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-rw-r--r--src/chsh.c541
1 files changed, 541 insertions, 0 deletions
diff --git a/src/chsh.c b/src/chsh.c
new file mode 100644
index 0000000..21d1c3e
--- /dev/null
+++ b/src/chsh.c
@@ -0,0 +1,541 @@
+/*
+ * SPDX-FileCopyrightText: 1989 - 1994, Julianne Frances Haugh
+ * SPDX-FileCopyrightText: 1996 - 2000, Marek Michałkiewicz
+ * SPDX-FileCopyrightText: 2001 - 2006, Tomasz Kłoczko
+ * SPDX-FileCopyrightText: 2007 - 2011, Nicolas François
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <config.h>
+
+#ident "$Id$"
+
+#include <fcntl.h>
+#include <getopt.h>
+#include <pwd.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include "defines.h"
+#include "getdef.h"
+#include "nscd.h"
+#include "sssd.h"
+#include "prototypes.h"
+#include "pwauth.h"
+#include "pwio.h"
+#ifdef USE_PAM
+#include "pam_defs.h"
+#endif
+/*@-exitarg@*/
+#include "exitcodes.h"
+#include "shadowlog.h"
+
+#ifndef SHELLS_FILE
+#define SHELLS_FILE "/etc/shells"
+#endif
+/*
+ * Global variables
+ */
+const char *Prog; /* Program name */
+static bool amroot; /* Real UID is root */
+static char loginsh[BUFSIZ]; /* Name of new login shell */
+/* command line options */
+static bool sflg = false; /* -s - set shell from command line */
+static bool pw_locked = false;
+
+/* external identifiers */
+
+/* local function prototypes */
+static /*@noreturn@*/void fail_exit (int code);
+static /*@noreturn@*/void usage (int status);
+static void new_fields (void);
+static bool shell_is_listed (const char *);
+static bool is_restricted_shell (const char *);
+static void process_flags (int argc, char **argv);
+static void check_perms (const struct passwd *pw);
+static void update_shell (const char *user, char *loginsh);
+
+/*
+ * fail_exit - do some cleanup and exit with the given error code
+ */
+static /*@noreturn@*/void fail_exit (int code)
+{
+ if (pw_locked) {
+ if (pw_unlock () == 0) {
+ fprintf (stderr, _("%s: failed to unlock %s\n"), Prog, pw_dbname ());
+ SYSLOG ((LOG_ERR, "failed to unlock %s", pw_dbname ()));
+ /* continue */
+ }
+ }
+
+ closelog ();
+
+ exit (code);
+}
+
+/*
+ * usage - print command line syntax and exit
+ */
+static /*@noreturn@*/void usage (int status)
+{
+ FILE *usageout = (E_SUCCESS != status) ? stderr : stdout;
+ (void) fprintf (usageout,
+ _("Usage: %s [options] [LOGIN]\n"
+ "\n"
+ "Options:\n"),
+ Prog);
+ (void) fputs (_(" -h, --help display this help message and exit\n"), usageout);
+ (void) fputs (_(" -R, --root CHROOT_DIR directory to chroot into\n"), usageout);
+ (void) fputs (_(" -s, --shell SHELL new login shell for the user account\n"), usageout);
+ (void) fputs ("\n", usageout);
+ exit (status);
+}
+
+/*
+ * new_fields - change the user's login shell information interactively
+ *
+ * prompt the user for the login shell and change it according to the
+ * response, or leave it alone if nothing was entered.
+ */
+static void new_fields (void)
+{
+ puts (_("Enter the new value, or press ENTER for the default"));
+ change_field (loginsh, sizeof loginsh, _("Login Shell"));
+}
+
+/*
+ * is_restricted_shell - return true if the shell is restricted
+ *
+ */
+static bool is_restricted_shell (const char *sh)
+{
+ /*
+ * Shells not listed in /etc/shells are considered to be restricted.
+ * Changed this to avoid confusion with "rc" (the plan9 shell - not
+ * restricted despite the name starting with 'r'). --marekm
+ */
+ return !shell_is_listed (sh);
+}
+
+/*
+ * shell_is_listed - see if the user's login shell is listed in /etc/shells
+ *
+ * The /etc/shells file is read for valid names of login shells. If the
+ * /etc/shells file does not exist the user cannot set any shell unless
+ * they are root.
+ *
+ * If getusershell() is available (Linux, *BSD, possibly others), use it
+ * instead of re-implementing it.
