Echidna printer: improve constant function detection

slither/core/declarations/function.py

@@ -599,7 +599,7 @@ def solidity_calls(self):
         """
             list(SolidityFunction): List of Soldity calls
         """
-        return list(self._internal_calls)
+        return list(self._solidity_calls)
 
     @property
     def high_level_calls(self):

slither/printers/guidance/echidna.py

@@ -3,17 +3,18 @@
 
 import json
 from collections import defaultdict
-from typing import Dict, List, Set, Tuple
+from typing import Dict, List, Set, Tuple, Union, NamedTuple
 
 from slither.core.cfg.node import Node
 from slither.core.declarations import Function
+from slither.core.declarations.solidity_variables import SolidityVariableComposed, SolidityFunction, SolidityVariable
+from slither.core.expressions import NewContract
 from slither.core.slither_core import Slither
-from slither.core.variables.variable import Variable
+from slither.core.variables.state_variable import StateVariable
 from slither.printers.abstract_printer import AbstractPrinter
-from slither.core.declarations.solidity_variables import SolidityVariableComposed, SolidityFunction, SolidityVariable
-from slither.slithir.operations import Member, Operation
+from slither.slithir.operations import Member, Operation, SolidityCall, LowLevelCall, HighLevelCall, EventCall, Send, \
+    Transfer, InternalDynamicCall, InternalCall, TypeConversion
 from slither.slithir.operations.binary import Binary, BinaryType
-from slither.core.variables.state_variable import StateVariable
 from slither.slithir.variables import Constant
 
 
@@ -46,10 +47,54 @@ def _extract_solidity_variable_usage(slither: Slither, sol_var: SolidityVariable
     return ret
 
 
+def _is_constant(f: Function) -> bool:
+    """
+    Heuristic:
+    - If view/pure with Solidity >= 0.4 -> Return true
+    - If it contains assembly -> Return false (Slither doesn't analyze asm)
+    - Otherwise check for the rules from
+    https://solidity.readthedocs.io/en/v0.5.0/contracts.html?highlight=pure#view-functions
+    with an exception: internal dynamic call are not correctly handled, so we consider them as non-constant
+    :param f:
+    :return:
+    """
+    if f.view or f.pure:
+        if not f.contract.slither.crytic_compile.compiler_version.version.startswith('0.4'):
+            return True
+    if f.payable:
+        return False
+    if not f.is_implemented:
+        return False
+    if f.contains_assembly:
+        return False
+    if f.all_state_variables_written():
+        return False
+    for ir in f.all_slithir_operations():
+        if isinstance(ir, InternalDynamicCall):
+            return False
+        if isinstance(ir, (EventCall, NewContract, LowLevelCall, Send, Transfer)):
+            return False
+        if isinstance(ir, SolidityCall) and ir.function in [SolidityFunction('selfdestruct(address)'),
+                                                            SolidityFunction('suicide(address)')]:
+            return False
+        if isinstance(ir, HighLevelCall):
+            if ir.function.view or ir.function.pure:
+                # External call to constant functions are ensured to be constant only for solidity >= 0.5
+                if f.contract.slither.crytic_compile.compiler_version.version.startswith('0.4'):
+                    return False
+            else:
+                return False
+        if isinstance(ir, InternalCall):
+            # Storage write are not properly handled by all_state_variables_written
+            if any(parameter.is_storage for parameter in ir.function.parameters):
+                return False
+    return True
+
+
 def _extract_constant_functions(slither: Slither) -> Dict[str, List[str]]:
     ret: Dict[str, List[str]] = {}
     for contract in slither.contracts:
-        cst_functions = [_get_name(f) for f in contract.functions_entry_points if f.view or f.pure]
+        cst_functions = [_get_name(f) for f in contract.functions_entry_points if _is_constant(f)]
         cst_functions += [v.function_name for v in contract.state_variables if v.visibility in ['public']]
         if cst_functions:
             ret[contract.name] = cst_functions
@@ -70,21 +115,42 @@ def _extract_assert(slither: Slither) -> Dict[str, List[str]]:
     return ret
 
 
+# Create a named tuple that is serialization in json
+def json_serializable(cls):
+    def as_dict(self):
+        yield {name: value for name, value in zip(
+            self._fields,
+            iter(super(cls, self).__iter__()))}
+
+    cls.__iter__ = as_dict
+    return cls
+
+
+@json_serializable
+class ConstantValue(NamedTuple):
+    value: Union[str, int, bool]
+    type: str
+
+
 def _extract_constants_from_irs(irs: List[Operation],
-                                all_cst_used: List,
-                                all_cst_used_in_binary: Dict,
+                                all_cst_used: List[ConstantValue],
+                                all_cst_used_in_binary: Dict[str, List[ConstantValue]],
                                 context_explored: Set[Node]):
     for ir in irs:
         if isinstance(ir, Binary):
             for r in ir.read:
                 if isinstance(r, Constant):
-                    all_cst_used_in_binary[BinaryType.str(ir.type)].append(r.value)
+                    all_cst_used_in_binary[BinaryType.str(ir.type)].append(ConstantValue(r.value, str(r.type)))
+        if isinstance(ir, TypeConversion):
+            if isinstance(ir.variable, Constant):
+                all_cst_used.append(ConstantValue(ir.variable.value, str(ir.type)))
+                continue
         for r in ir.read:
             # Do not report struct_name in a.struct_name
             if isinstance(ir, Member):
                 continue
             if isinstance(r, Constant):
-                all_cst_used.append(r.value)
+                all_cst_used.append(ConstantValue(r.value, str(r.type)))
             if isinstance(r, StateVariable):
                 if r.node_initialization:
                     if r.node_initialization.irs:
@@ -99,12 +165,14 @@ def _extract_constants_from_irs(irs: List[Operation],
 
