shadow/src/vipw.c
Todd C. Miller 7eca1112fb Fix vipw not resuming correctly when suspended
Closes #185

If vipw is suspended (e.g. via control-Z) and then resumed, it often gets
immediately suspended. This is easier to reproduce on a multi-core system.

root@buster:~# /usr/sbin/vipw

[1]+  Stopped                 /usr/sbin/vipw
root@buster:~# fg
/usr/sbin/vipw

[1]+  Stopped                 /usr/sbin/vipw

root@buster:~# fg
[vipw resumes on the second fg]

The problem is that vipw forks a child process and calls waitpid() with the
WUNTRACED flag. When the child process (running the editor) is suspended, the
parent sends itself SIGSTOP to suspend the main vipw process. However, because
the main vipw is in the same process group as the editor which received the ^Z,
the kernel already sent the main vipw SIGTSTP.

If the main vipw receives SIGTSTP before the child, it will be suspended and
then, once resumed, will proceed to suspend itself again.

To fix this, run the child process in its own process group as the foreground
process group. That way, control-Z will only affect the child process and the
parent can use the existing logic to suspend the parent.
2019-11-11 20:19:57 -06:00

608 lines
15 KiB
C

/*
vipw, vigr edit the password or group file
with -s will edit shadow or gshadow file
Copyright (c) 1997 , Guy Maor <maor@ece.utexas.edu>
Copyright (c) 1999 - 2000, Marek Michałkiewicz
Copyright (c) 2002 - 2006, Tomasz Kłoczko
Copyright (c) 2007 - 2013, Nicolas François
All rights reserved.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA. */
#include <config.h>
#ident "$Id$"
#include <errno.h>
#include <getopt.h>
#ifdef WITH_SELINUX
#include <selinux/selinux.h>
#endif /* WITH_SELINUX */
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <utime.h>
#include "defines.h"
#include "groupio.h"
#include "nscd.h"
#include "sssd.h"
#include "prototypes.h"
#include "pwio.h"
#include "sgroupio.h"
#include "shadowio.h"
/*@-exitarg@*/
#include "exitcodes.h"
#ifdef WITH_TCB
#include <tcb.h>
#include "tcbfuncs.h"
#endif /* WITH_TCB */
#define MSG_WARN_EDIT_OTHER_FILE _( \
"You have modified %s.\n"\
"You may need to modify %s for consistency.\n"\
"Please use the command '%s' to do so.\n")
/*
* Global variables
*/
const char *Prog;
static const char *filename, *fileeditname;
static bool filelocked = false;
static bool createedit = false;
static int (*unlock) (void);
static bool quiet = false;
#ifdef WITH_TCB
static const char *user = NULL;
static bool tcb_mode = false;
#define SHADOWTCB_SCRATCHDIR ":tmp"
#endif /* WITH_TCB */
/* local function prototypes */
static void usage (int status);
static int create_backup_file (FILE *, const char *, struct stat *);
static void vipwexit (const char *msg, int syserr, int ret);
static void vipwedit (const char *, int (*)(void), int (*)(void));
/*
* usage - display usage message and exit
*/
static void usage (int status)
{
