// bool b: true $\Longrightarrow$ interested
// false $\Longrightarrow$ not interested
static void sendInterest(tr_peerMsgs * msgs, bool b) {
struct evbuffer * out = msgs->outMessages; // buffer de saída
(...)
dbgmsg(msgs, "Sending %s", b ? "Interested" : "Not Interested");
evbuffer_add_uint32(out, sizeof(uint8_t)); // <tamanho> = 1 byte
// <ID da mensagem>: BT_INTERESTED (2) ou BT_NOT_INTERESTED (3)
evbuffer_add_uint8(out, b ? BT_INTERESTED : BT_NOT_INTERESTED);
(...)
}
static void sendBitfield(tr_peerMsgs * msgs) {
void * bytes; size_t byte_count = 0; // bitfield e seu comprimento
struct evbuffer * out = msgs->outMessages; // buffer de saída
(...)
// Cria o bitfield conforme as partes que possui no momento.
bytes = tr_cpCreatePieceBitfield(&msgs->torrent->completion, &byte_count);
// <tamanho> = 1 + tamanho do bitfield
evbuffer_add_uint32(out, sizeof(uint8_t) + byte_count);
evbuffer_add_uint8(out, BT_BITFIELD); // <ID da mensagem> = 5
evbuffer_add(out, bytes, byte_count); // <dados=mapa de bits>
dbgmsg(msgs, "sending bitfield... outMessage size is now %zu", evbuffer_get_length(out));
(...)
}
static int
readIA( tr_handshake * handshake,
struct evbuffer * inbuf )
{
const size_t needlen = handshake->ia_len;
struct evbuffer * outbuf;
uint32_t crypto_select;
dbgmsg( handshake, "reading IA... have %zu, need %zu",
evbuffer_get_length( inbuf ), needlen );
if( evbuffer_get_length( inbuf ) < needlen )
return READ_LATER;
/**
*** B->A: ENCRYPT(VC, crypto_select, len(padD), padD), ENCRYPT2(Payload Stream)
**/
tr_cryptoEncryptInit( handshake->crypto );
outbuf = evbuffer_new( );
dbgmsg( handshake, "sending vc" );
/* send VC */
{
uint8_t vc[VC_LENGTH];
memset( vc, 0, VC_LENGTH );
evbuffer_add( outbuf, vc, VC_LENGTH );
}
/* send crypto_select */
crypto_select = getCryptoSelect( handshake, handshake->crypto_provide );
if( crypto_select )
{
dbgmsg( handshake, "selecting crypto mode '%d'", (int)crypto_select );
evbuffer_add_uint32( outbuf, crypto_select );
}
else
{
dbgmsg( handshake, "peer didn't offer an encryption mode we like." );
evbuffer_free( outbuf );
return tr_handshakeDone( handshake, FALSE );
}
dbgmsg( handshake, "sending pad d" );
/* ENCRYPT(VC, crypto_provide, len(PadD), PadD
* PadD is reserved for future extensions to the handshake...
