new(tests): Identity precompile test

src/ethereum_test_forks/forks/forks.py

@@ -619,7 +619,11 @@ def valid_opcodes(
         cls,
     ) -> List[Opcodes]:
         """Return list of Opcodes that are valid to work on this fork."""
-        return [Opcodes.RETURNDATASIZE, Opcodes.STATICCALL] + super(Byzantium, cls).valid_opcodes()
+        return [
+            Opcodes.RETURNDATASIZE,
+            Opcodes.RETURNDATACOPY,
+            Opcodes.STATICCALL,
+        ] + super(Byzantium, cls).valid_opcodes()
 
 
 class Constantinople(Byzantium):

tests/frontier/opcodes/test_all_opcodes.py

@@ -34,6 +34,8 @@ def prepare_stack(opcode: Opcode) -> Bytecode:
         return Op.PUSH1(1) + Op.PUSH1(5)
     if opcode == Op.JUMP:
         return Op.PUSH1(3)
+    if opcode == Op.RETURNDATACOPY:
+        return Op.PUSH1(0x00) * 32
     return Op.PUSH1(0x01) * 32
 
 
@@ -65,8 +67,8 @@ def test_all_opcodes(state_test: StateTestFiller, pre: Alloc, fork: Fork):
     contract_address = pre.deploy_contract(
         code=sum(
             Op.SSTORE(
-                Op.PUSH1(opcode.int()),
-                Op.CALL(1_000_000, opcode_address, 0, 0, 0, 0, 0),
+                opcode.int(),
+                Op.CALL(gas=100_000, address=opcode_address),
             )
             for opcode, opcode_address in code_contract.items()
         )
@@ -82,7 +84,7 @@ def test_all_opcodes(state_test: StateTestFiller, pre: Alloc, fork: Fork):
 
     tx = Transaction(
         sender=pre.fund_eoa(),
-        gas_limit=500_000_000,
+        gas_limit=50_000_000,
         to=contract_address,
         data=b"",
         value=0,

tests/homestead/identity_precompile/__init__.py

@@ -0,0 +1 @@
+"""abstract: EIP-2: Homestead Precompile Identity Test Cases."""

tests/homestead/identity_precompile/test_identity.py

@@ -0,0 +1,103 @@
+"""abstract: EIP-2: Homestead Identity Precompile Test Cases."""
+
+import pytest
+
+from ethereum_test_tools import (
+    Account,
+    Alloc,
+    Environment,
+    StateTestFiller,
+    Transaction,
+    keccak256,
+)
+from ethereum_test_tools import Opcodes as Op
+
+
+@pytest.mark.with_all_call_opcodes(
+    selector=lambda call_opcode: call_opcode
+    not in [Op.EXTCALL, Op.EXTDELEGATECALL, Op.EXTSTATICCALL]
+    # EXT*CALL opcodes do not contain accept the return data size/offset as an argument
+)
+@pytest.mark.valid_from("Byzantium")
+def test_identity_return_overwrite(
+    state_test: StateTestFiller,
+    pre: Alloc,
+    call_opcode: Op,
+):
+    """Test the return data of the identity precompile overwriting its input."""
+    env = Environment()
+    code = (
+        sum(Op.MSTORE8(offset=i, value=(i + 1)) for i in range(4))  # memory = [1, 2, 3, 4]
+        + call_opcode(
+            address=4,
+            args_offset=0,
+            args_size=4,  # args = [1, 2, 3, 4]
+            ret_offset=1,
+            ret_size=4,
+        )  # memory = [1, 1, 2, 3, 4]
+        + Op.RETURNDATACOPY(
+            dest_offset=0, offset=0, size=Op.RETURNDATASIZE()
+        )  # memory correct = [1, 2, 3, 4, 4], corrupt = [1, 1, 2, 3, 4]
+        + Op.SSTORE(1, Op.SHA3(offset=0, size=Op.MSIZE))
+    )
+    contract_address = pre.deploy_contract(
+        code=code,
+    )
+    tx = Transaction(
+        sender=pre.fund_eoa(),
+        to=contract_address,
+        gas_limit=100_000,
+    )
+
+    post = {
+        contract_address: Account(
+            storage={
+                1: keccak256(bytes([1, 2, 3, 4, 4]).ljust(32, b"\0")),
+            },
+        ),
+    }
+
+    state_test(env=env, pre=pre, post=post, tx=tx)
+
+
+@pytest.mark.with_all_call_opcodes()
+@pytest.mark.valid_from("Byzantium")
+def test_identity_return_buffer_modify(
+    state_test: StateTestFiller,
+    pre: Alloc,
+    call_opcode: Op,
+):
+    """Test the modification of the input range to attempt to modify the return buffer."""
+    env = Environment()
+    code = (
+        sum(Op.MSTORE8(offset=i, value=(i + 1)) for i in range(4))  # memory = [1, 2, 3, 4]
+        + call_opcode(
+            address=4,
+            args_offset=0,
+            args_size=4,  # args = [1, 2, 3, 4]
+        )  # memory = [1, 2, 3, 4]
+        + Op.MSTORE8(offset=0, value=5)  # memory = [5, 2, 3, 4]
+        + Op.MSTORE8(offset=4, value=5)  # memory = [5, 2, 3, 4, 5]
+        + Op.RETURNDATACOPY(
+            dest_offset=0, offset=0, size=Op.RETURNDATASIZE()
+        )  # memory correct = [1, 2, 3, 4, 5], corrupt = [5, 2, 3, 4, 5]
+        + Op.SSTORE(1, Op.SHA3(offset=0, size=Op.MSIZE))
+    )
+    contract_address = pre.deploy_contract(
+        code=code,
+    )
+    tx = Transaction(
+        sender=pre.fund_eoa(),
+        to=contract_address,
+        gas_limit=100_000,
+    )
+
+    post = {
+        contract_address: Account(
+            storage={
+                1: keccak256(bytes([1, 2, 3, 4, 5]).ljust(32, b"\0")),
+            },
+        ),
+    }
+
+    state_test(env=env, pre=pre, post=post, tx=tx)