GetPAKKeysFromCommitment utility function

Author: instagibbs

src/validation.cpp

@@ -3342,6 +3342,75 @@ std::vector<unsigned char> GenerateCoinbaseCommitment(CBlock& block, const CBloc
     return commitment;
 }
 
+// ELEMENTS
+boost::optional<CPAKList> GetPAKKeysFromCommitment(const CTransaction& coinbase)
+{
+    std::vector<std::vector<unsigned char> > offline_keys;
+    std::vector<std::vector<unsigned char> > online_keys;
+    bool is_reject = false;
+    for (unsigned int i = 0; i < coinbase.vout.size(); i++) {
+        const CScript& scriptPubKey = coinbase.vout[i].scriptPubKey;
+
+        // OP + push + 4 bytes + push + 33 bytes + push + 33 bytes
+        // or
+        // OP + push + 4 bytes + push + 6 bytes (REJECT)
+
+        CScript::const_iterator pc = scriptPubKey.begin();
+        std::vector<unsigned char> data;
+        opcodetype opcode;
+
+        if (!scriptPubKey.GetOp(pc, opcode, data) || opcode != OP_RETURN){
+            continue;
+        }
+
+        if (!scriptPubKey.GetOp(pc, opcode, data) || data.size() != 4 ||
+                data[0] != 0xab || data[1] != 0x22 || data[2] != 0xaa || data[3] != 0xee) {
+            continue;
+        }
+
+        if (!scriptPubKey.GetOp(pc, opcode, data)){
+            continue;
+        }
+
+        // Check for pak list reject signal
+        // Returns an empty list regardless of other commitments
+        if (data.size() == 6 && data[0] == 'R' && data[1] == 'E' && data[2] == 'J' && data[3] == 'E' && data[4] == 'C' && data[5] == 'T') {
+            is_reject = true;
+            continue;
+        }
+
+        // Check for offline key
+        if (data.size() != 33) {
+            continue;
+        }
+
+        // Check for online key
+        std::vector<unsigned char> data_online;
+        if (!scriptPubKey.GetOp(pc, opcode, data_online) || data_online.size() != 33) {
+            continue;
+        }
+
+        offline_keys.push_back(data);
+        online_keys.push_back(data_online);
+    }
+    if (is_reject) {
+        offline_keys.clear();
+        online_keys.clear();
+    }
+    if (!is_reject && offline_keys.size() == 0) {
+        return boost::none;
+    }
+    CPAKList paklist;
+    if (!CPAKList::FromBytes(paklist, offline_keys, online_keys, is_reject)) {
+        return boost::none;
+    } else {
+        return paklist;
+    }
+}
+
+
+
+
 /** Context-dependent validity checks.
  *  By "context", we mean only the previous block headers, but not the UTXO
  *  set; UTXO-related validity checks are done in ConnectBlock().

src/validation.h

@@ -31,6 +31,9 @@
 
 #include <atomic>
 
+#include <boost/optional.hpp> // GetPAKKeysFromCommitment
+#include <primitives/pak.h> // CPAKList
+
 class CBlockIndex;
 class CBlockTreeDB;
 class CChainParams;
@@ -426,6 +429,10 @@ void UpdateUncommittedBlockStructures(CBlock& block, const CBlockIndex* pindexPr
 /** Produce the necessary coinbase commitment for a block (modifies the hash, don't call for mined blocks). */
 std::vector<unsigned char> GenerateCoinbaseCommitment(CBlock& block, const CBlockIndex* pindexPrev, const Consensus::Params& consensusParams);
 
+// ELEMENTS
+/** Extract pak commitment from coinbase, if it exists. List must be ordered, but not necessarily consecutive in output index */
+boost::optional<CPAKList> GetPAKKeysFromCommitment(const CTransaction& coinbase);
+
 /** RAII wrapper for VerifyDB: Verify consistency of the block and coin databases */
 class CVerifyDB {
 public: