->pw_name);
 			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 not allowed because a group is listed in DenyGroups",
 				    pw->pw_name);
 				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 not allowed because none of user's groups are listed in AllowGroups",
 				    pw->pw_name);
 				return 0;
 			}
 		ga_free();
 	}

 #ifdef WITH_AIXAUTHENTICATE
 	/*
 	 * Don't check loginrestrictions() for root account (use
 	 * PermitRootLogin to control logins via ssh), or if running as
 	 * non-root user (since loginrestrictions will always fail).
 	 */
 	if ((pw->pw_uid != 0) && (geteuid() == 0)) {
 		char *msg;

 	   	if (loginrestrictions(pw->pw_name, S_RLOGIN, NULL, &msg) != 0) {
 			int loginrestrict_errno = errno;

 			if (msg && *msg) {
 				buffer_append(&loginmsg, msg, strlen(msg));
 				aix_remove_embedded_newlines(msg);
 				logit("Login restricted for %s: %.100s",
 				    pw->pw_name, msg);
 			}
 			/* Don't fail if /etc/nologin  set */
 		    	if (!(loginrestrict_errno == EPERM &&
 			    stat(_PATH_NOLOGIN, &st) == 0))
 				return 0;
 		}
 	}
 #endif /* WITH_AIXAUTHENTICATE */

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

 Authctxt *
 authctxt_new(void)
 {
 	Authctxt *authctxt = xmalloc(sizeof(*authctxt));
 	memset(authctxt, 0, sizeof(*authctxt));
 	return authctxt;
 }

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

 	/* Raise logging level */
 	if (authenticated == 1 ||
 	    !authctxt->valid ||
 	    authctxt->failures >= AUTH_FAIL_LOG ||
 	    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 ? "" : "illegal user ",
 	    authctxt->user,
 	    get_remote_ipaddr(),
 	    get_remote_port(),
 	    info);

 #ifdef CUSTOM_FAILED_LOGIN
 	if (authenticated == 0 && strcmp(method, "password") == 0)
 		record_failed_login(authctxt->user, "ssh");
 #endif
 }

 /*
  * Check whether root logins are disallowed.
  */
 int
 auth_root_allowed(char *method)
 {
 	switch (options.permit_root_login) {
 	case PERMIT_YES:
 		return 1;
 		break;
 	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.
  */
 char *
 expand_filename(const char *filename, struct passwd *pw)
 {
 	Buffer buffer;
 	char *file;
 	const char *cp;

 	/*
 	 * Build the filename string in the buffer by making the appropriate
 	 * substitutions to the given file name.
 	 */
 	buffer_init(&buffer);
 	for (cp = filename; *cp; cp++) {
 		if (cp[0] == '%' && cp[1] == '%') {
 			buffer_append(&buffer, "%", 1);
 			cp++;
 			continue;
 		}
 		if (cp[0] == '%' && cp[1] == 'h') {
 			buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir));
 			cp++;
 			continue;
 		}
 		if (cp[0] == '%' && cp[1] == 'u') {
 			buffer_append(&buffer, pw->pw_name,
 			    strlen(pw->pw_name));
 			cp++;
 			continue;
 		}
 		buffer_append(&buffer, cp, 1);
 	}
 	buffer_append(&buffer, "\0", 1);

 	/*
 	 * Ensure that filename starts anchored. If not, be backward
 	 * compatible and prepend the '%h/'
 	 */
 	file = xmalloc(MAXPATHLEN);
 	cp = buffer_ptr(&buffer);
 	if (*cp != '/')
 		snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp);
 	else
 		strlcpy(file, cp, MAXPATHLEN);

 	buffer_free(&buffer);
 	return file;
 }

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

 char *
 authorized_keys_file2(struct passwd *pw)
 {
 	return expand_filename(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
  */
 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 passed 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;
 }

 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;

 	pw = getpwnam(user);
 	if (pw == NULL) {
 		logit("Illegal user %.100s from %.100s",
 		    user, get_remote_ipaddr());
 #ifdef CUSTOM_FAILED_LOGIN
 		record_failed_login(user, "ssh");
 #endif
 		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;
 	}
 }
	/*
	* 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"
	RCSID("$OpenBSD: auth.c,v 1.48 2003/06/02 09:17:34 markus Exp $");

	#ifdef HAVE_LOGIN_H
	#include <login.h>
	#endif
	#if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW)
	#include <shadow.h>
	#endif /* defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) */

	#ifdef HAVE_LIBGEN_H
	#include <libgen.h>
	#endif

	#include "xmalloc.h"
	#include "match.h"
	#include "groupaccess.h"
	#include "log.h"
	#include "servconf.h"
	#include "auth.h"
	#include "auth-options.h"
	#include "canohost.h"
	#include "buffer.h"
	#include "bufaux.h"
	#include "uidswap.h"
	#include "tildexpand.h"
	#include "misc.h"
	#include "bufaux.h"
	#include "packet.h"

	/* import */
	extern ServerOptions options;
	extern Buffer loginmsg;

	/* 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;
	char *shell;
	int i;
	#if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) && \
	defined(HAS_SHADOW_EXPIRE)
	struct spwd *spw;
	time_t today;
	#endif

