Merge #431: [0.17] blockheaders include block height, nodes validate it

2bfabb3 blockheaders include block height, nodes validate it (Gregory Sanders)
8f6bedf functional framework support for CScriptNum decode (Gregory Sanders)

Pull request description:

  The feature is enabled by default in custom chains; cannot be activated in legacy chains.

Tree-SHA512: d033b7dd0d853e5693efda584494cf58ed7ff43ce32d1f5d44e4ee52907b989e434c8dbb28a0f843da8b799548924d2499e8759a96ed5a7191b95f22b29c7f6e

Author: instagibbs

src/chain.h

@@ -210,6 +210,7 @@ class CBlockIndex
     int32_t nVersion;
     uint256 hashMerkleRoot;
     uint32_t nTime;
+    uint32_t block_height;
     uint32_t nBits;
     uint32_t nNonce;
 
@@ -238,6 +239,7 @@ class CBlockIndex
         nVersion       = 0;
         hashMerkleRoot = uint256();
         nTime          = 0;
+        block_height   = 0;
         nBits          = 0;
         nNonce         = 0;
     }
@@ -254,6 +256,7 @@ class CBlockIndex
         nVersion       = block.nVersion;
         hashMerkleRoot = block.hashMerkleRoot;
         nTime          = block.nTime;
+        block_height   = block.block_height;
         nBits          = block.nBits;
         nNonce         = block.nNonce;
     }
@@ -284,6 +287,7 @@ class CBlockIndex
             block.hashPrevBlock = pprev->GetBlockHash();
         block.hashMerkleRoot = hashMerkleRoot;
         block.nTime          = nTime;
+        block.block_height   = block_height;
         block.nBits          = nBits;
         block.nNonce         = nNonce;
         return block;
@@ -403,6 +407,7 @@ class CDiskBlockIndex : public CBlockIndex
         READWRITE(hashPrev);
         READWRITE(hashMerkleRoot);
         READWRITE(nTime);
+        READWRITE(block_height);
         READWRITE(nBits);
         READWRITE(nNonce);
     }
@@ -414,6 +419,7 @@ class CDiskBlockIndex : public CBlockIndex
         block.hashPrevBlock   = hashPrev;
         block.hashMerkleRoot  = hashMerkleRoot;
         block.nTime           = nTime;
+        block.block_height    = block_height;
         block.nBits           = nBits;
         block.nNonce          = nNonce;
         return block.GetHash();

src/chainparams.cpp

@@ -435,6 +435,10 @@ class CCustomParams : public CRegTestParams {
         // No subsidy for custom chains by default
         consensus.genesis_subsidy = args.GetArg("-con_blocksubsidy", 0);
 
+        // Note: This global is needed to avoid circular dependency
+        // Defaults to true for custom chains.
+        g_con_blockheightinheader = gArgs.GetBoolArg("-con_blockheightinheader", true);
+
         // All non-zero coinbase outputs must go to this scriptPubKey
         std::vector<unsigned char> man_bytes = ParseHex(gArgs.GetArg("-con_mandatorycoinbase", ""));
         consensus.mandatory_coinbase_destination = CScript(man_bytes.begin(), man_bytes.end()); // Blank script allows any coinbase destination

src/chainparamsbase.cpp

@@ -26,6 +26,7 @@ void SetupChainParamsBaseOptions()
     gArgs.AddArg("-con_mandatorycoinbase", "All non-zero valued coinbase outputs must go to this scriptPubKey, if set.", false, OptionsCategory::ELEMENTS);
     gArgs.AddArg("-con_blocksubsidy", "Defines the amount of block subsidy to start with, at genesis block.", false, OptionsCategory::ELEMENTS);
     gArgs.AddArg("-con_connect_coinbase", "Connect outputs in genesis block to utxo database.", false, OptionsCategory::ELEMENTS);
+    gArgs.AddArg("-con_blockheightinheader", "Whether the chain includes the block height directly in the header, for easier validation of block height in low-resource environments. (default: true)", false, OptionsCategory::CHAINPARAMS);
 }
 
 static std::unique_ptr<CBaseChainParams> globalChainBaseParams;

src/consensus/params.h

@@ -78,11 +78,11 @@ struct Params {
     int64_t DifficultyAdjustmentInterval() const { return nPowTargetTimespan / nPowTargetSpacing; }
     uint256 nMinimumChainWork;
     uint256 defaultAssumeValid;
-
     // Elements-specific chainparams
     CScript mandatory_coinbase_destination;
     CAmount genesis_subsidy;
     bool connect_genesis_outputs;
+    // g_con_blockheightinheader global hack instead of proper arg due to circular dep
 };
 } // namespace Consensus
 

