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#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#include "log.h"
#define EVENT_TIMEOUT 2000
void
child(char *runpath)
{
pid_t pid;
if (!(pid = fork())) {
dbg("running %s", runpath);
if (execlp(runpath, basename(runpath), NULL) < 0)
edie("execvp");
exit(0);
}
if (pid < 0)
edie("fork");
waitpid(pid, NULL, 0);
}
void
usage(void)
{
die("usage: %s [-dku] [-f subsystem] [-r run]\n", argv0);
}
int main(int argc, char *argv[])
{
struct pollfd fds;
int r;
char *runpath = "/bin/mdev";
char *subsystem = NULL;
int showudev, showkernel;
showudev = 1;
showkernel = 1;
ARGBEGIN {
case 'd':
dodebug = 1;
break;
case 'k':
showudev = 0;
break;
case 'u':
showkernel = 0;
break;
case 'r':
runpath = EARGF(usage());
break;
case 'f':
subsystem = EARGF(usage());
break;
default:
usage();
} ARGEND;
dbg("runpath=%s\n", runpath);
fds.fd = 0; /* stdin */
fds.events = POLLIN;
while ((r = poll(&fds, 1, EVENT_TIMEOUT)) > 0) {
size_t len;
int i, slen;
char *key, *value;
struct iovec iov;
char cbuf[CMSG_SPACE(sizeof(struct ucred))];
char buf[16384];
struct cmsghdr *chdr;
struct ucred *cred;
struct msghdr hdr;
struct sockaddr_nl cnls;
clearenv();
setenv("PATH", "/sbin:/bin", 1);
if (!(fds.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.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;
}
for (i = 0; i < len; i += slen + 1) {
key = buf + i;
value = strchr(key, '=');
slen = strlen(buf+i);
if (!slen || value == NULL)
continue;
if (subsystem && !strncmp(key, "SUBSYSTEM=", 10)
&& !strstr(key+10, subsystem)) {
dbg("subsystem filter '%s' applied.",
subsystem);
break;
}
value[0] = '\0';
value++;
/*
* We generally trust the kernel. But there
* might be some udev flaw. (It's >20k sloc!)
*/
if (strcmp(key, "PATH")) {
setenv(key, value, 1);
dbg("%s = \"%s\"", key, value);
}
}
if (getenv("ACTION") != NULL &&
getenv("DEVPATH") != NULL &&
getenv("SUBSYSTEM") != NULL &&
getenv("SEQNUM") != NULL) {
child(runpath);
}
if (fds.revents & POLLHUP) {
dbg("parent hung up\n");
return 0;
}
}
if (r == -1)
edie("poll");
if (r == 0)
dbg("exit due to timeout");
return 0;
}
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