Merge pull request #410 from frstrtr/dash/share-target-validity-conform

dash: restore share-target validity guard (target>MAX_TARGET) — conform vs p2pool-dash oracle

Author: frstrtr

src/impl/dash/share_check.hpp

@@ -158,6 +158,23 @@ inline std::vector<unsigned char> compute_gentx_before_refhash()
     return result;
 }
 
+// ── check_share_target_valid (Dash v16) ─────────────────────────────
+// Conformance with p2pool-dash oracle data.py Share.__init__:
+//     if self.target > net.MAX_TARGET: raise PeerMisbehavingError('share target invalid')
+// The claimed share target must be no easier than the network share-diff floor
+// (params.max_target == net.MAX_TARGET); a zero target is likewise invalid. This is
+// a structural validity guard on share_info['bits'], independent of the PoW check.
+// v36 3-bucket: the GUARD is v36-native SHARED validation (Bucket 2 — cross-coin
+// identical); only the per-coin max_target constant differs (a consensus param, not
+// an isolation primitive).
+inline void check_share_target_valid(const uint256& target, const core::CoinParams& params)
+{
+    if (target.IsNull())
+        throw std::invalid_argument("share target is zero");
+    if (target > params.max_target)
+        throw std::invalid_argument("share target invalid");
+}
+
 // ── share_init_verify (Dash v16) ─────────────────────────────────────────────
 // Verifies PoW, hash_link, merkle_link. Returns share hash (SHA256d of header).
 inline uint256 share_init_verify(const DashShare& share,
@@ -167,6 +184,10 @@ inline uint256 share_init_verify(const DashShare& share,
     if (share.m_coinbase.m_data.size() < 2 || share.m_coinbase.m_data.size() > 100)
         throw std::invalid_argument("bad coinbase size");
 
+    // ── Share target validity (oracle: target > MAX_TARGET → "share target invalid") ──
+    // Unconditional — NOT gated by check_pow, matching p2pool-dash Share.__init__.
+    check_share_target_valid(chain::bits_to_target(share.m_bits), params);
+
     // ── Compute ref_hash ──
     PackStream ref_stream;
     {
@@ -269,9 +290,6 @@ inline uint256 share_init_verify(const DashShare& share,
     if (check_pow)
     {
         uint256 target = chain::bits_to_target(share.m_bits);
-        if (target.IsNull())
-            throw std::invalid_argument("share target is zero");
-
         if (share_hash > target)
             throw std::invalid_argument("share PoW hash does not meet target");
     }

test/test_dash_conformance.cpp

@@ -367,6 +367,33 @@ TEST(DashConformanceDifficulty, BitsToDifficultyMatchesP2poolDash) {
     }
 }
 
+// ── Pillar-3 conformance: share-target validity guard vs p2pool-dash oracle ──
+// Oracle data.py Share.__init__ rejects `self.target > net.MAX_TARGET`
+// ("share target invalid") AND a zero target. c2pool share_init_verify previously
+// enforced only the zero case — no share-diff-floor upper bound. This pins the
+// restored guard against the mainnet floor (params.max_target == 0xFFFF*2**208).
+TEST(DashConformanceShareTarget, RejectsTargetEasierThanFloorAndZero) {
+    core::CoinParams params;
+    params.max_target = dash::PoolConfig::max_target();   // 00000000ffff00..00
+
+    const uint256 floor = params.max_target;
+
+    // exactly at the floor -> accepted (boundary, not "> floor")
+    EXPECT_NO_THROW(dash::check_share_target_valid(floor, params));
+
+    // strictly harder (numerically smaller target) -> accepted
+    uint256 harder; harder.SetHex("000000000000ffff000000000000000000000000000000000000000000000000");
+    EXPECT_NO_THROW(dash::check_share_target_valid(harder, params));
+
+    // strictly easier than the floor (numerically larger) -> rejected
+    uint256 easier; easier.SetHex("00000001ffff0000000000000000000000000000000000000000000000000000");
+    EXPECT_THROW(dash::check_share_target_valid(easier, params), std::invalid_argument);
+
+    // zero target -> rejected
+    uint256 zero;
+    EXPECT_THROW(dash::check_share_target_valid(zero, params), std::invalid_argument);
+}
+
 // ── PPLNS payout-SET equality conformance (S6 slice 6) ───────────────────────
 // The miner-facing output of the whole sharechain is the PPLNS payout SET:
 // the {scriptPubKey -> amount} map a coinbase pays. For DASH to be value-