reentrancy-no-eth: do not count staticcalls as reentrant (#1119)

* reentrancy-no-eth: do not count staticcalls as reentrant
* change can_reenter of low-level-calls to false for staticcall

slither/slithir/operations/high_level_call.py

@@ -96,6 +96,14 @@ def type_call(self):
     # region Analyses
     ###################################################################################
     ###################################################################################
+    def is_static_call(self):
+        # If solidity >0.5, STATICCALL is used
+        if self.compilation_unit.solc_version and self.compilation_unit.solc_version >= "0.5.0":
+            if isinstance(self.function, Function) and (self.function.view or self.function.pure):
+                return True
+            if isinstance(self.function, Variable):
+                return True
+        return False
 
     def can_reenter(self, callstack=None):
         """
@@ -105,12 +113,8 @@ def can_reenter(self, callstack=None):
         :param callstack: check for recursion
         :return: bool
         """
-        # If solidity >0.5, STATICCALL is used
-        if self.compilation_unit.solc_version and self.compilation_unit.solc_version >= "0.5.0":
-            if isinstance(self.function, Function) and (self.function.view or self.function.pure):
-                return False
-            if isinstance(self.function, Variable):
-                return False
+        if self.is_static_call():
+            return False
         # If there is a call to itself
         # We can check that the function called is
         # reentrancy-safe

slither/slithir/operations/library_call.py

@@ -17,6 +17,8 @@ def can_reenter(self, callstack=None):
         Must be called after slithIR analysis pass
         :return: bool
         """
+        if self.is_static_call():
+            return False
         # In case of recursion, return False
         callstack = [] if callstack is None else callstack
         if self.function in callstack:

slither/slithir/operations/low_level_call.py

@@ -61,6 +61,8 @@ def can_reenter(self, _callstack=None):
         Must be called after slithIR analysis pass
         :return: bool
         """
+        if self.function_name == "staticcall":
+            return False
         return True
 
     def can_send_eth(self):

tests/detectors/reentrancy-no-eth/0.5.16/no-reentrancy-staticcall.sol

@@ -0,0 +1,20 @@
+library MyLibrary {
+
+  function aViewCall(address token) internal view {
+    (bool success ,) = token.staticcall(abi.encodeWithSignature("decimals"));
+    require(success, "call failed");
+  }
+}
+
+contract A {
+  uint256 private protectMe = 1;
+  function good() external {
+    MyLibrary.aViewCall(0x6B175474E89094C44Da98b954EedeAC495271d0F);
+    protectMe += 1;
+  }
+  function good1() external {
+    (bool success,) = address(MyLibrary).staticcall(abi.encodeWithSignature("aViewCall(address)"));
+    require(success, "call failed");
+    protectMe += 1;
+  }
+}

tests/detectors/reentrancy-no-eth/0.5.16/no-reentrancy-staticcall.sol.0.5.16.ReentrancyReadBeforeWritten.json

@@ -0,0 +1,3 @@
+[
+    []
+]

tests/detectors/reentrancy-no-eth/0.6.11/no-reentrancy-staticcall.sol

@@ -0,0 +1,26 @@
+interface IERC20 {
+    function decimals() external view returns (uint8);
+}
+
+library MyLibrary {
+
+  function aViewCall(address token) internal view {
+    (bool success ,  ) = token.staticcall(
+            abi.encodeWithSelector(IERC20.decimals.selector)
+            );
+     require(success, "call failed");
+  }
+}
+
+contract A {
+  uint256 private protectMe = 1;
+  function good() external {
+    MyLibrary.aViewCall(0x6B175474E89094C44Da98b954EedeAC495271d0F);
+    protectMe += 1;
+  }
+  function good1() external {
+    (bool success,) = address(MyLibrary).staticcall(abi.encodeWithSignature("aViewCall(address)"));
+    require(success, "call failed");
+    protectMe += 1;
+  }
+}

tests/detectors/reentrancy-no-eth/0.6.11/no-reentrancy-staticcall.sol.0.6.11.ReentrancyReadBeforeWritten.json

@@ -0,0 +1,3 @@
+[
+    []
+]

tests/detectors/reentrancy-no-eth/0.7.6/no-reentrancy-staticcall.sol

@@ -0,0 +1,25 @@
+interface IERC20 {
+    function decimals() external view returns (uint8);
+}
+
+library MyLibrary {
+
+  function aViewCall(address token) internal view {
+    (bool success ,  ) = token.staticcall(
+            abi.encodeWithSelector(IERC20.decimals.selector)
+            );
+     require(success, "call failed");
+  }
+}
+
+contract A {
+  uint256 private protectMe = 1;  function good() external {
+    MyLibrary.aViewCall(0x6B175474E89094C44Da98b954EedeAC495271d0F);
+    protectMe += 1;
+  }
+  function good1() external {
+    (bool success,) = address(MyLibrary).staticcall(abi.encodeWithSignature("aViewCall(address)"));
+    require(success, "call failed");
+    protectMe += 1;
+  }
+}

tests/detectors/reentrancy-no-eth/0.7.6/no-reentrancy-staticcall.sol.0.7.6.ReentrancyReadBeforeWritten.json

@@ -0,0 +1,3 @@
+[
+    []
+]

tests/test_detectors.py

@@ -116,6 +116,21 @@ def id_test(test_item: Test):
         "DAO.sol",
         "0.4.25",
     ),
+    Test(
+        all_detectors.ReentrancyReadBeforeWritten,
+        "no-reentrancy-staticcall.sol",
+        "0.5.16",
+    ),
+    Test(
+        all_detectors.ReentrancyReadBeforeWritten,
+        "no-reentrancy-staticcall.sol",
+        "0.6.11",
+    ),
+    Test(
+        all_detectors.ReentrancyReadBeforeWritten,
+        "no-reentrancy-staticcall.sol",
+        "0.7.6",
+    ),
     Test(
         all_detectors.BooleanEquality,
         "boolean-constant-equality.sol",