From 3a71970808df0331af29418f5e85435a5a6290a5 Mon Sep 17 00:00:00 2001
From: Nick Kralevich <nnk@google.com>
Date: Mon, 18 Apr 2011 15:55:59 -0700
Subject: [PATCH] do not merge: Validate sender credentials on netlink msg
receive
Verify that netlink messages are actually from the kernel,
and not from a userspace program.
Change-Id: Ic6de75abc89df8969a8c4f84c06903d16208d35a
---
libsysutils/src/NetlinkListener.cpp | 29 ++++++++++++++++++++++++++---
1 file changed, 26 insertions(+), 3 deletions(-)
diff --git a/libsysutils/src/NetlinkListener.cpp b/libsysutils/src/NetlinkListener.cpp
index e2a354e4f0..fb088e1c3a 100644
--- a/libsysutils/src/NetlinkListener.cpp
+++ b/libsysutils/src/NetlinkListener.cpp
@@ -17,6 +17,7 @@
#include <sys/types.h>
#include <sys/socket.h>
+#include <linux/netlink.h>
#include <string.h>
#define LOG_TAG "NetlinkListener"
@@ -32,10 +33,32 @@ 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};
- if ((count = recv(socket, mBuffer, sizeof(mBuffer), 0)) < 0) {
- SLOGE("recv failed (%s)", strerror(errno));
+ if ((count = recvmsg(socket, &hdr, 0)) < 0) {
+ 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;
}
--
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