1 /* su for GNU. Run a shell with substitute user and group IDs.
2 Copyright (C) 92, 93, 94, 95, 96, 1997 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 HAVE_SYSLOG_H && HAVE_SYSLOG
83 # undef SYSLOG_SUCCESS
84 # undef SYSLOG_FAILURE
85 # undef SYSLOG_NON_ROOT
90 #else /* not _POSIX_VERSION */
91 struct passwd *getpwuid ();
92 struct group *getgrgid ();
94 # include <sys/param.h>
95 #endif /* not _POSIX_VERSION */
98 # define endgrent() ((void) 0)
101 #ifndef HAVE_ENDPWENT
102 # define endpwent() ((void) 0)
115 /* The default PATH for simulated logins to non-superuser accounts. */
117 # define DEFAULT_LOGIN_PATH _PATH_DEFPATH
119 # define DEFAULT_LOGIN_PATH ":/usr/ucb:/bin:/usr/bin"
122 /* The default PATH for simulated logins to superuser accounts. */
123 #ifdef _PATH_DEFPATH_ROOT
124 # define DEFAULT_ROOT_LOGIN_PATH _PATH_DEFPATH_ROOT
126 # define DEFAULT_ROOT_LOGIN_PATH "/usr/ucb:/bin:/usr/bin:/etc"
129 /* The shell to run if none is given in the user's passwd entry. */
130 #define DEFAULT_SHELL "/bin/sh"
132 /* The user to become if none is specified. */
133 #define DEFAULT_USER "root"
137 char *getusershell ();
138 void endusershell ();
139 void setusershell ();
146 extern char **environ;
148 /* The name this program was run with. */
151 /* If nonzero, display usage information and exit. */
152 static int show_help;
154 /* If nonzero, print the version on standard output and exit. */
155 static int show_version;
157 /* If nonzero, pass the `-f' option to the subshell. */
158 static int fast_startup;
160 /* If nonzero, simulate a login instead of just starting a shell. */
161 static int simulate_login;
163 /* If nonzero, change some environment vars to indicate the user su'd to. */
164 static int change_environment;
166 static struct option const longopts[] =
168 {"command", required_argument, 0, 'c'},
169 {"fast", no_argument, &fast_startup, 1},
170 {"help", no_argument, &show_help, 1},
171 {"login", no_argument, &simulate_login, 1},
172 {"preserve-environment", no_argument, &change_environment, 0},
173 {"shell", required_argument, 0, 's'},
174 {"version", no_argument, &show_version, 1},
178 /* Add VAL to the environment, checking for out of memory errors. */
181 xputenv (const char *val)
184 error (1, 0, _("virtual memory exhausted"));
187 /* Return a newly-allocated string whose contents concatenate
188 those of S1, S2, S3. */
191 concat (const char *s1, const char *s2, const char *s3)
193 int len1 = strlen (s1), len2 = strlen (s2), len3 = strlen (s3);
194 char *result = (char *) xmalloc (len1 + len2 + len3 + 1);
197 strcpy (result + len1, s2);
198 strcpy (result + len1 + len2, s3);
199 result[len1 + len2 + len3] = 0;
204 /* Return the number of elements in ARR, a null-terminated array. */
207 elements (char **arr)
211 for (n = 0; *arr; ++arr)
216 #if defined (SYSLOG_SUCCESS) || defined (SYSLOG_FAILURE)
217 /* Log the fact that someone has run su to the user given by PW;
218 if SUCCESSFUL is nonzero, they gave the correct password, etc. */
221 log_su (const struct passwd *pw, int successful)
223 const char *new_user, *old_user, *tty;
225 # ifndef SYSLOG_NON_ROOT
229 new_user = pw->pw_name;
230 /* The utmp entry (via getlogin) is probably the best way to identify
231 the user, especially if someone su's from a su-shell. */
232 old_user = getlogin ();
233 if (old_user == NULL)
235 /* getlogin can fail -- usually due to lack of utmp entry.
236 Resort to getpwuid. */
237 struct passwd *pwd = getpwuid (getuid ());
238 old_user = (pwd ? pwd->pw_name : "");
243 /* 4.2BSD openlog doesn't have the third parameter. */
244 openlog (base_name (program_name), 0
250 # ifdef SYSLOG_NON_ROOT
251 "%s(to %s) %s on %s",
255 successful ? "" : "FAILED SU ",
256 # ifdef SYSLOG_NON_ROOT
264 /* Ask the user for a password.
265 Return 1 if the user gives the correct password for entry PW,
266 0 if not. Return 1 without asking for a password if run by UID 0
267 or if PW has an empty password. */
270 correct_password (const struct passwd *pw)
272 char *unencrypted, *encrypted, *correct;
274 /* Shadow passwd stuff for SVR3 and maybe other systems. */
275 struct spwd *sp = getspnam (pw->pw_name);
279 correct = sp->sp_pwdp;
282 correct = pw->pw_passwd;
284 if (getuid () == 0 || correct == 0 || correct[0] == '\0')
287 unencrypted = getpass (_("Password:"));
288 if (unencrypted == NULL)
290 error (0, 0, _("getpass: cannot open /dev/tty"));
293 encrypted = crypt (unencrypted, correct);
294 memset (unencrypted, 0, strlen (unencrypted));
295 return strcmp (encrypted, correct) == 0;
298 /* Update `environ' for the new shell based on PW, with SHELL being
299 the value for the SHELL environment variable. */
302 modify_environment (const struct passwd *pw, const char *shell)
308 /* Leave TERM unchanged. Set HOME, SHELL, USER, LOGNAME, PATH.
309 Unset all other environment variables. */
310 term = getenv ("TERM");
311 environ = (char **) xmalloc (2 * sizeof (char *));
314 xputenv (concat ("TERM", "=", term));
315 xputenv (concat ("HOME", "=", pw->pw_dir));
316 xputenv (concat ("SHELL", "=", shell));
317 xputenv (concat ("USER", "=", pw->pw_name));
318 xputenv (concat ("LOGNAME", "=", pw->pw_name));
319 xputenv (concat ("PATH", "=", (pw->pw_uid
321 : 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 = base_name (shell);
379 arg0 = xmalloc (strlen (shell_basename) + 2);
381 strcpy (arg0 + 1, shell_basename);
385 args[0] = base_name (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);