first implementation of DHT security implementation. tie the node ID to the external IP

src/broadcast_socket.cpp

@@ -67,7 +67,8 @@ namespace libtorrent
 		return ((ip & 0xff000000) == 0x0a000000 // 10.x.x.x
 			|| (ip & 0xfff00000) == 0xac100000 // 172.16.x.x
 			|| (ip & 0xffff0000) == 0xc0a80000 // 192.168.x.x
-			|| (ip & 0xffff0000) == 0xa9fe0000); // 169.254.x.x
+			|| (ip & 0xffff0000) == 0xa9fe0000 // 169.254.x.x
+			|| (ip & 0xff000000) == 0x7f000000); // 127.x.x.x
 	}
 
 	bool is_loopback(address const& addr)

src/kademlia/node.cpp

@@ -183,9 +183,9 @@ node_impl::node_impl(libtorrent::aux::session_impl& ses
 	, node_id nid
 	, void* userdata)
 	: m_settings(settings)
-	, m_id(nid == (node_id::min)() ? generate_id() : nid)
+	, m_id(nid == (node_id::min)() || !verify_id(nid, ses.external_address()) ? generate_id(ses.external_address()) : nid)
 	, m_table(m_id, 8, settings)
-	, m_rpc(m_id, m_table, f, userdata)
+	, m_rpc(m_id, m_table, f, userdata, ses)
 	, m_last_tracker_tick(time_now())
 	, m_ses(ses)
 	, m_send(f)
@@ -702,6 +702,11 @@ void node_impl::incoming_request(msg const& m, entry& e)
 	entry& reply = e["r"];
 	m_rpc.add_our_id(reply);
 
+	// if this nodes ID doesn't match its IP, tell it what
+	// its IP is
+	if (!verify_id(id, m.addr.address()))
+		reply["ip"] = address_to_bytes(m.addr.address());
+
 	if (strcmp(query, "ping") == 0)
 	{
 		// we already have 't' and 'id' in the response
@@ -848,6 +853,7 @@ void node_impl::incoming_request(msg const& m, entry& e)
 		++g_announces;
 #endif
 	}
+/*
 	else if (strcmp(query, "find_torrent") == 0)
 	{
 		key_desc_t msg_desc[] = {
@@ -921,6 +927,7 @@ void node_impl::incoming_request(msg const& m, entry& e)
 
 		i->second.publish(msg_keys[2]->string_value(), in_tags, num_tags);
 	}
+*/
 	else
 	{
 		// if we don't recognize the message but there's a

src/kademlia/node_id.cpp

@@ -38,6 +38,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/kademlia/node_id.hpp"
 #include "libtorrent/hasher.hpp"
 #include "libtorrent/assert.hpp"
+#include "libtorrent/broadcast_socket.hpp" // for is_local et.al
 
 namespace libtorrent { namespace dht
 {
@@ -94,19 +95,52 @@ int distance_exp(node_id const& n1, node_id const& n2)
 }
 
 struct static_ { static_() { std::srand(std::time(0)); } } static__;
-	
-node_id generate_id()
+
+void hash_address(address const& ip, sha1_hash& h)
 {
+	if (ip.is_v4())
+	{
+		address_v4::bytes_type b = ip.to_v4().to_bytes();
+		h = hasher((char*)&b[0], b.size()).final();
+	}
+	else
+	{
+		address_v6::bytes_type b = ip.to_v6().to_bytes();
+		h = hasher((char*)&b[0], b.size()).final();
+	}
+}
+
+// verifies whether a node-id matches the IP it's used from
+// returns true if the node-id is OK coming from this source
+// and false otherwise.
+bool verify_id(node_id const& nid, address const& source_ip)
+{
+	// no need to verify local IPs, they would be incorrect anyway
+	if (is_local(source_ip)) return true;
+
+	node_id h;
+	hash_address(source_ip, h);
+	return memcmp(&nid[0], &h[0], 4) == 0;
+}
+	
+node_id generate_id(address const& external_ip)
+{
+	node_id h;
 	char random[20];
 #ifdef _MSC_VER
 	std::generate(random, random + 20, &rand);
 #else
 	std::generate(random, random + 20, &std::rand);
 #endif
+	h = hasher(random, 20).final();
 
-	hasher h;
-	h.update(random, 20);
-	return h.final();
+	if (!is_local(external_ip))
+	{
+		node_id ph;
+		hash_address(external_ip, ph);
+		memcpy(&h[0], &ph[0], 4);
+	}
+	return h;
 }
 