src/miner.cpp

@@ -168,6 +168,9 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& sc
     // Fill in header
     pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
     UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);
+    if (g_con_blockheightinheader) {
+        pblock->block_height = nHeight;
+    }
     pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
     pblock->nNonce         = 0;
     pblocktemplate->vTxSigOpsCost[0] = WITNESS_SCALE_FACTOR * GetLegacySigOpCount(*pblock->vtx[0]);

src/primitives/block.cpp

@@ -10,6 +10,8 @@
 #include <utilstrencodings.h>
 #include <crypto/common.h>
 
+bool g_con_blockheightinheader = false;
+
 uint256 CBlockHeader::GetHash() const
 {
     return SerializeHash(*this);

src/primitives/block.h

@@ -10,6 +10,8 @@
 #include <serialize.h>
 #include <uint256.h>
 
+extern bool g_con_blockheightinheader;
+
 /** Nodes collect new transactions into a block, hash them into a hash tree,
  * and scan through nonce values to make the block's hash satisfy proof-of-work
  * requirements.  When they solve the proof-of-work, they broadcast the block
@@ -25,6 +27,9 @@ class CBlockHeader
     uint256 hashPrevBlock;
     uint256 hashMerkleRoot;
     uint32_t nTime;
+    // Height in header as well as in coinbase for easier hsm validation
+    // Is set for serialization with `-con_blockheightinheader=1`
+    uint32_t block_height;
     uint32_t nBits;
     uint32_t nNonce;
 
@@ -41,6 +46,9 @@ class CBlockHeader
         READWRITE(hashPrevBlock);
         READWRITE(hashMerkleRoot);
         READWRITE(nTime);
+        if (g_con_blockheightinheader) {
+            READWRITE(block_height);
+        }
         READWRITE(nBits);
         READWRITE(nNonce);
     }
@@ -51,6 +59,7 @@ class CBlockHeader
         hashPrevBlock.SetNull();
         hashMerkleRoot.SetNull();
         nTime = 0;
+        block_height = 0;
         nBits = 0;
         nNonce = 0;
     }
@@ -111,6 +120,7 @@ class CBlock : public CBlockHeader
         block.hashPrevBlock  = hashPrevBlock;
         block.hashMerkleRoot = hashMerkleRoot;
         block.nTime          = nTime;
+        block.block_height   = block_height;
         block.nBits          = nBits;
         block.nNonce         = nNonce;
         return block;

src/txdb.cpp

@@ -263,6 +263,7 @@ bool CBlockTreeDB::LoadBlockIndexGuts(const Consensus::Params& consensusParams,
                 CBlockIndex* pindexNew = insertBlockIndex(diskindex.GetBlockHash());
                 pindexNew->pprev          = insertBlockIndex(diskindex.hashPrev);
                 pindexNew->nHeight        = diskindex.nHeight;
+                pindexNew->block_height   = diskindex.block_height;
                 pindexNew->nFile          = diskindex.nFile;
                 pindexNew->nDataPos       = diskindex.nDataPos;
                 pindexNew->nUndoPos       = diskindex.nUndoPos;

src/validation.cpp

@@ -3271,6 +3271,11 @@ static bool ContextualCheckBlockHeader(const CBlockHeader& block, CValidationSta
     if (block.GetBlockTime() <= pindexPrev->GetMedianTimePast())
         return state.Invalid(false, REJECT_INVALID, "time-too-old", "block's timestamp is too early");
 
+    // Check height in header against prev
+    if (g_con_blockheightinheader && (uint32_t)nHeight != block.block_height)
+        return state.Invalid(error("%s: block height in header is incorrect", __func__),
+                             REJECT_INVALID, "bad-header-height");
+
     // Check timestamp
     if (block.GetBlockTime() > nAdjustedTime + MAX_FUTURE_BLOCK_TIME)
         return state.Invalid(false, REJECT_INVALID, "time-too-new", "block timestamp too far in the future");

test/bitcoin_functional/functional/test_framework/util.py

@@ -308,6 +308,7 @@ def initialize_datadir(dirname, n, chain):
         f.write("con_blocksubsidy=5000000000\n")
         f.write("con_connect_coinbase=0\n")
         f.write("anyonecanspendaremine=0\n")
+        f.write("con_blockheightinheader=0\n")
         os.makedirs(os.path.join(datadir, 'stderr'), exist_ok=True)
         os.makedirs(os.path.join(datadir, 'stdout'), exist_ok=True)
     return datadir