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 $SHELL instead of USER's shell from /etc/passwd
56 unless not the superuser and USER's shell is
58 Overridden by --login and --shell.
59 -s, --shell=shell Run SHELL instead of USER's shell from /etc/passwd
60 unless not the superuser and USER's shell is
64 -DSYSLOG_SUCCESS Log successful su's (by default, to root) with syslog.
65 -DSYSLOG_FAILURE Log failed su's (by default, to root) with syslog.
67 -DSYSLOG_NON_ROOT Log all su's, not just those to root (UID 0).
68 Never logs attempted su's to nonexistent accounts.
70 Written by David MacKenzie <djm@gnu.ai.mit.edu>. */
73 #if defined (CONFIG_BROKETS)
74 /* We use <config.h> instead of "config.h" so that a compilation
75 using -I. -I$srcdir will use ./config.h rather than $srcdir/config.h
76 (which it would do because it found this file in $srcdir). */
85 #include <sys/types.h>
92 static void log_su ();
93 #else /* !HAVE_SYSLOG_H */
100 #ifdef SYSLOG_NON_ROOT
101 #undef SYSLOG_NON_ROOT
103 #endif /* !HAVE_SYSLOG_H */
105 #ifdef _POSIX_VERSION
110 #define NGROUPS_MAX sysconf (_SC_NGROUPS_MAX)
111 #else /* not _POSIX_VERSION */
112 struct passwd *getpwuid ();
113 struct group *getgrgid ();
115 #include <sys/param.h>
116 #if !defined(NGROUPS_MAX) && defined(NGROUPS)
117 #define NGROUPS_MAX NGROUPS
119 #endif /* not _POSIX_VERSION */
121 #ifndef HAVE_ENDGRENT
125 #ifndef HAVE_ENDPWENT
135 /* The default PATH for simulated logins to non-superuser accounts. */
136 #define DEFAULT_LOGIN_PATH ":/usr/ucb:/bin:/usr/bin"
138 /* The default PATH for simulated logins to superuser accounts. */
139 #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 ();
159 static char *concat ();
160 static int correct_password ();
161 static int elements ();
162 static int restricted_shell ();
163 static void change_identity ();
164 static void modify_environment ();
165 static void run_shell ();
166 static void usage ();
167 static void xputenv ();
169 extern char **environ;
171 /* The name this program was run with. */
174 /* If non-zero, display usage information and exit. */
175 static int show_help;
177 /* If non-zero, print the version on standard output and exit. */
178 static int show_version;
180 /* If nonzero, pass the `-f' option to the subshell. */
181 static int fast_startup;
183 /* If nonzero, simulate a login instead of just starting a shell. */
184 static int simulate_login;
186 /* If nonzero, change some environment vars to indicate the user su'd to. */
187 static int change_environment;
189 static struct option const longopts[] =
191 {"command", required_argument, 0, 'c'},
192 {"fast", no_argument, &fast_startup, 1},
193 {"help", no_argument, &show_help, 1},
194 {"login", no_argument, &simulate_login, 1},
195 {"preserve-environment", no_argument, &change_environment, 0},
196 {"shell", required_argument, 0, 's'},
197 {"version", no_argument, &show_version, 1},
207 char *new_user = DEFAULT_USER;
209 char **additional_args = 0;
212 struct passwd pw_copy;
214 program_name = argv[0];
217 change_environment = 1;
219 while ((optc = getopt_long (argc, argv, "c:flmps:", longopts, (int *) 0))
241 change_environment = 0;
255 printf ("su - %s\n", version_string);
262 if (optind < argc && !strcmp (argv[optind], "-"))
268 new_user = argv[optind++];
270 additional_args = argv + optind;
272 pw = getpwnam (new_user);
274 error (1, 0, "user %s does not exist", new_user);
277 /* Make a copy of the password information and point pw at the local
278 copy instead. Otherwise, some systems (e.g. Linux) would clobber
279 the static data through the getlogin call from log_su. */
282 pw->pw_name = xstrdup (pw->pw_name);
283 pw->pw_dir = xstrdup (pw->pw_dir);
284 pw->pw_shell = xstrdup (pw->pw_shell);
286 if (!correct_password (pw))
288 #ifdef SYSLOG_FAILURE
291 error (1, 0, "incorrect password");
293 #ifdef SYSLOG_SUCCESS
300 if (pw->pw_shell == 0 || pw->pw_shell[0] == 0)
301 pw->pw_shell = DEFAULT_SHELL;
302 if (shell == 0 && change_environment == 0)
303 shell = getenv ("SHELL");
304 if (shell != 0 && getuid () && restricted_shell (pw->pw_shell))
306 /* The user being su'd to has a nonstandard shell, and so is
307 probably a uucp account or has restricted access. Don't
308 compromise the account by allowing access with a standard
310 error (0, 0, "using restricted shell %s", pw->pw_shell);
315 shell = xstrdup (pw->pw_shell);
317 modify_environment (pw, shell);
319 change_identity (pw);
320 if (simulate_login && chdir (pw->pw_dir))
321 error (0, errno, "warning: cannot change directory to %s", pw->pw_dir);
323 run_shell (shell, command, additional_args);
326 /* Ask the user for a password.
