core: new /getrandom_rctouts.bin binary RPC call

to get random ringct outputs to mix with

src/cryptonote_core/blockchain.cpp

@@ -1597,6 +1597,104 @@ bool Blockchain::get_random_outs_for_amounts(const COMMAND_RPC_GET_RANDOM_OUTPUT
   return true;
 }
 //------------------------------------------------------------------
+// This function adds the ringct output at index i to the list
+// unlocked and other such checks should be done by here.
+void Blockchain::add_out_to_get_rct_random_outs(std::list<COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::out_entry>& outs, size_t i) const
+{
+  LOG_PRINT_L3("Blockchain::" << __func__);
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::out_entry& oen = *outs.insert(outs.end(), COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::out_entry());
+  oen.global_amount_index = i;
+  output_data_t data = m_db->get_output_key(0, i);
+  oen.out_key = data.pubkey;
+  oen.commitment = m_db->get_rct_commitment(i);
+}
+//------------------------------------------------------------------
+// This function takes an RPC request for mixins and creates an RPC response
+// with the requested mixins.
+// TODO: figure out why this returns boolean / if we should be returning false
+// in some cases
+bool Blockchain::get_random_rct_outs(const COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::request& req, COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::response& res) const
+{
+  LOG_PRINT_L3("Blockchain::" << __func__);
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  // for each amount that we need to get mixins for, get <n> random outputs
+  // from BlockchainDB where <n> is req.outs_count (number of mixins).
+  auto num_outs = m_db->get_num_outputs(0);
+  // ensure we don't include outputs that aren't yet eligible to be used
+  // outpouts are sorted by height
+  while (num_outs > 0)
+  {
+    const tx_out_index toi = m_db->get_output_tx_and_index(0, num_outs - 1);
+    const uint64_t height = m_db->get_tx_block_height(toi.first);
+    if (height + CRYPTONOTE_DEFAULT_TX_SPENDABLE_AGE <= m_db->height())
+      break;
+    --num_outs;
+  }
+
+  std::unordered_set<uint64_t> seen_indices;
+
+  // if there aren't enough outputs to mix with (or just enough),
+  // use all of them.  Eventually this should become impossible.
+  if (num_outs <= req.outs_count)
+  {
+    for (uint64_t i = 0; i < num_outs; i++)
+    {
+      // get tx_hash, tx_out_index from DB
+      tx_out_index toi = m_db->get_output_tx_and_index(0, i);
+
+      // if tx is unlocked, add output to result_outs
+      if (is_tx_spendtime_unlocked(m_db->get_tx_unlock_time(toi.first)))
+      {
+        add_out_to_get_rct_random_outs(res.outs, i);
+      }
+    }
+  }
+  else
+  {
+    // while we still need more mixins
+    while (res.outs.size() < req.outs_count)
+    {
+      // if we've gone through every possible output, we've gotten all we can
+      if (seen_indices.size() == num_outs)
+      {
+        break;
+      }
+
+      // get a random output index from the DB.  If we've already seen it,
+      // return to the top of the loop and try again, otherwise add it to the
+      // list of output indices we've seen.
+
+      // triangular distribution over [a,b) with a=0, mode c=b=up_index_limit
+      uint64_t r = crypto::rand<uint64_t>() % ((uint64_t)1 << 53);
+      double frac = std::sqrt((double)r / ((uint64_t)1 << 53));
+      uint64_t i = (uint64_t)(frac*num_outs);
+      // just in case rounding up to 1 occurs after sqrt
+      if (i == num_outs)
+        --i;
+
+      if (seen_indices.count(i))
+      {
+        continue;
+      }
+      seen_indices.emplace(i);
+
+      // get tx_hash, tx_out_index from DB
+      tx_out_index toi = m_db->get_output_tx_and_index(0, i);
+
+      // if the output's transaction is unlocked, add the output's index to
+      // our list.
+      if (is_tx_spendtime_unlocked(m_db->get_tx_unlock_time(toi.first)))
+      {
+        add_out_to_get_rct_random_outs(res.outs, i);
+      }
+    }
+  }
+  return true;
+}
+//------------------------------------------------------------------
 bool Blockchain::get_outs(const COMMAND_RPC_GET_OUTPUTS::request& req, COMMAND_RPC_GET_OUTPUTS::response& res) const
 {
   LOG_PRINT_L3("Blockchain::" << __func__);