 
 def _extract_constants(slither: Slither) -> Tuple[Dict[str, Dict[str, List]], Dict[str, Dict[str, Dict]]]:
-    ret_cst_used: Dict[str, Dict[str, List]] = defaultdict(dict)
-    ret_cst_used_in_binary: Dict[str, Dict[str, Dict]] = defaultdict(dict)
+    # contract -> function -> [ {"value": value, "type": type} ]
+    ret_cst_used: Dict[str, Dict[str, List[ConstantValue]]] = defaultdict(dict)
+    # contract -> function -> binary_operand -> [ {"value": value, "type": type ]
+    ret_cst_used_in_binary: Dict[str, Dict[str, Dict[str, List[ConstantValue]]]] = defaultdict(dict)
     for contract in slither.contracts:
         for function in contract.functions_entry_points:
-            all_cst_used = []
-            all_cst_used_in_binary = defaultdict(list)
+            all_cst_used: List = []
+            all_cst_used_in_binary: Dict = defaultdict(list)
 
             context_explored = set()
             context_explored.add(function)
@@ -113,13 +181,37 @@ def _extract_constants(slither: Slither) -> Tuple[Dict[str, Dict[str, List]], Di
                                         all_cst_used_in_binary,
                                         context_explored)
 
+            # Note: use list(set()) instead of set
+            # As this is meant to be serialized in JSON, and JSON does not support set
             if all_cst_used:
-                ret_cst_used[contract.name][function.full_name] = all_cst_used
+                ret_cst_used[contract.name][_get_name(function)] = list(set(all_cst_used))
             if all_cst_used_in_binary:
-                ret_cst_used_in_binary[contract.name][function.full_name] = all_cst_used_in_binary
+                ret_cst_used_in_binary[contract.name][_get_name(function)] = {k: list(set(v)) for k, v in
+                                                                              all_cst_used_in_binary.items()}
     return ret_cst_used, ret_cst_used_in_binary
 
 
+def _extract_function_relations(slither: Slither) -> Dict[str, Dict[str, Dict[str, List[str]]]]:
+    # contract -> function -> [functions]
+    ret: Dict[str, Dict[str, Dict[str, List[str]]]] = defaultdict(dict)
+    for contract in slither.contracts:
+        ret[contract.name] = defaultdict(dict)
+        written = {_get_name(function): function.all_state_variables_written()
+                   for function in contract.functions_entry_points}
+        read = {_get_name(function): function.all_state_variables_read()
+                for function in contract.functions_entry_points}
+        for function in contract.functions_entry_points:
+            ret[contract.name][_get_name(function)] = {"impacts": [],
+                                                      "is_impacted_by": []}
+            for candidate, varsWritten in written.items():
+                if any((r in varsWritten for r in function.all_state_variables_read())):
+                    ret[contract.name][_get_name(function)]["is_impacted_by"].append(candidate)
+            for candidate, varsRead in read.items():
+                if any((r in varsRead for r in function.all_state_variables_written())):
+                    ret[contract.name][_get_name(function)]["impacts"].append(candidate)
+    return ret
+
+
 class Echidna(AbstractPrinter):
     ARGUMENT = 'echidna'
     HELP = 'Export Echidna guiding information'
@@ -148,6 +240,11 @@ def output(self, filename):
         cst_functions = _extract_constant_functions(self.slither)
         (cst_used, cst_used_in_binary) = _extract_constants(self.slither)
 
+        functions_relations = _extract_function_relations(self.slither)
+
+        constructors = {contract.name: contract.constructor.full_name
+                        for contract in self.slither.contracts if contract.constructor}
+
         d = {'payable': payable,
              'timestamp': timestamp,
              'block_number': block_number,
@@ -156,7 +253,9 @@ def output(self, filename):
              'assert': assert_usage,
              'constant_functions': cst_functions,
              'constants_used': cst_used,
-             'constants_used_in_binary': cst_used_in_binary}
+             'constants_used_in_binary': cst_used_in_binary,
+             'functions_relations': functions_relations,
+             'constructors': constructors}
 
         self.info(json.dumps(d, indent=4))