DNS checkpoint updating added, and daemon flag to enforce them

The daemon should now check for updated checkpoints from
checkpoints.moneropulse.org as well as from the configured json file
every ~1hr (and on launch).

The daemon now has a flag to enable enforcing these checkpoints (rather
    than just printing a warning when they fail).

TODO: an easily configurable list of DNS servers to check for
checkpoints as opposed to the hard-coded "checkpoints.moneropulse.org"

src/cryptonote_core/blockchain_storage.cpp

@@ -442,6 +442,13 @@ difficulty_type blockchain_storage::get_difficulty_for_next_block()
 bool blockchain_storage::rollback_blockchain_switching(std::list<block>& original_chain, size_t rollback_height)
 {
   CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  // fail if rollback_height passed is too high
+  if (rollback_height > m_blocks.size())
+  {
+    return true;
+  }
+
   //remove failed subchain
   for(size_t i = m_blocks.size()-1; i >=rollback_height; i--)
   {
@@ -1775,13 +1782,11 @@ bool blockchain_storage::add_new_block(const block& bl_, block_verification_cont
   return handle_block_to_main_chain(bl, id, bvc);
 }
 //------------------------------------------------------------------
-void blockchain_storage::update_checkpoints(const std::string& file_path)
+bool blockchain_storage::update_checkpoints(const std::string& file_path)
 {
-  // if a path is supplied, updated checkpoints from json.
-  // if not, probably fetch from DNS TXT Records.
-  if (file_path.size() > 0)
+  if (!cryptonote::load_new_checkpoints(m_checkpoints, file_path))
   {
-    cryptonote::load_checkpoints_from_json(m_checkpoints, file_path);
+    return false;
   }
 
   const auto& points = m_checkpoints.get_points();
@@ -1790,7 +1795,22 @@ void blockchain_storage::update_checkpoints(const std::string& file_path)
   {
     if (!m_checkpoints.check_block(pt.first, get_block_hash(m_blocks[pt.first].bl)))
     {
-      LOG_ERROR("Checkpoint failed when adding new checkpoints from json file, this could be very bad.");
+      // if we're enforcing dns checkpoints, roll back to a couple of blocks before the checkpoint
+      if (m_enforce_dns_checkpoints)
+      {
+	LOG_ERROR("Checkpoint failed when adding new checkpoints, rolling back!");
+	std::list<block> empty;
+	rollback_blockchain_switching(empty, pt.first - 2);
+      }
+      else
+      {
+	LOG_ERROR("Checkpoint failed when adding new checkpoints, this could be very bad.");
+      }
     }
   }
+  return true;
+}
+void blockchain_storage::set_enforce_dns_checkpoints(bool enforce_checkpoints)
+{
+  m_enforce_dns_checkpoints = enforce_checkpoints;
 }

src/cryptonote_core/blockchain_storage.h

@@ -78,7 +78,7 @@ namespace cryptonote
       uint64_t already_generated_coins;
     };
 
-    blockchain_storage(tx_memory_pool& tx_pool):m_tx_pool(tx_pool), m_current_block_cumul_sz_limit(0), m_is_in_checkpoint_zone(false), m_is_blockchain_storing(false)
+    blockchain_storage(tx_memory_pool& tx_pool):m_tx_pool(tx_pool), m_current_block_cumul_sz_limit(0), m_is_in_checkpoint_zone(false), m_is_blockchain_storing(false), m_enforce_dns_checkpoints(false)
     {};
 
     bool init() { return init(tools::get_default_data_dir(), true); }
@@ -180,7 +180,8 @@ namespace cryptonote
     void print_blockchain(uint64_t start_index, uint64_t end_index);
     void print_blockchain_index();
     void print_blockchain_outs(const std::string& file);
-    void update_checkpoints(const std::string& file_path);
+    bool update_checkpoints(const std::string& file_path);
+    void set_enforce_dns_checkpoints(bool enforce_checkpoints);
 
   private:
     typedef std::unordered_map<crypto::hash, size_t> blocks_by_id_index;
@@ -215,6 +216,8 @@ namespace cryptonote
     std::atomic<bool> m_is_in_checkpoint_zone;
     std::atomic<bool> m_is_blockchain_storing;
 