FILE *usageout = (E_SUCCESS != status) ? stderr : stdout;
(void) fprintf (stderr,
_("Usage: %s [options]\n"
"\n"
"Options:\n"),
Prog);
(void) fputs (_(" -g, --group edit group database\n"), usageout);
(void) fputs (_(" -h, --help display this help message and exit\n"), usageout);
(void) fputs (_(" -p, --passwd edit passwd database\n"), usageout);
(void) fputs (_(" -q, --quiet quiet mode\n"), usageout);
(void) fputs (_(" -R, --root CHROOT_DIR directory to chroot into\n"), usageout);
(void) fputs (_(" -s, --shadow edit shadow or gshadow database\n"), usageout);
#ifdef WITH_TCB
(void) fputs (_(" -u, --user which user's tcb shadow file to edit\n"), usageout);
#endif /* WITH_TCB */
(void) fputs (_("\n"), usageout);
exit (status);
}
/*
*
*/
static int create_backup_file (FILE * fp, const char *backup, struct stat *sb)
{
struct utimbuf ub;
FILE *bkfp;
int c;
mode_t mask;
mask = umask (077);
bkfp = fopen (backup, "w");
(void) umask (mask);
if (NULL == bkfp) {
return -1;
}
c = 0;
if (fseeko (fp, 0, SEEK_SET) == 0)
while ((c = getc (fp)) != EOF) {
if (putc (c, bkfp) == EOF) {
break;
}
}
if ((EOF != c) || (ferror (fp) != 0) || (fflush (bkfp) != 0)) {
fclose (bkfp);
unlink (backup);
return -1;
}
if (fsync (fileno (bkfp)) != 0) {
(void) fclose (bkfp);
unlink (backup);
return -1;
}
if (fclose (bkfp) != 0) {
unlink (backup);
return -1;
}
ub.actime = sb->st_atime;
ub.modtime = sb->st_mtime;
if ( (utime (backup, &ub) != 0)
|| (chmod (backup, sb->st_mode) != 0)
|| (chown (backup, sb->st_uid, sb->st_gid) != 0)) {
unlink (backup);
return -1;
}
return 0;
}
/*
*
*/
static void vipwexit (const char *msg, int syserr, int ret)
{
int err = errno;
if (createedit) {
if (unlink (fileeditname) != 0) {
fprintf (stderr, _("%s: failed to remove %s\n"), Prog, fileeditname);
/* continue */
}
}
if (filelocked) {
if ((*unlock) () == 0) {
fprintf (stderr, _("%s: failed to unlock %s\n"), Prog, fileeditname);
SYSLOG ((LOG_ERR, "failed to unlock %s", fileeditname));
/* continue */
}
}
if (NULL != msg) {
fprintf (stderr, "%s: %s", Prog, msg);
}
if (0 != syserr) {
fprintf (stderr, ": %s", strerror (err));
}
if ( (NULL != msg)
|| (0 != syserr)) {
(void) fputs ("\n", stderr);
}
if (!quiet) {
fprintf (stdout, _("%s: %s is unchanged\n"), Prog,
filename);
}
exit (ret);
}
#ifndef DEFAULT_EDITOR
#define DEFAULT_EDITOR "vi"
#endif
/*
*
*/
static void
vipwedit (const char *file, int (*file_lock) (void), int (*file_unlock) (void))
{
const char *editor;
pid_t pid;
struct stat st1, st2;
int status;
FILE *f;
pid_t orig_pgrp, editor_pgrp = -1;
sigset_t mask, omask;
/* FIXME: the following should have variable sizes */
char filebackup[1024], fileedit[1024];
char *to_rename;
snprintf (filebackup, sizeof filebackup, "%s-", file);
#ifdef WITH_TCB
if (tcb_mode) {
if ( (mkdir (TCB_DIR "/" SHADOWTCB_SCRATCHDIR, 0700) != 0)
&& (errno != EEXIST)) {
vipwexit (_("failed to create scratch directory"), errno, 1);
}
