Merge #18267: BIP-325: Signet [consensus]

8258c4c0076bb5f27efdc117a04b27fcd6dd00b2 test: some sanity checks for consensus logic (Anthony Towns)
e47ad375bf17557f805bd206e789b8db78c6338a test: basic signet tests (Karl-Johan Alm)
4c189abdc452f08dfa758564b5381bc78c42d481 test: add small signet fuzzer (practicalswift)
ec9b25d046793be50da1c11ba61d1b4b13b295b0 test: signet network selection tests (Karl-Johan Alm)
3efe298dccb248f25d6b01ab6a80b1cd6c9e1a1e signet: hard-coded parameters for Signet Global Network VI (2020-09-07) (Karl-Johan Alm)
c7898bca4e1ccbc6edafd3b72eaf80df38e3af32 qt: update QT to support signet network (Karl-Johan Alm)
a8de47a1c9033fac3355590f1fe2158a95011bb3 consensus: add signet validation (Karl-Johan Alm)
e8990f121405af8cd539b904ef082439261e6c93 add signet chain and accompanying parameters (Karl-Johan Alm)
404682b7cdb54494e7c98f0ba0cac8b51f379750 add signet basic support (signet.cpp) (Karl-Johan Alm)
a2147d7dadec1febcd9c2b8ebbbf78dce6d0556b validation: move GetWitnessCommitmentIndex to consensus/validation (Karl-Johan Alm)

Pull request description:

  This PR is a part of BIP-325 (https://github.com/bitcoin/bips/blob/master/bip-0325.mediawiki), and is a sub-PR of #16411.

  * Signet consensus (this)
  * Signet RPC tools (pending)
  * Signet utility scripts (contrib/signet) (pending)

ACKs for top commit:
  jonatack:
    re-ACK 8258c4c0076bb5f27efdc117a04b27fcd6dd00b per `git diff dbeea65 8258c4c`, only change since last review is updated `-signet*` config option naming.
  fjahr:
    re-ACK 8258c4c
  laanwj:
    ACK 8258c4c0076bb5f27efdc117a04b27fcd6dd00b2
  MarcoFalke:
    Approach ACK 8258c4c007 🌵

Tree-SHA512: 5d158add96755910837feafa8214e13695b769a6aec3a2da753cf672618bef377fac43b0f4b772a87b25dd9f0c1c9b29f2789785d7a7d47a155cdcf48f7c975d

1 files changed, 14 insertions, 23 deletions

diff --git a/src/validation.cpp b/src/validation.cpp
index 0823c6b124..a96913e3a0 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -33,6 +33,7 @@
 #include <script/script.h>
 #include <script/sigcache.h>
 #include <shutdown.h>
+#include <signet.h>
 #include <timedata.h>
 #include <tinyformat.h>
 #include <txdb.h>
@@ -1169,6 +1170,11 @@ bool ReadBlockFromDisk(CBlock& block, const FlatFilePos& pos, const Consensus::P
     if (!CheckProofOfWork(block.GetHash(), block.nBits, consensusParams))
         return error("ReadBlockFromDisk: Errors in block header at %s", pos.ToString());
 
+    // Signet only: check block solution
+    if (consensusParams.signet_blocks && !CheckSignetBlockSolution(block, consensusParams)) {
+        return error("ReadBlockFromDisk: Errors in block solution at %s", pos.ToString());
+    }
+
     return true;
 }
 
@@ -3346,6 +3352,11 @@ bool CheckBlock(const CBlock& block, BlockValidationState& state, const Consensu
     if (!CheckBlockHeader(block, state, consensusParams, fCheckPOW))
         return false;
 
+    // Signet only: check block solution
+    if (consensusParams.signet_blocks && fCheckPOW && !CheckSignetBlockSolution(block, consensusParams)) {
+        return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-signet-blksig", "signet block signature validation failure");
+    }
+
     // Check the merkle root.
     if (fCheckMerkleRoot) {
         bool mutated;
@@ -3409,31 +3420,11 @@ bool IsWitnessEnabled(const CBlockIndex* pindexPrev, const Consensus::Params& pa
     return (height >= params.SegwitHeight);
 }
 
-int GetWitnessCommitmentIndex(const CBlock& block)
-{
-    int commitpos = -1;
-    if (!block.vtx.empty()) {
-        for (size_t o = 0; o < block.vtx[0]->vout.size(); o++) {
-            const CTxOut& vout = block.vtx[0]->vout[o];
-            if (vout.scriptPubKey.size() >= MINIMUM_WITNESS_COMMITMENT &&
-                vout.scriptPubKey[0] == OP_RETURN &&
-                vout.scriptPubKey[1] == 0x24 &&
-                vout.scriptPubKey[2] == 0xaa &&
-                vout.scriptPubKey[3] == 0x21 &&
-                vout.scriptPubKey[4] == 0xa9 &&
-                vout.scriptPubKey[5] == 0xed) {
-                commitpos = o;
-            }
-        }
-    }
-    return commitpos;
-}
-
 void UpdateUncommittedBlockStructures(CBlock& block, const CBlockIndex* pindexPrev, const Consensus::Params& consensusParams)
 {
     int commitpos = GetWitnessCommitmentIndex(block);
     static const std::vector<unsigned char> nonce(32, 0x00);
-    if (commitpos != -1 && IsWitnessEnabled(pindexPrev, consensusParams) && !block.vtx[0]->HasWitness()) {
+    if (commitpos != NO_WITNESS_COMMITMENT && IsWitnessEnabled(pindexPrev, consensusParams) && !block.vtx[0]->HasWitness()) {
         CMutableTransaction tx(*block.vtx[0]);
         tx.vin[0].scriptWitness.stack.resize(1);
         tx.vin[0].scriptWitness.stack[0] = nonce;
@@ -3447,7 +3438,7 @@ std::vector<unsigned char> GenerateCoinbaseCommitment(CBlock& block, const CBloc
     int commitpos = GetWitnessCommitmentIndex(block);
     std::vector<unsigned char> ret(32, 0x00);
     if (consensusParams.SegwitHeight != std::numeric_limits<int>::max()) {
-        if (commitpos == -1) {
+        if (commitpos == NO_WITNESS_COMMITMENT) {
             uint256 witnessroot = BlockWitnessMerkleRoot(block, nullptr);
             CHash256().Write(witnessroot).Write(ret).Finalize(witnessroot);
             CTxOut out;
@@ -3585,7 +3576,7 @@ static bool ContextualCheckBlock(const CBlock& block, BlockValidationState& stat
     bool fHaveWitness = false;
     if (nHeight >= consensusParams.SegwitHeight) {
         int commitpos = GetWitnessCommitmentIndex(block);
-        if (commitpos != -1) {
+        if (commitpos != NO_WITNESS_COMMITMENT) {
             bool malleated = false;
             uint256 hashWitness = BlockWitnessMerkleRoot(block, &malleated);
             // The malleation check is ignored; as the transaction tree itself