zeek/src/analyzer/protocol/teredo/Teredo.cc

#include "Teredo.h"
#include "TunnelEncapsulation.h"
#include "Conn.h"
#include "IP.h"
#include "Reporter.h"
#include "Sessions.h"
#include "BroString.h"

#include "events.bif.h"

using namespace analyzer::teredo;

void Teredo_Analyzer::Done()
	{
	Analyzer::Done();
	Event(udp_session_done);
	}

bool TeredoEncapsulation::DoParse(const u_char* data, int& len,
                                  bool found_origin, bool found_auth)
	{
	if ( len < 2 )
		{
		Weird("truncated_Teredo");
		return false;
		}

	uint16_t tag = ntohs((*((const uint16_t*)data)));

	if ( tag == 0 )
		{
		// Origin Indication
		if ( found_origin )
			// can't have multiple origin indications
			return false;

		if ( len < 8 )
			{
			Weird("truncated_Teredo_origin_indication");
			return false;
			}

		origin_indication = data;
		len -= 8;
		data += 8;
		return DoParse(data, len, true, found_auth);
		}

	else if ( tag == 1 )
		{
		// Authentication
		if ( found_origin || found_auth )
			// can't have multiple authentication headers and can't come after
			// an origin indication
			return false;

		if ( len < 4 )
			{
			Weird("truncated_Teredo_authentication");
			return false;
			}

		uint8_t id_len = data[2];
		uint8_t au_len = data[3];
		uint16_t tot_len = 4 + id_len + au_len + 8 + 1;

		if ( len < tot_len )
			{
			Weird("truncated_Teredo_authentication");
			return false;
			}

		auth = data;
		len -= tot_len;
		data += tot_len;
		return DoParse(data, len, found_origin, true);
		}

	else if ( ((tag & 0xf000)>>12) == 6 )
		{
		// IPv6
		if ( len < 40 )
			{
			Weird("truncated_IPv6_in_Teredo");
			return false;
			}

		// There's at least a possible IPv6 header, we'll decide what to do
		// later if the payload length field doesn't match the actual length
		// of the packet.
		inner_ip = data;
		return true;
		}

	return false;
	}

zeek::RecordValPtr TeredoEncapsulation::BuildVal(const IP_Hdr* inner) const
	{
	static auto teredo_hdr_type = zeek::id::find_type<zeek::RecordType>("teredo_hdr");
	static auto teredo_auth_type = zeek::id::find_type<zeek::RecordType>("teredo_auth");
	static auto teredo_origin_type = zeek::id::find_type<zeek::RecordType>("teredo_origin");

	auto teredo_hdr = zeek::make_intrusive<zeek::RecordVal>(teredo_hdr_type);

	if ( auth )
		{
		auto teredo_auth = zeek::make_intrusive<zeek::RecordVal>(teredo_auth_type);
		uint8_t id_len = *((uint8_t*)(auth + 2));
		uint8_t au_len = *((uint8_t*)(auth + 3));
		uint64_t nonce = ntohll(*((uint64_t*)(auth + 4 + id_len + au_len)));
		uint8_t conf = *((uint8_t*)(auth + 4 + id_len + au_len + 8));
		teredo_auth->Assign(0, zeek::make_intrusive<zeek::StringVal>(
		    new zeek::String(auth + 4, id_len, true)));
		teredo_auth->Assign(1, zeek::make_intrusive<zeek::StringVal>(
		    new zeek::String(auth + 4 + id_len, au_len, true)));
		teredo_auth->Assign(2, zeek::val_mgr->Count(nonce));
		teredo_auth->Assign(3, zeek::val_mgr->Count(conf));
		teredo_hdr->Assign(0, std::move(teredo_auth));
		}

	if ( origin_indication )
		{
		auto teredo_origin = zeek::make_intrusive<zeek::RecordVal>(teredo_origin_type);
		uint16_t port = ntohs(*((uint16_t*)(origin_indication + 2))) ^ 0xFFFF;
		uint32_t addr = ntohl(*((uint32_t*)(origin_indication + 4))) ^ 0xFFFFFFFF;
		teredo_origin->Assign(0, zeek::val_mgr->Port(port, TRANSPORT_UDP));
		teredo_origin->Assign(1, zeek::make_intrusive<zeek::AddrVal>(htonl(addr)));
		teredo_hdr->Assign(1, std::move(teredo_origin));
		}

	teredo_hdr->Assign(2, inner->ToPktHdrVal());
	return teredo_hdr;
	}

void Teredo_Analyzer::DeliverPacket(int len, const u_char* data, bool orig,
                                    uint64_t seq, const IP_Hdr* ip, int caplen)
	{
	Analyzer::DeliverPacket(len, data, orig, seq, ip, caplen);

	if ( orig )
		valid_orig = false;
	else
		valid_resp = false;

	TeredoEncapsulation te(this);

	if ( ! te.Parse(data, len) )
		{
		ProtocolViolation("Bad Teredo encapsulation", (const char*) data, len);
		return;
		}

	const EncapsulationStack* e = Conn()->GetEncapsulation();

	if ( e && e->Depth() >= zeek::BifConst::Tunnel::max_depth )
		{
		Weird("tunnel_depth", true);
		return;
		}

	IP_Hdr* inner = nullptr;
	int rslt = sessions->ParseIPPacket(len, te.InnerIP(), IPPROTO_IPV6, inner);

	if ( rslt > 0 )
		{
		if ( inner->NextProto() == IPPROTO_NONE && inner->PayloadLen() == 0 )
			// Teredo bubbles having data after IPv6 header isn't strictly a
			// violation, but a little weird.
			Weird("Teredo_bubble_with_payload", true);
		else
			{
			delete inner;
			ProtocolViolation("Teredo payload length", (const char*) data, len);
			return;
			}
		}

	if ( rslt == 0 || rslt > 0 )
		{
		if ( orig )
			valid_orig = true;
		else
			valid_resp = true;

		Confirm();
		}

	else
		{
		delete inner;
		ProtocolViolation("Truncated Teredo or invalid inner IP version", (const char*) data, len);
		return;
		}

	zeek::ValPtr teredo_hdr;

	if ( teredo_packet )
		{
		teredo_hdr = te.BuildVal(inner);
		Conn()->EnqueueEvent(teredo_packet, nullptr, ConnVal(), teredo_hdr);
		}

	if ( te.Authentication() && teredo_authentication )
		{
		if ( ! teredo_hdr )
			teredo_hdr = te.BuildVal(inner);

		Conn()->EnqueueEvent(teredo_authentication, nullptr, ConnVal(), teredo_hdr);
		}

	if ( te.OriginIndication() && teredo_origin_indication )
		{
		if ( ! teredo_hdr )
			teredo_hdr = te.BuildVal(inner);

		Conn()->EnqueueEvent(teredo_origin_indication, nullptr, ConnVal(), teredo_hdr);
		}

	if ( inner->NextProto() == IPPROTO_NONE && teredo_bubble )
		{
		if ( ! teredo_hdr )
			teredo_hdr = te.BuildVal(inner);

		Conn()->EnqueueEvent(teredo_bubble, nullptr, ConnVal(), teredo_hdr);
		}

	EncapsulatingConn ec(Conn(), BifEnum::Tunnel::TEREDO);

	sessions->DoNextInnerPacket(network_time, nullptr, inner, e, ec);
	}