1 /* su for GNU. Run a shell with substitute user and group IDs.
2 Copyright (C) 92, 93, 1994 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
16 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, 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>. */
78 #include <sys/types.h>
85 static void log_su ();
86 #else /* !HAVE_SYSLOG_H */
93 #ifdef SYSLOG_NON_ROOT
94 #undef SYSLOG_NON_ROOT
96 #endif /* !HAVE_SYSLOG_H */
103 #define NGROUPS_MAX sysconf (_SC_NGROUPS_MAX)
104 #else /* not _POSIX_VERSION */
105 struct passwd *getpwuid ();
106 struct group *getgrgid ();
108 #include <sys/param.h>
109 #if !defined(NGROUPS_MAX) && defined(NGROUPS)
110 #define NGROUPS_MAX NGROUPS
112 #endif /* not _POSIX_VERSION */
114 #ifndef HAVE_ENDGRENT
118 #ifndef HAVE_ENDPWENT
128 /* The default PATH for simulated logins to non-superuser accounts. */
129 #define DEFAULT_LOGIN_PATH ":/usr/ucb:/bin:/usr/bin"
131 /* The default PATH for simulated logins to superuser accounts. */
132 #define DEFAULT_ROOT_LOGIN_PATH "/usr/ucb:/bin:/usr/bin:/etc"
134 /* The shell to run if none is given in the user's passwd entry. */
135 #define DEFAULT_SHELL "/bin/sh"
137 /* The user to become if none is specified. */
138 #define DEFAULT_USER "root"
142 char *getusershell ();
143 void endusershell ();
144 void setusershell ();
152 static char *concat ();
153 static int correct_password ();
154 static int elements ();
155 static int restricted_shell ();
156 static void change_identity ();
157 static void modify_environment ();
158 static void run_shell ();
159 static void usage ();
160 static void xputenv ();
162 extern char **environ;
164 /* The name this program was run with. */
167 /* If non-zero, display usage information and exit. */
168 static int show_help;
170 /* If non-zero, print the version on standard output and exit. */
171 static int show_version;
173 /* If nonzero, pass the `-f' option to the subshell. */
174 static int fast_startup;
176 /* If nonzero, simulate a login instead of just starting a shell. */
177 static int simulate_login;
179 /* If nonzero, change some environment vars to indicate the user su'd to. */
180 static int change_environment;
182 static struct option const longopts[] =
184 {"command", required_argument, 0, 'c'},
185 {"fast", no_argument, &fast_startup, 1},
186 {"help", no_argument, &show_help, 1},
187 {"login", no_argument, &simulate_login, 1},
188 {"preserve-environment", no_argument, &change_environment, 0},
189 {"shell", required_argument, 0, 's'},
190 {"version", no_argument, &show_version, 1},
200 const char *new_user = DEFAULT_USER;
202 char **additional_args = 0;
205 struct passwd pw_copy;
207 program_name = argv[0];
210 change_environment = 1;
212 while ((optc = getopt_long (argc, argv, "c:flmps:", longopts, (int *) 0))
234 change_environment = 0;
248 printf ("su - %s\n", version_string);
255 if (optind < argc && !strcmp (argv[optind], "-"))
261 new_user = argv[optind++];
263 additional_args = argv + optind;
265 pw = getpwnam (new_user);
267 error (1, 0, "user %s does not exist", new_user);
270 /* Make a copy of the password information and point pw at the local
271 copy instead. Otherwise, some systems (e.g. Linux) would clobber
272 the static data through the getlogin call from log_su. */
275 pw->pw_name = xstrdup (pw->pw_name);
276 pw->pw_dir = xstrdup (pw->pw_dir);
277 pw->pw_shell = xstrdup (pw->pw_shell);
279 if (!correct_password (pw))
281 #ifdef SYSLOG_FAILURE
284 error (1, 0, "incorrect password");
286 #ifdef SYSLOG_SUCCESS
293 if (pw->pw_shell == 0 || pw->pw_shell[0] == 0)
294 pw->pw_shell = (char *) DEFAULT_SHELL;
295 if (shell == 0 && change_environment == 0)
296 shell = getenv ("SHELL");
297 if (shell != 0 && getuid () && restricted_shell (pw->pw_shell))
299 /* The user being su'd to has a nonstandard shell, and so is
300 probably a uucp account or has restricted access. Don't
301 compromise the account by allowing access with a standard
303 error (0, 0, "using restricted shell %s", pw->pw_shell);
308 shell = xstrdup (pw->pw_shell);
310 modify_environment (pw, shell);
312 change_identity (pw);
313 if (simulate_login && chdir (pw->pw_dir))
314 error (0, errno, "warning: cannot change directory to %s", pw->pw_dir);
316 run_shell (shell, command, additional_args);
319 /* Ask the user for a password.
320 Return 1 if the user gives the correct password for entry PW,
321 0 if not. Return 1 without asking for a password if run by UID 0
322 or if PW has an empty password. */
325 correct_password (pw)
328 char *unencrypted, *encrypted, *correct;
330 /* Shadow passwd stuff for SVR3 and maybe other systems. */
331 struct spwd *sp = getspnam (pw->pw_name);
335 correct = sp->sp_pwdp;
338 correct = pw->pw_passwd;
340 if (getuid () == 0 || correct == 0 || correct[0] == '\0')
343 unencrypted = getpass ("Password:");
344 if (unencrypted == NULL)
346 error (0, 0, "getpass: cannot open /dev/tty");
349 encrypted = crypt (unencrypted, correct);
350 bzero (unencrypted, strlen (unencrypted));
351 return strcmp (encrypted, correct) == 0;
354 /* Update `environ' for the new shell based on PW, with SHELL being
355 the value for the SHELL environment variable. */
358 modify_environment (pw, shell)
366 /* Leave TERM unchanged. Set HOME, SHELL, USER, LOGNAME, PATH.
