fix: GatekeeperOne exploit

leovct · Nov 25, 2024 · 6a95dea · 6a95dea
1 parent 2e24168
commit 6a95dea
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Showing 3 changed files with 11 additions and 11 deletions.
diff --git a/src/EthernautCTF/GatekeeperOne.sol b/src/EthernautCTF/GatekeeperOne.sol
@@ -5,27 +5,27 @@ contract GatekeeperOne {
   address public entrant;
 
   modifier gateOne() {
-    require(msg.sender != tx.origin);
+    require(msg.sender != tx.origin, 'Gate 1');
     _;
   }
 
   modifier gateTwo() {
-    require(gasleft() % 8191 == 0);
+    require(gasleft() % 8191 == 0, 'Gate 2');
     _;
   }
 
   modifier gateThree(bytes8 _gateKey) {
     require(
       uint32(uint64(_gateKey)) == uint16(uint64(_gateKey)),
-      'GatekeeperOne: invalid gateThree part one'
+      'Gate 3.1'
     );
     require(
       uint32(uint64(_gateKey)) != uint64(_gateKey),
-      'GatekeeperOne: invalid gateThree part two'
+      'Gate 3.2'
     );
     require(
       uint32(uint64(_gateKey)) == uint16(uint160(tx.origin)),
-      'GatekeeperOne: invalid gateThree part three'
+      'Gate 3.3'
     );
     _;
   }

diff --git a/src/EthernautCTF/GatekeeperThree.sol b/src/EthernautCTF/GatekeeperThree.sol
@@ -41,13 +41,13 @@ contract GatekeeperThree {
   }
 
   modifier gateOne() {
-    require(msg.sender == owner);
-    require(tx.origin != owner);
+    require(msg.sender == owner, 'Gate 1.1');
+    require(tx.origin != owner, 'Gate 1.2');
     _;
   }
 
   modifier gateTwo() {
-    require(allowEntrance == true);
+    require(allowEntrance == true, 'Gate 2');
     _;
   }
 

diff --git a/test/EthernautCTF/GatekeeperOneExploit.t.sol b/test/EthernautCTF/GatekeeperOneExploit.t.sol
@@ -16,10 +16,10 @@ contract Helper1 {
     // I started with a higher base because I noticed that using 10k or 20k gas reverts with an OutOfGas error.
     // 3. Tried base + 250 gas = 82,160. This failed.
     // 4. Iteratively narrowed down:
-    //    - base + 267 gas (82,177) failed
-    //    - base + 268 gas (82,178) succeeded
+    //    - base + 264 gas => failed
+    //    - base + 265 gas => succeeded
     require(
-      GatekeeperOne(_target).enter{gas: 8191 * 10 + 268}(_gateKey),
+      GatekeeperOne(_target).enter{gas: 8191 * 10 + 265}(_gateKey),
       'Exploit succeeded'
     );
   }