feat: change default code_offset in create_from_blueprint (#3454)

change default `code_offset` to 3 for `create_from_blueprint`, per
ERC5202 standard

---------

Co-authored-by: Charles Cooper <cooper.charles.m@gmail.com>

docs/built-in-functions.rst

@@ -184,15 +184,15 @@ Vyper has three built-ins for contract creation; all three contract creation bui
     The implementation of ``create_copy_of`` assumes that the code at ``target`` is smaller than 16MB. While this is much larger than the EIP-170 constraint of 24KB, it is a conservative size limit intended to future-proof deployer contracts in case the EIP-170 constraint is lifted. If the code at ``target`` is larger than 16MB, the behavior of ``create_copy_of`` is undefined.
 
 
-.. py:function:: create_from_blueprint(target: address, *args, value: uint256 = 0, raw_args: bool = False, code_offset: int = 0, [, salt: bytes32]) -> address
+.. py:function:: create_from_blueprint(target: address, *args, value: uint256 = 0, raw_args: bool = False, code_offset: int = 3, [, salt: bytes32]) -> address
 
     Copy the code of ``target`` into memory and execute it as initcode. In other words, this operation interprets the code at ``target`` not as regular runtime code, but directly as initcode. The ``*args`` are interpreted as constructor arguments, and are ABI-encoded and included when executing the initcode.
 
     * ``target``: Address of the blueprint to invoke
     * ``*args``: Constructor arguments to forward to the initcode.
     * ``value``: The wei value to send to the new contract address (Optional, default 0)
     * ``raw_args``: If ``True``, ``*args`` must be a single ``Bytes[...]`` argument, which will be interpreted as a raw bytes buffer to forward to the create operation (which is useful for instance, if pre- ABI-encoded data is passed in from elsewhere). (Optional, default ``False``)
-    * ``code_offset``: The offset to start the ``EXTCODECOPY`` from (Optional, default 0)
+    * ``code_offset``: The offset to start the ``EXTCODECOPY`` from (Optional, default 3)
     * ``salt``: A ``bytes32`` value utilized by the deterministic ``CREATE2`` opcode (Optional, if not supplied, ``CREATE`` is used)
 
     Returns the address of the created contract. If the create operation fails (for instance, in the case of a ``CREATE2`` collision), execution will revert. If ``code_offset >= target.codesize`` (ex. if there is no code at ``target``), execution will revert.
@@ -209,9 +209,13 @@ Vyper has three built-ins for contract creation; all three contract creation bui
 
     To properly deploy a blueprint contract, special deploy bytecode must be used. The output of ``vyper -f blueprint_bytecode`` will produce bytecode which deploys an ERC-5202 compatible blueprint.
 
+.. note::
+
+  Prior to Vyper version ``0.4.0``, the ``code_offset`` parameter defaulted to ``0``.
+
 .. warning::
 
-    It is recommended to deploy blueprints with the ERC-5202 preamble ``0xFE7100`` to guard them from being called as regular contracts. This is particularly important for factories where the constructor has side effects (including ``SELFDESTRUCT``!), as those could get executed by *anybody* calling the blueprint contract directly. The ``code_offset=`` kwarg is provided to enable this pattern:
+    It is recommended to deploy blueprints with an `ERC-5202 <https://eips.ethereum.org/EIPS/eip-5202>`_ preamble like ``0xFE7100`` to guard them from being called as regular contracts. This is particularly important for factories where the constructor has side effects (including ``SELFDESTRUCT``!), as those could get executed by *anybody* calling the blueprint contract directly. The ``code_offset=`` kwarg is provided (and defaults to the ERC-5202 default of 3) to enable this pattern:
 
     .. code-block:: vyper
 

tests/conftest.py

@@ -22,6 +22,7 @@
 from vyper.compiler.input_bundle import FilesystemInputBundle, InputBundle
 from vyper.compiler.settings import OptimizationLevel, Settings, _set_debug_mode
 from vyper.ir import compile_ir, optimizer
+from vyper.utils import ERC5202_PREFIX
 
 # Import the base fixtures
 pytest_plugins = ["tests.fixtures.memorymock"]
@@ -377,7 +378,9 @@ def get_contract_module(source_code, *args, **kwargs):
     return get_contract_module
 
