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Documentation improvements and some very minor pre-emptive security stuff.

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This commit is contained in:
Adam Ierymenko 2013-08-05 12:16:25 -04:00
parent bf5c07f79a
commit b9aeec9f29
2 changed files with 89 additions and 50 deletions
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133
node/PacketDecoder.cpp
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@ -35,6 +35,21 @@
#include "Filter.hpp" #include "Filter.hpp"
#include "Service.hpp" #include "Service.hpp"
/*
* The big picture:
*
* tryDecode() gets called for a given fully-assembled packet until it returns
* true or the packet's time to live has been exceeded. The state machine must
* therefore be re-entrant if it ever returns false. Take care here!
*
* Stylistic note:
*
* There's a lot of unnecessary if nesting. It's mostly to allow TRACE to
* print informative messages on every possible reason something gets
* rejected or fails. Sometimes it also makes code more explicit and thus
* easier to understand.
*/
namespace ZeroTier { namespace ZeroTier {
bool PacketDecoder::tryDecode(const RuntimeEnvironment *_r) bool PacketDecoder::tryDecode(const RuntimeEnvironment *_r)
@ -50,14 +65,15 @@ bool PacketDecoder::tryDecode(const RuntimeEnvironment *_r)
SharedPtr<Peer> peer = _r->topology->getPeer(source()); SharedPtr<Peer> peer = _r->topology->getPeer(source());
if (peer) { if (peer) {
if (_step == DECODE_STEP_WAITING_FOR_ORIGINAL_SUBMITTER_LOOKUP) { // Resume saved state?
// This means we've already decoded, decrypted, decompressed, and if (_step == DECODE_WAITING_FOR_MULTICAST_FRAME_ORIGINAL_SENDER_LOOKUP) {
// validated, and we're processing a MULTICAST_FRAME. We're waiting // In this state we have already authenticated and decrypted the
// for a lookup on the frame's original submitter. So try again and // packet and are waiting for the lookup of the original sender
// see if we have it. // for a multicast frame. So check to see if we've got it.
return _doMULTICAST_FRAME(_r,peer); return _doMULTICAST_FRAME(_r,peer);
} }
// No saved state? Verify MAC before we proceed.
if (!hmacVerify(peer->macKey())) { if (!hmacVerify(peer->macKey())) {
TRACE("dropped packet from %s(%s), HMAC authentication failed (size: %u)",source().toString().c_str(),_remoteAddress.toString().c_str(),size()); TRACE("dropped packet from %s(%s), HMAC authentication failed (size: %u)",source().toString().c_str(),_remoteAddress.toString().c_str(),size());
return true; return true;
@ -80,8 +96,9 @@ bool PacketDecoder::tryDecode(const RuntimeEnvironment *_r)
Packet::Verb v = verb(); Packet::Verb v = verb();
// Validated packets that have passed HMAC can result in us learning a new // Once a packet is determined to be basically valid, it can be used
// path to this peer. // to passively learn a new network path to the sending peer. It
// also results in statistics updates.
peer->onReceive(_r,_localPort,_remoteAddress,hops(),v,Utils::now()); peer->onReceive(_r,_localPort,_remoteAddress,hops(),v,Utils::now());
switch(v) { switch(v) {
@ -89,7 +106,7 @@ bool PacketDecoder::tryDecode(const RuntimeEnvironment *_r)
TRACE("NOP from %s(%s)",source().toString().c_str(),_remoteAddress.toString().c_str()); TRACE("NOP from %s(%s)",source().toString().c_str(),_remoteAddress.toString().c_str());
return true; return true;
case Packet::VERB_HELLO: case Packet::VERB_HELLO:
return _doHELLO(_r); return _doHELLO(_r); // encrypted HELLO is technically allowed, but kind of pointless... :)
case Packet::VERB_ERROR: case Packet::VERB_ERROR:
return _doERROR(_r,peer); return _doERROR(_r,peer);
case Packet::VERB_OK: case Packet::VERB_OK:
@ -118,7 +135,7 @@ bool PacketDecoder::tryDecode(const RuntimeEnvironment *_r)
return true; return true;
} }
} else { } else {
_step = DECODE_STEP_WAITING_FOR_SENDER_LOOKUP; _step = DECODE_WAITING_FOR_SENDER_LOOKUP; // should already be this...