+    bool m_enforce_dns_checkpoints;
+
     bool switch_to_alternative_blockchain(std::list<blocks_ext_by_hash::iterator>& alt_chain, bool discard_disconnected_chain);
     bool pop_block_from_blockchain();
     bool purge_block_data_from_blockchain(const block& b, size_t processed_tx_count);

src/cryptonote_core/checkpoints_create.cpp

@@ -29,6 +29,9 @@
 // Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
 
 #include "checkpoints_create.h"
+#include "common/dns_utils.h"
+#include "include_base_utils.h"
+#include <sstream>
 #include "storages/portable_storage_template_helper.h" // epee json include
 
 namespace cryptonote
@@ -107,4 +110,51 @@ bool load_checkpoints_from_json(cryptonote::checkpoints& checkpoints, std::strin
   return true;
 }
 
+bool load_checkpoints_from_dns(cryptonote::checkpoints& checkpoints, const std::string& url)
+{
+  bool avail, valid;
+  auto records = tools::DNSResolver::instance().get_txt_record(url, avail, valid);
+
+  if (avail && !valid)
+  {
+    LOG_ERROR("DNSSEC present and failed validation for query to" << url);
+    return false;
+  }
+
+  for (auto& record : records)
+  {
+    auto pos = record.find(":");
+    if (pos != std::string::npos)
+    {
+      uint64_t height;
+      crypto::hash hash;
+
+      // parse the first part as uint64_t,
+      // if this fails move on to the next record
+      std::stringstream ss(record.substr(0, pos));
+      if (!(ss >> height))
+      {
+	continue;
+      }
+
+      // parse the second part as crypto::hash,
+      // if this fails move on to the next record
+      std::string hashStr = record.substr(pos + 1);
+      if (!epee::string_tools::parse_tpod_from_hex_string(hashStr, hash))
+      {
+	continue;
+      }
+
+      ADD_CHECKPOINT(height, hashStr);
+    }
+  }
+  return true;
+}
+
+bool load_new_checkpoints(cryptonote::checkpoints& checkpoints, std::string json_hashfile_fullpath)
+{
+  // TODO: replace hard-coded url with const string or #define
+  return (load_checkpoints_from_json(checkpoints, json_hashfile_fullpath) && load_checkpoints_from_dns(checkpoints, "checkpoints.moneropulse.org"));
+}
+
 }  // namespace cryptonote

src/cryptonote_core/checkpoints_create.h

@@ -42,5 +42,7 @@ namespace cryptonote
   bool create_checkpoints(cryptonote::checkpoints& checkpoints);
 
   bool load_checkpoints_from_json(cryptonote::checkpoints& checkpoints, std::string json_hashfile_fullpath);
+  bool load_checkpoints_from_dns(cryptonote::checkpoints& checkpoints);
+  bool load_new_checkpoints(cryptonote::checkpoints& checkpoints, std::string json_hashfile_fullpath);
 
 }  // namespace cryptonote

src/cryptonote_core/cryptonote_core.cpp

@@ -54,7 +54,9 @@ namespace cryptonote
               m_miner(this),
               m_miner_address(boost::value_initialized<account_public_address>()), 
               m_starter_message_showed(false),
-              m_target_blockchain_height(0)
+              m_target_blockchain_height(0),
+              m_checkpoints_path(""),
+              m_last_checkpoints_update(0)
   {
     set_cryptonote_protocol(pprotocol);
   }
@@ -69,21 +71,27 @@ namespace cryptonote
   void core::set_checkpoints(checkpoints&& chk_pts)
   {
     m_blockchain_storage.set_checkpoints(std::move(chk_pts));
-    m_last_checkpoints_update = time(NULL);
   }
   //-----------------------------------------------------------------------------------
   void core::set_checkpoints_file_path(const std::string& path)
   {
     m_checkpoints_path = path;
   }
+  //-----------------------------------------------------------------------------------
+  void core::set_enforce_dns_checkpoints(bool enforce_dns)
+  {
+    m_blockchain_storage.set_enforce_dns_checkpoints(enforce_dns);
+  }
   //-----------------------------------------------------------------------------------------------
-  void core::update_checkpoints()
+  bool core::update_checkpoints()
   {
+    bool res = true;
     if (time(NULL) - m_last_checkpoints_update >= 3600)
     {
-      m_blockchain_storage.update_checkpoints(m_checkpoints_path);
+      res = m_blockchain_storage.update_checkpoints(m_checkpoints_path);
       m_last_checkpoints_update = time(NULL);
     }
+    return res;
   }
   //-----------------------------------------------------------------------------------
   void core::init_options(boost::program_options::options_description& /*desc*/)

