1 /* su for GNU. Run a shell with substitute user and group IDs.
2 Copyright (C) 92, 93, 94, 95, 1996 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>
80 #if defined(HAVE_SYSLOG_H) && defined(HAVE_SYSLOG)
82 #else /* !HAVE_SYSLOG_H */
89 #ifdef SYSLOG_NON_ROOT
90 #undef SYSLOG_NON_ROOT
92 #endif /* !HAVE_SYSLOG_H */
96 #else /* not _POSIX_VERSION */
97 struct passwd *getpwuid ();
98 struct group *getgrgid ();
100 #include <sys/param.h>
101 #endif /* not _POSIX_VERSION */
103 #ifndef HAVE_ENDGRENT
104 # define endgrent() ((void) 0)
107 #ifndef HAVE_ENDPWENT
108 # define endpwent() ((void) 0)
121 /* The default PATH for simulated logins to non-superuser accounts. */
123 #define DEFAULT_LOGIN_PATH _PATH_DEFPATH
125 #define DEFAULT_LOGIN_PATH ":/usr/ucb:/bin:/usr/bin"
128 /* The default PATH for simulated logins to superuser accounts. */
129 #ifdef _PATH_DEFPATH_ROOT
130 #define DEFAULT_ROOT_LOGIN_PATH _PATH_DEFPATH_ROOT
132 #define DEFAULT_ROOT_LOGIN_PATH "/usr/ucb:/bin:/usr/bin:/etc"
135 /* The shell to run if none is given in the user's passwd entry. */
136 #define DEFAULT_SHELL "/bin/sh"
138 /* The user to become if none is specified. */
139 #define DEFAULT_USER "root"
143 char *getusershell ();
144 void endusershell ();
145 void setusershell ();
152 extern char **environ;
154 /* The name this program was run with. */
157 /* If nonzero, display usage information and exit. */
158 static int show_help;
160 /* If nonzero, print the version on standard output and exit. */
161 static int show_version;
163 /* If nonzero, pass the `-f' option to the subshell. */
164 static int fast_startup;
166 /* If nonzero, simulate a login instead of just starting a shell. */
167 static int simulate_login;
169 /* If nonzero, change some environment vars to indicate the user su'd to. */
170 static int change_environment;
172 static struct option const longopts[] =
174 {"command", required_argument, 0, 'c'},
175 {"fast", no_argument, &fast_startup, 1},
176 {"help", no_argument, &show_help, 1},
177 {"login", no_argument, &simulate_login, 1},
178 {"preserve-environment", no_argument, &change_environment, 0},
179 {"shell", required_argument, 0, 's'},
180 {"version", no_argument, &show_version, 1},
184 /* Add VAL to the environment, checking for out of memory errors. */
187 xputenv (const char *val)
190 error (1, 0, _("virtual memory exhausted"));
193 /* Return a newly-allocated string whose contents concatenate
194 those of S1, S2, S3. */
197 concat (const char *s1, const char *s2, const char *s3)
199 int len1 = strlen (s1), len2 = strlen (s2), len3 = strlen (s3);
200 char *result = (char *) xmalloc (len1 + len2 + len3 + 1);
203 strcpy (result + len1, s2);
204 strcpy (result + len1 + len2, s3);
205 result[len1 + len2 + len3] = 0;
210 /* Return the number of elements in ARR, a null-terminated array. */
213 elements (char **arr)
217 for (n = 0; *arr; ++arr)
222 #if defined (SYSLOG_SUCCESS) || defined (SYSLOG_FAILURE)
223 /* Log the fact that someone has run su to the user given by PW;
224 if SUCCESSFUL is nonzero, they gave the correct password, etc. */
227 log_su (const struct passwd *pw, int successful)
229 const char *new_user, *old_user, *tty;
231 #ifndef SYSLOG_NON_ROOT
235 new_user = pw->pw_name;
236 /* The utmp entry (via getlogin) is probably the best way to identify
237 the user, especially if someone su's from a su-shell. */
238 old_user = getlogin ();
239 if (old_user == NULL)
244 /* 4.2BSD openlog doesn't have the third parameter. */
245 openlog (basename (program_name), 0
251 #ifdef SYSLOG_NON_ROOT
252 "%s(to %s) %s on %s",
256 successful ? "" : "FAILED SU ",
257 #ifdef SYSLOG_NON_ROOT
265 /* Ask the user for a password.
266 Return 1 if the user gives the correct password for entry PW,
267 0 if not. Return 1 without asking for a password if run by UID 0
268 or if PW has an empty password. */
271 correct_password (const struct passwd *pw)
273 char *unencrypted, *encrypted, *correct;
275 /* Shadow passwd stuff for SVR3 and maybe other systems. */
276 struct spwd *sp = getspnam (pw->pw_name);
280 correct = sp->sp_pwdp;
283 correct = pw->pw_passwd;
285 if (getuid () == 0 || correct == 0 || correct[0] == '\0')
288 unencrypted = getpass (_("Password:"));
289 if (unencrypted == NULL)
291 error (0, 0, _("getpass: cannot open /dev/tty"));
294 encrypted = crypt (unencrypted, correct);
295 memset (unencrypted, 0, strlen (unencrypted));
296 return strcmp (encrypted, correct) == 0;
299 /* Update `environ' for the new shell based on PW, with SHELL being
300 the value for the SHELL environment variable. */
303 modify_environment (const struct passwd *pw, const char *shell)
309 /* Leave TERM unchanged. Set HOME, SHELL, USER, LOGNAME, PATH.
