/* su for GNU. Run a shell with substitute user and group IDs.
Copyright (C) 92, 93, 94, 1995 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
/* Run a shell with the real and effective UID and GID and groups
of USER, default `root'.
The shell run is taken from USER's password entry, /bin/sh if
none is specified there. If the account has a password, su
prompts for a password unless run by a user with real UID 0.
Does not change the current directory.
Sets `HOME' and `SHELL' from the password entry for USER, and if
USER is not root, sets `USER' and `LOGNAME' to USER.
The subshell is not a login shell.
If one or more ARGs are given, they are passed as additional
arguments to the subshell.
Does not handle /bin/sh or other shells specially
(setting argv[0] to "-su", passing -c only to certain shells, etc.).
I don't see the point in doing that, and it's ugly.
This program intentionally does not support a "wheel group" that
restricts who can su to UID 0 accounts. RMS considers that to
be fascist.
Options:
-, -l, --login Make the subshell a login shell.
Unset all environment variables except
TERM, HOME and SHELL (set as above), and USER
and LOGNAME (set unconditionally as above), and
set PATH to a default value.
Change to USER's home directory.
Prepend "-" to the shell's name.
-c, --commmand=COMMAND
Pass COMMAND to the subshell with a -c option
instead of starting an interactive shell.
-f, --fast Pass the -f option to the subshell.
-m, -p, --preserve-environment
Do not change HOME, USER, LOGNAME, SHELL.
Run $SHELL instead of USER's shell from /etc/passwd
unless not the superuser and USER's shell is
restricted.
Overridden by --login and --shell.
-s, --shell=shell Run SHELL instead of USER's shell from /etc/passwd
unless not the superuser and USER's shell is
restricted.
Compile-time options:
-DSYSLOG_SUCCESS Log successful su's (by default, to root) with syslog.
-DSYSLOG_FAILURE Log failed su's (by default, to root) with syslog.
-DSYSLOG_NON_ROOT Log all su's, not just those to root (UID 0).
Never logs attempted su's to nonexistent accounts.
Written by David MacKenzie <djm@gnu.ai.mit.edu>. */
#include <config.h>
#include <stdio.h>
#include <getopt.h>
#include <sys/types.h>
#include <pwd.h>
#include <grp.h>
#include "system.h"
#if defined(HAVE_SYSLOG_H) && defined(HAVE_SYSLOG)
#include <syslog.h>
static void log_su ();
#else /* !HAVE_SYSLOG_H */
#ifdef SYSLOG_SUCCESS
#undef SYSLOG_SUCCESS
#endif
#ifdef SYSLOG_FAILURE
#undef SYSLOG_FAILURE
#endif
#ifdef SYSLOG_NON_ROOT
#undef SYSLOG_NON_ROOT
#endif
#endif /* !HAVE_SYSLOG_H */
#ifdef _POSIX_VERSION
#include <limits.h>
#ifdef NGROUPS_MAX
#undef NGROUPS_MAX
#endif
#define NGROUPS_MAX sysconf (_SC_NGROUPS_MAX)
#else /* not _POSIX_VERSION */
struct passwd *getpwuid ();
struct group *getgrgid ();
uid_t getuid ();
#include <sys/param.h>
#if !defined(NGROUPS_MAX) && defined(NGROUPS)
#define NGROUPS_MAX NGROUPS
#endif
#endif /* not _POSIX_VERSION */
#ifndef HAVE_ENDGRENT
#define endgrent()
#endif
#ifndef HAVE_ENDPWENT
#define endpwent()
#endif
#ifdef HAVE_SHADOW_H
#include <shadow.h>
#endif
#include "version.h"
#include "error.h"
/* The default PATH for simulated logins to non-superuser accounts. */
#define DEFAULT_LOGIN_PATH ":/usr/ucb:/bin:/usr/bin"
/* The default PATH for simulated logins to superuser accounts. */
#define DEFAULT_ROOT_LOGIN_PATH "/usr/ucb:/bin:/usr/bin:/etc"
/* The shell to run if none is given in the user's passwd entry. */
#define DEFAULT_SHELL "/bin/sh"
/* The user to become if none is specified. */
#define DEFAULT_USER "root"
char *crypt ();
char *getpass ();
