2WP: Allow signed blocks chains as parent chains for pegs

ElementsProject · May 25, 2018 · 30ec4dd · 30ec4dd
1 parent c849ded
commit 30ec4dd
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Showing 3 changed files with 46 additions and 15 deletions.
diff --git a/src/chainparams.cpp b/src/chainparams.cpp
@@ -130,6 +130,7 @@ class CCustomParams : public CChainParams {
         consensus.defaultAssumeValid = uint256S(GetArg("-con_defaultassumevalid", "0x00"));
         consensus.pegin_min_depth = GetArg("-peginconfirmationdepth", DEFAULT_PEGIN_CONFIRMATION_DEPTH);
         consensus.mandatory_coinbase_destination = StrHexToScriptWithDefault(GetArg("-con_mandatorycoinbase", ""), CScript()); // Blank script allows any coinbase destination
+        consensus.parent_chain_has_pow = GetBoolArg("-con_parent_chain_has_pow", true);
         // bitcoin regtest is the parent chain by default
         parentGenesisBlockHash = uint256S(GetArg("-parentgenesisblockhash", "0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206"));
         initialFreeCoins = GetArg("-initialfreecoins", 0);

diff --git a/src/consensus/params.h b/src/consensus/params.h
@@ -71,6 +71,7 @@ struct Params {
     uint256 defaultAssumeValid;
     uint32_t pegin_min_depth;
     CScript mandatory_coinbase_destination;
+    bool parent_chain_has_pow;
 };
 } // namespace Consensus
 

diff --git a/src/validation.cpp b/src/validation.cpp
@@ -17,6 +17,7 @@
 #include "crypto/hmac_sha256.h"
 #include "init.h"
 #include "issuance.h"
+#include "merkleblock.h"
 #include "policy/fees.h"
 #include "policy/policy.h"
 #include "pow.h"
@@ -2357,6 +2358,30 @@ CScript calculate_contract(const CScript& federationRedeemScript, const CScript&
     return scriptDestination;
 }
 
+template<typename T>
+static bool GetBlockAndTxFromMerkleBlock(uint256& block_hash, uint256& tx_hash, T& merkle_block, const std::vector<unsigned char>& merkle_block_raw)
+{
+    try {
+        std::vector<uint256> txHashes;
+        std::vector<unsigned int> txIndices;
+        CDataStream merkleBlockStream(merkle_block_raw, SER_NETWORK, PROTOCOL_VERSION);
+        merkleBlockStream >> merkle_block;
+        block_hash = merkle_block.header.GetHash();
+
+        if (!merkleBlockStream.empty()) {
+           return false;
+        }
+        if (merkle_block.txn.ExtractMatches(txHashes, txIndices) != merkle_block.header.hashMerkleRoot || txHashes.size() != 1) {
+            return false;
+        }
+        tx_hash = txHashes[0];
+    } catch (std::exception& e) {
+        // Invalid encoding of merkle block
+        return false;
+    }
+    return true;
+}
+
 bool IsValidPeginWitness(const CScriptWitness& pegin_witness, const COutPoint& prevout, bool check_depth) {
 
     // Format on stack is as follows:
@@ -2421,22 +2446,26 @@ bool IsValidPeginWitness(const CScriptWitness& pegin_witness, const COutPoint& p
     }
 
     // Get txout proof
-    Sidechain::Bitcoin::CMerkleBlock merkle_block;
-    std::vector<uint256> txHashes;
-    std::vector<unsigned int> txIndices;
-
-    try {
-        CDataStream merkleBlockStream(stack[5], SER_NETWORK, PROTOCOL_VERSION);
-        merkleBlockStream >> merkle_block;
-        if (!merkleBlockStream.empty() || !CheckBitcoinProof(merkle_block.header.GetHash(), merkle_block.header.nBits)) {
-           return false;
+    bool parent_chain_has_pow = true;
+    uint256 block_hash;
+    uint256 tx_hash;
+    if (Params().GetConsensus().parent_chain_has_pow) {
+        Sidechain::Bitcoin::CMerkleBlock merkle_block_pow;
+        if (!GetBlockAndTxFromMerkleBlock(block_hash, tx_hash, merkle_block_pow, stack[5])) {
+            return false;
         }
-        if (merkle_block.txn.ExtractMatches(txHashes, txIndices) != merkle_block.header.hashMerkleRoot || txHashes.size() != 1) {
+        // TODO do this inside to prever DoS ?
+        if (!CheckBitcoinProof(block_hash, merkle_block_pow.header.nBits)) {
+            return false;
+        }
+    } else {
+        CMerkleBlock merkle_block;
+        if (!GetBlockAndTxFromMerkleBlock(block_hash, tx_hash, merkle_block, stack[5])) {
+            return false;
+        }
+        if (!CheckProof(merkle_block.header, Params().GetConsensus())) {
             return false;
         }
-    } catch (std::exception& e) {
-        // Invalid encoding of merkle block
-        return false;
     }
 
     // Check that transaction matches txid
@@ -2445,7 +2474,7 @@ bool IsValidPeginWitness(const CScriptWitness& pegin_witness, const COutPoint& p
     }
 
     // Check that the merkle proof corresponds to the txid
-    if (prevout.hash != txHashes[0]) {
+    if (prevout.hash != tx_hash) {
         return false;
     }
 
@@ -2474,7 +2503,7 @@ bool IsValidPeginWitness(const CScriptWitness& pegin_witness, const COutPoint& p
 
     // Finally, validate peg-in via rpc call
     if (check_depth && GetBoolArg("-validatepegin", DEFAULT_VALIDATE_PEGIN)) {
-        return IsConfirmedBitcoinBlock(merkle_block.header.GetHash(), Params().GetConsensus().pegin_min_depth);
+        return IsConfirmedBitcoinBlock(block_hash, Params().GetConsensus().pegin_min_depth);
     }
     return true;
 }