src/cryptonote_core/blockchain.h

@@ -454,6 +454,23 @@ namespace cryptonote
      */
     bool get_outs(const COMMAND_RPC_GET_OUTPUTS::request& req, COMMAND_RPC_GET_OUTPUTS::response& res) const;
 
+    /**
+     * @brief gets random ringct outputs to mix with
+     *
+     * This function takes an RPC request for outputs to mix with
+     * and creates an RPC response with the resultant output indices
+     * and the matching keys.
+     *
+     * Outputs to mix with are randomly selected from the utxo set
+     * for each output amount in the request.
+     *
+     * @param req the output amounts and number of mixins to select
+     * @param res return-by-reference the resultant output indices
+     *
+     * @return true
+     */
+    bool get_random_rct_outs(const COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::request& req, COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::response& res) const;
+
     /**
      * @brief gets the global indices for outputs from a given transaction
      *
@@ -1053,6 +1070,14 @@ namespace cryptonote
      */
     void add_out_to_get_random_outs(COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::outs_for_amount& result_outs, uint64_t amount, size_t i) const;
 
+    /**
+     * @brief adds the given output to the requested set of random ringct outputs
+     *
+     * @param outs return-by-reference the set the output is to be added to
+     * @param i the rct output index
+     */
+    void add_out_to_get_rct_random_outs(std::list<COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::out_entry>& outs, size_t i) const;
+
     /**
      * @brief checks if a transaction is unlocked (its outputs spendable)
      *

src/cryptonote_core/cryptonote_core.cpp

@@ -706,6 +706,11 @@ namespace cryptonote
     return m_blockchain_storage.get_outs(req, res);
   }
   //-----------------------------------------------------------------------------------------------
+  bool core::get_random_rct_outs(const COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::request& req, COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::response& res) const
+  {
+    return m_blockchain_storage.get_random_rct_outs(req, res);
+  }
+  //-----------------------------------------------------------------------------------------------
   bool core::get_tx_outputs_gindexs(const crypto::hash& tx_id, std::vector<uint64_t>& indexs) const
   {
     return m_blockchain_storage.get_tx_outputs_gindexs(tx_id, indexs);

src/cryptonote_core/cryptonote_core.h

@@ -479,6 +479,14 @@ namespace cryptonote
       */
      bool get_outs(const COMMAND_RPC_GET_OUTPUTS::request& req, COMMAND_RPC_GET_OUTPUTS::response& res) const;
 
+     /**
+      *
+      * @copydoc Blockchain::get_random_rct_outs
+      *
+      * @note see Blockchain::get_random_rct_outs
+      */
+     bool get_random_rct_outs(const COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::request& req, COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::response& res) const;
+
 
