1 files changed, 183 insertions, 0 deletions
diff --git a/src/rpc/txoutproof.cpp b/src/rpc/txoutproof.cpp
new file mode 100644
index 0000000000..2700fb400c
--- /dev/null
+++ b/src/rpc/txoutproof.cpp
@@ -0,0 +1,183 @@
+// Copyright (c) 2010 Satoshi Nakamoto
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <chain.h>
+#include <chainparams.h>
+#include <coins.h>
+#include <index/txindex.h>
+#include <merkleblock.h>
+#include <node/blockstorage.h>
+#include <primitives/transaction.h>
+#include <rpc/server.h>
+#include <rpc/server_util.h>
+#include <rpc/util.h>
+#include <univalue.h>
+#include <util/strencodings.h>
+#include <validation.h>
+
+using node::GetTransaction;
+using node::ReadBlockFromDisk;
+
+static RPCHelpMan gettxoutproof()
+{
+    return RPCHelpMan{"gettxoutproof",
+        "\nReturns a hex-encoded proof that \"txid\" was included in a block.\n"
+        "\nNOTE: By default this function only works sometimes. This is when there is an\n"
+        "unspent output in the utxo for this transaction. To make it always work,\n"
+        "you need to maintain a transaction index, using the -txindex command line option or\n"
+        "specify the block in which the transaction is included manually (by blockhash).\n",
+        {
+            {"txids", RPCArg::Type::ARR, RPCArg::Optional::NO, "The txids to filter",
+                {
+                    {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::OMITTED, "A transaction hash"},
+                },
+            },
+            {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::OMITTED_NAMED_ARG, "If specified, looks for txid in the block with this hash"},
+        },
+        RPCResult{
+            RPCResult::Type::STR, "data", "A string that is a serialized, hex-encoded data for the proof."
+        },
+        RPCExamples{""},
+        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
+        {
+            std::set<uint256> setTxids;
+            UniValue txids = request.params[0].get_array();
+            if (txids.empty()) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Parameter 'txids' cannot be empty");
+            }
+            for (unsigned int idx = 0; idx < txids.size(); idx++) {
+                auto ret = setTxids.insert(ParseHashV(txids[idx], "txid"));
+                if (!ret.second) {
+                    throw JSONRPCError(RPC_INVALID_PARAMETER, std::string("Invalid parameter, duplicated txid: ") + txids[idx].get_str());
+                }
+            }
+
+            const CBlockIndex* pblockindex = nullptr;
+            uint256 hashBlock;
+            ChainstateManager& chainman = EnsureAnyChainman(request.context);
+            if (!request.params[1].isNull()) {
+                LOCK(cs_main);
+                hashBlock = ParseHashV(request.params[1], "blockhash");
+                pblockindex = chainman.m_blockman.LookupBlockIndex(hashBlock);
+                if (!pblockindex) {
+                    throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
+                }
+            } else {
+                LOCK(cs_main);
+                CChainState& active_chainstate = chainman.ActiveChainstate();
+
+                // Loop through txids and try to find which block they're in. Exit loop once a block is found.
+                for (const auto& tx : setTxids) {
+                    const Coin& coin = AccessByTxid(active_chainstate.CoinsTip(), tx);
+                    if (!coin.IsSpent()) {
+                        pblockindex = active_chainstate.m_chain[coin.nHeight];
+                        break;
+                    }
+                }
+            }
+
+
+            // Allow txindex to catch up if we need to query it and before we acquire cs_main.
+            if (g_txindex && !pblockindex) {
+                g_txindex->BlockUntilSyncedToCurrentChain();
+            }
+
+            LOCK(cs_main);
+
+            if (pblockindex == nullptr) {
+                const CTransactionRef tx = GetTransaction(/* block_index */ nullptr, /* mempool */ nullptr, *setTxids.begin(), Params().GetConsensus(), hashBlock);
+                if (!tx || hashBlock.IsNull()) {
+                    throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Transaction not yet in block");
+                }
+                pblockindex = chainman.m_blockman.LookupBlockIndex(hashBlock);
+                if (!pblockindex) {
+                    throw JSONRPCError(RPC_INTERNAL_ERROR, "Transaction index corrupt");
+                }
+            }
+
+            CBlock block;
+            if (!ReadBlockFromDisk(block, pblockindex, Params().GetConsensus())) {
+                throw JSONRPCError(RPC_INTERNAL_ERROR, "Can't read block from disk");
+            }
+
+            unsigned int ntxFound = 0;
+            for (const auto& tx : block.vtx) {
+                if (setTxids.count(tx->GetHash())) {
+                    ntxFound++;
+                }
+            }
+            if (ntxFound != setTxids.size()) {
+                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Not all transactions found in specified or retrieved block");
+            }
+
+            CDataStream ssMB(SER_NETWORK, PROTOCOL_VERSION | SERIALIZE_TRANSACTION_NO_WITNESS);
+            CMerkleBlock mb(block, setTxids);
+            ssMB << mb;
+            std::string strHex = HexStr(ssMB);
+            return strHex;
+        },
+    };
+}
+
+static RPCHelpMan verifytxoutproof()
+{
+    return RPCHelpMan{"verifytxoutproof",
+        "\nVerifies that a proof points to a transaction in a block, returning the transaction it commits to\n"
+        "and throwing an RPC error if the block is not in our best chain\n",
+        {
+            {"proof", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The hex-encoded proof generated by gettxoutproof"},
+        },
+        RPCResult{
+            RPCResult::Type::ARR, "", "",
+            {
+                {RPCResult::Type::STR_HEX, "txid", "The txid(s) which the proof commits to, or empty array if the proof cannot be validated."},
+            }
+        },
+        RPCExamples{""},
+        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
+        {
+            CDataStream ssMB(ParseHexV(request.params[0], "proof"), SER_NETWORK, PROTOCOL_VERSION | SERIALIZE_TRANSACTION_NO_WITNESS);
+            CMerkleBlock merkleBlock;
+            ssMB >> merkleBlock;
+
+            UniValue res(UniValue::VARR);
+
+            std::vector<uint256> vMatch;
+            std::vector<unsigned int> vIndex;
+            if (merkleBlock.txn.ExtractMatches(vMatch, vIndex) != merkleBlock.header.hashMerkleRoot)
+                return res;
+
+            ChainstateManager& chainman = EnsureAnyChainman(request.context);
+            LOCK(cs_main);
+
+            const CBlockIndex* pindex = chainman.m_blockman.LookupBlockIndex(merkleBlock.header.GetHash());
+            if (!pindex || !chainman.ActiveChain().Contains(pindex) || pindex->nTx == 0) {
+                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found in chain");
+            }
+
+            // Check if proof is valid, only add results if so
+            if (pindex->nTx == merkleBlock.txn.GetNumTransactions()) {
+                for (const uint256& hash : vMatch) {
+                    res.push_back(hash.GetHex());
+                }
+            }
+
+            return res;
+        },
+    };
+}
+
+void RegisterTxoutProofRPCCommands(CRPCTable& t)
+{
+    static const CRPCCommand commands[]{
+        // category     actor (function)
+        // --------     ----------------
+        {"blockchain", &gettxoutproof},
+        {"blockchain", &verifytxoutproof},
+    };
+    for (const auto& c : commands) {
+        t.appendCommand(c.name, &c);
+    }
+}