From 6000752a920b56ac3e13ecc18b8c3366cbdd5bbd Mon Sep 17 00:00:00 2001
From: Gregory Sanders <gsanders87@gmail.com>
Date: Wed, 19 Jun 2019 11:42:04 -0400
Subject: [PATCH] Enforce PAK checks on dynafed proposals

---
 src/primitives/pak.h               |  2 ++
 src/validation.cpp                 | 10 ++++++++++
 test/functional/feature_dynafed.py |  7 ++++++-
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/primitives/pak.h b/src/primitives/pak.h
index c9611fb5aa..2a24a86be0 100644
--- a/src/primitives/pak.h
+++ b/src/primitives/pak.h
@@ -61,6 +61,8 @@ public:
  **/
 bool ScriptHasValidPAKProof(const CScript& script, const uint256& genesis_hash, const CPAKList& paklist);
 
+CPAKList CreatePAKListFromExtensionSpace(const std::vector<std::vector<unsigned char>>& extension_space);
+
 CPAKList GetActivePAKList(const CBlockIndex* pblockindex, const Consensus::Params& params);
 
 bool IsPAKValidOutput(const CTxOut& txout, const CPAKList& paklist);
diff --git a/src/validation.cpp b/src/validation.cpp
index fa33ac45a8..01c926538f 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -3524,6 +3524,16 @@ static bool ContextualCheckDynaFedHeader(const CBlockHeader& block, CValidationS
                 return state.Invalid(false, REJECT_INVALID, "invalid-dyna-fed", "Proposed fedpegscript starts with OP_DEPTH, which is illegal");
             }
         }
+
+        // When enforcing PAK, extension_space must give non-empty PAK list when
+        // the vector itself is non-empty. Otherwise this means there were "junk"
+        // entries
+        if (params.GetEnforcePak()) {
+            if (!proposed.m_extension_space.empty() &&
+                    CreatePAKListFromExtensionSpace(proposed.m_extension_space).IsReject()) {
+                return state.Invalid(false, REJECT_INVALID, "invalid-dyna-fed", "Extension space is not list of valid PAK entries");
+            }
+        }
     }
     return true;
 }
diff --git a/test/functional/feature_dynafed.py b/test/functional/feature_dynafed.py
index 86244f48e9..78ad49a770 100755
--- a/test/functional/feature_dynafed.py
+++ b/test/functional/feature_dynafed.py
@@ -133,6 +133,11 @@ class DynaFedTest(BitcoinTestFramework):
         assert_raises_rpc_error(-1, "invalid-dyna-fed, proposed signblockscript must be native segwit scriptPubkey", self.nodes[0].getnewblockhex, 0, {"signblockscript":"51", "max_block_witness":100, "fedpegscript":"51", "extension_space":[]})
         assert_raises_rpc_error(-1, "invalid-dyna-fed, proposed signblockscript must be native segwit scriptPubkey", self.nodes[0].getnewblockhex, 0, {"signblockscript":"00"+WSH_OP_TRUE, "max_block_witness":100, "fedpegscript":"51", "extension_space":[]})
 
+        # Since we're enforcing PAK, extension space entries *must* be 66 bytes
+        # each 33 of which are serialized compressed pubkeys
+        assert_raises_rpc_error(-1, "invalid-dyna-fed, Extension space is not list of valid PAK entries", self.nodes[0].getnewblockhex, 0, {"signblockscript":WSH_OP_TRUE, "max_block_witness":100, "fedpegscript":"51", "extension_space":["00"]})
+        assert_raises_rpc_error(-1, "invalid-dyna-fed, Extension space is not list of valid PAK entries", self.nodes[0].getnewblockhex, 0, {"signblockscript":WSH_OP_TRUE, "max_block_witness":100, "fedpegscript":"51", "extension_space":["", initial_extension[0]]})
+
     def test_no_vote(self):
         self.log.info("Testing no-vote epoch...")
         go_to_epoch_end(self.nodes[0])
@@ -360,7 +365,7 @@ class DynaFedTest(BitcoinTestFramework):
 
         # Now have node 1 transition to new pak and fedpegscript
         pak_prop["fedpegscript"] = "52"
-        pak_prop["extension_space"] = ["deadbeef"]
+        pak_prop["extension_space"] = initial_extension
         for _ in range(10):
             raw_pool = self.nodes[0].getrawmempool()
             assert claim_id in raw_pool