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util.c
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util.c
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/* $Id$ */
/*
* Copyright (c) 2012 KAMADA Ken'ichi.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include "pathnames.h"
#include "util.h"
static void lose_pidfile(struct pidfile *pf);
int
run_as(const char *user)
{
struct passwd *pw;
if ((pw = getpwnam(user)) == NULL) {
LERR("%s: user not found", user);
return -1;
}
if (setgid(pw->pw_gid) == -1) {
LERR("setgid: %s", strerror(errno));
return -1;
}
if (setgroups(1, &pw->pw_gid) == -1) {
LERR("setgroups: %s", strerror(errno));
return -1;
}
if (setuid(pw->pw_uid) == -1) {
LERR("setuid: %s", strerror(errno));
return -1;
}
return 0;
}
struct pidfile *
make_pidfile(const char *myname)
{
struct pidfile *pf;
size_t dirlen, pathlen;
int ret;
dirlen = strlen(PIDFILE_DIR);
pathlen = dirlen + 1 + strlen(myname) + 4 + 1;
if (sizeof(*pf) + pathlen < sizeof(*pf) ||
(pf = (struct pidfile *)malloc(sizeof(*pf) + pathlen)) == NULL) {
LERR("out of memory");
return NULL;
}
pf->fd = -1;
pf->dirfd = -1;
ret = snprintf(pf->path, pathlen, "%s/%s.pid", PIDFILE_DIR, myname);
if (ret < 0 || (size_t)ret >= pathlen) {
LERR("too long PID file path");
lose_pidfile(pf);
return NULL;
}
pf->name = pf->path + dirlen + 1;
#if defined(ENABLE_CAPSICUM)
if ((pf->dirfd = open(PIDFILE_DIR, O_DIRECTORY)) == -1) {
LERR("open: %s: %s", PIDFILE_DIR, strerror(errno));
lose_pidfile(pf);
return NULL;
}
#endif
/*
* On BSD systems, use flock(2); otherwise, use fcntl(2).
* The fcntl locks are not inherited by a child process, so
* fcntl locking is done in write_pidfile().
*/
#ifdef O_EXLOCK
# define OPEN_FLAGS (O_WRONLY | O_CREAT | O_EXLOCK | O_NONBLOCK)
#else
# define OPEN_FLAGS (O_WRONLY | O_CREAT)
#endif
if ((pf->fd = open(pf->path, OPEN_FLAGS, 0644)) == -1) {
LERR("%s: open: %s", pf->path, strerror(errno));
lose_pidfile(pf);
return NULL;
}
#undef OPEN_FLAGS
return pf;
}
int
write_pidfile(struct pidfile *pf)
{
char pidstr[16];
pid_t pid;
int ret;
#ifndef O_EXLOCK
/* .l_start and .l_len are 0 to lock the entire file. */
if (fcntl(pf->fd, F_SETLK,
&(struct flock) { .l_whence = SEEK_SET, .l_type = F_WRLCK }
) == -1) {
LERR("%s: fcntl(F_SETLK): %s", pf->path, strerror(errno));
pf->name = NULL; /* mark to call lose_pidfile() */
return -1;
}
#endif
if (ftruncate(pf->fd, 0) == -1) {
LERR("%s: ftruncate: %s", pf->path, strerror(errno));
return -1;
}
pid = getpid();
ret = snprintf(pidstr, sizeof(pidstr), "%d\n", (int)pid);
if (ret < 0 || (size_t)ret >= sizeof(pidstr)) {
LERR("too large PID");
return -1;
}
if (write(pf->fd, pidstr, strlen(pidstr)) == -1) {
LERR("%s: write: %s", pf->path, strerror(errno));
return -1;
}
return 0;
}
void
cleanup_pidfile(struct pidfile *pf)
{
struct stat sb1, sb2;
if (pf == NULL)
return;
if (pf->name == NULL) {
lose_pidfile(pf);
return;
}
/* NB: race between stat() and unlink() */
if (fstat(pf->fd, &sb1) == -1)
LERR("fstat PID file failed: %s", strerror(errno));
#if defined(ENABLE_CAPSICUM)
else if (fstatat(pf->dirfd, pf->name, &sb2, 0) == -1)
LERR("%s: fstatat: %s", pf->path, strerror(errno));
#else
else if (stat(pf->path, &sb2) == -1)
LERR("%s: stat: %s", pf->path, strerror(errno));
#endif
else if (sb1.st_dev != sb2.st_dev || sb1.st_ino != sb2.st_ino)
LERR("PID file is replaced; exiting without unlinking it");
else {
/* If root priv has been dropped, unlink will fail. */
#if defined(ENABLE_CAPSICUM)
if (unlinkat(pf->dirfd, pf->name, 0) == -1 &&
ftruncate(pf->fd, 0) == -1)
LERR("%s: ftruncate: %s", pf->path, strerror(errno));
#else
if (unlink(pf->path) == -1 &&
ftruncate(pf->fd, 0) == -1)
LERR("%s: ftruncate: %s", pf->path, strerror(errno));
#endif
}
close(pf->fd);
if (pf->dirfd != -1)
close(pf->dirfd);
free(pf);
}
/* Unlike cleanup_pidfile(), this will never unlink the file. */
static void
lose_pidfile(struct pidfile *pf)
{
if (pf->fd != -1)
close(pf->fd);
if (pf->dirfd != -1)
close(pf->dirfd);
free(pf);
}