+ */
+static bool shell_is_listed (const char *sh)
+{
+ char *cp;
+ bool found = false;
+
+#ifndef HAVE_GETUSERSHELL
+ char buf[BUFSIZ];
+ FILE *fp;
+#endif
+
+#ifdef HAVE_GETUSERSHELL
+ setusershell ();
+ while ((cp = getusershell ())) {
+ if (strcmp (cp, sh) == 0) {
+ found = true;
+ break;
+ }
+ }
+ endusershell ();
+#else
+ fp = fopen (SHELLS_FILE, "r");
+ if (NULL == fp) {
+ return false;
+ }
+
+ while (fgets (buf, sizeof (buf), fp) == buf) {
+ cp = strrchr (buf, '\n');
+ if (NULL != cp) {
+ *cp = '\0';
+ }
+
+ if (buf[0] == '#') {
+ continue;
+ }
+
+ if (strcmp (buf, sh) == 0) {
+ found = true;
+ break;
+ }
+ }
+ fclose (fp);
+#endif
+ return found;
+}
+
+/*
+ * process_flags - parse the command line options
+ *
+ * It will not return if an error is encountered.
+ */
+static void process_flags (int argc, char **argv)
+{
+ int c;
+ static struct option long_options[] = {
+ {"help", no_argument, NULL, 'h'},
+ {"root", required_argument, NULL, 'R'},
+ {"shell", required_argument, NULL, 's'},
+ {NULL, 0, NULL, '\0'}
+ };
+
+ while ((c = getopt_long (argc, argv, "hR:s:",
+ long_options, NULL)) != -1) {
+ switch (c) {
+ case 'h':
+ usage (E_SUCCESS);
+ /*@notreached@*/break;
+ case 'R': /* no-op, handled in process_root_flag () */
+ break;
+ case 's':
+ sflg = true;
+ STRFCPY (loginsh, optarg);
+ break;
+ default:
+ usage (E_USAGE);
+ }
+ }
+
+ /*
+ * There should be only one remaining argument at most and it should
+ * be the user's name.
+ */
+ if (argc > (optind + 1)) {
+ usage (E_USAGE);
+ }
+}
+
+/*
+ * check_perms - check if the caller is allowed to add a group
+ *
+ * Non-root users are only allowed to change their shell, if their current
+ * shell is not a restricted shell.
+ *
+ * Non-root users must be authenticated.
+ *
+ * It will not return if the user is not allowed.
+ */
+static void check_perms (const struct passwd *pw)
+{
+#ifdef USE_PAM
+ pam_handle_t *pamh = NULL;
+ int retval;
+ struct passwd *pampw;
+#endif
+
+ /*
+ * Non-privileged users are only allowed to change the shell if the
+ * UID of the user matches the current real UID.
+ */
+ if (!amroot && pw->pw_uid != getuid ()) {
+ SYSLOG ((LOG_WARN, "can't change shell for '%s'", pw->pw_name));
+ fprintf (stderr,
+ _("You may not change the shell for '%s'.\n"),
+ pw->pw_name);
+ fail_exit (1);
+ }
+
+ /*
+ * Non-privileged users are only allowed to change the shell if it
+ * is not a restricted one.
+ */
+ if (!amroot && is_restricted_shell (pw->pw_shell)) {
+ SYSLOG ((LOG_WARN, "can't change shell for '%s'", pw->pw_name));
+ fprintf (stderr,
+ _("You may not change the shell for '%s'.\n"),
+ pw->pw_name);
+ fail_exit (1);
+ }
+#ifdef WITH_SELINUX
+ /*
+ * If the UID of the user does not match the current real UID,
+ * check if the change is allowed by SELinux policy.
