1 /* su for GNU. Run a shell with substitute user and group IDs.
2 Copyright (C) 1992-1999 Free Software Foundation, Inc.
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2, or (at your option)
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software Foundation,
16 Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
18 /* Run a shell with the real and effective UID and GID and groups
19 of USER, default `root'.
21 The shell run is taken from USER's password entry, /bin/sh if
22 none is specified there. If the account has a password, su
23 prompts for a password unless run by a user with real UID 0.
25 Does not change the current directory.
26 Sets `HOME' and `SHELL' from the password entry for USER, and if
27 USER is not root, sets `USER' and `LOGNAME' to USER.
28 The subshell is not a login shell.
30 If one or more ARGs are given, they are passed as additional
31 arguments to the subshell.
33 Does not handle /bin/sh or other shells specially
34 (setting argv[0] to "-su", passing -c only to certain shells, etc.).
35 I don't see the point in doing that, and it's ugly.
37 This program intentionally does not support a "wheel group" that
38 restricts who can su to UID 0 accounts. RMS considers that to
42 -, -l, --login Make the subshell a login shell.
43 Unset all environment variables except
44 TERM, HOME and SHELL (set as above), and USER
45 and LOGNAME (set unconditionally as above), and
46 set PATH to a default value.
47 Change to USER's home directory.
48 Prepend "-" to the shell's name.
49 -c, --commmand=COMMAND
50 Pass COMMAND to the subshell with a -c option
51 instead of starting an interactive shell.
52 -f, --fast Pass the -f option to the subshell.
53 -m, -p, --preserve-environment
54 Do not change HOME, USER, LOGNAME, SHELL.
55 Run $SHELL instead of USER's shell from /etc/passwd
56 unless not the superuser and USER's shell is
58 Overridden by --login and --shell.
59 -s, --shell=shell Run SHELL instead of USER's shell from /etc/passwd
60 unless not the superuser and USER's shell is
64 -DSYSLOG_SUCCESS Log successful su's (by default, to root) with syslog.
65 -DSYSLOG_FAILURE Log failed su's (by default, to root) with syslog.
67 -DSYSLOG_NON_ROOT Log all su's, not just those to root (UID 0).
68 Never logs attempted su's to nonexistent accounts.
70 Written by David MacKenzie <djm@gnu.ai.mit.edu>. */
75 #include <sys/types.h>
79 /* Hide any system prototype for getusershell.
80 This is necessary because some Cray systems have a conflicting
81 prototype (returning `int') in <unistd.h>. */
82 #define getusershell _getusershell_sys_proto_
85 #include "long-options.h"
89 #if HAVE_SYSLOG_H && HAVE_SYSLOG
92 # undef SYSLOG_SUCCESS
93 # undef SYSLOG_FAILURE
94 # undef SYSLOG_NON_ROOT
97 #ifndef _POSIX_VERSION
98 struct passwd *getpwuid ();
99 struct group *getgrgid ();
101 # include <sys/param.h>
102 #endif /* not _POSIX_VERSION */
104 #ifndef HAVE_ENDGRENT
105 # define endgrent() ((void) 0)
108 #ifndef HAVE_ENDPWENT
109 # define endpwent() ((void) 0)
118 /* The official name of this program (e.g., no `g' prefix). */
119 #define PROGRAM_NAME "su"
121 #define AUTHORS "David MacKenzie"
127 /* The default PATH for simulated logins to non-superuser accounts. */
129 # define DEFAULT_LOGIN_PATH _PATH_DEFPATH
131 # define DEFAULT_LOGIN_PATH ":/usr/ucb:/bin:/usr/bin"
134 /* The default PATH for simulated logins to superuser accounts. */
135 #ifdef _PATH_DEFPATH_ROOT
136 # define DEFAULT_ROOT_LOGIN_PATH _PATH_DEFPATH_ROOT
138 # define DEFAULT_ROOT_LOGIN_PATH "/usr/ucb:/bin:/usr/bin:/etc"
141 /* The shell to run if none is given in the user's passwd entry. */
142 #define DEFAULT_SHELL "/bin/sh"
144 /* The user to become if none is specified. */
145 #define DEFAULT_USER "root"
149 char *getusershell ();
150 void endusershell ();
151 void setusershell ();
156 extern char **environ;
158 /* The name this program was run with. */
161 /* If nonzero, pass the `-f' option to the subshell. */
162 static int fast_startup;
164 /* If nonzero, simulate a login instead of just starting a shell. */
165 static int simulate_login;
167 /* If nonzero, change some environment vars to indicate the user su'd to. */
