static int
readPadD (tr_handshake * handshake,
struct evbuffer * inbuf)
{
const size_t needlen = handshake->pad_d_len;
dbgmsg (handshake, "pad d: need %zu, got %zu",
needlen, evbuffer_get_length (inbuf));
if (evbuffer_get_length (inbuf) < needlen)
return READ_LATER;
tr_peerIoDrain (handshake->io, inbuf, needlen);
tr_peerIoSetEncryption (handshake->io, handshake->crypto_select);
setState (handshake, AWAITING_HANDSHAKE);
return READ_NOW;
}
tr_handshake*
tr_handshakeNew (tr_peerIo * io,
tr_encryption_mode encryptionMode,
handshakeDoneCB doneCB,
void * doneUserData)
{
tr_handshake * handshake;
tr_session * session = tr_peerIoGetSession (io);
handshake = tr_new0 (tr_handshake, 1);
handshake->io = io;
handshake->crypto = tr_peerIoGetCrypto (io);
handshake->encryptionMode = encryptionMode;
handshake->doneCB = doneCB;
handshake->doneUserData = doneUserData;
handshake->session = session;
handshake->timeout_timer = evtimer_new (session->event_base, handshakeTimeout, handshake);
tr_timerAdd (handshake->timeout_timer, HANDSHAKE_TIMEOUT_SEC, 0);
tr_peerIoRef (io); /* balanced by the unref in tr_handshakeFree */
tr_peerIoSetIOFuncs (handshake->io, canRead, NULL, gotError, handshake);
tr_peerIoSetEncryption (io, PEER_ENCRYPTION_NONE);
if (tr_peerIoIsIncoming (handshake->io))
{
setReadState (handshake, AWAITING_HANDSHAKE);
}
else if (encryptionMode != TR_CLEAR_PREFERRED)
{
sendYa (handshake);
}
else
{
uint8_t msg[HANDSHAKE_SIZE];
buildHandshakeMessage (handshake, msg);
handshake->haveSentBitTorrentHandshake = 1;
setReadState (handshake, AWAITING_HANDSHAKE);
tr_peerIoWriteBytes (handshake->io, msg, sizeof (msg), false);
}
return handshake;
}
/* 2 $A \leftarrow B$: Diffie Hellman $Y_B$, PadB */
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;
(...)
isEncrypted = memcmp(evbuffer_pullup(inbuf, HANDSHAKE_NAME_LEN),
HANDSHAKE_NAME, HANDSHAKE_NAME_LEN);
(...)
tr_peerIoSetEncryption(handshake->io, isEncrypted ? PEER_ENCRYPTION_RC4
: PEER_ENCRYPTION_NONE);
if (!isEncrypted) {
setState(handshake, AWAITING_HANDSHAKE); // Handshake não encriptado acaba aqui.
return READ_NOW;
}
(...)
/* compute the secret $S$*/
evbuffer_remove(inbuf, yb, KEY_LEN);
secret = tr_cryptoComputeSecret(handshake->crypto, yb);
memcpy(handshake->mySecret, secret, KEY_LEN);
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
readHandshake( tr_handshake * handshake,
struct evbuffer * inbuf )
{
uint8_t pstrlen;
uint8_t * pstr;
uint8_t reserved[HANDSHAKE_FLAGS_LEN];
uint8_t hash[SHA_DIGEST_LENGTH];
dbgmsg( handshake, "payload: need %d, got %zu",
INCOMING_HANDSHAKE_LEN, evbuffer_get_length( inbuf ) );
if( evbuffer_get_length( inbuf ) < INCOMING_HANDSHAKE_LEN )
return READ_LATER;
handshake->haveReadAnythingFromPeer = TRUE;
pstrlen = evbuffer_pullup( inbuf, 1 )[0]; /* peek, don't read. We may be
handing inbuf to AWAITING_YA */
if( pstrlen == 19 ) /* unencrypted */
{
tr_peerIoSetEncryption( handshake->io, PEER_ENCRYPTION_NONE );
if( handshake->encryptionMode == TR_ENCRYPTION_REQUIRED )
{
dbgmsg( handshake,
"peer is unencrypted, and we're disallowing that" );
return tr_handshakeDone( handshake, FALSE );
}
}
else /* encrypted or corrupt */
{
tr_peerIoSetEncryption( handshake->io, PEER_ENCRYPTION_RC4 );
if( tr_peerIoIsIncoming( handshake->io ) )
{
dbgmsg( handshake,
"I think peer is sending us an encrypted handshake..." );
setState( handshake, AWAITING_YA );
return READ_NOW;
}
tr_cryptoDecrypt( handshake->crypto, 1, &pstrlen, &pstrlen );
if( pstrlen != 19 )
{
dbgmsg( handshake,
"I think peer has sent us a corrupt handshake..." );
return tr_handshakeDone( handshake, FALSE );
}
}
evbuffer_drain( inbuf, 1 );
/* pstr (BitTorrent) */
pstr = tr_new( uint8_t, pstrlen + 1 );
tr_peerIoReadBytes( handshake->io, inbuf, pstr, pstrlen );
pstr[pstrlen] = '\0';
if( strcmp( (char*)pstr, "BitTorrent protocol" ) )
{
tr_free( pstr );
return tr_handshakeDone( handshake, FALSE );
}
tr_free( pstr );
/* reserved bytes */
tr_peerIoReadBytes( handshake->io, inbuf, reserved, sizeof( reserved ) );
/**
*** Extensions
**/
tr_peerIoEnableLTEP( handshake->io, HANDSHAKE_HAS_LTEP( reserved ) );
tr_peerIoEnableFEXT( handshake->io, HANDSHAKE_HAS_FASTEXT( reserved ) );
tr_peerIoEnableDHT( handshake->io, HANDSHAKE_HAS_DHT( reserved ) );
/* torrent hash */
tr_peerIoReadBytes( handshake->io, inbuf, hash, sizeof( hash ) );
if( tr_peerIoIsIncoming( handshake->io ) )
{
if( !tr_torrentExists( handshake->session, hash ) )
{
dbgmsg( handshake, "peer is trying to connect to us for a torrent we don't have." );
return tr_handshakeDone( handshake, FALSE );
}
else
{
assert( !tr_peerIoHasTorrentHash( handshake->io ) );
tr_peerIoSetTorrentHash( handshake->io, hash );
}
}
else /* outgoing */
{
assert( tr_peerIoHasTorrentHash( handshake->io ) );
if( memcmp( hash, tr_peerIoGetTorrentHash( handshake->io ),
SHA_DIGEST_LENGTH ) )
{
dbgmsg( handshake, "peer returned the wrong hash. wtf?" );
return tr_handshakeDone( handshake, FALSE );
}
}
/**
*** If it's an incoming message, we need to send a response handshake
**/
if( !handshake->haveSentBitTorrentHandshake )
{
uint8_t msg[HANDSHAKE_SIZE];
buildHandshakeMessage( handshake, msg );
tr_peerIoWriteBytes( handshake->io, msg, sizeof( msg ), FALSE );
handshake->haveSentBitTorrentHandshake = 1;
}
setReadState( handshake, AWAITING_PEER_ID );
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;
}