327 Return 1 if the user gives the correct password for entry PW,
328 0 if not. Return 1 without asking for a password if run by UID 0
329 or if PW has an empty password. */
332 correct_password (pw)
335 char *unencrypted, *encrypted, *correct;
337 /* Shadow passwd stuff for SVR3 and maybe other systems. */
338 struct spwd *sp = getspnam (pw->pw_name);
342 correct = sp->sp_pwdp;
345 correct = pw->pw_passwd;
347 if (getuid () == 0 || correct == 0 || correct[0] == '\0')
350 unencrypted = getpass ("Password:");
351 if (unencrypted == NULL)
353 error (0, 0, "getpass: cannot open /dev/tty");
356 encrypted = crypt (unencrypted, correct);
357 bzero (unencrypted, strlen (unencrypted));
358 return strcmp (encrypted, correct) == 0;
361 /* Update `environ' for the new shell based on PW, with SHELL being
362 the value for the SHELL environment variable. */
365 modify_environment (pw, shell)
373 /* Leave TERM unchanged. Set HOME, SHELL, USER, LOGNAME, PATH.
374 Unset all other environment variables. */
375 term = getenv ("TERM");
376 environ = (char **) xmalloc (2 * sizeof (char *));
379 xputenv (concat ("TERM", "=", term));
380 xputenv (concat ("HOME", "=", pw->pw_dir));
381 xputenv (concat ("SHELL", "=", shell));
382 xputenv (concat ("USER", "=", pw->pw_name));
383 xputenv (concat ("LOGNAME", "=", pw->pw_name));
384 xputenv (concat ("PATH", "=", pw->pw_uid
385 ? DEFAULT_LOGIN_PATH : DEFAULT_ROOT_LOGIN_PATH));
389 /* Set HOME, SHELL, and if not becoming a super-user,
391 if (change_environment)
393 xputenv (concat ("HOME", "=", pw->pw_dir));
394 xputenv (concat ("SHELL", "=", shell));
397 xputenv (concat ("USER", "=", pw->pw_name));
398 xputenv (concat ("LOGNAME", "=", pw->pw_name));
404 /* Become the user and group(s) specified by PW. */
412 if (initgroups (pw->pw_name, pw->pw_gid) == -1)
413 error (1, errno, "cannot set groups");
416 if (setgid (pw->pw_gid))
417 error (1, errno, "cannot set group id");
418 if (setuid (pw->pw_uid))
419 error (1, errno, "cannot set user id");
422 /* Run SHELL, or DEFAULT_SHELL if SHELL is empty.
423 If COMMAND is nonzero, pass it to the shell with the -c option.
424 If ADDITIONAL_ARGS is nonzero, pass it to the shell as more
428 run_shell (shell, command, additional_args)
431 char **additional_args;
437 args = (char **) xmalloc (sizeof (char *)
438 * (10 + elements (additional_args)));
440 args = (char **) xmalloc (sizeof (char *) * 10);
443 args[0] = xmalloc (strlen (shell) + 2);
445 strcpy (args[0] + 1, basename (shell));
448 args[0] = basename (shell);
450 args[argno++] = "-f";
453 args[argno++] = "-c";
454 args[argno++] = command;
457 for (; *additional_args; ++additional_args)
458 args[argno++] = *additional_args;
461 error (1, errno, "cannot run %s", shell);
464 #if defined (SYSLOG_SUCCESS) || defined (SYSLOG_FAILURE)
465 /* Log the fact that someone has run su to the user given by PW;
466 if SUCCESSFUL is nonzero, they gave the correct password, etc. */
469 log_su (pw, successful)
473 char *new_user, *old_user, *tty;
475 #ifndef SYSLOG_NON_ROOT
479 new_user = pw->pw_name;
480 /* The utmp entry (via getlogin) is probably the best way to identify
481 the user, especially if someone su's from a su-shell. */
482 old_user = getlogin ();
483 if (old_user == NULL)
488 /* 4.2BSD openlog doesn't have the third parameter. */
489 openlog (basename (program_name), 0
495 #ifdef SYSLOG_NON_ROOT
496 "%s(to %s) %s on %s",
500 successful ? "" : "FAILED SU ",
501 #ifdef SYSLOG_NON_ROOT
509 /* Return 1 if SHELL is a restricted shell (one not returned by
510 getusershell), else 0, meaning it is a standard shell. */
513 restricted_shell (shell)
519 while ((line = getusershell ()) != NULL)
521 if (*line != '#' && strcmp (line, shell) == 0)
531 /* Return the number of elements in ARR, a null-terminated array. */
539 for (n = 0; *arr; ++arr)
544 /* Add VAL to the environment, checking for out of memory errors. */
551 error (1, 0, "virtual memory exhausted");
554 /* Return a newly-allocated string whose contents concatenate
555 those of S1, S2, S3. */
561 int len1 = strlen (s1), len2 = strlen (s2), len3 = strlen (s3);
562 char *result = (char *) xmalloc (len1 + len2 + len3 + 1);
565 strcpy (result + len1, s2);
566 strcpy (result + len1 + len2, s3);
567 result[len1 + len2 + len3] = 0;
577 fprintf (stderr, "Try `%s --help' for more information.\n",
581 printf ("Usage: %s [OPTION]... [-] [USER [ARG]...]\n", program_name);
584 -l, --login make the shell a login shell\n\
585 -c, --commmand=COMMAND pass a single COMMAND to the shell with -c\n\
586 -f, --fast pass -f to the shell (for csh or tcsh)\n\
587 -m, --preserve-environment do not reset environment variables\n\
589 -s, --shell=SHELL run SHELL if /etc/shells allows it\n\
590 --help display this help and exit\n\
591 --version output version information and exit\n\
593 A mere - implies -l. If USER not given, assume root.\n\