char *getusershell ();
void endusershell ();
void setusershell ();
char *basename ();
char *xmalloc ();
char *xrealloc ();
char *xstrdup ();
static char *concat ();
static int correct_password ();
static int elements ();
static int restricted_shell ();
static void change_identity ();
static void modify_environment ();
static void run_shell ();
static void usage ();
static void xputenv ();
extern char **environ;
/* The name this program was run with. */
char *program_name;
/* If non-zero, display usage information and exit. */
static int show_help;
/* If non-zero, print the version on standard output and exit. */
static int show_version;
/* If nonzero, pass the `-f' option to the subshell. */
static int fast_startup;
/* If nonzero, simulate a login instead of just starting a shell. */
static int simulate_login;
/* If nonzero, change some environment vars to indicate the user su'd to. */
static int change_environment;
static struct option const longopts[] =
{
{"command", required_argument, 0, 'c'},
{"fast", no_argument, &fast_startup, 1},
{"help", no_argument, &show_help, 1},
{"login", no_argument, &simulate_login, 1},
{"preserve-environment", no_argument, &change_environment, 0},
{"shell", required_argument, 0, 's'},
{"version", no_argument, &show_version, 1},
{0, 0, 0, 0}
};
void
main (argc, argv)
int argc;
char **argv;
{
int optc;
const char *new_user = DEFAULT_USER;
char *command = 0;
char **additional_args = 0;
char *shell = 0;
struct passwd *pw;
struct passwd pw_copy;
program_name = argv[0];
fast_startup = 0;
simulate_login = 0;
change_environment = 1;
while ((optc = getopt_long (argc, argv, "c:flmps:", longopts, (int *) 0))
!= EOF)
{
switch (optc)
{
case 0:
break;
case 'c':
command = optarg;
break;
case 'f':
fast_startup = 1;
break;
case 'l':
simulate_login = 1;
break;
case 'm':
case 'p':
change_environment = 0;
break;
case 's':
shell = optarg;
break;
default:
usage (1);
}
}
if (show_version)
{
printf ("su - %s\n", version_string);
exit (0);
}
if (show_help)
usage (0);
if (optind < argc && !strcmp (argv[optind], "-"))
{
simulate_login = 1;
++optind;
}
if (optind < argc)
new_user = argv[optind++];
if (optind < argc)
additional_args = argv + optind;
pw = getpwnam (new_user);
if (pw == 0)
error (1, 0, "user %s does not exist", new_user);
endpwent ();
/* Make a copy of the password information and point pw at the local
copy instead. Otherwise, some systems (e.g. Linux) would clobber
the static data through the getlogin call from log_su. */
pw_copy = *pw;
pw = &pw_copy;
pw->pw_name = xstrdup (pw->pw_name);
pw->pw_dir = xstrdup (pw->pw_dir);
pw->pw_shell = xstrdup (pw->pw_shell);
if (!correct_password (pw))
{
#ifdef SYSLOG_FAILURE
log_su (pw, 0);
#endif
error (1, 0, "incorrect password");
}
#ifdef SYSLOG_SUCCESS
else
{
log_su (pw, 1);
}
#endif
if (pw->pw_shell == 0 || pw->pw_shell[0] == 0)
pw->pw_shell = (char *) DEFAULT_SHELL;
if (shell == 0 && change_environment == 0)
shell = getenv ("SHELL");
if (shell != 0 && getuid () && restricted_shell (pw->pw_shell))
{
/* The user being su'd to has a nonstandard shell, and so is
probably a uucp account or has restricted access. Don't
compromise the account by allowing access with a standard
shell. */
error (0, 0, "using restricted shell %s", pw->pw_shell);
shell = 0;
}
if (shell == 0)
{
shell = xstrdup (pw->pw_shell);
}
modify_environment (pw, shell);
change_identity (pw);
if (simulate_login && chdir (pw->pw_dir))
error (0, errno, "warning: cannot change directory to %s", pw->pw_dir);
run_shell (shell, command, additional_args);
}
/* Ask the user for a password.
