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Validate sender credentials on netlink msg receive

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Verify that netlink messages are actually from the kernel,
and not from a userspace program.

This is a manual cherry-pick from b620a0b1c7

Change-Id: I237f0a5cb56393bb3aab64a7ae5898f2bdc95cef
This commit is contained in:
Nick Kralevich 2011-04-18 15:55:59 -07:00
parent 71ead18353
commit 6bc0828010
1 changed files with 26 additions and 3 deletions
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29
libsysutils/src/NetlinkListener.cpp
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@ -17,6 +17,7 @@
#include <sys/types.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#include <string.h>
#define LOG_TAG "NetlinkListener"
@ -32,11 +33,33 @@ NetlinkListener::NetlinkListener(int socket) :
bool NetlinkListener::onDataAvailable(SocketClient *cli)
{
int socket = cli->getSocket();
int count;
ssize_t count;
char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
struct sockaddr_nl snl;
struct iovec iov = {mBuffer, sizeof(mBuffer)};
struct msghdr hdr = {&snl, sizeof(snl), &iov, 1, cred_msg, sizeof(cred_msg), 0};
count = TEMP_FAILURE_RETRY(recv(socket, mBuffer, sizeof(mBuffer), 0));
count = TEMP_FAILURE_RETRY(recvmsg(socket, &hdr, 0));
if (count < 0) {
SLOGE("recv failed (%s)", strerror(errno));
SLOGE("recvmsg failed (%s)", strerror(errno));
return false;
}
if ((snl.nl_groups != 1) || (snl.nl_pid != 0)) {
SLOGE("ignoring non-kernel netlink multicast message");
return false;
}
struct cmsghdr * cmsg = CMSG_FIRSTHDR(&hdr);
if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
SLOGE("ignoring message with no sender credentials");
return false;
}
struct ucred * cred = (struct ucred *)CMSG_DATA(cmsg);
if (cred->uid != 0) {
SLOGE("ignoring message from non-root UID %d", cred->uid);
return false;
}