1 /* su for GNU. Run a shell with substitute user and group IDs.
2 Copyright (C) 1992-2000 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_
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 ();
155 extern char **environ;
157 static void run_shell (const char *, const char *, char **)
160 /* The name this program was run with. */
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, NULL, 'f'},
176 {"login", no_argument, NULL, 'l'},
177 {"preserve-environment", no_argument, &change_environment, 0},
178 {"shell", required_argument, 0, 's'},
179 {GETOPT_HELP_OPTION_DECL},
180 {GETOPT_VERSION_OPTION_DECL},
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)
241 /* getlogin can fail -- usually due to lack of utmp entry.
242 Resort to getpwuid. */
243 struct passwd *pwd = getpwuid (getuid ());
244 old_user = (pwd ? pwd->pw_name : "");
249 /* 4.2BSD openlog doesn't have the third parameter. */
250 openlog (base_name (program_name), 0
256 # ifdef SYSLOG_NON_ROOT
257 "%s(to %s) %s on %s",
261 successful ? "" : "FAILED SU ",
262 # ifdef SYSLOG_NON_ROOT
270 /* Ask the user for a password.
271 Return 1 if the user gives the correct password for entry PW,
272 0 if not. Return 1 without asking for a password if run by UID 0
273 or if PW has an empty password. */
276 correct_password (const struct passwd *pw)
278 char *unencrypted, *encrypted, *correct;
279 #if HAVE_GETSPNAM && HAVE_STRUCT_SPWD_SP_PWDP
280 /* Shadow passwd stuff for SVR3 and maybe other systems. */
281 struct spwd *sp = getspnam (pw->pw_name);
285 correct = sp->sp_pwdp;
288 correct = pw->pw_passwd;
290 if (getuid () == 0 || correct == 0 || correct[0] == '\0')
293 unencrypted = getpass (_("Password:"));
294 if (unencrypted == NULL)
296 error (0, 0, _("getpass: cannot open /dev/tty"));
299 encrypted = crypt (unencrypted, correct);
300 memset (unencrypted, 0, strlen (unencrypted));
301 return strcmp (encrypted, correct) == 0;
304 /* Update `environ' for the new shell based on PW, with SHELL being
305 the value for the SHELL environment variable. */
308 modify_environment (const struct passwd *pw, const char *shell)
314 /* Leave TERM unchanged. Set HOME, SHELL, USER, LOGNAME, PATH.
315 Unset all other environment variables. */
316 term = getenv ("TERM");
317 environ = (char **) xmalloc (2 * sizeof (char *));
320 xputenv (concat ("TERM", "=", term));
321 xputenv (concat ("HOME", "=", pw->pw_dir));
322 xputenv (concat ("SHELL", "=", shell));
323 xputenv (concat ("USER", "=", pw->pw_name));
324 xputenv (concat ("LOGNAME", "=", pw->pw_name));
325 xputenv (concat ("PATH", "=", (pw->pw_uid
327 : DEFAULT_ROOT_LOGIN_PATH)));
331 /* Set HOME, SHELL, and if not becoming a super-user,
333 if (change_environment)
335 xputenv (concat ("HOME", "=", pw->pw_dir));
336 xputenv (concat ("SHELL", "=", shell));
339 xputenv (concat ("USER", "=", pw->pw_name));
340 xputenv (concat ("LOGNAME", "=", pw->pw_name));
346 /* Become the user and group(s) specified by PW. */
349 change_identity (const struct passwd *pw)
351 #ifdef HAVE_INITGROUPS
353 if (initgroups (pw->pw_name, pw->pw_gid) == -1)
354 error (1, errno, _("cannot set groups"));
357 if (setgid (pw->pw_gid))
358 error (1, errno, _("cannot set group id"));
359 if (setuid (pw->pw_uid))
360 error (1, errno, _("cannot set user id"));
363 /* Run SHELL, or DEFAULT_SHELL if SHELL is empty.