if (shadowtcb_drop_priv () == SHADOWTCB_FAILURE) {
vipwexit (_("failed to drop privileges"), errno, 1);
}
snprintf (fileedit, sizeof fileedit,
TCB_DIR "/" SHADOWTCB_SCRATCHDIR "/.vipw.shadow.%s",
user);
} else {
#endif /* WITH_TCB */
snprintf (fileedit, sizeof fileedit, "%s.edit", file);
#ifdef WITH_TCB
}
#endif /* WITH_TCB */
unlock = file_unlock;
filename = file;
fileeditname = fileedit;
if (access (file, F_OK) != 0) {
vipwexit (file, 1, 1);
}
#ifdef WITH_SELINUX
/* if SE Linux is enabled then set the context of all new files
to be the context of the file we are editing */
if (is_selinux_enabled () != 0) {
security_context_t passwd_context=NULL;
int ret = 0;
if (getfilecon (file, &passwd_context) < 0) {
vipwexit (_("Couldn't get file context"), errno, 1);
}
ret = setfscreatecon (passwd_context);
freecon (passwd_context);
if (0 != ret) {
vipwexit (_("setfscreatecon () failed"), errno, 1);
}
}
#endif /* WITH_SELINUX */
#ifdef WITH_TCB
if (tcb_mode && (shadowtcb_gain_priv () == SHADOWTCB_FAILURE)) {
vipwexit (_("failed to gain privileges"), errno, 1);
}
#endif /* WITH_TCB */
if (file_lock () == 0) {
vipwexit (_("Couldn't lock file"), errno, 5);
}
filelocked = true;
#ifdef WITH_TCB
if (tcb_mode && (shadowtcb_drop_priv () == SHADOWTCB_FAILURE)) {
vipwexit (_("failed to drop privileges"), errno, 1);
}
#endif /* WITH_TCB */
/* edited copy has same owners, perm */
if (stat (file, &st1) != 0) {
vipwexit (file, 1, 1);
}
f = fopen (file, "r");
if (NULL == f) {
vipwexit (file, 1, 1);
}
#ifdef WITH_TCB
if (tcb_mode && (shadowtcb_gain_priv () == SHADOWTCB_FAILURE))
vipwexit (_("failed to gain privileges"), errno, 1);
#endif /* WITH_TCB */
if (create_backup_file (f, fileedit, &st1) != 0) {
vipwexit (_("Couldn't make backup"), errno, 1);
}
(void) fclose (f);
createedit = true;
editor = getenv ("VISUAL");
if (NULL == editor) {
editor = getenv ("EDITOR");
}
if (NULL == editor) {
editor = DEFAULT_EDITOR;
}
orig_pgrp = tcgetpgrp(STDIN_FILENO);
pid = fork ();
if (-1 == pid) {
vipwexit ("fork", 1, 1);
} else if (0 == pid) {
/* use the system() call to invoke the editor so that it accepts
command line args in the EDITOR and VISUAL environment vars */
char *buf;
int status;
/* Wait for parent to make us the foreground pgrp. */
if (orig_pgrp != -1) {
pid = getpid();
setpgid(0, 0);
while (tcgetpgrp(STDIN_FILENO) != pid)
continue;
}
buf = (char *) malloc (strlen (editor) + strlen (fileedit) + 2);
snprintf (buf, strlen (editor) + strlen (fileedit) + 2,
"%s %s", editor, fileedit);
status = system (buf);
if (-1 == status) {
fprintf (stderr, _("%s: %s: %s\n"), Prog, editor,
strerror (errno));
exit (1);
} else if ( WIFEXITED (status)
&& (WEXITSTATUS (status) != 0)) {
fprintf (stderr, _("%s: %s returned with status %d\n"),
Prog, editor, WEXITSTATUS (status));
exit (WEXITSTATUS (status));
} else if (WIFSIGNALED (status)) {
fprintf (stderr, _("%s: %s killed by signal %d\n"),
Prog, editor, WTERMSIG (status));