_r->sw->requestWhois(source()); _r->sw->requestWhois(source());
return false; return false;
} }
@ -213,27 +230,26 @@ bool PacketDecoder::_doHELLO(const RuntimeEnvironment *_r)
uint64_t timestamp = at<uint64_t>(ZT_PROTO_VERB_HELLO_IDX_TIMESTAMP); uint64_t timestamp = at<uint64_t>(ZT_PROTO_VERB_HELLO_IDX_TIMESTAMP);
Identity id(*this,ZT_PROTO_VERB_HELLO_IDX_IDENTITY); Identity id(*this,ZT_PROTO_VERB_HELLO_IDX_IDENTITY);
// Create a new candidate peer that we might decide to add to our
// database. We create it now since we want its keys to send replies
// even in the error case, and the code for keying is in Peer.
SharedPtr<Peer> candidate(new Peer(_r->identity,id)); SharedPtr<Peer> candidate(new Peer(_r->identity,id));
candidate->setPathAddress(_remoteAddress,false); candidate->setPathAddress(_remoteAddress,false);
// Initial sniff test // The initial sniff test... is the identity valid, and is it
if (id.address().isReserved()) { // the sender's identity?
TRACE("rejected HELLO from %s(%s): identity has reserved address",source().toString().c_str(),_remoteAddress.toString().c_str()); if ((id.address().isReserved())||(id.address() != source())) {
#ifdef ZT_TRACE
if (id.address().isReserved()) {
TRACE("rejected HELLO from %s(%s): identity has reserved address",source().toString().c_str(),_remoteAddress.toString().c_str());
} else {
TRACE("rejected HELLO from %s(%s): identity is not for sender of packet (HELLO is a self-announcement)",source().toString().c_str(),_remoteAddress.toString().c_str());
}
#endif
Packet outp(source(),_r->identity.address(),Packet::VERB_ERROR); Packet outp(source(),_r->identity.address(),Packet::VERB_ERROR);
outp.append((unsigned char)Packet::VERB_HELLO); outp.append((unsigned char)Packet::VERB_HELLO);
outp.append(packetId()); outp.append(packetId());
outp.append((unsigned char)Packet::ERROR_IDENTITY_INVALID); outp.append((unsigned char)((id.address().isReserved()) ? Packet::ERROR_IDENTITY_INVALID : Packet::ERROR_INVALID_REQUEST));
outp.encrypt(candidate->cryptKey());
outp.hmacSet(candidate->macKey());
_r->demarc->send(_localPort,_remoteAddress,outp.data(),outp.size(),-1);
return true;
}
if (id.address() != source()) {
TRACE("rejected HELLO from %s(%s): identity is not for sender of packet (HELLO is a self-announcement)",source().toString().c_str(),_remoteAddress.toString().c_str());
Packet outp(source(),_r->identity.address(),Packet::VERB_ERROR);
outp.append((unsigned char)Packet::VERB_HELLO);
outp.append(packetId());
outp.append((unsigned char)Packet::ERROR_INVALID_REQUEST);
outp.encrypt(candidate->cryptKey()); outp.encrypt(candidate->cryptKey());
outp.hmacSet(candidate->macKey()); outp.hmacSet(candidate->macKey());
_r->demarc->send(_localPort,_remoteAddress,outp.data(),outp.size(),-1); _r->demarc->send(_localPort,_remoteAddress,outp.data(),outp.size(),-1);
@ -257,7 +273,9 @@ bool PacketDecoder::_doHELLO(const RuntimeEnvironment *_r)
return true; return true;
} }
// Otherwise we call addPeer() and set up a callback to handle the verdict // Otherwise we call addPeer() and set up a callback to handle the verdict.
// Topology evaluates the peer in the background, possibly doing the entire
// expensive analysis before determining whether to add it to the database.