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

	#if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) && \
	defined(HAS_SHADOW_EXPIRE)
	#define DAY (24L * 60 * 60) /* 1 day in seconds */
	if (!options.use_pam && (spw = getspnam(pw->pw_name)) != NULL) {
	today = time(NULL) / DAY;
	debug3("allowed_user: today %d sp_expire %d sp_lstchg %d"
	" sp_max %d", (int)today, (int)spw->sp_expire,
	(int)spw->sp_lstchg, (int)spw->sp_max);

	/*
	* We assume account and password expiration occurs the
	* day after the day specified.
	*/
	if (spw->sp_expire != -1 && today > spw->sp_expire) {
	logit("Account %.100s has expired", pw->pw_name);
	return 0;
	}

	if (spw->sp_lstchg == 0) {
	logit("User %.100s password has expired (root forced)",
	pw->pw_name);
	return 0;
	}

	if (spw->sp_max != -1 &&
	today > spw->sp_lstchg + spw->sp_max) {
	logit("User %.100s password has expired (password aged)",
	pw->pw_name);
	return 0;
	}
	}
	#endif

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

	/* 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);
	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);
	return 0;
	}

	if (options.num_deny_users > 0 \|\| options.num_allow_users > 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 not allowed because listed in DenyUsers",
	pw->pw_name);
	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 not allowed because not listed in AllowUsers",
	pw->pw_name);
	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 not allowed because not in any group",
	pw->pw_name);
	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 not allowed because a group is listed in DenyGroups",
	pw->pw_name);
	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 not allowed because none of user's groups are listed in AllowGroups",
	pw->pw_name);
	return 0;
	}
	ga_free();
	}

	#ifdef WITH_AIXAUTHENTICATE
	/*
	* Don't check loginrestrictions() for root account (use
	* PermitRootLogin to control logins via ssh), or if running as
	* non-root user (since loginrestrictions will always fail).
	*/
	if ((pw->pw_uid != 0) && (geteuid() == 0)) {
	char *msg;

	if (loginrestrictions(pw->pw_name, S_RLOGIN, NULL, &msg) != 0) {
	int loginrestrict_errno = errno;

	if (msg && *msg) {
	buffer_append(&loginmsg, msg, strlen(msg));
	aix_remove_embedded_newlines(msg);
	logit("Login restricted for %s: %.100s",
	pw->pw_name, msg);
	}
	/* Don't fail if /etc/nologin set */
	if (!(loginrestrict_errno == EPERM &&
	stat(_PATH_NOLOGIN, &st) == 0))
	return 0;
	}
	}
	#endif /* WITH_AIXAUTHENTICATE */

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

	Authctxt *
	authctxt_new(void)
	{
	Authctxt authctxt = xmalloc(sizeof(authctxt));
	memset(authctxt, 0, sizeof(*authctxt));
	return authctxt;
	}

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

	/* Raise logging level */
	if (authenticated == 1 \|\|
	!authctxt->valid \|\|
	authctxt->failures >= AUTH_FAIL_LOG \|\|
	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 ? "" : "illegal user ",
	authctxt->user,
	get_remote_ipaddr(),
	get_remote_port(),
	info);

	#ifdef CUSTOM_FAILED_LOGIN
	if (authenticated == 0 && strcmp(method, "password") == 0)
	record_failed_login(authctxt->user, "ssh");
	#endif
	}

	/*
	* Check whether root logins are disallowed.
	*/
	int
	auth_root_allowed(char *method)
	{
	switch (options.permit_root_login) {
	case PERMIT_YES:
	return 1;
	break;
	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.
	*/
	char *
	expand_filename(const char filename, struct passwd pw)
	{
	Buffer buffer;
	char *file;
	const char *cp;

	/*
	* Build the filename string in the buffer by making the appropriate
	* substitutions to the given file name.
	*/
	buffer_init(&buffer);
	for (cp = filename; *cp; cp++) {
	if (cp[0] == '%' && cp[1] == '%') {
	buffer_append(&buffer, "%", 1);
	cp++;
	continue;
	}
	if (cp[0] == '%' && cp[1] == 'h') {
	buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir));
	cp++;
	continue;
	}
	if (cp[0] == '%' && cp[1] == 'u') {
	buffer_append(&buffer, pw->pw_name,
	strlen(pw->pw_name));
	cp++;
	continue;
	}
	buffer_append(&buffer, cp, 1);
	}
	buffer_append(&buffer, "\0", 1);

	/*
	* Ensure that filename starts anchored. If not, be backward
	* compatible and prepend the '%h/'
	*/
	file = xmalloc(MAXPATHLEN);
	cp = buffer_ptr(&buffer);
	if (*cp != '/')
	snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp);
	else
	strlcpy(file, cp, MAXPATHLEN);

	buffer_free(&buffer);
	return file;
	}

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

	char *
	authorized_keys_file2(struct passwd *pw)
	{
	return expand_filename(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
	*/
	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 passed 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;
	}

	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;

	pw = getpwnam(user);
	if (pw == NULL) {
	logit("Illegal user %.100s from %.100s",
	user, get_remote_ipaddr());
	#ifdef CUSTOM_FAILED_LOGIN
	record_failed_login(user, "ssh");
	#endif
	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;
	}
	}