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openssh/auth.c

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/*
* 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 1.26 2001/06/27 04:48:52 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"
/* import */
extern ServerOptions options;
/*
* 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;
#ifdef WITH_AIXAUTHENTICATE
char *loginmsg;
#endif /* WITH_AIXAUTHENTICATE */
#if !defined(USE_PAM) && defined(HAVE_SHADOW_H) && \
!defined(DISABLE_SHADOW) && defined(HAS_SHADOW_EXPIRE)
struct spwd *spw;
/* Shouldn't be called if pw is NULL, but better safe than sorry... */
if (!pw || !pw->pw_name)
return 0;
spw = getspnam(pw->pw_name);
if (spw != NULL) {
int days = time(NULL) / 86400;
/* Check account expiry */
if ((spw->sp_expire >= 0) && (days > spw->sp_expire))
return 0;
/* Check password expiry */
if ((spw->sp_lstchg >= 0) && (spw->sp_max >= 0) &&
(days > (spw->sp_lstchg + spw->sp_max)))
return 0;
}
#else
/* Shouldn't be called if pw is NULL, but better safe than sorry... */
if (!pw || !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)
return 0;
if (!((st.st_mode & S_IFREG) && (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP))))
return 0;
if (options.num_deny_users > 0 || options.num_allow_users > 0) {
hostname = get_canonical_hostname(options.reverse_mapping_check);
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]))
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)
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)
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();
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();
return 0;
}
ga_free();
}
#ifdef WITH_AIXAUTHENTICATE
if (loginrestrictions(pw->pw_name, S_RLOGIN, NULL, &loginmsg) != 0) {
if (loginmsg && *loginmsg) {
/* Remove embedded newlines (if any) */
char *p;
for (p = loginmsg; *p; p++) {
if (*p == '\n')
*p = ' ';
}
/* Remove trailing newline */
*--p = '\0';
log("Login restricted for %s: %.100s", pw->pw_name, loginmsg);
}
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 = log;
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->valid && authctxt->pw->pw_uid == 0 ? "ROOT" : authctxt->user,
get_remote_ipaddr(),
get_remote_port(),
info);
}
/*
* 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) {
log("Root login accepted for forced command.");
return 1;
}
break;
}
log("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;
int 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)) {
log("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 either 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 homedir[MAXPATHLEN];
char buf[MAXPATHLEN];
char *cp;
struct stat st;
strlcpy(homedir, dirname(pw->pw_dir), sizeof(homedir));
if (realpath(file, buf) == NULL) {
snprintf(err, errlen, "realpath %s failed: %s", file,
strerror(errno));
return -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;
}
debug3("secure_filename: terminating check at '%s'", homedir);
/* 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));
/* If are passed the homedir then we can stop */
if (strcmp(buf, homedir) == 0)
break;
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;
}
/*
* 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;
}
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