_CBaddPeerFromHello_Data *arg = new _CBaddPeerFromHello_Data; _CBaddPeerFromHello_Data *arg = new _CBaddPeerFromHello_Data;
arg->renv = _r; arg->renv = _r;
arg->source = source(); arg->source = source();
@ -288,19 +306,21 @@ bool PacketDecoder::_doOK(const RuntimeEnvironment *_r,const SharedPtr<Peer> &pe
TRACE("%s(%s): OK(HELLO), latency: %u",source().toString().c_str(),_remoteAddress.toString().c_str(),latency); TRACE("%s(%s): OK(HELLO), latency: %u",source().toString().c_str(),_remoteAddress.toString().c_str(),latency);
peer->setLatency(_remoteAddress,latency); peer->setLatency(_remoteAddress,latency);
} break; } break;
case Packet::VERB_WHOIS: case Packet::VERB_WHOIS: {
// Right now we only query supernodes for WHOIS and only accept
// OK back from them. If we query other nodes, we'll have to
// do something to prevent WHOIS cache poisoning such as
// using the packet ID field in the OK packet to match with the
// original query. Technically we should be doing this anyway.
TRACE("%s(%s): OK(%s)",source().toString().c_str(),_remoteAddress.toString().c_str(),Packet::verbString(inReVerb)); TRACE("%s(%s): OK(%s)",source().toString().c_str(),_remoteAddress.toString().c_str(),Packet::verbString(inReVerb));
if (_r->topology->isSupernode(source())) if (_r->topology->isSupernode(source())) {
// Right now, only supernodes are queried for WHOIS so we only
// accept OK(WHOIS) from supernodes. Otherwise peers could
// potentially cache-poison. A more elegant but memory-intensive
// solution would be to remember packet IDs of WHOIS requests.
_r->topology->addPeer(SharedPtr<Peer>(new Peer(_r->identity,Identity(*this,ZT_PROTO_VERB_WHOIS__OK__IDX_IDENTITY))),&PacketDecoder::_CBaddPeerFromWhois,const_cast<void *>((const void *)_r)); _r->topology->addPeer(SharedPtr<Peer>(new Peer(_r->identity,Identity(*this,ZT_PROTO_VERB_WHOIS__OK__IDX_IDENTITY))),&PacketDecoder::_CBaddPeerFromWhois,const_cast<void *>((const void *)_r));
break; }
} break;
case Packet::VERB_NETWORK_CONFIG_REQUEST: { case Packet::VERB_NETWORK_CONFIG_REQUEST: {
SharedPtr<Network> nw(_r->nc->network(at<uint64_t>(ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST__OK__IDX_NETWORK_ID))); SharedPtr<Network> nw(_r->nc->network(at<uint64_t>(ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST__OK__IDX_NETWORK_ID)));
if ((nw)&&(nw->controller() == source())) { if ((nw)&&(nw->controller() == source())) {
// Only accept OK(NETWORK_CONFIG_REQUEST) from masters for
// networks we have.
unsigned int dictlen = at<uint16_t>(ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST__OK__IDX_DICT_LEN); unsigned int dictlen = at<uint16_t>(ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST__OK__IDX_DICT_LEN);
std::string dict((const char *)field(ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST__OK__IDX_DICT,dictlen),dictlen); std::string dict((const char *)field(ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST__OK__IDX_DICT,dictlen),dictlen);
if (dict.length()) { if (dict.length()) {
@ -357,20 +377,38 @@ bool PacketDecoder::_doWHOIS(const RuntimeEnvironment *_r,const SharedPtr<Peer>
bool PacketDecoder::_doRENDEZVOUS(const RuntimeEnvironment *_r,const SharedPtr<Peer> &peer) bool PacketDecoder::_doRENDEZVOUS(const RuntimeEnvironment *_r,const SharedPtr<Peer> &peer)
{ {
try { try {
Address with(field(ZT_PROTO_VERB_RENDEZVOUS_IDX_ZTADDRESS,ZT_ADDRESS_LENGTH),ZT_ADDRESS_LENGTH); //
SharedPtr<Peer> withPeer(_r->topology->getPeer(with)); // At the moment, we only obey RENDEZVOUS if it comes from a designated
if (withPeer) { // supernode. If relay offloading is implemented to scale the net, this
unsigned int port = at<uint16_t>(ZT_PROTO_VERB_RENDEZVOUS_IDX_PORT); // will need reconsideration.
unsigned int addrlen = (*this)[ZT_PROTO_VERB_RENDEZVOUS_IDX_ADDRLEN]; //
if ((port > 0)&&((addrlen == 4)||(addrlen == 16))) { // The reason is that RENDEZVOUS could technically be used to cause a
InetAddress atAddr(field(ZT_PROTO_VERB_RENDEZVOUS_IDX_ADDRESS,addrlen),addrlen,port); // peer to send a weird encrypted UDP packet to an arbitrary IP:port.
