Add aggressive restrictions to pre-handshake p2p buffer limit

contrib/epee/include/net/levin_base.h

@@ -72,7 +72,8 @@ namespace levin
 
 
 #define LEVIN_DEFAULT_TIMEOUT_PRECONFIGURED 0
-#define LEVIN_DEFAULT_MAX_PACKET_SIZE 100000000      //100MB by default
+#define LEVIN_INITIAL_MAX_PACKET_SIZE  256*1024      // 256 KiB before handshake
+#define LEVIN_DEFAULT_MAX_PACKET_SIZE 100000000      //100MB by default after handshake
 
 #define LEVIN_PACKET_REQUEST			0x00000001
 #define LEVIN_PACKET_RESPONSE		0x00000002

contrib/epee/include/net/levin_protocol_handler_async.h

@@ -84,7 +84,8 @@ class async_protocol_handler_config
 
 public:
   typedef t_connection_context connection_context;
-  uint64_t m_max_packet_size; 
+  uint64_t m_initial_max_packet_size;
+  uint64_t m_max_packet_size;
   uint64_t m_invoke_timeout;
 
   int invoke(int command, const epee::span<const uint8_t> in_buff, std::string& buff_out, boost::uuids::uuid connection_id);
@@ -105,7 +106,7 @@ public:
   size_t get_in_connections_count();
   void set_handler(levin_commands_handler<t_connection_context>* handler, void (*destroy)(levin_commands_handler<t_connection_context>*) = NULL);
 
-  async_protocol_handler_config():m_pcommands_handler(NULL), m_pcommands_handler_destroy(NULL), m_max_packet_size(LEVIN_DEFAULT_MAX_PACKET_SIZE), m_invoke_timeout(LEVIN_DEFAULT_TIMEOUT_PRECONFIGURED)
+  async_protocol_handler_config():m_pcommands_handler(NULL), m_pcommands_handler_destroy(NULL), m_initial_max_packet_size(LEVIN_INITIAL_MAX_PACKET_SIZE), m_max_packet_size(LEVIN_DEFAULT_MAX_PACKET_SIZE), m_invoke_timeout(LEVIN_DEFAULT_TIMEOUT_PRECONFIGURED)
   {}
   ~async_protocol_handler_config() { set_handler(NULL, NULL); }
   void del_out_connections(size_t count);
@@ -162,6 +163,7 @@ public:
   net_utils::i_service_endpoint* m_pservice_endpoint; 
   config_type& m_config;
   t_connection_context& m_connection_context;
+  std::atomic<uint64_t> m_max_packet_size;
 
   net_utils::buffer m_cache_in_buffer;
   stream_state m_state;
@@ -289,7 +291,8 @@ public:
             m_current_head(bucket_head2()),
             m_pservice_endpoint(psnd_hndlr), 
             m_config(config), 
-            m_connection_context(conn_context), 
+            m_connection_context(conn_context),
+            m_max_packet_size(config.m_initial_max_packet_size),
             m_cache_in_buffer(4 * 1024),
             m_state(stream_state_head)
   {
@@ -399,13 +402,14 @@ public:
     }
 
     // these should never fail, but do runtime check for safety
-    CHECK_AND_ASSERT_MES(m_config.m_max_packet_size >= m_cache_in_buffer.size(), false, "Bad m_cache_in_buffer.size()");
+    const uint64_t max_packet_size = m_max_packet_size;
-    CHECK_AND_ASSERT_MES(m_config.m_max_packet_size - m_cache_in_buffer.size() >= m_fragment_buffer.size(), false, "Bad m_cache_in_buffer.size() + m_fragment_buffer.size()");
+    CHECK_AND_ASSERT_MES(max_packet_size >= m_cache_in_buffer.size(), false, "Bad m_cache_in_buffer.size()");
+    CHECK_AND_ASSERT_MES(max_packet_size - m_cache_in_buffer.size() >= m_fragment_buffer.size(), false, "Bad m_cache_in_buffer.size() + m_fragment_buffer.size()");
 
