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Avoid reacting to our own error packets, should the happen to end up on our interface with a spoofed source IP. Thanks to zorun.

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This commit is contained in:
Dirk Engling 2015-06-05 13:34:19 +02:00
parent 27499d7a55
commit f0026ed1e0
1 changed files with 14 additions and 5 deletions
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19
ot_udp.c
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@ -20,7 +20,9 @@
#include "ot_stats.h"
#include "ot_rijndael.h"
#if 0
static const uint8_t g_static_connid[8] = { 0x23, 0x42, 0x05, 0x17, 0xde, 0x41, 0x50, 0xff };
#endif
static uint32_t g_rijndael_round_key[44] = {0};
static uint32_t g_key_of_the_hour[2] = {0};
static ot_time g_hour_of_the_key;
@ -61,6 +63,7 @@ int handle_udp6( int64 serversocket, struct ot_workstruct *ws ) {
uint32_t *outpacket = (uint32_t*)ws->outbuf;
uint32_t numwant, left, event, scopeid;
uint32_t connid[2];
uint32_t action;
uint16_t port, remoteport;
size_t byte_count, scrape_count;
@ -74,6 +77,11 @@ int handle_udp6( int64 serversocket, struct ot_workstruct *ws ) {
if( byte_count < 16 )
return 1;
/* Get action to take. Ignore error messages and broken packets */
action = ntohl( inpacket[2] );
if( action > 2 )
return 1;
/* Generate the connection id we give out and expect to and from
the requesting ip address, this prevents udp spoofing */
udp_make_connectionid( connid, remoteip, 0 );
@ -82,16 +90,16 @@ int handle_udp6( int64 serversocket, struct ot_workstruct *ws ) {
ws->hash = NULL;
ws->peer_id = NULL;
/* If action is not a ntohl(a) == a == 0, then we
expect the derived connection id in first 64 bit */
if( inpacket[2] && ( inpacket[0] != connid[0] || inpacket[1] != connid[1] ) ) {
/* If action is not 0 (connect), then we expect the derived
connection id in first 64 bit */
if( ( action > 0 ) && ( inpacket[0] != connid[0] || inpacket[1] != connid[1] ) ) {
/* If connection id does not match, try the one that was
valid in the previous hour. Only if this also does not
match, return an error packet */
udp_make_connectionid( connid, remoteip, 1 );
if( inpacket[0] != connid[0] || inpacket[1] != connid[1] ) {
const size_t s = sizeof( "Connection ID missmatch." );
outpacket[0] = 3; outpacket[1] = inpacket[3];
outpacket[0] = htonl( 3 ); outpacket[1] = inpacket[3];
memcpy( &outpacket[2], "Connection ID missmatch.", s );
socket_send6( serversocket, ws->outbuf, 8 + s, remoteip, remoteport, 0 );
stats_issue_event( EVENT_CONNID_MISSMATCH, FLAG_UDP, 8 + s );
@ -99,7 +107,7 @@ int handle_udp6( int64 serversocket, struct ot_workstruct *ws ) {
}
}
switch( ntohl( inpacket[2] ) ) {
switch( action ) {
case 0: /* This is a connect action */
/* look for udp bittorrent magic id */
if( (ntohl(inpacket[0]) != 0x00000417) || (ntohl(inpacket[1]) != 0x27101980) )
@ -121,6 +129,7 @@ int handle_udp6( int64 serversocket, struct ot_workstruct *ws ) {
/* We do only want to know, if it is zero */
left = inpacket[64/4] | inpacket[68/4];
/* Limit amount of peers to 200 */
numwant = ntohl( inpacket[92/4] );
if (numwant > 200) numwant = 200;