fix the blockhash issue by forking at block

README.md

@@ -47,31 +47,32 @@ npx hardhat run scripts/deploy.js
 ## Full Challenge / Response
 
 ```
-# testing on hardhat (forked mainnet)
-npx hardhat node --fork https://mainnet.infura.io/v3/9aa3d95b3bc440fa88ea12eaa4456161
+# testing on hardhat (forked mainnet, a few blocks ahead of challenge)
+npx hardhat node --fork https://mainnet.infura.io/v3/9aa3d95b3bc440fa88ea12eaa4456161 --fork-block-number 13284495
 
-# challenger is pretending the block 10 transition is the transition for 1171895
+# challenger is pretending the block 13284491 transition is the transition for 13284469
 # this will conflict at the first step
 rm -rf /tmp/cannon/*
 mipsevm/mipsevm
 npx hardhat run scripts/deploy.js --network hosthat
 
-minigeth/go-ethereum 1171895 && mipsevm/mipsevm 1171895
-minigeth/go-ethereum 10 && mipsevm/mipsevm 10
-BLOCK=1171895 npx hardhat run scripts/challenge.js --network hosthat
+# compute the MIPS checkpoints
+minigeth/go-ethereum 13284491 && mipsevm/mipsevm 13284491
+minigeth/go-ethereum 13284469 && mipsevm/mipsevm 13284469
+BLOCK=13284469 npx hardhat run scripts/challenge.js --network hosthat
 
 # do binary search
 for i in {1..23}
 do
-ID=0 BLOCK=10 CHALLENGER=1 npx hardhat run scripts/respond.js --network hosthat
-ID=0 BLOCK=1171895 npx hardhat run scripts/respond.js --network hosthat
+ID=0 BLOCK=13284491 CHALLENGER=1 npx hardhat run scripts/respond.js --network hosthat
+ID=0 BLOCK=13284469 npx hardhat run scripts/respond.js --network hosthat
 done
 
 # assert as challenger (fails)
-ID=0 BLOCK=10 CHALLENGER=1 npx hardhat run scripts/assert.js --network hosthat
+ID=0 BLOCK=13284491 CHALLENGER=1 npx hardhat run scripts/assert.js --network hosthat
 
 # assert as defender (passes)
-ID=0 BLOCK=1171895 npx hardhat run scripts/assert.js --network hosthat
+ID=0 BLOCK=13284469 npx hardhat run scripts/assert.js --network hosthat
 ```
 
 ## State Oracle API

contracts/Challenge.sol

@@ -105,18 +105,17 @@ contract Challenge {
     bytes32 blockNumberNHash = blockhash(blockNumberN);
     bytes32 blockNumberNp1Hash = blockhash(blockNumberN+1);
 
-    // TODO: this is only removed for testing. zero security without it
-    /*if (blockNumberNHash == bytes32(0) || blockNumberNp1Hash == bytes32(0)) {
+    if (blockNumberNHash == bytes32(0) || blockNumberNp1Hash == bytes32(0)) {
       revert("block number too old to challenge");
     }
-    require(blockNumberNp1Hash == computedBlockHash, "end block hash wrong");*/
+    require(blockNumberNp1Hash == computedBlockHash, "end block hash wrong");
 
     // decode the blocks
     bytes32 inputHash;
     {
       Lib_RLPReader.RLPItem[] memory blockNp1 = Lib_RLPReader.readList(blockHeaderNp1);
       bytes32 parentHash = Lib_RLPReader.readBytes32(blockNp1[0]);
-      //require(blockNumberNHash == parentHash, "parent block hash somehow wrong");
+      require(blockNumberNHash == parentHash, "parent block hash somehow wrong");
 
       bytes32 newroot = Lib_RLPReader.readBytes32(blockNp1[3]);
       require(assertionRoot != newroot, "asserting that the real state is correct is not a challenge");

mipsevm/main.go

@@ -58,7 +58,6 @@ func main() {
 					mu.RegWrite(uc.MIPS_REG_PC, 0x5ead0004)
 				}
 			}
-			// TODO: is this where the plus 1 goes?
 			lastStep = step + 1
 		})
 

scripts/challenge.js

@@ -21,9 +21,9 @@ async function main() {
   /*const assertionRoot = "0x1111111111111111111111111111111111111111111111111111111111111111"
   let finalTrie = JSON.parse(fs.readFileSync("/tmp/cannon/0_"+blockNumberN.toString()+"/checkpoint_final.json"))*/
 
-  // we are submitting the (wrong) transition for block 10 as the attacker
-  const assertionRoot = "0x03f930c087b70f3385db68fe6bf128719e2d9a4b0a133e53b32db2fa25d345fd"
-  let finalTrie = JSON.parse(fs.readFileSync("/tmp/cannon/0_10/checkpoint_final.json"))
+  // we are submitting the (wrong) transition for block 13284469 as the attacker
+  const assertionRoot = "0xb0b8fc0cf929b8b7a1a31059e1dfb321e78ff0dfe5912d5c615beaf37ec608e7"
+  let finalTrie = JSON.parse(fs.readFileSync("/tmp/cannon/0_13284491/checkpoint_final.json"))
 
   let preimages = Object.assign({}, startTrie['preimages'], finalTrie['preimages']);
   const finalSystemState = finalTrie['root']