310 Unset all other environment variables. */
311 term = getenv ("TERM");
312 environ = (char **) xmalloc (2 * sizeof (char *));
315 xputenv (concat ("TERM", "=", term));
316 xputenv (concat ("HOME", "=", pw->pw_dir));
317 xputenv (concat ("SHELL", "=", shell));
318 xputenv (concat ("USER", "=", pw->pw_name));
319 xputenv (concat ("LOGNAME", "=", pw->pw_name));
320 xputenv (concat ("PATH", "=", pw->pw_uid
321 ? DEFAULT_LOGIN_PATH : DEFAULT_ROOT_LOGIN_PATH));
325 /* Set HOME, SHELL, and if not becoming a super-user,
327 if (change_environment)
329 xputenv (concat ("HOME", "=", pw->pw_dir));
330 xputenv (concat ("SHELL", "=", shell));
333 xputenv (concat ("USER", "=", pw->pw_name));
334 xputenv (concat ("LOGNAME", "=", pw->pw_name));
340 /* Become the user and group(s) specified by PW. */
343 change_identity (const struct passwd *pw)
345 #ifdef HAVE_INITGROUPS
347 if (initgroups (pw->pw_name, pw->pw_gid) == -1)
348 error (1, errno, _("cannot set groups"));
351 if (setgid (pw->pw_gid))
352 error (1, errno, _("cannot set group id"));
353 if (setuid (pw->pw_uid))
354 error (1, errno, _("cannot set user id"));
357 /* Run SHELL, or DEFAULT_SHELL if SHELL is empty.
358 If COMMAND is nonzero, pass it to the shell with the -c option.
359 If ADDITIONAL_ARGS is nonzero, pass it to the shell as more
363 run_shell (const char *shell, const char *command, char **additional_args)
369 args = (const char **) xmalloc (sizeof (char *)
370 * (10 + elements (additional_args)));
372 args = (const char **) xmalloc (sizeof (char *) * 10);
376 char *shell_basename;
378 shell_basename = basename (shell);
379 arg0 = xmalloc (strlen (shell_basename) + 2);
381 strcpy (arg0 + 1, shell_basename);
385 args[0] = basename (shell);
387 args[argno++] = "-f";
390 args[argno++] = "-c";
391 args[argno++] = command;
394 for (; *additional_args; ++additional_args)
395 args[argno++] = *additional_args;
397 execv (shell, (char **) args);
398 error (1, errno, _("cannot run %s"), shell);
401 /* Return 1 if SHELL is a restricted shell (one not returned by
402 getusershell), else 0, meaning it is a standard shell. */
405 restricted_shell (const char *shell)
410 while ((line = getusershell ()) != NULL)
412 if (*line != '#' && strcmp (line, shell) == 0)
426 fprintf (stderr, _("Try `%s --help' for more information.\n"),
430 printf (_("Usage: %s [OPTION]... [-] [USER [ARG]...]\n"), program_name);
432 Change the effective user id and group id to that of USER.\n\
434 -, -l, --login make the shell a login shell\n\
435 -c, --commmand=COMMAND pass a single COMMAND to the shell with -c\n\
436 -f, --fast pass -f to the shell (for csh or tcsh)\n\
437 -m, --preserve-environment do not reset environment variables\n\
439 -s, --shell=SHELL run SHELL if /etc/shells allows it\n\
440 --help display this help and exit\n\
441 --version output version information and exit\n\
443 A mere - implies -l. If USER not given, assume root.\n\
445 puts (_("\nReport bugs to <sh-utils-bugs@gnu.ai.mit.edu>."));
451 main (int argc, char **argv)
454 const char *new_user = DEFAULT_USER;
456 char **additional_args = 0;
459 struct passwd pw_copy;
461 program_name = argv[0];
462 setlocale (LC_ALL, "");
463 bindtextdomain (PACKAGE, LOCALEDIR);
464 textdomain (PACKAGE);
468 change_environment = 1;
470 while ((optc = getopt_long (argc, argv, "c:flmps:", longopts, NULL)) != -1)
491 change_environment = 0;
505 printf ("su (%s) %s\n", GNU_PACKAGE, VERSION);
512 if (optind < argc && !strcmp (argv[optind], "-"))
518 new_user = argv[optind++];
520 additional_args = argv + optind;
522 pw = getpwnam (new_user);
524 error (1, 0, _("user %s does not exist"), new_user);
527 /* Make a copy of the password information and point pw at the local
528 copy instead. Otherwise, some systems (e.g. Linux) would clobber
529 the static data through the getlogin call from log_su. */
532 pw->pw_name = xstrdup (pw->pw_name);
533 pw->pw_dir = xstrdup (pw->pw_dir);
534 pw->pw_shell = xstrdup (pw->pw_shell);
536 if (!correct_password (pw))
538 #ifdef SYSLOG_FAILURE
541 error (1, 0, _("incorrect password"));
543 #ifdef SYSLOG_SUCCESS
550 if (pw->pw_shell == 0 || pw->pw_shell[0] == 0)
551 pw->pw_shell = (char *) DEFAULT_SHELL;
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);