blockheaders include block height, nodes validate it

Author: instagibbs

src/chain.h

@@ -14,6 +14,8 @@
 
 #include <vector>
 
+#include <util.h>
+
 /**
  * Maximum amount of time that a block timestamp is allowed to exceed the
  * current network-adjusted time before the block will be accepted.
@@ -210,6 +212,7 @@ class CBlockIndex
     int32_t nVersion;
     uint256 hashMerkleRoot;
     uint32_t nTime;
+    uint32_t block_height;
     uint32_t nBits;
     uint32_t nNonce;
 
@@ -238,6 +241,7 @@ class CBlockIndex
         nVersion       = 0;
         hashMerkleRoot = uint256();
         nTime          = 0;
+        block_height   = 0;
         nBits          = 0;
         nNonce         = 0;
     }
@@ -254,6 +258,7 @@ class CBlockIndex
         nVersion       = block.nVersion;
         hashMerkleRoot = block.hashMerkleRoot;
         nTime          = block.nTime;
+        block_height   = block.block_height;
         nBits          = block.nBits;
         nNonce         = block.nNonce;
     }
@@ -284,6 +289,7 @@ 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 +409,7 @@ class CDiskBlockIndex : public CBlockIndex
         READWRITE(hashPrev);
         READWRITE(hashMerkleRoot);
         READWRITE(nTime);
+        READWRITE(block_height);
         READWRITE(nBits);
         READWRITE(nNonce);
     }
@@ -414,6 +421,7 @@ 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

@@ -118,7 +118,11 @@ class CMainParams : public CChainParams {
 
         genesis = CreateGenesisBlock(1231006505, 2083236893, 0x1d00ffff, 1, 50 * COIN);
         consensus.hashGenesisBlock = genesis.GetHash();
-        assert(consensus.hashGenesisBlock == uint256S("0x000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"));
+        consensus.blockheight_in_header = gArgs.GetBoolArg("-con_blockheightinheader", false);
+        // Serialization will not match if true
+        if (!consensus.blockheight_in_header) {
+            assert(consensus.hashGenesisBlock == uint256S("0x000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"));
+        }
         assert(genesis.hashMerkleRoot == uint256S("0x4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"));
 
         // Note that of those which support the service bits prefix, most only support a subset of
@@ -227,7 +231,11 @@ class CTestNetParams : public CChainParams {
 
         genesis = CreateGenesisBlock(1296688602, 414098458, 0x1d00ffff, 1, 50 * COIN);
         consensus.hashGenesisBlock = genesis.GetHash();
-        assert(consensus.hashGenesisBlock == uint256S("0x000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943"));
+        consensus.blockheight_in_header = gArgs.GetBoolArg("-con_blockheightinheader", false);
+        // Serialization will not match if true
+        if (!consensus.blockheight_in_header) {
+            assert(consensus.hashGenesisBlock == uint256S("0x000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943"));
+        }
         assert(genesis.hashMerkleRoot == uint256S("0x4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"));
 
         vFixedSeeds.clear();
@@ -318,7 +326,11 @@ class CRegTestParams : public CChainParams {
 
         genesis = CreateGenesisBlock(1296688602, 2, 0x207fffff, 1, 50 * COIN);
         consensus.hashGenesisBlock = genesis.GetHash();
-        assert(consensus.hashGenesisBlock == uint256S("0x0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206"));
+        consensus.blockheight_in_header = gArgs.GetBoolArg("-con_blockheightinheader", false);
+        // Serialization will not match if true
+        if (!consensus.blockheight_in_header) {
+            assert(consensus.hashGenesisBlock == uint256S("0x0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206"));
+        }
         assert(genesis.hashMerkleRoot == uint256S("0x4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"));
 
         vFixedSeeds.clear(); //!< Regtest mode doesn't have any fixed seeds.
@@ -420,6 +432,10 @@ class CCustomParams : public CRegTestParams {
         consensus.nMinimumChainWork = uint256S(args.GetArg("-con_nminimumchainwork", "0x0"));
         consensus.defaultAssumeValid = uint256S(args.GetArg("-con_defaultassumevalid", "0x00"));
 
+        // Note: This gArg is accessed one more time in block.h for serialization to avoid
+        // circular dependency
+        consensus.blockheight_in_header = gArgs.GetBoolArg("-con_blockheightinheader", false);
+
         // 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

@@ -24,6 +24,7 @@ void SetupChainParamsBaseOptions()
     gArgs.AddArg("-vbparams=deployment:start:end", "Use given start/end times for specified version bits deployment (regtest or custom only)", true, OptionsCategory::CHAINPARAMS);
     gArgs.AddArg("-con_mandatorycoinbase", "All non-zero valued coinbase outputs must go to this scriptPubKey, if set.", false, OptionsCategory::CHAINPARAMS);
     gArgs.AddArg("-seednode=<ip>", "Use specified node as seed node. This option can be specified multiple times to connect to multiple nodes. (custom only)", true, OptionsCategory::CHAINPARAMS);
+    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.", false, OptionsCategory::CHAINPARAMS);
 }
 
 static std::unique_ptr<CBaseChainParams> globalChainBaseParams;

src/consensus/params.h

@@ -77,9 +77,9 @@ struct Params {
     int64_t DifficultyAdjustmentInterval() const { return nPowTargetTimespan / nPowTargetSpacing; }
     uint256 nMinimumChainWork;
     uint256 defaultAssumeValid;
-
     // Elements-specific chainparams
     CScript mandatory_coinbase_destination;
+    bool blockheight_in_header;
 };
 } // 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 (Params().GetConsensus().blockheight_in_header) {
+        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.h

@@ -9,6 +9,7 @@
 #include <primitives/transaction.h>
 #include <serialize.h>
 #include <uint256.h>
+#include <util.h>
 
 /** 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
@@ -25,6 +26,9 @@ 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 +45,10 @@ class CBlockHeader
         READWRITE(hashPrevBlock);
         READWRITE(hashMerkleRoot);
         READWRITE(nTime);
+        // Also found in consensus params as blockheight_in_header (circular dep otherwise)
+        if (gArgs.GetBoolArg("-con_blockheightinheader", false)) {
+            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/validation.cpp

@@ -3263,6 +3263,11 @@ 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 (consensusParams.blockheight_in_header && (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");