exit (1);
} else {
exit (0);
}
}
/* Run child in a new pgrp and make it the foreground pgrp. */
if (orig_pgrp != -1) {
setpgid(pid, pid);
tcsetpgrp(STDIN_FILENO, pid);
/* Avoid SIGTTOU when changing foreground pgrp below. */
sigemptyset(&mask);
sigaddset(&mask, SIGTTOU);
sigprocmask(SIG_BLOCK, &mask, &omask);
}
for (;;) {
pid = waitpid (pid, &status, WUNTRACED);
if ((pid != -1) && (WIFSTOPPED (status) != 0)) {
/* The child (editor) was suspended.
* Restore terminal pgrp and suspend vipw. */
if (orig_pgrp != -1) {
editor_pgrp = tcgetpgrp(STDIN_FILENO);
if (editor_pgrp == -1) {
fprintf (stderr, "%s: %s: %s", Prog,
"tcgetpgrp", strerror (errno));
}
if (tcsetpgrp(STDIN_FILENO, orig_pgrp) == -1) {
fprintf (stderr, "%s: %s: %s", Prog,
"tcsetpgrp", strerror (errno));
}
}
kill (getpid (), SIGSTOP);
/* wake child when resumed */
if (editor_pgrp != -1) {
if (tcsetpgrp(STDIN_FILENO, editor_pgrp) == -1) {
fprintf (stderr, "%s: %s: %s", Prog,
"tcsetpgrp", strerror (errno));
}
}
killpg (pid, SIGCONT);
} else {
break;
}
}
if (orig_pgrp != -1)
sigprocmask(SIG_SETMASK, &omask, NULL);
if (-1 == pid) {
vipwexit (editor, 1, 1);
} else if ( WIFEXITED (status)
&& (WEXITSTATUS (status) != 0)) {
vipwexit (NULL, 0, WEXITSTATUS (status));
} else if (WIFSIGNALED (status)) {
fprintf (stderr, _("%s: %s killed by signal %d\n"),
Prog, editor, WTERMSIG(status));
vipwexit (NULL, 0, 1);
}
if (stat (fileedit, &st2) != 0) {
vipwexit (fileedit, 1, 1);
}
if (st1.st_mtime == st2.st_mtime) {
vipwexit (0, 0, 0);
}
#ifdef WITH_SELINUX
/* unset the fscreatecon */
if (is_selinux_enabled () != 0) {
if (setfscreatecon (NULL) != 0) {
vipwexit (_("setfscreatecon () failed"), errno, 1);
}
}
#endif /* WITH_SELINUX */
/*
* XXX - here we should check fileedit for errors; if there are any,
* ask the user what to do (edit again, save changes anyway, or quit
* without saving). Use pwck or grpck to do the check. --marekm
*/
createedit = false;
#ifdef WITH_TCB
if (tcb_mode) {
f = fopen (fileedit, "r");
if (NULL == f) {
vipwexit (_("failed to open scratch file"), errno, 1);
}
if (unlink (fileedit) != 0) {
vipwexit (_("failed to unlink scratch file"), errno, 1);
}
if (shadowtcb_drop_priv () == SHADOWTCB_FAILURE) {
vipwexit (_("failed to drop privileges"), errno, 1);
}
if (stat (file, &st1) != 0) {
vipwexit (_("failed to stat edited file"), errno, 1);
}
to_rename = malloc (strlen (file) + 2);
if (NULL == to_rename) {
vipwexit (_("failed to allocate memory"), errno, 1);
}
snprintf (to_rename, strlen (file) + 2, "%s+", file);
if (create_backup_file (f, to_rename, &st1) != 0) {
free (to_rename);
vipwexit (_("failed to create backup file"), errno, 1);
}
(void) fclose (f);
} else {
#endif /* WITH_TCB */
to_rename = fileedit;
#ifdef WITH_TCB
}
#endif /* WITH_TCB */
unlink (filebackup);
link (file, filebackup);
if (rename (to_rename, file) == -1) {
fprintf (stderr,
_("%s: can't restore %s: %s (your changes are in %s)\n"),