+ */
+ if ((pw->pw_uid != getuid ())
+ && (check_selinux_permit("chsh") != 0)) {
+ SYSLOG ((LOG_WARN, "can't change shell for '%s'", pw->pw_name));
+ fprintf (stderr,
+ _("You may not change the shell for '%s'.\n"),
+ pw->pw_name);
+ fail_exit (1);
+ }
+#endif
+
+#ifndef USE_PAM
+ /*
+ * Non-privileged users are optionally authenticated (must enter
+ * the password of the user whose information is being changed)
+ * before any changes can be made. Idea from util-linux
+ * chfn/chsh. --marekm
+ */
+ if (!amroot && getdef_bool ("CHSH_AUTH")) {
+ passwd_check (pw->pw_name, pw->pw_passwd, "chsh");
+ }
+
+#else /* !USE_PAM */
+ pampw = getpwuid (getuid ()); /* local, no need for xgetpwuid */
+ if (NULL == pampw) {
+ fprintf (stderr,
+ _("%s: Cannot determine your user name.\n"),
+ Prog);
+ exit (E_NOPERM);
+ }
+
+ retval = pam_start ("chsh", pampw->pw_name, &conv, &pamh);
+
+ if (PAM_SUCCESS == retval) {
+ retval = pam_authenticate (pamh, 0);
+ }
+
+ if (PAM_SUCCESS == retval) {
+ retval = pam_acct_mgmt (pamh, 0);
+ }
+
+ if (PAM_SUCCESS != retval) {
+ fprintf (stderr, _("%s: PAM: %s\n"),
+ Prog, pam_strerror (pamh, retval));
+ SYSLOG((LOG_ERR, "%s", pam_strerror (pamh, retval)));
+ if (NULL != pamh) {
+ (void) pam_end (pamh, retval);
+ }
+ exit (E_NOPERM);
+ }
+ (void) pam_end (pamh, retval);
+#endif /* USE_PAM */
+}
+
+/*
+ * update_shell - update the user's shell in the passwd database
+ *
+ * Commit the user's entry after changing her shell field.
+ *
+ * It will not return in case of error.
+ */
+static void update_shell (const char *user, char *newshell)
+{
+ const struct passwd *pw; /* Password entry from /etc/passwd */
+ struct passwd pwent; /* New password entry */
+
+ /*
+ * Before going any further, raise the ulimit to prevent
+ * colliding into a lowered ulimit, and set the real UID
+ * to root to protect against unexpected signals. Any
+ * keyboard signals are set to be ignored.
+ */
+ if (setuid (0) != 0) {
+ SYSLOG ((LOG_ERR, "can't setuid(0)"));
+ fputs (_("Cannot change ID to root.\n"), stderr);
+ fail_exit (1);
+ }
+ pwd_init ();
+
+ /*
+ * The passwd entry is now ready to be committed back to
+ * the password file. Get a lock on the file and open it.
+ */
+ if (pw_lock () == 0) {
+ fprintf (stderr, _("%s: cannot lock %s; try again later.\n"),
+ Prog, pw_dbname ());
+ fail_exit (1);
+ }
+ pw_locked = true;
+ if (pw_open (O_CREAT | O_RDWR) == 0) {
+ fprintf (stderr, _("%s: cannot open %s\n"), Prog, pw_dbname ());
+ SYSLOG ((LOG_WARN, "cannot open %s", pw_dbname ()));
+ fail_exit (1);
+ }
+
+ /*
+ * Get the entry to update using pw_locate() - we want the real
+ * one from /etc/passwd, not the one from getpwnam() which could
+ * contain the shadow password if (despite the warnings) someone
+ * enables AUTOSHADOW (or SHADOW_COMPAT in libc). --marekm
+ */
+ pw = pw_locate (user);
+ if (NULL == pw) {
+ fprintf (stderr,
+ _("%s: user '%s' does not exist in %s\n"),
+ Prog, user, pw_dbname ());
+ fail_exit (1);
+ }
+
+ /*
+ * Make a copy of the entry, then change the shell field. The other
+ * fields remain unchanged.
+ */
+ pwent = *pw;
+ pwent.pw_shell = newshell;
+
+ /*
+ * Update the passwd file entry. If there is a DBM file, update
+ * that entry as well.
+ */
+ if (pw_update (&pwent) == 0) {
+ fprintf (stderr,
+ _("%s: failed to prepare the new %s entry '%s'\n"),
+ Prog, pw_dbname (), pwent.pw_name);
+ fail_exit (1);
+ }
+
+ /*
+ * Changes have all been made, so commit them and unlock the file.
+ */
+ if (pw_close () == 0) {
+ fprintf (stderr, _("%s: failure while writing changes to %s\n"), Prog, pw_dbname ());
+ SYSLOG ((LOG_ERR, "failure while writing changes to %s", pw_dbname ()));
+ fail_exit (1);
+ }
+ if (pw_unlock () == 0) {
+ fprintf (stderr, _("%s: failed to unlock %s\n"), Prog, pw_dbname ());
+ SYSLOG ((LOG_ERR, "failed to unlock %s", pw_dbname ()));
+ /* continue */
+ }
+ pw_locked= false;
+}
+
+/*
+ * chsh - this command controls changes to the user's shell
+ *
+ * The only supported option is -s which permits the the login shell to
+ * be set from the command line.