 } }  // namespace libtorrent::dht

src/kademlia/routing_table.cpp

@@ -176,7 +176,7 @@ bool routing_table::need_refresh(node_id& target) const
 	if (time_now() - i->last_active < minutes(15)) return false;
 
 	// generate a random node_id within the given bucket
-	target = generate_id();
+	target = generate_id(address());
 	int num_bits = std::distance(m_buckets.begin(), i) + 1;
 	node_id mask(0);
 	for (int i = 0; i < num_bits; ++i) mask[i/8] |= 0x80 >> (i&7);

src/kademlia/rpc_manager.cpp

@@ -33,10 +33,14 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/pch.hpp"
 #include "libtorrent/socket.hpp"
 
+// TODO: it would be nice to not have this dependency here
+#include "libtorrent/aux_/session_impl.hpp"
+
 #include <boost/bind.hpp>
 
 #include <libtorrent/io.hpp>
 #include <libtorrent/invariant_check.hpp>
+#include <libtorrent/kademlia/node_id.hpp> // for generate_id
 #include <libtorrent/kademlia/rpc_manager.hpp>
 #include <libtorrent/kademlia/logging.hpp>
 #include <libtorrent/kademlia/routing_table.hpp>
@@ -150,8 +154,6 @@ void observer::timeout()
 	m_algorithm->failed(observer_ptr(this));
 }
 
-node_id generate_id();
-
 enum { observer_size = max3<
 	sizeof(find_data_observer)
 	, sizeof(announce_observer)
@@ -161,7 +163,7 @@ enum { observer_size = max3<
 
 rpc_manager::rpc_manager(node_id const& our_id
 	, routing_table& table, send_fun const& sf
-	, void* userdata)
+	, void* userdata, aux::session_impl& ses)
 	: m_pool_allocator(observer_size, 10)
 	, m_next_transaction_id(std::rand() % max_transaction_id)
 	, m_send(sf)
@@ -172,6 +174,7 @@ rpc_manager::rpc_manager(node_id const& our_id
 	, m_random_number(generate_id())
 	, m_allocated_observers(0)
 	, m_destructing(false)
+	, m_ses(ses)
 {
 	std::srand(time(0));
 
@@ -339,6 +342,22 @@ bool rpc_manager::incoming(msg const& m, node_id* id)
 		return false;
 	}
 
+	lazy_entry const* ext_ip = ret_ent->dict_find_string("ip");
+	if (ext_ip && ext_ip->string_length() == 4)
+	{
+		// this node claims we use the wrong node-ID!
+		address_v4::bytes_type b;
+		memcpy(&b[0], ext_ip->string_ptr(), 4);
+		m_ses.set_external_address(address_v4(b));
+	}
+	else if (ext_ip && ext_ip->string_length() == 16)
+	{
+		// this node claims we use the wrong node-ID!
+		address_v6::bytes_type b;
+		memcpy(&b[0], ext_ip->string_ptr(), 16);
+		m_ses.set_external_address(address_v6(b));
+	}
+
 #ifdef TORRENT_DHT_VERBOSE_LOGGING
 	TORRENT_LOG(rpc) << "[" << o->m_algorithm.get() << "] Reply with transaction id: " 
 		<< tid << " from " << m.addr;

src/session_impl.cpp

@@ -4353,6 +4353,12 @@ namespace aux {
 		m_external_address = ip;
 		if (m_alerts.should_post<external_ip_alert>())
 			m_alerts.post_alert(external_ip_alert(ip));
+
+		// since we have a new external IP now, we need to
+		// restart the DHT with a new node ID
+#ifndef TORRENT_DISABLE_DHT
+		start_dht(m_dht_state);
+#endif
 	}
 
 	void session_impl::free_disk_buffer(char* buf)

src/socket_io.cpp

@@ -47,6 +47,20 @@ namespace libtorrent
 		return addr.to_string(ec);
 	}
 
+	std::string address_to_bytes(address const& a)
+	{
+		if (a.is_v4())
+		{
+			address_v4::bytes_type b = a.to_v4().to_bytes();
+			return std::string((char*)&b[0], b.size());
+		}
+		else
+		{
+			address_v6::bytes_type b = a.to_v6().to_bytes();
+			return std::string((char*)&b[0], b.size());
+		}
+	}
+
 	std::string print_endpoint(tcp::endpoint const& ep)
 	{
 		error_code ec;