367 Unset all other environment variables. */
368 term = getenv ("TERM");
369 environ = (char **) xmalloc (2 * sizeof (char *));
372 xputenv (concat ("TERM", "=", term));
373 xputenv (concat ("HOME", "=", pw->pw_dir));
374 xputenv (concat ("SHELL", "=", shell));
375 xputenv (concat ("USER", "=", pw->pw_name));
376 xputenv (concat ("LOGNAME", "=", pw->pw_name));
377 xputenv (concat ("PATH", "=", pw->pw_uid
378 ? DEFAULT_LOGIN_PATH : DEFAULT_ROOT_LOGIN_PATH));
382 /* Set HOME, SHELL, and if not becoming a super-user,
384 if (change_environment)
386 xputenv (concat ("HOME", "=", pw->pw_dir));
387 xputenv (concat ("SHELL", "=", shell));
390 xputenv (concat ("USER", "=", pw->pw_name));
391 xputenv (concat ("LOGNAME", "=", pw->pw_name));
397 /* Become the user and group(s) specified by PW. */
405 if (initgroups (pw->pw_name, pw->pw_gid) == -1)
406 error (1, errno, "cannot set groups");
409 if (setgid (pw->pw_gid))
410 error (1, errno, "cannot set group id");
411 if (setuid (pw->pw_uid))
412 error (1, errno, "cannot set user id");
415 /* Run SHELL, or DEFAULT_SHELL if SHELL is empty.
416 If COMMAND is nonzero, pass it to the shell with the -c option.
417 If ADDITIONAL_ARGS is nonzero, pass it to the shell as more
421 run_shell (shell, command, additional_args)
424 char **additional_args;
430 args = (const char **) xmalloc (sizeof (char *)
431 * (10 + elements (additional_args)));
433 args = (const char **) xmalloc (sizeof (char *) * 10);
437 char *shell_basename;
439 shell_basename = basename (shell);
440 arg0 = xmalloc (strlen (shell_basename) + 2);
442 strcpy (arg0 + 1, shell_basename);
446 args[0] = basename (shell);
448 args[argno++] = "-f";
451 args[argno++] = "-c";
452 args[argno++] = command;
455 for (; *additional_args; ++additional_args)
456 args[argno++] = *additional_args;
458 execv (shell, (char **) args);
459 error (1, errno, "cannot run %s", shell);
462 #if defined (SYSLOG_SUCCESS) || defined (SYSLOG_FAILURE)
463 /* Log the fact that someone has run su to the user given by PW;
464 if SUCCESSFUL is nonzero, they gave the correct password, etc. */
467 log_su (pw, successful)
471 const char *new_user, *old_user, *tty;
473 #ifndef SYSLOG_NON_ROOT
477 new_user = pw->pw_name;
478 /* The utmp entry (via getlogin) is probably the best way to identify
479 the user, especially if someone su's from a su-shell. */
480 old_user = getlogin ();
481 if (old_user == NULL)
486 /* 4.2BSD openlog doesn't have the third parameter. */
487 openlog (basename (program_name), 0
493 #ifdef SYSLOG_NON_ROOT
494 "%s(to %s) %s on %s",
498 successful ? "" : "FAILED SU ",
499 #ifdef SYSLOG_NON_ROOT
507 /* Return 1 if SHELL is a restricted shell (one not returned by
508 getusershell), else 0, meaning it is a standard shell. */
511 restricted_shell (shell)
517 while ((line = getusershell ()) != NULL)
519 if (*line != '#' && strcmp (line, shell) == 0)
529 /* Return the number of elements in ARR, a null-terminated array. */
537 for (n = 0; *arr; ++arr)
542 /* Add VAL to the environment, checking for out of memory errors. */
549 error (1, 0, "virtual memory exhausted");
552 /* Return a newly-allocated string whose contents concatenate
553 those of S1, S2, S3. */
559 int len1 = strlen (s1), len2 = strlen (s2), len3 = strlen (s3);
560 char *result = (char *) xmalloc (len1 + len2 + len3 + 1);
563 strcpy (result + len1, s2);
564 strcpy (result + len1 + len2, s3);
565 result[len1 + len2 + len3] = 0;
575 fprintf (stderr, "Try `%s --help' for more information.\n",
579 printf ("Usage: %s [OPTION]... [-] [USER [ARG]...]\n", program_name);
582 -l, --login make the shell a login shell\n\
583 -c, --commmand=COMMAND pass a single COMMAND to the shell with -c\n\
584 -f, --fast pass -f to the shell (for csh or tcsh)\n\
585 -m, --preserve-environment do not reset environment variables\n\
587 -s, --shell=SHELL run SHELL if /etc/shells allows it\n\
588 --help display this help and exit\n\
589 --version output version information and exit\n\
591 A mere - implies -l. If USER not given, assume root.\n\