fix: finalize dictionary in RIPEMD160 (#191)

Closes #147

Finalize dict and set the pointer start to the correct value

Note to reviewer: this is a fix imported from C4 mitigation, ensure the
fix was correctly ported by looking at the corresponding issue and PR.

cairo/src/precompiles/ripemd160.cairo

@@ -459,8 +459,10 @@ func finish{range_check_ptr, bitwise_ptr: BitwiseBuiltin*}(
     let (local arr_x: felt*) = alloc();
     dict_to_array{dict_ptr=x}(arr_x, 16);
     let (buf, bufsize) = compress(buf, bufsize, arr_x, 16);
+    default_dict_finalize(start, x, 0);
     // reset dict to all 0.
     let (x) = default_dict_new(0);
+    tempvar start = x;
 
     dict_write{dict_ptr=x}(14, val);
     dict_write{dict_ptr=x}(15, val_15);

cairo/tests/src/precompiles/test_ripemd160.py

@@ -3,6 +3,9 @@
 from hypothesis import given, settings
 from hypothesis.strategies import binary
 
+from tests.utils.errors import cairo_error
+from tests.utils.hints import insert_hint
+
 
 @pytest.mark.slow
 class TestRIPEMD160:
@@ -17,3 +20,20 @@ def test_ripemd160_should_return_correct_hash(self, cairo_run, msg_bytes):
         expected_hash = ripemd160_crypto.hexdigest()
 
         assert expected_hash.rjust(64, "0") == bytes(precompile_hash).hex()
+
+    def test_finalized_dict_ripemd160(self, cairo_program, cairo_run):
+        msg_bytes = bytes([0x00] * 57)
+        with (
+            insert_hint(
+                cairo_program,
+                "ripemd160.cairo:154",
+                "try:\n"
+                "    dict_tracker = __dict_manager.get_tracker(ids.dict_ptr)\n"
+                "    dict_tracker.data[ids.index_4] = 1\n"
+                "except Exception: pass\n",
+            ),
+            cairo_error(
+                message="An ASSERT_EQ instruction failed"
+            ),  # fails with an assertion error from default_dict_finalize_inner
+        ):
+            cairo_run("test__ripemd160", msg=list(msg_bytes))

cairo/tests/utils/errors.py

@@ -13,6 +13,6 @@ def cairo_error(message=None):
             return
         error = re.search(r"Error message: (.*)", str(e.value))
         error = error.group(1) if error else str(e.value)
-        assert message == error, f"Expected {message}, got {error}"
+        assert message in error, f"Expected {message}, got {error}"
     finally:
         pass

cairo/tests/utils/hints.py

@@ -197,6 +197,36 @@ def patch_hint(program, hint, new_hint, scope: Optional[str] = None):
         yield
 
 
+@contextmanager
+def insert_hint(program, location: str, hint):
+    """
+    Insert a hint at a given location in the program.
+
+    The location should be file_name:line_number.
+
+    """
+    instructions = {
+        index: loc
+        for index, loc in program.debug_info.instruction_locations.items()
+        if location in str(loc.inst)
+    }
+    if not instructions:
+        raise ValueError(f"Location {location} not found in program.")
+    pc, instruction = list(instructions.items())[0]
+    hint = CairoHint(
+        accessible_scopes=instruction.accessible_scopes,
+        flow_tracking_data=instruction.flow_tracking_data,
+        code=hint,
+    )
+    new_hints = program.hints.copy()
+    new_hints[pc] = [*new_hints.get(pc, []), hint]
+    with (
+        patch.object(instruction, "hints", new=new_hints.get(pc, [])),
+        patch.object(program, "hints", new=new_hints),
+    ):
+        yield
+
+
 def oracle(program, serde, main_path, gen_arg):
 
     def _factory(ids, reference: Optional[str] = None):