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/* Copyright (C) 2022 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
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 3 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, see <https://www.gnu.org/licenses/>.
*/
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include "knot/common/log.h"
#include "knot/common/process.h"
#include "knot/conf/conf.h"
#include "libknot/errcode.h"
static char* pid_filename(void)
{
conf_val_t val = conf_get(conf(), C_SRV, C_RUNDIR);
char *rundir = conf_abs_path(&val, NULL);
val = conf_get(conf(), C_SRV, C_PIDFILE);
char *pidfile = conf_abs_path(&val, rundir);
free(rundir);
return pidfile;
}
static pid_t pid_read(const char *filename)
{
if (filename == NULL) {
return 0;
}
size_t len = 0;
char buf[64] = { 0 };
FILE *fp = fopen(filename, "r");
if (fp == NULL) {
return 0;
}
/* Read the content of the file. */
len = fread(buf, 1, sizeof(buf) - 1, fp);
fclose(fp);
if (len < 1) {
return 0;
}
/* Convert pid. */
errno = 0;
char *end = 0;
unsigned long pid = strtoul(buf, &end, 10);
if (end == buf || *end != '\0'|| errno != 0) {
return 0;
}
return (pid_t)pid;
}
static int pid_write(const char *filename, pid_t pid)
{
if (filename == NULL) {
return KNOT_EINVAL;
}
/* Convert. */
char buf[64];
int len = 0;
len = snprintf(buf, sizeof(buf), "%lu", (unsigned long)pid);
if (len < 0 || len >= sizeof(buf)) {
return KNOT_ENOMEM;
}
/* Create file. */
int ret = KNOT_EOK;
int fd = open(filename, O_RDWR|O_CREAT, S_IRUSR|S_IWUSR|S_IRGRP);
if (fd >= 0) {
if (write(fd, buf, len) != len) {
ret = knot_map_errno();
}
close(fd);
} else {
ret = knot_map_errno();
}
return ret;
}
unsigned long pid_check_and_create(void)
{
struct stat st;
char *pidfile = pid_filename();
pid_t pid = pid_read(pidfile);
/* Check PID for existence and liveness. */
if (pid > 0 && pid_running(pid)) {
log_fatal("server PID found, already running");
free(pidfile);
return 0;
} else if (stat(pidfile, &st) == 0) {
assert(pidfile);
log_warning("removing stale PID file '%s'", pidfile);
pid_cleanup();
}
/* Get current PID. */
pid = getpid();
/* Create a PID file. */
int ret = pid_write(pidfile, pid);
if (ret != KNOT_EOK) {
log_fatal("failed to create a PID file '%s' (%s)", pidfile,
knot_strerror(ret));
free(pidfile);
return 0;
}
free(pidfile);
return (unsigned long)pid;
}
void pid_cleanup(void)
{
char *pidfile = pid_filename();
if (pidfile != NULL) {
(void)unlink(pidfile);
free(pidfile);
}
}
bool pid_running(pid_t pid)
{
return kill(pid, 0) == 0;
}
int proc_update_privileges(int uid, int gid)
{
#ifdef HAVE_SETGROUPS
/* Drop supplementary groups. */
if ((uid_t)uid != getuid() || (gid_t)gid != getgid()) {
if (setgroups(0, NULL) < 0) {
log_warning("failed to drop supplementary groups for "
"UID %d (%s)", getuid(), strerror(errno));
}
# ifdef HAVE_INITGROUPS
struct passwd *pw;
if ((pw = getpwuid(uid)) == NULL) {
log_warning("failed to get passwd entry for UID %d (%s)",
uid, strerror(errno));
} else {
if (initgroups(pw->pw_name, gid) < 0) {
log_warning("failed to set supplementary groups "
"for UID %d (%s)", uid, strerror(errno));
}
}
# endif /* HAVE_INITGROUPS */
}
#endif /* HAVE_SETGROUPS */
/* Watch uid/gid. */
if ((gid_t)gid != getgid()) {
log_info("changing GID to %d", gid);
if (setregid(gid, gid) < 0) {
log_error("failed to change GID to %d", gid);
return KNOT_ERROR;
}
}
if ((uid_t)uid != getuid()) {
log_info("changing UID to %d", uid);
if (setreuid(uid, uid) < 0) {
log_error("failed to change UID to %d", uid);
return KNOT_ERROR;
}
}
return KNOT_EOK;
}
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