TRACE("RENDEZVOUS from %s says %s might be at %s, starting NAT-t",source().toString().c_str(),with.toString().c_str(),atAddr.toString().c_str()); // The sender of RENDEZVOUS has no control over the content of this
_r->sw->contact(withPeer,atAddr); // packet, but it's still maybe something we want to not allow just
// anyone to order due to possible DDOS or network forensic implications.
// So if we diversify relays, we'll need some way of deciding whether the
// sender is someone we should trust with a RENDEZVOUS hint. Or maybe
// we just need rate limiting to prevent DDOS and amplification attacks.
//
if (_r->topology->isSupernode(source())) {
Address with(field(ZT_PROTO_VERB_RENDEZVOUS_IDX_ZTADDRESS,ZT_ADDRESS_LENGTH),ZT_ADDRESS_LENGTH);
SharedPtr<Peer> withPeer(_r->topology->getPeer(with));
if (withPeer) {
unsigned int port = at<uint16_t>(ZT_PROTO_VERB_RENDEZVOUS_IDX_PORT);
unsigned int addrlen = (*this)[ZT_PROTO_VERB_RENDEZVOUS_IDX_ADDRLEN];
if ((port > 0)&&((addrlen == 4)||(addrlen == 16))) {
InetAddress atAddr(field(ZT_PROTO_VERB_RENDEZVOUS_IDX_ADDRESS,addrlen),addrlen,port);
TRACE("RENDEZVOUS from %s says %s might be at %s, starting NAT-t",source().toString().c_str(),with.toString().c_str(),atAddr.toString().c_str());
_r->sw->contact(withPeer,atAddr);
} else {
TRACE("dropped corrupt RENDEZVOUS from %s(%s) (bad address or port)",source().toString().c_str(),_remoteAddress.toString().c_str());
}
} else { } else {
TRACE("dropped corrupt RENDEZVOUS from %s(%s) (bad address or port)",source().toString().c_str(),_remoteAddress.toString().c_str()); TRACE("ignored RENDEZVOUS from %s(%s) to meet unknown peer %s",source().toString().c_str(),_remoteAddress.toString().c_str(),with.toString().c_str());
} }
} else { } else {
TRACE("ignored RENDEZVOUS from %s(%s) to meet unknown peer %s",source().toString().c_str(),_remoteAddress.toString().c_str(),with.toString().c_str()); TRACE("ignored RENDEZVOUS from %s(%s): source not supernode",source().toString().c_str(),_remoteAddress.toString().c_str());
} }
} catch (std::exception &ex) { } catch (std::exception &ex) {
TRACE("dropped RENDEZVOUS from %s(%s): %s",source().toString().c_str(),_remoteAddress.toString().c_str(),ex.what()); TRACE("dropped RENDEZVOUS from %s(%s): %s",source().toString().c_str(),_remoteAddress.toString().c_str(),ex.what());
@ -487,7 +525,7 @@ bool PacketDecoder::_doMULTICAST_FRAME(const RuntimeEnvironment *_r,const Shared
if (!originalSubmitter) { if (!originalSubmitter) {
TRACE("requesting WHOIS on original multicast frame submitter %s",originalSubmitterAddress.toString().c_str()); TRACE("requesting WHOIS on original multicast frame submitter %s",originalSubmitterAddress.toString().c_str());
_r->sw->requestWhois(originalSubmitterAddress); _r->sw->requestWhois(originalSubmitterAddress);
_step = DECODE_STEP_WAITING_FOR_ORIGINAL_SUBMITTER_LOOKUP; _step = DECODE_WAITING_FOR_MULTICAST_FRAME_ORIGINAL_SENDER_LOOKUP;
return false; // try again if/when we get OK(WHOIS) return false; // try again if/when we get OK(WHOIS)
