Adds staking ability to transfer_split RPC

Added parameters are:

    stake_transfer - must be true to do a staking transfer
    supernode_public_id - the SN pubkey
    supernode_signature - a SN signature value
    allow_low_stake - set to true to allow staking less than a T1 (for
                      example, to submit an "upgrade" stake amount).

The transfer must also be sent to a single address (which has to match
the one configured in the SN for the signature to be valid).

src/wallet/wallet_rpc_server.cpp

@@ -49,6 +49,7 @@ using namespace epee;
 #include "rpc/rpc_args.h"
 #include "rpc/core_rpc_server_commands_defs.h"
 #include "utils/cryptmsg.h"
+#include "graft_rta_config.h"
 
 #undef MONERO_DEFAULT_LOG_CATEGORY
 #define MONERO_DEFAULT_LOG_CATEGORY "wallet.rpc"
@@ -679,6 +680,73 @@ namespace tools
       return false;
     }
 
+    if (req.stake_transfer) {
+      crypto::signature supernode_signature;
+      if (!epee::string_tools::hex_to_pod(req.supernode_signature, supernode_signature))
+      {
+        er.code = WALLET_RPC_ERROR_CODE_WRONG_SIGNATURE;
+        er.message = "failed to parse supernode signature";
+        return false;
+      }
+
+      crypto::public_key W;
+      if (!epee::string_tools::hex_to_pod(req.supernode_public_id, W) || !check_key(W))
+      {
+        er.code = WALLET_RPC_ERROR_CODE_WRONG_SUPERNODE_KEY;
+        er.message = "invalid supernode public identifier";
+        return false;
+      }
+      const cryptonote::account_public_address& supernode_public_address = dsts.front().addr;
+      std::string supernode_public_address_str = cryptonote::get_account_address_as_str(m_wallet->testnet(), supernode_public_address);
+      std::string data = supernode_public_address_str + ":" + req.supernode_public_id;
+      crypto::hash hash;
+      crypto::cn_fast_hash(data.data(), data.size(), hash);
+
+      if (!crypto::check_signature(hash, W, supernode_signature))
+      {
+        er.code = WALLET_RPC_ERROR_CODE_WRONG_SIGNATURE;
+        er.message = "invalid supernode signature";
+        return false;
+      }
+
+      auto current_height = m_wallet->get_blockchain_current_height();
+      if (req.unlock_time < current_height + config::graft::STAKE_MIN_UNLOCK_TIME_FOR_WALLET)
+      {
+        er.code = WALLET_RPC_ERROR_CODE_GENERIC_TRANSFER_ERROR;
+        er.message = "unlock_time is too low";
+        return false;
+      }
+
+      if (req.unlock_time > current_height + config::graft::STAKE_MAX_UNLOCK_TIME)
+      {
+        er.code = WALLET_RPC_ERROR_CODE_GENERIC_TRANSFER_ERROR;
+        er.message = "unlock_time is too high";
+        return false;
+      }
+
+      if (dsts.size() != 1)
+      {
+        er.code = WALLET_RPC_ERROR_CODE_GENERIC_TRANSFER_ERROR;
+        er.message = "stake transfer must go to exactly one recipient";
+        return false;
+      }
+
+      uint64_t amount = dsts.front().amount;
+      if (amount < config::graft::TIER1_STAKE_AMOUNT && !req.allow_low_stake)
+      {
+        er.code = WALLET_RPC_ERROR_CODE_GENERIC_TRANSFER_ERROR;
+        er.message = "staked amount is too low";
+        return false;
+      }
+
+      if (!add_graft_stake_tx_extra_to_extra(extra, req.supernode_public_id, supernode_public_address, supernode_signature))
+      {
+        er.code = WALLET_RPC_ERROR_CODE_GENERIC_TRANSFER_ERROR;
+        er.message = "failed to add stake transaction extra fields";
+        return false;
+      }
+    }
+
     try
     {
       uint64_t mixin = adjust_mixin(req.mixin);

src/wallet/wallet_rpc_server_commands_defs.h

@@ -165,6 +165,11 @@ namespace wallet_rpc
       bool do_not_relay;
       bool get_tx_hex;
 
+      bool stake_transfer;
+      std::string supernode_public_id;
+      std::string supernode_signature;
+      bool allow_low_stake;
+
       BEGIN_KV_SERIALIZE_MAP()
         KV_SERIALIZE(destinations)
         KV_SERIALIZE(priority)
@@ -174,6 +179,11 @@ namespace wallet_rpc
         KV_SERIALIZE(get_tx_keys)
         KV_SERIALIZE_OPT(do_not_relay, false)
         KV_SERIALIZE_OPT(get_tx_hex, false)
+
+        KV_SERIALIZE_OPT(stake_transfer, false)
+        KV_SERIALIZE(supernode_public_id)
+        KV_SERIALIZE(supernode_signature)
+        KV_SERIALIZE_OPT(allow_low_stake, false)
       END_KV_SERIALIZE_MAP()
     };