Prog, file, strerror (errno), to_rename);
#ifdef WITH_TCB
if (tcb_mode) {
free (to_rename);
}
#endif /* WITH_TCB */
vipwexit (0, 0, 1);
}
#ifdef WITH_TCB
if (tcb_mode) {
free (to_rename);
if (shadowtcb_gain_priv () == SHADOWTCB_FAILURE) {
vipwexit (_("failed to gain privileges"), errno, 1);
}
}
#endif /* WITH_TCB */
if ((*file_unlock) () == 0) {
fprintf (stderr, _("%s: failed to unlock %s\n"), Prog, fileeditname);
SYSLOG ((LOG_ERR, "failed to unlock %s", fileeditname));
/* continue */
}
SYSLOG ((LOG_INFO, "file %s edited", fileeditname));
}
int main (int argc, char **argv)
{
bool editshadow = false;
bool do_vipw;
Prog = Basename (argv[0]);
(void) setlocale (LC_ALL, "");
(void) bindtextdomain (PACKAGE, LOCALEDIR);
(void) textdomain (PACKAGE);
process_root_flag ("-R", argc, argv);
do_vipw = (strcmp (Prog, "vigr") != 0);
OPENLOG (do_vipw ? "vipw" : "vigr");
{
/*
* Parse the command line options.
*/
int c;
static struct option long_options[] = {
{"group", no_argument, NULL, 'g'},
{"help", no_argument, NULL, 'h'},
{"passwd", no_argument, NULL, 'p'},
{"quiet", no_argument, NULL, 'q'},
{"root", required_argument, NULL, 'R'},
{"shadow", no_argument, NULL, 's'},
#ifdef WITH_TCB
{"user", required_argument, NULL, 'u'},
#endif /* WITH_TCB */
{NULL, 0, NULL, '\0'}
};
while ((c = getopt_long (argc, argv,
#ifdef WITH_TCB
"ghpqR:su:",
#else /* !WITH_TCB */
"ghpqR:s",
#endif /* !WITH_TCB */
long_options, NULL)) != -1) {
switch (c) {
case 'g':
do_vipw = false;
break;
case 'h':
usage (E_SUCCESS);
break;
case 'p':
do_vipw = true;
break;
case 'q':
quiet = true;
break;
case 'R': /* no-op, handled in process_root_flag () */
break;
case 's':
editshadow = true;
break;
#ifdef WITH_TCB
case 'u':
user = optarg;
break;
#endif /* WITH_TCB */
default:
usage (E_USAGE);
}
}
if (optind != argc) {
usage (E_USAGE);
}
}
if (do_vipw) {
if (editshadow) {
#ifdef WITH_TCB
if (getdef_bool ("USE_TCB") && (NULL != user)) {
if (shadowtcb_set_user (user) == SHADOWTCB_FAILURE) {
fprintf (stderr,
_("%s: failed to find tcb directory for %s\n"),
Prog, user);
return E_SHADOW_NOTFOUND;
}
tcb_mode = true;
}
#endif /* WITH_TCB */
vipwedit (spw_dbname (), spw_lock, spw_unlock);
printf (MSG_WARN_EDIT_OTHER_FILE,
spw_dbname (),
pw_dbname (),
"vipw");
} else {
vipwedit (pw_dbname (), pw_lock, pw_unlock);
if (spw_file_present ()) {
printf (MSG_WARN_EDIT_OTHER_FILE,
pw_dbname (),
spw_dbname (),
"vipw -s");
}
}
} else {
#ifdef SHADOWGRP
if (editshadow) {
vipwedit (sgr_dbname (), sgr_lock, sgr_unlock);
printf (MSG_WARN_EDIT_OTHER_FILE,
sgr_dbname (),
gr_dbname (),
"vigr");
} else {
#endif /* SHADOWGRP */
vipwedit (gr_dbname (), gr_lock, gr_unlock);
#ifdef SHADOWGRP
if (sgr_file_present ()) {
printf (MSG_WARN_EDIT_OTHER_FILE,
gr_dbname (),
sgr_dbname (),
"vigr -s");
}
}
#endif /* SHADOWGRP */
}
nscd_flush_cache ("passwd");
nscd_flush_cache ("group");
sssd_flush_cache (SSSD_DB_PASSWD | SSSD_DB_GROUP);
return E_SUCCESS;
}