     // flipped to subtraction; prevent overflow since m_max_packet_size is variable and public
-    if(cb > m_config.m_max_packet_size - m_cache_in_buffer.size() - m_fragment_buffer.size())
+    if(cb > max_packet_size - m_cache_in_buffer.size() - m_fragment_buffer.size())
     {
-      MWARNING(m_connection_context << "Maximum packet size exceed!, m_max_packet_size = " << m_config.m_max_packet_size
+      MWARNING(m_connection_context << "Maximum packet size exceed!, m_max_packet_size = " << max_packet_size
                           << ", packet received " << m_cache_in_buffer.size() +  cb 
                           << ", connection will be closed.");
       return false;
@@ -519,6 +523,10 @@ public:
                 m_current_head.m_command, buff_to_invoke, return_buff, m_connection_context
               );
 
+              // peer_id remains unset if dropped
+              if (m_current_head.m_command == m_connection_context.handshake_command() && m_connection_context.handshake_complete())
+                m_max_packet_size = m_config.m_max_packet_size;
+
               bucket_head2 head = make_header(m_current_head.m_command, return_buff.size(), LEVIN_PACKET_RESPONSE, false);
               head.m_return_code = SWAP32LE(return_code);
 
@@ -576,9 +584,9 @@ public:
           m_cache_in_buffer.erase(sizeof(bucket_head2));
           m_state = stream_state_body;
           m_oponent_protocol_ver = m_current_head.m_protocol_version;
-          if(m_current_head.m_cb > m_config.m_max_packet_size)
+          if(m_current_head.m_cb > max_packet_size)
           {
-            LOG_ERROR_CC(m_connection_context, "Maximum packet size exceed!, m_max_packet_size = " << m_config.m_max_packet_size 
+            LOG_ERROR_CC(m_connection_context, "Maximum packet size exceed!, m_max_packet_size = " << max_packet_size
               << ", packet header received " << m_current_head.m_cb 
               << ", connection will be closed.");
             return false;
@@ -633,6 +641,9 @@ public:
       boost::interprocess::ipcdetail::atomic_write32(&m_invoke_buf_ready, 0);
       CRITICAL_REGION_BEGIN(m_invoke_response_handlers_lock);
 
+      if (command == m_connection_context.handshake_command())
+        m_max_packet_size = m_config.m_max_packet_size;
+
       if(!send_message(command, in_buff, LEVIN_PACKET_REQUEST, true))
       {
         LOG_ERROR_CC(m_connection_context, "Failed to do_send");
@@ -674,6 +685,9 @@ public:
 
     boost::interprocess::ipcdetail::atomic_write32(&m_invoke_buf_ready, 0);
 
+    if (command == m_connection_context.handshake_command())
+      m_max_packet_size = m_config.m_max_packet_size;
+
     if (!send_message(command, in_buff, LEVIN_PACKET_REQUEST, true))
     {
       LOG_ERROR_CC(m_connection_context, "Failed to send request");

src/cryptonote_basic/connection_context.h

@@ -55,6 +55,8 @@ namespace cryptonote
       state_normal
     };
 
+    bool handshake_complete() const noexcept { return m_state != state_before_handshake; }
+
     state m_state;
     std::vector<std::pair<crypto::hash, uint64_t>> m_needed_objects;
     std::unordered_set<crypto::hash> m_requested_objects;

src/cryptonote_protocol/cryptonote_protocol_handler.inl

@@ -2634,6 +2634,7 @@ skip:
     std::vector<std::pair<epee::net_utils::zone, boost::uuids::uuid>> fullConnections, fluffyConnections;
     m_p2p->for_each_connection([this, &exclude_context, &fullConnections, &fluffyConnections](connection_context& context, nodetool::peerid_type peer_id, uint32_t support_flags)
     {
+      // peer_id also filters out connections before handshake
       if (peer_id && exclude_context.m_connection_id != context.m_connection_id && context.m_remote_address.get_zone() == epee::net_utils::zone::public_)
       {
         if(m_core.fluffy_blocks_enabled() && (support_flags & P2P_SUPPORT_FLAG_FLUFFY_BLOCKS))

