/* $OpenBSD: auth.c,v 1.79 2008/07/02 12:03:51 dtucker 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;

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 = (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 ||

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 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;

}

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)

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);

}