168 static int change_environment;
170 static struct option const longopts[] =
172 {"command", required_argument, 0, 'c'},
173 {"fast", no_argument, NULL, 'f'},
174 {"login", no_argument, NULL, 'l'},
175 {"preserve-environment", no_argument, &change_environment, 0},
176 {"shell", required_argument, 0, 's'},
180 /* Add VAL to the environment, checking for out of memory errors. */
183 xputenv (const char *val)
186 error (1, 0, _("virtual memory exhausted"));
189 /* Return a newly-allocated string whose contents concatenate
190 those of S1, S2, S3. */
193 concat (const char *s1, const char *s2, const char *s3)
195 int len1 = strlen (s1), len2 = strlen (s2), len3 = strlen (s3);
196 char *result = (char *) xmalloc (len1 + len2 + len3 + 1);
199 strcpy (result + len1, s2);
200 strcpy (result + len1 + len2, s3);
201 result[len1 + len2 + len3] = 0;
206 /* Return the number of elements in ARR, a null-terminated array. */
209 elements (char **arr)
213 for (n = 0; *arr; ++arr)
218 #if defined (SYSLOG_SUCCESS) || defined (SYSLOG_FAILURE)
219 /* Log the fact that someone has run su to the user given by PW;
220 if SUCCESSFUL is nonzero, they gave the correct password, etc. */
223 log_su (const struct passwd *pw, int successful)
225 const char *new_user, *old_user, *tty;
227 # ifndef SYSLOG_NON_ROOT
231 new_user = pw->pw_name;
232 /* The utmp entry (via getlogin) is probably the best way to identify
233 the user, especially if someone su's from a su-shell. */
234 old_user = getlogin ();
235 if (old_user == NULL)
237 /* getlogin can fail -- usually due to lack of utmp entry.
238 Resort to getpwuid. */
239 struct passwd *pwd = getpwuid (getuid ());
240 old_user = (pwd ? pwd->pw_name : "");
245 /* 4.2BSD openlog doesn't have the third parameter. */
246 openlog (base_name (program_name), 0
252 # ifdef SYSLOG_NON_ROOT
253 "%s(to %s) %s on %s",
257 successful ? "" : "FAILED SU ",
258 # ifdef SYSLOG_NON_ROOT
266 /* Ask the user for a password.
267 Return 1 if the user gives the correct password for entry PW,
268 0 if not. Return 1 without asking for a password if run by UID 0
269 or if PW has an empty password. */
272 correct_password (const struct passwd *pw)
274 char *unencrypted, *encrypted, *correct;
276 /* Shadow passwd stuff for SVR3 and maybe other systems. */
277 struct spwd *sp = getspnam (pw->pw_name);
281 correct = sp->sp_pwdp;
284 correct = pw->pw_passwd;
286 if (getuid () == 0 || correct == 0 || correct[0] == '\0')
289 unencrypted = getpass (_("Password:"));
290 if (unencrypted == NULL)
292 error (0, 0, _("getpass: cannot open /dev/tty"));
295 encrypted = crypt (unencrypted, correct);
296 memset (unencrypted, 0, strlen (unencrypted));
297 return strcmp (encrypted, correct) == 0;
300 /* Update `environ' for the new shell based on PW, with SHELL being
301 the value for the SHELL environment variable. */
304 modify_environment (const struct passwd *pw, const char *shell)
310 /* Leave TERM unchanged. Set HOME, SHELL, USER, LOGNAME, PATH.
311 Unset all other environment variables. */
312 term = getenv ("TERM");
313 environ = (char **) xmalloc (2 * sizeof (char *));
316 xputenv (concat ("TERM", "=", term));
317 xputenv (concat ("HOME", "=", pw->pw_dir));
318 xputenv (concat ("SHELL", "=", shell));
319 xputenv (concat ("USER", "=", pw->pw_name));
320 xputenv (concat ("LOGNAME", "=", pw->pw_name));
321 xputenv (concat ("PATH", "=", (pw->pw_uid
323 : DEFAULT_ROOT_LOGIN_PATH)));
327 /* Set HOME, SHELL, and if not becoming a super-user,
329 if (change_environment)
331 xputenv (concat ("HOME", "=", pw->pw_dir));
332 xputenv (concat ("SHELL", "=", shell));
335 xputenv (concat ("USER", "=", pw->pw_name));
336 xputenv (concat ("LOGNAME", "=", pw->pw_name));
342 /* Become the user and group(s) specified by PW. */
345 change_identity (const struct passwd *pw)
347 #ifdef HAVE_INITGROUPS
349 if (initgroups (pw->pw_name, pw->pw_gid) == -1)
350 error (1, errno, _("cannot set groups"));
353 if (setgid (pw->pw_gid))
354 error (1, errno, _("cannot set group id"));
355 if (setuid (pw->pw_uid))
356 error (1, errno, _("cannot set user id"));
359 /* Run SHELL, or DEFAULT_SHELL if SHELL is empty.
