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Brad House's validation that DNS response address matches the request address

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Yang Tse
2008-08-25 03:34:50 +00:00
parent a5b66d3293
commit 09d10cb5c5
3 changed files with 28 additions and 1 deletions
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16
ares_process.c
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@ -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);