Return 1 if the user gives the correct password for entry PW,
0 if not. Return 1 without asking for a password if run by UID 0
or if PW has an empty password. */
static int
correct_password (pw)
struct passwd *pw;
{
char *unencrypted, *encrypted, *correct;
#ifdef HAVE_SHADOW_H
/* Shadow passwd stuff for SVR3 and maybe other systems. */
struct spwd *sp = getspnam (pw->pw_name);
endspent ();
if (sp)
correct = sp->sp_pwdp;
else
#endif
correct = pw->pw_passwd;
if (getuid () == 0 || correct == 0 || correct[0] == '\0')
return 1;
unencrypted = getpass ("Password:");
if (unencrypted == NULL)
{
error (0, 0, "getpass: cannot open /dev/tty");
return 0;
}
encrypted = crypt (unencrypted, correct);
memset (unencrypted, 0, strlen (unencrypted));
return strcmp (encrypted, correct) == 0;
}
/* Update `environ' for the new shell based on PW, with SHELL being
the value for the SHELL environment variable. */
static void
modify_environment (pw, shell)
struct passwd *pw;
char *shell;
{
char *term;
if (simulate_login)
{
/* Leave TERM unchanged. Set HOME, SHELL, USER, LOGNAME, PATH.
Unset all other environment variables. */
term = getenv ("TERM");
environ = (char **) xmalloc (2 * sizeof (char *));
environ[0] = 0;
if (term)
xputenv (concat ("TERM", "=", term));
xputenv (concat ("HOME", "=", pw->pw_dir));
xputenv (concat ("SHELL", "=", shell));
xputenv (concat ("USER", "=", pw->pw_name));
xputenv (concat ("LOGNAME", "=", pw->pw_name));
xputenv (concat ("PATH", "=", pw->pw_uid
? DEFAULT_LOGIN_PATH : DEFAULT_ROOT_LOGIN_PATH));
}
else
{
/* Set HOME, SHELL, and if not becoming a super-user,
USER and LOGNAME. */
if (change_environment)
{
xputenv (concat ("HOME", "=", pw->pw_dir));
xputenv (concat ("SHELL", "=", shell));
if (pw->pw_uid)
{
xputenv (concat ("USER", "=", pw->pw_name));
xputenv (concat ("LOGNAME", "=", pw->pw_name));
}
}
}
}
/* Become the user and group(s) specified by PW. */
static void
change_identity (pw)
struct passwd *pw;
{
#ifdef HAVE_INITGROUPS
errno = 0;
if (initgroups (pw->pw_name, pw->pw_gid) == -1)
error (1, errno, "cannot set groups");
endgrent ();
#endif
if (setgid (pw->pw_gid))
error (1, errno, "cannot set group id");
if (setuid (pw->pw_uid))
error (1, errno, "cannot set user id");
}
/* Run SHELL, or DEFAULT_SHELL if SHELL is empty.
If COMMAND is nonzero, pass it to the shell with the -c option.
