Reject block versions lower than 4

Closes zcash#1556

src/Makefile.gtest.include

@@ -5,6 +5,7 @@ bin_PROGRAMS += zcash-gtest
 zcash_gtest_SOURCES = \
 	gtest/main.cpp \
 	gtest/utils.cpp \
+	gtest/test_checkblock.cpp \
 	gtest/test_checktransaction.cpp \
 	gtest/json_test_vectors.cpp \
         gtest/json_test_vectors.h \

src/consensus/consensus.h

@@ -6,6 +6,8 @@
 #ifndef BITCOIN_CONSENSUS_CONSENSUS_H
 #define BITCOIN_CONSENSUS_CONSENSUS_H
 
+/** The minimum allowed block version (network rule) */
+static const int32_t MIN_BLOCK_VERSION = 4;
 /** The minimum allowed transaction version (network rule) */
 static const int32_t MIN_TX_VERSION = 1;
 /** The maximum allowed size for a serialized block, in bytes (network rule) */

src/gtest/test_checkblock.cpp

@@ -0,0 +1,31 @@
+#include <gtest/gtest.h>
+#include <gmock/gmock.h>
+
+#include "consensus/validation.h"
+#include "main.h"
+
+class MockCValidationState : public CValidationState {
+public:
+    MOCK_METHOD5(DoS, bool(int level, bool ret,
+             unsigned char chRejectCodeIn, std::string strRejectReasonIn,
+             bool corruptionIn));
+    MOCK_METHOD3(Invalid, bool(bool ret,
+                 unsigned char _chRejectCode, std::string _strRejectReason));
+    MOCK_METHOD1(Error, bool(std::string strRejectReasonIn));
+    MOCK_CONST_METHOD0(IsValid, bool());
+    MOCK_CONST_METHOD0(IsInvalid, bool());
+    MOCK_CONST_METHOD0(IsError, bool());
+    MOCK_CONST_METHOD1(IsInvalid, bool(int &nDoSOut));
+    MOCK_CONST_METHOD0(CorruptionPossible, bool());
+    MOCK_CONST_METHOD0(GetRejectCode, unsigned char());
+    MOCK_CONST_METHOD0(GetRejectReason, std::string());
+};
+
+TEST(CheckBlock, VersionTooLow) {
+    CBlock block;
+    block.nVersion = 1;
+
+    MockCValidationState state;
+    EXPECT_CALL(state, DoS(100, false, REJECT_INVALID, "version-too-low", false)).Times(1);
+    EXPECT_FALSE(CheckBlock(block, state, false, false));
+}

src/main.cpp

@@ -2940,6 +2940,11 @@ bool FindUndoPos(CValidationState &state, int nFile, CDiskBlockPos &pos, unsigne
 
 bool CheckBlockHeader(const CBlockHeader& block, CValidationState& state, bool fCheckPOW)
 {
+    // Check block version
+    if (block.nVersion < MIN_BLOCK_VERSION)
+        return state.DoS(100, error("CheckBlockHeader(): block version too low"),
+                         REJECT_INVALID, "version-too-low");
+
     // Check Equihash solution is valid
     if (fCheckPOW && !CheckEquihashSolution(&block, Params()))
         return state.DoS(100, error("CheckBlockHeader(): Equihash solution invalid"),