+ */
+int main (int argc, char **argv)
+{
+ char *user; /* User name */
+ const struct passwd *pw; /* Password entry from /etc/passwd */
+
+ sanitize_env ();
+
+ /*
+ * Get the program name. The program name is used as a prefix to
+ * most error messages.
+ */
+ Prog = Basename (argv[0]);
+ log_set_progname(Prog);
+ log_set_logfd(stderr);
+
+ (void) setlocale (LC_ALL, "");
+ (void) bindtextdomain (PACKAGE, LOCALEDIR);
+ (void) textdomain (PACKAGE);
+
+ process_root_flag ("-R", argc, argv);
+
+ /*
+ * This command behaves different for root and non-root users.
+ */
+ amroot = (getuid () == 0);
+
+ OPENLOG ("chsh");
+
+ /* parse the command line options */
+ process_flags (argc, argv);
+
+ /*
+ * Get the name of the user to check. It is either the command line
+ * name, or the name getlogin() returns.
+ */
+ if (optind < argc) {
+ user = argv[optind];
+ pw = xgetpwnam (user);
+ if (NULL == pw) {
+ fprintf (stderr,
+ _("%s: user '%s' does not exist\n"), Prog, user);
+ fail_exit (1);
+ }
+ } else {
+ pw = get_my_pwent ();
+ if (NULL == pw) {
+ fprintf (stderr,
+ _("%s: Cannot determine your user name.\n"),
+ Prog);
+ SYSLOG ((LOG_WARN, "Cannot determine the user name of the caller (UID %lu)",
+ (unsigned long) getuid ()));
+ fail_exit (1);
+ }
+ user = xstrdup (pw->pw_name);
+ }
+
+#ifdef USE_NIS
+ /*
+ * Now we make sure this is a LOCAL password entry for this user ...
+ */
+ if (__ispwNIS ()) {
+ char *nis_domain;
+ char *nis_master;
+
+ fprintf (stderr,
+ _("%s: cannot change user '%s' on NIS client.\n"),
+ Prog, user);
+
+ if (!yp_get_default_domain (&nis_domain) &&
+ !yp_master (nis_domain, "passwd.byname", &nis_master)) {
+ fprintf (stderr,
+ _("%s: '%s' is the NIS master for this client.\n"),
+ Prog, nis_master);
+ }
+ fail_exit (1);
+ }
+#endif
+
+ check_perms (pw);
+
+ /*
+ * Now get the login shell. Either get it from the password
+ * file, or use the value from the command line.
+ */
+ if (!sflg) {
+ STRFCPY (loginsh, pw->pw_shell);
+ }
+
+ /*
+ * If the login shell was not set on the command line, let the user
+ * interactively change it.
+ */
+ if (!sflg) {
+ printf (_("Changing the login shell for %s\n"), user);
+ new_fields ();
+ }
+
+ /*
+ * Check all of the fields for valid information. The shell
+ * field may not contain any illegal characters. Non-privileged
+ * users are restricted to using the shells in /etc/shells.
+ * The shell must be executable by the user.
+ */
+ if (valid_field (loginsh, ":,=\n") != 0) {
+ fprintf (stderr, _("%s: Invalid entry: %s\n"), Prog, loginsh);
+ fail_exit (1);
+ }
+ if ( !amroot
+ && ( is_restricted_shell (loginsh)
+ || (access (loginsh, X_OK) != 0))) {
+ fprintf (stderr, _("%s: %s is an invalid shell\n"), Prog, loginsh);
+ fail_exit (1);
+ }
+
+ /* Even for root, warn if an invalid shell is specified. */
+ if (access (loginsh, F_OK) != 0) {
+ fprintf (stderr, _("%s: Warning: %s does not exist\n"), Prog, loginsh);
+ } else if (access (loginsh, X_OK) != 0) {
+ fprintf (stderr, _("%s: Warning: %s is not executable\n"), Prog, loginsh);
+ }
+
+ update_shell (user, loginsh);
+
+ SYSLOG ((LOG_INFO, "changed user '%s' shell to '%s'", user, loginsh));
+
+ nscd_flush_cache ("passwd");
+ sssd_flush_cache (SSSD_DB_PASSWD);
+
+ closelog ();
+ exit (E_SUCCESS);
+}
+
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