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-rw-r--r--ares/CHANGES12
-rw-r--r--ares/RELEASE-NOTES1
-rw-r--r--ares/ares_process.c16
3 files changed, 28 insertions, 1 deletions
diff --git a/ares/CHANGES b/ares/CHANGES
index dff8e8d67..16e55bebe 100644
--- a/ares/CHANGES
+++ b/ares/CHANGES
@@ -1,5 +1,17 @@
Changelog for the c-ares project
+* Aug 25 2008 (Yang Tse)
+- Improvement by Brad House:
+
+ This patch addresses an issue in which a response could be sent back to the
+ source port of a client from a different address than the request was made to.
+ This is one form of a DNS cache poisoning attack.
+
+ The patch simply uses recvfrom() rather than recv() and validates that the
+ address returned from recvfrom() matches the address of the server we have
+ connected to. Only necessary on UDP sockets as they are connection-less, TCP
+ is unaffected.
+
* Aug 4 2008 (Daniel Stenberg)
- Fix by Tofu Linden:
diff --git a/ares/RELEASE-NOTES b/ares/RELEASE-NOTES
index eb9110dcf..388816052 100644
--- a/ares/RELEASE-NOTES
+++ b/ares/RELEASE-NOTES
@@ -9,6 +9,7 @@ This is what's new and changed in the c-ares 1.5.3 release:
o library will now be built with _REENTRANT symbol defined if needed
o Improved configure detection of number of arguments for getservbyport_r
o Improved query-ID randomness
+ o Validate that DNS response address matches the request address
Thanks go to these friendly people for their efforts and contributions:
diff --git a/ares/ares_process.c b/ares/ares_process.c
index becbfced1..0a99a1bb4 100644
--- a/ares/ares_process.c
+++ b/ares/ares_process.c
@@ -429,6 +429,8 @@ static void read_udp_packets(ares_channel channel, fd_set *read_fds,
int i;
ssize_t count;
unsigned char buf[PACKETSZ + 1];
+ struct sockaddr_in from;
+ socklen_t fromlen;
if(!read_fds && (read_fd == ARES_SOCKET_BAD))
/* no possible action */
@@ -462,11 +464,23 @@ static void read_udp_packets(ares_channel channel, fd_set *read_fds,
/* To reduce event loop overhead, read and process as many
* packets as we can. */
do {
- count = sread(server->udp_socket, buf, sizeof(buf));
+ /* Must memset 'from' to 0 as recvfrom() on some systems may
+ * not use 'from' at all if it doesn't support receiving the
+ * source address of the response */
+ memset(&from, 0, sizeof(from));
+ fromlen = sizeof(from);
+ count = (ssize_t)recvfrom(server->udp_socket, (void *)buf, sizeof(buf),
+ 0, (struct sockaddr *)&from, &fromlen);
if (count == -1 && try_again(SOCKERRNO))
continue;
else if (count <= 0)
handle_error(channel, i, now);
+ else if (fromlen && from.sin_addr.s_addr != 0 &&
+ from.sin_addr.s_addr != server->addr.s_addr)
+ /* Address response came from did not match the address
+ * we sent the request to. Someone may be attempting
+ * to perform a cache poisoning attack */
+ break;
else
process_answer(channel, buf, (int)count, i, 0, now);
} while (count > 0);