360 If COMMAND is nonzero, pass it to the shell with the -c option.
361 If ADDITIONAL_ARGS is nonzero, pass it to the shell as more
365 run_shell (const char *shell, const char *command, char **additional_args)
371 args = (const char **) xmalloc (sizeof (char *)
372 * (10 + elements (additional_args)));
374 args = (const char **) xmalloc (sizeof (char *) * 10);
378 char *shell_basename;
380 shell_basename = base_name (shell);
381 arg0 = xmalloc (strlen (shell_basename) + 2);
383 strcpy (arg0 + 1, shell_basename);
387 args[0] = base_name (shell);
389 args[argno++] = "-f";
392 args[argno++] = "-c";
393 args[argno++] = command;
396 for (; *additional_args; ++additional_args)
397 args[argno++] = *additional_args;
399 execv (shell, (char **) args);
400 error (1, errno, _("cannot run %s"), shell);
403 /* Return 1 if SHELL is a restricted shell (one not returned by
404 getusershell), else 0, meaning it is a standard shell. */
407 restricted_shell (const char *shell)
412 while ((line = getusershell ()) != NULL)
414 if (*line != '#' && strcmp (line, shell) == 0)
428 fprintf (stderr, _("Try `%s --help' for more information.\n"),
432 printf (_("Usage: %s [OPTION]... [-] [USER [ARG]...]\n"), program_name);
434 Change the effective user id and group id to that of USER.\n\
436 -, -l, --login make the shell a login shell\n\
437 -c, --commmand=COMMAND pass a single COMMAND to the shell with -c\n\
438 -f, --fast pass -f to the shell (for csh or tcsh)\n\
439 -m, --preserve-environment do not reset environment variables\n\
441 -s, --shell=SHELL run SHELL if /etc/shells allows it\n\
442 --help display this help and exit\n\
443 --version output version information and exit\n\
445 A mere - implies -l. If USER not given, assume root.\n\
447 puts (_("\nReport bugs to <bug-sh-utils@gnu.org>."));
453 main (int argc, char **argv)
456 const char *new_user = DEFAULT_USER;
458 char **additional_args = 0;
461 struct passwd pw_copy;
463 program_name = argv[0];
464 setlocale (LC_ALL, "");
465 bindtextdomain (PACKAGE, LOCALEDIR);
466 textdomain (PACKAGE);
468 parse_long_options (argc, argv, PROGRAM_NAME, GNU_PACKAGE, VERSION,
473 change_environment = 1;
475 while ((optc = getopt_long (argc, argv, "c:flmps:", longopts, NULL)) != -1)
496 change_environment = 0;
508 if (optind < argc && !strcmp (argv[optind], "-"))
514 new_user = argv[optind++];
516 additional_args = argv + optind;
518 pw = getpwnam (new_user);
520 error (1, 0, _("user %s does not exist"), new_user);
523 /* Make sure pw->pw_shell is non-NULL. It may be NULL when NEW_USER
524 is a username that is retrieved via NIS (YP), but that doesn't have
525 a default shell listed. */
526 if (pw->pw_shell == NULL || pw->pw_shell[0] == '\0')
527 pw->pw_shell = (char *) DEFAULT_SHELL;
529 /* Make a copy of the password information and point pw at the local
530 copy instead. Otherwise, some systems (e.g. Linux) would clobber
531 the static data through the getlogin call from log_su. */
534 pw->pw_name = xstrdup (pw->pw_name);
535 pw->pw_dir = xstrdup (pw->pw_dir);
536 pw->pw_shell = xstrdup (pw->pw_shell);
538 if (!correct_password (pw))
540 #ifdef SYSLOG_FAILURE
543 error (1, 0, _("incorrect password"));
545 #ifdef SYSLOG_SUCCESS
552 if (shell == 0 && change_environment == 0)
553 shell = getenv ("SHELL");
554 if (shell != 0 && getuid () && restricted_shell (pw->pw_shell))
556 /* The user being su'd to has a nonstandard shell, and so is
557 probably a uucp account or has restricted access. Don't
558 compromise the account by allowing access with a standard
560 error (0, 0, _("using restricted shell %s"), pw->pw_shell);
565 shell = xstrdup (pw->pw_shell);
567 modify_environment (pw, shell);
569 change_identity (pw);
570 if (simulate_login && chdir (pw->pw_dir))
571 error (0, errno, _("warning: cannot change directory to %s"), pw->pw_dir);
573 run_shell (shell, command, additional_args);