* standard practice at this time is for it to be zero-length */
{
const uint16_t len = 0;
evbuffer_add_uint16( outbuf, len );
}
/* maybe de-encrypt our connection */
if( crypto_select == CRYPTO_PROVIDE_PLAINTEXT )
{
tr_peerIoWriteBuf( handshake->io, outbuf, FALSE );
tr_peerIoSetEncryption( handshake->io, PEER_ENCRYPTION_NONE );
}
dbgmsg( handshake, "sending handshake" );
/* send our handshake */
{
uint8_t msg[HANDSHAKE_SIZE];
buildHandshakeMessage( handshake, msg );
evbuffer_add( outbuf, msg, sizeof( msg ) );
handshake->haveSentBitTorrentHandshake = 1;
}
/* send it out */
tr_peerIoWriteBuf( handshake->io, outbuf, FALSE );
evbuffer_free( outbuf );
/* now await the handshake */
setState( handshake, AWAITING_PAYLOAD_STREAM );
return READ_NOW;
}
static int
readYb( tr_handshake * handshake, struct evbuffer * inbuf )
{
int isEncrypted;
const uint8_t * secret;
uint8_t yb[KEY_LEN];
struct evbuffer * outbuf;
size_t needlen = HANDSHAKE_NAME_LEN;
if( evbuffer_get_length( inbuf ) < needlen )
return READ_LATER;
isEncrypted = memcmp( evbuffer_pullup( inbuf, HANDSHAKE_NAME_LEN ), HANDSHAKE_NAME, HANDSHAKE_NAME_LEN );
if( isEncrypted )
{
needlen = KEY_LEN;
if( evbuffer_get_length( inbuf ) < needlen )
return READ_LATER;
}
dbgmsg( handshake, "got a %s handshake",
( isEncrypted ? "encrypted" : "plaintext" ) );
tr_peerIoSetEncryption( handshake->io, isEncrypted ? PEER_ENCRYPTION_RC4
: PEER_ENCRYPTION_NONE );
if( !isEncrypted )
{
setState( handshake, AWAITING_HANDSHAKE );
return READ_NOW;
}
handshake->haveReadAnythingFromPeer = TRUE;
/* compute the secret */
evbuffer_remove( inbuf, yb, KEY_LEN );
secret = tr_cryptoComputeSecret( handshake->crypto, yb );
memcpy( handshake->mySecret, secret, KEY_LEN );
/* now send these: HASH('req1', S), HASH('req2', SKEY) xor HASH('req3', S),
* ENCRYPT(VC, crypto_provide, len(PadC), PadC, len(IA)), ENCRYPT(IA) */
outbuf = evbuffer_new( );
/* HASH('req1', S) */
{
uint8_t req1[SHA_DIGEST_LENGTH];
tr_sha1( req1, "req1", 4, secret, KEY_LEN, NULL );
evbuffer_add( outbuf, req1, SHA_DIGEST_LENGTH );
}
/* HASH('req2', SKEY) xor HASH('req3', S) */
{
int i;
uint8_t req2[SHA_DIGEST_LENGTH];
uint8_t req3[SHA_DIGEST_LENGTH];
uint8_t buf[SHA_DIGEST_LENGTH];
tr_sha1( req2, "req2", 4,
tr_cryptoGetTorrentHash( handshake->crypto ),
SHA_DIGEST_LENGTH, NULL );
tr_sha1( req3, "req3", 4, secret, KEY_LEN, NULL );
for( i = 0; i < SHA_DIGEST_LENGTH; ++i )
buf[i] = req2[i] ^ req3[i];
evbuffer_add( outbuf, buf, SHA_DIGEST_LENGTH );
}
/* ENCRYPT(VC, crypto_provide, len(PadC), PadC
* PadC is reserved for future extensions to the handshake...
* standard practice at this time is for it to be zero-length */
{
uint8_t vc[VC_LENGTH] = { 0, 0, 0, 0, 0, 0, 0, 0 };
tr_peerIoWriteBuf( handshake->io, outbuf, FALSE );
tr_cryptoEncryptInit( handshake->crypto );
tr_peerIoSetEncryption( handshake->io, PEER_ENCRYPTION_RC4 );
evbuffer_add ( outbuf, vc, VC_LENGTH );
evbuffer_add_uint32 ( outbuf, getCryptoProvide( handshake ) );
evbuffer_add_uint16 ( outbuf, 0 );
}
/* ENCRYPT len(IA)), ENCRYPT(IA) */
{
uint8_t msg[HANDSHAKE_SIZE];
buildHandshakeMessage( handshake, msg );
evbuffer_add_uint16 ( outbuf, sizeof( msg ) );
evbuffer_add ( outbuf, msg, sizeof( msg ) );
handshake->haveSentBitTorrentHandshake = 1;
}
/* send it */
tr_cryptoDecryptInit( handshake->crypto );
setReadState( handshake, AWAITING_VC );
tr_peerIoWriteBuf( handshake->io, outbuf, FALSE );
/* cleanup */
evbuffer_free( outbuf );
return READ_LATER;
}