364 If COMMAND is nonzero, pass it to the shell with the -c option.
365 If ADDITIONAL_ARGS is nonzero, pass it to the shell as more
369 run_shell (const char *shell, const char *command, char **additional_args)
375 args = (const char **) xmalloc (sizeof (char *)
376 * (10 + elements (additional_args)));
378 args = (const char **) xmalloc (sizeof (char *) * 10);
382 char *shell_basename;
384 shell_basename = base_name (shell);
385 arg0 = xmalloc (strlen (shell_basename) + 2);
387 strcpy (arg0 + 1, shell_basename);
391 args[0] = base_name (shell);
393 args[argno++] = "-f";
396 args[argno++] = "-c";
397 args[argno++] = command;
400 for (; *additional_args; ++additional_args)
401 args[argno++] = *additional_args;
403 execv (shell, (char **) args);
404 error (0, errno, _("cannot run %s"), shell);
408 /* Return 1 if SHELL is a restricted shell (one not returned by
409 getusershell), else 0, meaning it is a standard shell. */
412 restricted_shell (const char *shell)
417 while ((line = getusershell ()) != NULL)
419 if (*line != '#' && strcmp (line, shell) == 0)
433 fprintf (stderr, _("Try `%s --help' for more information.\n"),
437 printf (_("Usage: %s [OPTION]... [-] [USER [ARG]...]\n"), program_name);
439 Change the effective user id and group id to that of USER.\n\
441 -, -l, --login make the shell a login shell\n\
442 -c, --commmand=COMMAND pass a single COMMAND to the shell with -c\n\
443 -f, --fast pass -f to the shell (for csh or tcsh)\n\
444 -m, --preserve-environment do not reset environment variables\n\
446 -s, --shell=SHELL run SHELL if /etc/shells allows it\n\
447 --help display this help and exit\n\
448 --version output version information and exit\n\
450 A mere - implies -l. If USER not given, assume root.\n\
452 puts (_("\nReport bugs to <bug-sh-utils@gnu.org>."));
459 main (int argc, char **argv)
462 const char *new_user = DEFAULT_USER;
464 char **additional_args = 0;
467 struct passwd pw_copy;
469 program_name = argv[0];
470 setlocale (LC_ALL, "");
471 bindtextdomain (PACKAGE, LOCALEDIR);
472 textdomain (PACKAGE);
476 change_environment = 1;
478 while ((optc = getopt_long (argc, argv, "c:flmps:", longopts, NULL)) != -1)
499 change_environment = 0;
506 case_GETOPT_HELP_CHAR;
508 case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
515 if (optind < argc && !strcmp (argv[optind], "-"))
521 new_user = argv[optind++];
523 additional_args = argv + optind;
525 pw = getpwnam (new_user);
527 error (1, 0, _("user %s does not exist"), new_user);
530 /* Make sure pw->pw_shell is non-NULL. It may be NULL when NEW_USER
531 is a username that is retrieved via NIS (YP), but that doesn't have
532 a default shell listed. */
533 if (pw->pw_shell == NULL || pw->pw_shell[0] == '\0')
534 pw->pw_shell = (char *) DEFAULT_SHELL;
536 /* Make a copy of the password information and point pw at the local
537 copy instead. Otherwise, some systems (e.g. Linux) would clobber
538 the static data through the getlogin call from log_su. */
541 pw->pw_name = xstrdup (pw->pw_name);
542 pw->pw_dir = xstrdup (pw->pw_dir);
543 pw->pw_shell = xstrdup (pw->pw_shell);
545 if (!correct_password (pw))
547 #ifdef SYSLOG_FAILURE
550 error (1, 0, _("incorrect password"));
552 #ifdef SYSLOG_SUCCESS
559 if (shell == 0 && change_environment == 0)
560 shell = getenv ("SHELL");
561 if (shell != 0 && getuid () && restricted_shell (pw->pw_shell))
563 /* The user being su'd to has a nonstandard shell, and so is
564 probably a uucp account or has restricted access. Don't
565 compromise the account by allowing access with a standard
567 error (0, 0, _("using restricted shell %s"), pw->pw_shell);
572 shell = xstrdup (pw->pw_shell);
574 modify_environment (pw, shell);
576 change_identity (pw);
577 if (simulate_login && chdir (pw->pw_dir))
578 error (0, errno, _("warning: cannot change directory to %s"), pw->pw_dir);
580 run_shell (shell, command, additional_args);