      /**
       * @copydoc miner::pause

src/rpc/core_rpc_server.cpp

@@ -250,6 +250,30 @@ namespace cryptonote
     return true;
   }
   //------------------------------------------------------------------------------------------------------------------------------
+  bool core_rpc_server::on_get_random_rct_outs(const COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::request& req, COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::response& res)
+  {
+    CHECK_CORE_BUSY();
+    res.status = "Failed";
+    if(!m_core.get_random_rct_outs(req, res))
+    {
+      return true;
+    }
+
+    res.status = CORE_RPC_STATUS_OK;
+    std::stringstream ss;
+    typedef COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::out_entry out_entry;
+    CHECK_AND_ASSERT_MES(res.outs.size(), true, "internal error: res.outs.size() is empty");
+    std::for_each(res.outs.begin(), res.outs.end(), [&](out_entry& oe)
+      {
+        ss << oe.global_amount_index << " ";
+      });
+    ss << ENDL;
+    std::string s = ss.str();
+    LOG_PRINT_L2("COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS: " << ENDL << s);
+    res.status = CORE_RPC_STATUS_OK;
+    return true;
+  }
+  //------------------------------------------------------------------------------------------------------------------------------
   bool core_rpc_server::on_get_indexes(const COMMAND_RPC_GET_TX_GLOBAL_OUTPUTS_INDEXES::request& req, COMMAND_RPC_GET_TX_GLOBAL_OUTPUTS_INDEXES::response& res)
   {
     CHECK_CORE_BUSY();

src/rpc/core_rpc_server.h

@@ -79,6 +79,7 @@ namespace cryptonote
       MAP_URI_AUTO_BIN2("/get_o_indexes.bin", on_get_indexes, COMMAND_RPC_GET_TX_GLOBAL_OUTPUTS_INDEXES)      
       MAP_URI_AUTO_BIN2("/getrandom_outs.bin", on_get_random_outs, COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS)      
       MAP_URI_AUTO_BIN2("/get_outs.bin", on_get_outs, COMMAND_RPC_GET_OUTPUTS)      
+      MAP_URI_AUTO_BIN2("/getrandom_rctouts.bin", on_get_random_rct_outs, COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS)
       MAP_URI_AUTO_JON2("/gettransactions", on_get_transactions, COMMAND_RPC_GET_TRANSACTIONS)
       MAP_URI_AUTO_JON2("/is_key_image_spent", on_is_key_image_spent, COMMAND_RPC_IS_KEY_IMAGE_SPENT)
       MAP_URI_AUTO_JON2("/sendrawtransaction", on_send_raw_tx, COMMAND_RPC_SEND_RAW_TX)
@@ -128,6 +129,7 @@ namespace cryptonote
     bool on_mining_status(const COMMAND_RPC_MINING_STATUS::request& req, COMMAND_RPC_MINING_STATUS::response& res);
     bool on_get_random_outs(const COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::request& req, COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::response& res);        
     bool on_get_outs(const COMMAND_RPC_GET_OUTPUTS::request& req, COMMAND_RPC_GET_OUTPUTS::response& res);        
+    bool on_get_random_rct_outs(const COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::request& req, COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS::response& res);
     bool on_get_info(const COMMAND_RPC_GET_INFO::request& req, COMMAND_RPC_GET_INFO::response& res);        
     bool on_save_bc(const COMMAND_RPC_SAVE_BC::request& req, COMMAND_RPC_SAVE_BC::response& res);
     bool on_get_peer_list(const COMMAND_RPC_GET_PEER_LIST::request& req, COMMAND_RPC_GET_PEER_LIST::response& res);

src/rpc/core_rpc_server_commands_defs.h

@@ -315,6 +315,36 @@ namespace cryptonote
       END_KV_SERIALIZE_MAP()
     };
   };
+
+  struct COMMAND_RPC_GET_RANDOM_RCT_OUTPUTS
+  {
+    struct request
+    {
+      uint64_t outs_count;
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(outs_count)
+      END_KV_SERIALIZE_MAP()
+    };
+
+#pragma pack (push, 1)
+    struct out_entry
+    {
+      uint64_t global_amount_index;
+      crypto::public_key out_key;
+      rct::key commitment;
+    };
+#pragma pack(pop)
+
+    struct response
+    {
+      std::list<out_entry> outs;
+      std::string status;
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE_CONTAINER_POD_AS_BLOB(outs)
+        KV_SERIALIZE(status)
+      END_KV_SERIALIZE_MAP()
+    };
+  };
   //-----------------------------------------------
   struct COMMAND_RPC_SEND_RAW_TX
   {