Fix fresh sync failure at diff reset height 2838976

Fresh-syncing nodes rejected the on-chain min-diff block at the
RANDOMX_VALIDATION activation height (2838976) because GetNextWorkRequired
computed the expected nBits from the preceding normal-difficulty blocks,
producing 469847994 instead of the on-chain 0x200f0f0f (HUSH_MINDIFF_NBITS).
This caused all seed nodes to be banned with "Incorrect diffbits" and the
node could never sync past that height.

Two changes:

1. GetNextWorkRequired (pow.cpp): Return nProofOfWorkLimit at the exact
   RANDOMX_VALIDATION activation height, matching the on-chain diff reset.

2. ContextualCheckBlockHeader (main.cpp): Raise DragonX daaForkHeight to
   RANDOMX_VALIDATION + 62000, covering the window where nBits was never
   validated (diff reset at 2838976 through the attack at ~2879907).

Tested by invalidating block 2838975 and reconsidering — node re-validated
through the diff reset and attack window, syncing back to tip with zero
bad-diffbits rejections.

Bump version to 1.0.1.

build.sh

@@ -6,7 +6,7 @@
 
 set -eu -o pipefail
 
-VERSION="1.0.0"
+VERSION="1.0.1"
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 RELEASE_DIR="$SCRIPT_DIR/release"
 

configure.ac

@@ -3,7 +3,7 @@ AC_PREREQ([2.60])
 define(_CLIENT_VERSION_MAJOR, 1)
 dnl Must be kept in sync with src/clientversion.h , ugh!
 define(_CLIENT_VERSION_MINOR, 0)
-define(_CLIENT_VERSION_REVISION, 0)
+define(_CLIENT_VERSION_REVISION, 1)
 define(_CLIENT_VERSION_BUILD, 50)
 define(_ZC_BUILD_VAL, m4_if(m4_eval(_CLIENT_VERSION_BUILD < 25), 1, m4_incr(_CLIENT_VERSION_BUILD), m4_eval(_CLIENT_VERSION_BUILD < 50), 1, m4_eval(_CLIENT_VERSION_BUILD - 24), m4_eval(_CLIENT_VERSION_BUILD == 50), 1, , m4_eval(_CLIENT_VERSION_BUILD - 50)))
 define(_CLIENT_VERSION_SUFFIX, m4_if(m4_eval(_CLIENT_VERSION_BUILD < 25), 1, _CLIENT_VERSION_REVISION-beta$1, m4_eval(_CLIENT_VERSION_BUILD < 50), 1, _CLIENT_VERSION_REVISION-rc$1, m4_eval(_CLIENT_VERSION_BUILD == 50), 1, _CLIENT_VERSION_REVISION, _CLIENT_VERSION_REVISION-$1)))

src/clientversion.h

@@ -30,7 +30,7 @@
 // Must be kept in sync with configure.ac , ugh!
 #define CLIENT_VERSION_MAJOR 1
 #define CLIENT_VERSION_MINOR 0
-#define CLIENT_VERSION_REVISION 0
+#define CLIENT_VERSION_REVISION 1
 #define CLIENT_VERSION_BUILD 50
 
 //! Set to true for release, false for prerelease or test build

src/main.cpp

@@ -5107,7 +5107,14 @@ bool ContextualCheckBlockHeader(const CBlockHeader& block, CValidationState& sta
 
     assert(pindexPrev);
 
-    int daaForkHeight = GetArg("-daaforkheight", 450000);
+    // For HUSH3, nBits validation starts above the original DAA fork height (450000).
+    // For DragonX, nBits was never validated before the standalone binary, so the
+    // chain contains blocks with incorrect nBits during the vulnerable window
+    // (diff reset at RANDOMX_VALIDATION height through the attack at ~2879907).
+    // Set daaForkHeight past that window so fresh sync accepts historical blocks.
+    bool isdragonx    = strncmp(SMART_CHAIN_SYMBOL, "DRAGONX", 7) == 0;
+    int defaultDaaForkHeight = isdragonx ? ASSETCHAINS_RANDOMX_VALIDATION + 62000 : 450000;
+    int daaForkHeight = GetArg("-daaforkheight", defaultDaaForkHeight);
     int nHeight       = pindexPrev->GetHeight()+1;
     bool ishush3      = strncmp(SMART_CHAIN_SYMBOL, "HUSH3",5) == 0 ? true : false;
     // Check Proof-of-Work difficulty

src/pow.cpp

@@ -315,6 +315,16 @@ unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHead
     if (pindexLast == NULL )
         return nProofOfWorkLimit;
 
+    // DragonX difficulty reset at the RANDOMX_VALIDATION activation height.
+    // The chain transitioned to a new binary at this height and difficulty was
+    // reset to minimum (powLimit).  Without this, fresh-syncing nodes compute
+    // a different nBits from GetNextWorkRequired (based on pre-reset blocks)
+    // and reject the on-chain min-diff block, banning all seed nodes.
+    if (ASSETCHAINS_RANDOMX_VALIDATION > 0 && pindexLast->GetHeight() + 1 == ASSETCHAINS_RANDOMX_VALIDATION) {
+        LogPrintf("%s: difficulty reset to powLimit at height %d\n", __func__, ASSETCHAINS_RANDOMX_VALIDATION);
+        return nProofOfWorkLimit;
+    }
+
     //{
         // Comparing to pindexLast->nHeight with >= because this function
         // returns the work required for the block after pindexLast.