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/* This software was written by Dirk Engling <erdgeist@erdgeist.org>
It is considered beerware. Prost. Skol. Cheers or whatever.
$id$ */
/* System */
#include <stdlib.h>
#include <pthread.h>
#include <string.h>
#include <arpa/inet.h>
#include <stdio.h>
/* Libowfat */
#include "socket.h"
#include "io.h"
/* Opentracker */
#include "trackerlogic.h"
#include "ot_udp.h"
#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;
static void udp_generate_rijndael_round_key() {
uint32_t key[16];
key[0] = random();
key[1] = random();
key[2] = random();
key[3] = random();
rijndaelKeySetupEnc128( g_rijndael_round_key, (uint8_t*)key );
g_key_of_the_hour[0] = random();
g_hour_of_the_key = g_now_minutes;
}
/* Generate current and previous connection id for ip */
static void udp_make_connectionid( uint32_t connid[2], const ot_ip6 remoteip, int age ) {
uint32_t plain[4], crypt[4];
int i;
if( g_now_minutes + 60 > g_hour_of_the_key ) {
g_hour_of_the_key = g_now_minutes;
g_key_of_the_hour[1] = g_key_of_the_hour[0];
g_key_of_the_hour[0] = random();
}
memcpy( plain, remoteip, sizeof( plain ) );
for( i=0; i<4; ++i ) plain[i] ^= g_key_of_the_hour[age];
rijndaelEncrypt128( g_rijndael_round_key, (uint8_t*)remoteip, (uint8_t*)crypt );
connid[0] = crypt[0] ^ crypt[1];
connid[1] = crypt[2] ^ crypt[3];
}
/* UDP implementation according to http://xbtt.sourceforge.net/udp_tracker_protocol.html */
int handle_udp6( int64 serversocket, struct ot_workstruct *ws ) {
ot_ip6 remoteip;
uint32_t *inpacket = (uint32_t*)ws->inbuf;
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;
byte_count = socket_recv6( serversocket, ws->inbuf, G_INBUF_SIZE, remoteip, &remoteport, &scopeid );
if( !byte_count ) return 0;
stats_issue_event( EVENT_ACCEPT, FLAG_UDP, (uintptr_t)remoteip );
stats_issue_event( EVENT_READ, FLAG_UDP, byte_count );
/* Minimum udp tracker packet size, also catches error */
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 );
/* Initialise hash pointer */
ws->hash = NULL;
ws->peer_id = NULL;
/* 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] = 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 );
return 1;
}
}
switch( action ) {
case 0: /* This is a connect action */
/* look for udp bittorrent magic id */
if( (ntohl(inpacket[0]) != 0x00000417) || (ntohl(inpacket[1]) != 0x27101980) )
return 1;
outpacket[0] = 0;
outpacket[1] = inpacket[3];
outpacket[2] = connid[0];
outpacket[3] = connid[1];
socket_send6( serversocket, ws->outbuf, 16, remoteip, remoteport, 0 );
stats_issue_event( EVENT_CONNECT, FLAG_UDP, 16 );
break;
case 1: /* This is an announce action */
/* Minimum udp announce packet size */
if( byte_count < 98 )
return 1;
/* 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;
event = ntohl( inpacket[80/4] );
port = *(uint16_t*)( ((char*)inpacket) + 96 );
ws->hash = (ot_hash*)( ((char*)inpacket) + 16 );
OT_SETIP( &ws->peer, remoteip );
OT_SETPORT( &ws->peer, &port );
OT_PEERFLAG( &ws->peer ) = 0;
switch( event ) {
case 1: OT_PEERFLAG( &ws->peer ) |= PEER_FLAG_COMPLETED; break;
case 3: OT_PEERFLAG( &ws->peer ) |= PEER_FLAG_STOPPED; break;
default: break;
}
if( !left )
OT_PEERFLAG( &ws->peer ) |= PEER_FLAG_SEEDING;
outpacket[0] = htonl( 1 ); /* announce action */
outpacket[1] = inpacket[12/4];
if( OT_PEERFLAG( &ws->peer ) & PEER_FLAG_STOPPED ) { /* Peer is gone. */
ws->reply = ws->outbuf;
ws->reply_size = remove_peer_from_torrent( FLAG_UDP, ws );
} else {
ws->reply = ws->outbuf + 8;
ws->reply_size = 8 + add_peer_to_torrent_and_return_peers( FLAG_UDP, ws, numwant );
}
socket_send6( serversocket, ws->outbuf, ws->reply_size, remoteip, remoteport, 0 );
stats_issue_event( EVENT_ANNOUNCE, FLAG_UDP, ws->reply_size );
break;
case 2: /* This is a scrape action */
outpacket[0] = htonl( 2 ); /* scrape action */
outpacket[1] = inpacket[12/4];
for( scrape_count = 0; ( scrape_count * 20 < byte_count - 16) && ( scrape_count <= 74 ); scrape_count++ )
return_udp_scrape_for_torrent( *(ot_hash*)( ((char*)inpacket) + 16 + 20 * scrape_count ), ((char*)outpacket) + 8 + 12 * scrape_count );
socket_send6( serversocket, ws->outbuf, 8 + 12 * scrape_count, remoteip, remoteport, 0 );
stats_issue_event( EVENT_SCRAPE, FLAG_UDP, scrape_count );
break;
}
return 1;
}
static void* udp_worker( void * args ) {
int64 sock = (int64)args;
struct ot_workstruct ws;
memset( &ws, 0, sizeof(ws) );
ws.inbuf=malloc(G_INBUF_SIZE);
ws.outbuf=malloc(G_OUTBUF_SIZE);
#ifdef _DEBUG_HTTPERROR
ws.debugbuf=malloc(G_DEBUGBUF_SIZE);
#endif
while( g_opentracker_running )
handle_udp6( sock, &ws );
free( ws.inbuf );
free( ws.outbuf );
#ifdef _DEBUG_HTTPERROR
free( ws.debugbuf );
#endif
return NULL;
}
void udp_init( int64 sock, unsigned int worker_count ) {
pthread_t thread_id;
if( !g_rijndael_round_key[0] )
udp_generate_rijndael_round_key();
#ifdef _DEBUG
fprintf( stderr, " installing %d workers on udp socket %ld", worker_count, (unsigned long)sock );
#endif
while( worker_count-- )
pthread_create( &thread_id, NULL, udp_worker, (void *)sock );
}
const char *g_version_udp_c = "$Source$: $Revision$\n";
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