} else if (Multicaster::verifyMulticastPacket(originalSubmitter->identity(),network->id(),fromMac,mg,etherType,dataAndSignature,datalen,dataAndSignature + datalen,signaturelen)) { } else if (Multicaster::verifyMulticastPacket(originalSubmitter->identity(),network->id(),fromMac,mg,etherType,dataAndSignature,datalen,dataAndSignature + datalen,signaturelen)) {
_r->multicaster->addToDedupHistory(mccrc,now); _r->multicaster->addToDedupHistory(mccrc,now);
@ -538,7 +576,7 @@ bool PacketDecoder::_doMULTICAST_FRAME(const RuntimeEnvironment *_r,const Shared
//TRACE("terminating MULTICAST_FRAME propagation from %s(%s): max depth reached",source().toString().c_str(),_remoteAddress.toString().c_str()); //TRACE("terminating MULTICAST_FRAME propagation from %s(%s): max depth reached",source().toString().c_str(),_remoteAddress.toString().c_str());
} }
} else { } else {
LOG("rejected MULTICAST_FRAME from %s(%s) due to failed signature check (claims original sender %s)",source().toString().c_str(),_remoteAddress.toString().c_str(),originalSubmitterAddress.toString().c_str()); LOG("rejected MULTICAST_FRAME from %s(%s) due to failed signature check (falsely claims origin %s)",source().toString().c_str(),_remoteAddress.toString().c_str(),originalSubmitterAddress.toString().c_str());
} }
} else { } else {
TRACE("dropped redundant MULTICAST_FRAME from %s(%s)",source().toString().c_str(),_remoteAddress.toString().c_str()); TRACE("dropped redundant MULTICAST_FRAME from %s(%s)",source().toString().c_str(),_remoteAddress.toString().c_str());
@ -575,9 +613,10 @@ bool PacketDecoder::_doNETWORK_CONFIG_REQUEST(const RuntimeEnvironment *_r,const
#ifndef __WINDOWS__ #ifndef __WINDOWS__
if (_r->netconfService) { if (_r->netconfService) {
unsigned int dictLen = at<uint16_t>(ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST_IDX_DICT_LEN); unsigned int dictLen = at<uint16_t>(ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST_IDX_DICT_LEN);
std::string dict((const char *)field(ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST_IDX_DICT,dictLen),dictLen);
Dictionary request; Dictionary request;
if (dictLen)
request["meta"] = std::string((const char *)field(ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST_IDX_DICT,dictLen),dictLen);
request["type"] = "netconf-request"; request["type"] = "netconf-request";
request["peerId"] = peer->identity().toString(false); request["peerId"] = peer->identity().toString(false);
sprintf(tmp,"%llx",(unsigned long long)nwid); sprintf(tmp,"%llx",(unsigned long long)nwid);

6
node/PacketDecoder.hpp
View file

@ -65,7 +65,7 @@ public:
_receiveTime(Utils::now()), _receiveTime(Utils::now()),
_localPort(localPort), _localPort(localPort),
_remoteAddress(remoteAddress), _remoteAddress(remoteAddress),
_step(DECODE_STEP_WAITING_FOR_SENDER_LOOKUP), _step(DECODE_WAITING_FOR_SENDER_LOOKUP),
__refCount() __refCount()
{ {
} }
@ -131,8 +131,8 @@ private:
InetAddress _remoteAddress; InetAddress _remoteAddress;
enum { enum {
DECODE_STEP_WAITING_FOR_SENDER_LOOKUP, // on initial receipt, we need peer's identity DECODE_WAITING_FOR_SENDER_LOOKUP, // on initial receipt, we need peer's identity
DECODE_STEP_WAITING_FOR_ORIGINAL_SUBMITTER_LOOKUP // this only applies to MULTICAST_FRAME DECODE_WAITING_FOR_MULTICAST_FRAME_ORIGINAL_SENDER_LOOKUP,
} _step; } _step;
AtomicCounter __refCount; AtomicCounter __refCount;