src/cryptonote_protocol/levin_notify.cpp

@@ -443,7 +443,7 @@ namespace levin
         zone->p2p->foreach_connection([txs, now, &zone, &source, &in_duration, &out_duration, &next_flush] (detail::p2p_context& context)
         {
           // When i2p/tor, only fluff to outbound connections
-          if (source != context.m_connection_id && (zone->nzone == epee::net_utils::zone::public_ || !context.m_is_income))
+          if (context.handshake_complete() && source != context.m_connection_id && (zone->nzone == epee::net_utils::zone::public_ || !context.m_is_income))
           {
             if (context.fluff_txs.empty())
               context.flush_time = now + (context.m_is_income ? in_duration() : out_duration());

src/p2p/net_node.h

@@ -118,6 +118,8 @@ namespace nodetool
         m_in_timedsync(false)
     {}
 
+    static constexpr int handshake_command() noexcept { return 1001; }
+
     std::vector<cryptonote::blobdata> fluff_txs;
     std::chrono::steady_clock::time_point flush_time;
     peerid_type peer_id;
@@ -139,6 +141,7 @@ namespace nodetool
 
     typedef COMMAND_HANDSHAKE_T<typename t_payload_net_handler::payload_type> COMMAND_HANDSHAKE;
     typedef COMMAND_TIMED_SYNC_T<typename t_payload_net_handler::payload_type> COMMAND_TIMED_SYNC;
+    static_assert(p2p_connection_context::handshake_command() == COMMAND_HANDSHAKE::ID, "invalid handshake command id");
 
     typedef epee::net_utils::boosted_tcp_server<epee::levin::async_protocol_handler<p2p_connection_context>> net_server;
 

tests/fuzz/levin.cpp

@@ -52,6 +52,8 @@ namespace
 
   struct test_levin_connection_context : public epee::net_utils::connection_context_base
   {
+    static constexpr int handshake_command() noexcept { return 1001; }
+    static constexpr bool handshake_complete() noexcept { return true; }
   };
 
   typedef epee::levin::async_protocol_handler_config<test_levin_connection_context> test_levin_protocol_handler_config;

tests/net_load_tests/net_load_tests.h

@@ -48,6 +48,8 @@ namespace net_load_tests
   struct test_connection_context : epee::net_utils::connection_context_base
   {
     test_connection_context(): epee::net_utils::connection_context_base(boost::uuids::nil_uuid(), {}, false, false), m_closed(false) {}
+    static constexpr int handshake_command() noexcept { return 1001; }
+    static constexpr bool handshake_complete() noexcept { return true; }
     volatile bool m_closed;
   };
 

tests/unit_tests/epee_levin_protocol_handler_async.cpp

@@ -43,6 +43,8 @@ namespace
 {
   struct test_levin_connection_context : public epee::net_utils::connection_context_base
   {
+    static constexpr int handshake_command() noexcept { return 1001; }
+    static constexpr bool handshake_complete() noexcept { return true; }
   };
 
   typedef epee::levin::async_protocol_handler_config<test_levin_connection_context> test_levin_protocol_handler_config;
@@ -193,6 +195,7 @@ namespace
     {
       m_handler_config.set_handler(m_pcommands_handler, [](epee::levin::levin_commands_handler<test_levin_connection_context> *handler) { delete handler; });
       m_handler_config.m_invoke_timeout = invoke_timeout;
+      m_handler_config.m_initial_max_packet_size = max_packet_size;
       m_handler_config.m_max_packet_size = max_packet_size;
     }
 

tests/unit_tests/levin.cpp

@@ -178,6 +178,7 @@ namespace
         {
             using base_type = epee::net_utils::connection_context_base;
             static_cast<base_type&>(context_) = base_type{random_generator(), {}, is_incoming, false};
+            context_.m_state = cryptonote::cryptonote_connection_context::state_normal;
             handler_.after_init_connection();
         }