If ADDITIONAL_ARGS is nonzero, pass it to the shell as more
arguments. */
static void
run_shell (shell, command, additional_args)
char *shell;
char *command;
char **additional_args;
{
const char **args;
int argno = 1;
if (additional_args)
args = (const char **) xmalloc (sizeof (char *)
* (10 + elements (additional_args)));
else
args = (const char **) xmalloc (sizeof (char *) * 10);
if (simulate_login)
{
char *arg0;
char *shell_basename;
shell_basename = basename (shell);
arg0 = xmalloc (strlen (shell_basename) + 2);
arg0[0] = '-';
strcpy (arg0 + 1, shell_basename);
args[0] = arg0;
}
else
args[0] = basename (shell);
if (fast_startup)
args[argno++] = "-f";
if (command)
{
args[argno++] = "-c";
args[argno++] = command;
}
if (additional_args)
for (; *additional_args; ++additional_args)
args[argno++] = *additional_args;
args[argno] = NULL;
execv (shell, (char **) args);
error (1, errno, "cannot run %s", shell);
}
#if defined (SYSLOG_SUCCESS) || defined (SYSLOG_FAILURE)
/* Log the fact that someone has run su to the user given by PW;
if SUCCESSFUL is nonzero, they gave the correct password, etc. */
static void
log_su (pw, successful)
struct passwd *pw;
int successful;
{
const char *new_user, *old_user, *tty;
#ifndef SYSLOG_NON_ROOT
if (pw->pw_uid)
return;
#endif
new_user = pw->pw_name;
/* The utmp entry (via getlogin) is probably the best way to identify
the user, especially if someone su's from a su-shell. */
old_user = getlogin ();
if (old_user == NULL)
old_user = "";
tty = ttyname (2);
if (tty == NULL)
tty = "";
/* 4.2BSD openlog doesn't have the third parameter. */
openlog (basename (program_name), 0
#ifdef LOG_AUTH
, LOG_AUTH
#endif
);
syslog (LOG_NOTICE,
#ifdef SYSLOG_NON_ROOT
"%s(to %s) %s on %s",
#else
"%s%s on %s",
#endif
successful ? "" : "FAILED SU ",
#ifdef SYSLOG_NON_ROOT
new_user,
#endif
old_user, tty);
closelog ();
}
#endif
/* Return 1 if SHELL is a restricted shell (one not returned by
getusershell), else 0, meaning it is a standard shell. */
static int
restricted_shell (shell)
char *shell;
{
char *line;
setusershell ();
while ((line = getusershell ()) != NULL)
{
if (*line != '#' && strcmp (line, shell) == 0)
{
endusershell ();
return 0;
}
}
endusershell ();
return 1;
}
/* Return the number of elements in ARR, a null-terminated array. */
static int
elements (arr)
char **arr;
{
int n = 0;
for (n = 0; *arr; ++arr)
++n;
return n;
}
/* Add VAL to the environment, checking for out of memory errors. */
static void
xputenv (val)
char *val;
{
if (putenv (val))
error (1, 0, "virtual memory exhausted");
}
/* Return a newly-allocated string whose contents concatenate
those of S1, S2, S3. */
static char *
concat (s1, s2, s3)
char *s1, *s2, *s3;
{
int len1 = strlen (s1), len2 = strlen (s2), len3 = strlen (s3);
char *result = (char *) xmalloc (len1 + len2 + len3 + 1);
strcpy (result, s1);
strcpy (result + len1, s2);
strcpy (result + len1 + len2, s3);
result[len1 + len2 + len3] = 0;
return result;
}
static void
usage (status)
int status;
{
if (status != 0)
fprintf (stderr, "Try `%s --help' for more information.\n",
program_name);
else
{
printf ("Usage: %s [OPTION]... [-] [USER [ARG]...]\n", program_name);
printf ("\
\n\
-l, --login make the shell a login shell\n\
-c, --commmand=COMMAND pass a single COMMAND to the shell with -c\n\
-f, --fast pass -f to the shell (for csh or tcsh)\n\
-m, --preserve-environment do not reset environment variables\n\
-p same as -m\n\
-s, --shell=SHELL run SHELL if /etc/shells allows it\n\
--help display this help and exit\n\
--version output version information and exit\n\
\n\
A mere - implies -l. If USER not given, assume root.\n\
");
}
exit (status);
}
