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/*
* Copy me if you can.
* by 20h
*/
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <poll.h>
#include <ctype.h>
#include <string.h>
#include <errno.h>
#include <signal.h>
#include <libgen.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <linux/types.h>
#include <linux/netlink.h>
#include "arg.h"
#include "log.h"
int listfd = -1;
int dofork = 0;
struct handler {
int fd;
int argc;
char **argv;
};
void
disableoom(void)
{
int fd;
fd = open("/proc/self/oom_score_adj", O_RDWR);
if (fd < 0) {
fd = open("/proc/self/oom_adj", O_RDWR);
if (fd < 0)
edie("disabling oom failed.");
write(fd, "-17", 3);
close(fd);
} else {
write(fd, "-1000", 5);
close(fd);
}
}
void
spawn_handler(struct handler *child)
{
int pipefd[2];
if (pipe(pipefd) == -1)
edie("pipe");
pid_t pid = fork();
if (pid < 0)
edie("fork");
if (pid == 0) {
close(pipefd[1]);
dup2(pipefd[0], 0);
execv(child->argv[0], child->argv);
edie("execl");
}
close(pipefd[0]);
child->fd = pipefd[1];
}
int
write_to_handler(struct handler *child, const char *buf, size_t count)
{
if (child->fd == -1)
spawn_handler(child);
return write(child->fd, buf, count);
}
void
sighandler(int sig)
{
switch(sig) {
case SIGHUP:
case SIGINT:
case SIGQUIT:
case SIGABRT:
case SIGTERM:
if (listfd >= 0) {
shutdown(listfd, SHUT_RDWR);
close(listfd);
}
exit(0);
break;
default:
break;
}
}
void
initsignals(void)
{
signal(SIGHUP, sighandler);
signal(SIGINT, sighandler);
signal(SIGQUIT, sighandler);
signal(SIGABRT, sighandler);
signal(SIGTERM, sighandler);
signal(SIGCHLD, SIG_IGN);
signal(SIGPIPE, SIG_IGN);
}
int
init_netlink_socket(void)
{
struct sockaddr_nl nls;
int fd, slen;
memset(&nls, 0, sizeof(nls));
nls.nl_family = AF_NETLINK;
nls.nl_pid = getpid();
nls.nl_groups = -1;
fd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
if (fd < 0)
edie("socket");
slen = 128*1024*1024;
if (setsockopt(fd, SOL_SOCKET, SO_RCVBUFFORCE, &slen,
sizeof(slen)) < 0) {
edie("setsockopt");
}
slen = 1;
if (setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &slen,
sizeof(slen)) < 0) {
edie("setsockopt");
}
if (bind(fd, (void *)&nls, sizeof(nls)))
edie("bind");
return fd;
}
void
usage(void)
{
die("usage: %s [-hdb] [-ku] [-- run [...]]\n", argv0);
}
int
main(int argc, char *argv[])
{
struct sockaddr_nl cnls;
struct pollfd fds[2];
struct msghdr hdr;
struct iovec iov;
char buf[4097], cbuf[CMSG_SPACE(sizeof(struct ucred))];
struct cmsghdr *chdr;
struct ucred *cred;
int len, showudev, showkernel;
struct handler child;
showkernel = 1;
showudev = 1;
ARGBEGIN {
case 'b':
dofork = 1;
break;
case 'd':
dodebug = 1;
break;
case 'k':
showudev = 0;
break;
case 'u':
showkernel = 0;
break;
default:
usage();
} ARGEND;
child.fd = -1;
child.argc = argc;
child.argv = argv;
fds[0].events = POLLIN;
fds[0].fd = init_netlink_socket();
fds[1].fd = child.fd;
fds[1].events = POLLERR;
listfd = fds[0].fd;
if (dofork) {
if (daemon(0, 0) < 0)
edie("daemon");
umask(022);
}
initsignals();
disableoom();
buf[sizeof(buf)-1] = '\0';
while (poll(fds, 2, -1) > -1) {
if (fds[1].revents & POLLERR) {
dbg("handler exited");
close(child.fd);
fds[1].fd = child.fd = -1;
}
if (!(fds[0].revents & POLLIN))
continue;
iov.iov_base = &buf;
iov.iov_len = sizeof(buf);
memset(&hdr, 0, sizeof(hdr));
hdr.msg_iov = &iov;
hdr.msg_iovlen = 1;
hdr.msg_control = cbuf;
hdr.msg_controllen = sizeof(cbuf);
hdr.msg_name = &cnls;
hdr.msg_namelen = sizeof(cnls);
len = recvmsg(fds[0].fd, &hdr, 0);
if (len < 0) {
if (errno == EINTR)
continue;
edie("recvmsg");
}
if (len < 32 || len >= sizeof(buf))
continue;
chdr = CMSG_FIRSTHDR(&hdr);
if (chdr == NULL || chdr->cmsg_type != SCM_CREDENTIALS)
continue;
/*
* Don't allow anyone but root to send us messages.
*
* We will allow users to send us messages, when
* udev is enabled. Udev is just a toy you should
* only use for testing.
*/
cred = (struct ucred *)CMSG_DATA(chdr);
if (cred->uid != 0 && !showudev)
continue;
if (!memcmp(buf, "libudev", 8)) {
/*
* Receiving messages from udev is insecure.
*/
if (!showudev)
continue;
} else {
if (!showkernel)
continue;
/*
* Kernel messages shouldn't come from the
* userspace.
*/
if (cnls.nl_pid > 0)
continue;
}
write_to_handler(&child, buf, len);
fds[1].fd = child.fd;
}
shutdown(listfd, SHUT_RDWR);
close(listfd);
return 0;
}
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