src/cryptonote_core/cryptonote_core.h

@@ -95,6 +95,7 @@ namespace cryptonote
      void set_cryptonote_protocol(i_cryptonote_protocol* pprotocol);
      void set_checkpoints(checkpoints&& chk_pts);
      void set_checkpoints_file_path(const std::string& path);
+     void set_enforce_dns_checkpoints(bool enforce_dns);
 
      bool get_pool_transactions(std::list<transaction>& txs);
      size_t get_pool_transactions_count();
@@ -122,9 +123,9 @@ namespace cryptonote
      void set_target_blockchain_height(uint64_t target_blockchain_height);
      uint64_t get_target_blockchain_height() const;
 
-   private:
-     void update_checkpoints();
+     bool update_checkpoints();
 
+   private:
      bool add_new_tx(const transaction& tx, const crypto::hash& tx_hash, const crypto::hash& tx_prefix_hash, size_t blob_size, tx_verification_context& tvc, bool keeped_by_block);
      bool add_new_tx(const transaction& tx, tx_verification_context& tvc, bool keeped_by_block);
      bool add_new_block(const block& b, block_verification_context& bvc);

src/daemon/daemon.cpp

@@ -69,6 +69,7 @@ namespace
     , "Run on testnet. The wallet must be launched with --testnet flag."
     , false
     };
+  const command_line::arg_descriptor<bool>        arg_dns_checkpoints  = {"enforce-dns-checkpointing", "checkpoints from DNS server will be enforced", false};
 }
 
 bool command_line_preprocessor(const boost::program_options::variables_map& vm)
@@ -135,6 +136,7 @@ int main(int argc, char* argv[])
   command_line::add_arg(desc_cmd_sett, arg_log_level);
   command_line::add_arg(desc_cmd_sett, arg_console);
   command_line::add_arg(desc_cmd_sett, arg_testnet_on);
+  command_line::add_arg(desc_cmd_sett, arg_dns_checkpoints);
 
   cryptonote::core::init_options(desc_cmd_sett);
   cryptonote::core_rpc_server::init_options(desc_cmd_sett);
@@ -206,17 +208,21 @@ int main(int argc, char* argv[])
   CHECK_AND_ASSERT_MES(res, 1, "Failed to initialize checkpoints");
   boost::filesystem::path json(JSON_HASH_FILE_NAME);
   boost::filesystem::path checkpoint_json_hashfile_fullpath = data_dir / json;
-  res = cryptonote::load_checkpoints_from_json(checkpoints, checkpoint_json_hashfile_fullpath.string().c_str());
-  CHECK_AND_ASSERT_MES(res, 1, "Failed to load initial checkpoints");
 
   //create objects and link them
   cryptonote::core ccore(NULL);
 
+  // tell core if we're enforcing dns checkpoints
+  bool enforce_dns = command_line::get_arg(vm, arg_dns_checkpoints);
+  ccore.set_enforce_dns_checkpoints(enforce_dns);
+
   if (testnet_mode) {
     LOG_PRINT_L0("Starting in testnet mode!");
   } else {
     ccore.set_checkpoints(std::move(checkpoints));
     ccore.set_checkpoints_file_path(checkpoint_json_hashfile_fullpath.string());
+    res = ccore.update_checkpoints();
+    CHECK_AND_ASSERT_MES(res, 1, "Failed to load initial checkpoints");
   }
 
   cryptonote::t_cryptonote_protocol_handler<cryptonote::core> cprotocol(ccore, NULL);