97 lines
2.0 KiB
C
97 lines
2.0 KiB
C
#include "uevent.h"
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#include <errno.h>
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#include <stdbool.h>
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#include <string.h>
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#include <strings.h>
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#include <sys/socket.h>
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#include <sys/un.h>
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#include <unistd.h>
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#include <linux/netlink.h>
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#define SCM_CREDENTIALS 0x02 /* Credentials passing. */
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#ifdef __cplusplus
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extern "C" {
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#endif
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int uevent_open_socket(int buf_sz, bool passcred)
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{
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struct sockaddr_nl addr;
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int on = passcred;
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int s;
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memset(&addr, 0, sizeof(addr));
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addr.nl_pid = getpid();
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addr.nl_family = AF_NETLINK;
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addr.nl_groups = 0xffffffff;
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s = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
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if(s < 0)
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return -1;
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setsockopt(s, SOL_SOCKET, SO_RCVBUFFORCE, &buf_sz, sizeof(buf_sz));
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setsockopt(s, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on));
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if(bind(s, (struct sockaddr *) &addr, sizeof(addr)) < 0) {
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close(s);
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return -1;
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}
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return s;
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}
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ssize_t uevent_kernel_multicast_recv(int socket, void *buffer, size_t length) {
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struct sockaddr_nl addr;
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struct iovec iov = { buffer, length };
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struct cmsghdr *cmsg;
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struct ucred *cred;
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char control[CMSG_SPACE(sizeof(struct ucred))];
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struct msghdr hdr = {
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&addr,
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sizeof(addr),
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&iov,
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1,
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control,
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sizeof(control),
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0,
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};
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ssize_t n = recvmsg(socket, &hdr, 0);
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if (n <= 0) {
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return n;
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}
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if (addr.nl_groups == 0 || addr.nl_pid != 0) {
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/* ignoring non-kernel or unicast netlink message */
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goto out;
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}
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cmsg = CMSG_FIRSTHDR(&hdr);
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if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
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/* ignoring netlink message with no sender credentials */
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goto out;
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}
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cred = (struct ucred *)CMSG_DATA(cmsg);
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if (cred->uid != 0) {
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/* ignoring netlink message from non-root user */
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goto out;
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}
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return n;
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out:
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/* clear residual potentially malicious data */
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bzero(buffer, length);
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errno = EIO;
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return -1;
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}
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#ifdef __cplusplus
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}
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#endif
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