 
-def _deploy_blueprint_for(w3, source_code, optimize, output_formats, initcode_prefix=b"", **kwargs):
+def _deploy_blueprint_for(
+    w3, source_code, optimize, output_formats, initcode_prefix=ERC5202_PREFIX, **kwargs
+):
     settings = Settings()
     settings.evm_version = kwargs.pop("evm_version", None)
     settings.optimize = optimize

tests/functional/builtins/codegen/test_create_functions.py

@@ -6,7 +6,7 @@
 import vyper.ir.compile_ir as compile_ir
 from vyper.codegen.ir_node import IRnode
 from vyper.compiler.settings import OptimizationLevel
-from vyper.utils import EIP_170_LIMIT, checksum_encode, keccak256
+from vyper.utils import EIP_170_LIMIT, ERC5202_PREFIX, checksum_encode, keccak256
 
 
 # initcode used by create_minimal_proxy_to
@@ -148,7 +148,7 @@ def test(_salt: bytes32) -> address:
 
 # test blueprints with various prefixes - 0xfe would block calls to the blueprint
 # contract, and 0xfe7100 is ERC5202 magic
-@pytest.mark.parametrize("blueprint_prefix", [b"", b"\xfe", b"\xfe\71\x00"])
+@pytest.mark.parametrize("blueprint_prefix", [b"", b"\xfe", ERC5202_PREFIX])
 def test_create_from_blueprint(
     get_contract, deploy_blueprint_for, w3, keccak, create2_address_of, tx_failed, blueprint_prefix
 ):
@@ -208,6 +208,66 @@ def test2(target: address, salt: bytes32):
         d.test2(f.address, salt)
 
 
+# test blueprints with 0xfe7100 prefix, which is the EIP 5202 standard.
+# code offset by default should be 3 here.
+def test_create_from_blueprint_default_offset(
+    get_contract, deploy_blueprint_for, w3, keccak, create2_address_of, tx_failed
+):
+    code = """
+@external
+def foo() -> uint256:
+    return 123
+    """
+
+    deployer_code = """
+created_address: public(address)
+
+@external
+def test(target: address):
+    self.created_address = create_from_blueprint(target)
+
+@external
+def test2(target: address, salt: bytes32):
+    self.created_address = create_from_blueprint(target, salt=salt)
+    """
+
+    # deploy a foo so we can compare its bytecode with factory deployed version
+    foo_contract = get_contract(code)
+    expected_runtime_code = w3.eth.get_code(foo_contract.address)
+
+    f, FooContract = deploy_blueprint_for(code)
+
+    d = get_contract(deployer_code)
+
+    d.test(f.address, transact={})
+
+    test = FooContract(d.created_address())
+    assert w3.eth.get_code(test.address) == expected_runtime_code
+    assert test.foo() == 123
+
+    # extcodesize check
+    zero_address = "0x" + "00" * 20
+    with tx_failed():
+        d.test(zero_address)
+
+    # now same thing but with create2
+    salt = keccak(b"vyper")
+    d.test2(f.address, salt, transact={})
+
+    test = FooContract(d.created_address())
+    assert w3.eth.get_code(test.address) == expected_runtime_code
+    assert test.foo() == 123
+
+    # check if the create2 address matches our offchain calculation
+    initcode = w3.eth.get_code(f.address)
+    initcode = initcode[len(ERC5202_PREFIX) :]  # strip the prefix
+    assert HexBytes(test.address) == create2_address_of(d.address, salt, initcode)
+
+    # can't collide addresses
+    with tx_failed():
+        d.test2(f.address, salt)
+
+
 def test_create_from_blueprint_bad_code_offset(
     get_contract, get_contract_from_ir, deploy_blueprint_for, w3, tx_failed
 ):
@@ -238,8 +298,6 @@ def test(code_ofst: uint256) -> address:
     tx_info = {"from": w3.eth.accounts[0], "value": 0, "gasPrice": 0}
     tx_hash = deploy_transaction.transact(tx_info)
     blueprint_address = w3.eth.get_transaction_receipt(tx_hash)["contractAddress"]
-    blueprint_code = w3.eth.get_code(blueprint_address)
-    print("BLUEPRINT CODE:", blueprint_code)
 
     d = get_contract(deployer_code, blueprint_address)
 
@@ -320,7 +378,7 @@ def should_fail(target: address, arg1: String[129], arg2: Bar):
 
     d = get_contract(deployer_code)
 
-    initcode = w3.eth.get_code(f.address)
+    initcode = w3.eth.get_code(f.address)[3:]
 
     d.test(f.address, FOO, BAR, transact={})
 

vyper/builtins/functions.py

@@ -1828,7 +1828,7 @@ class CreateFromBlueprint(_CreateBase):
         "value": KwargSettings(UINT256_T, zero_value),
         "salt": KwargSettings(BYTES32_T, empty_value),
         "raw_args": KwargSettings(BoolT(), False, require_literal=True),
-        "code_offset": KwargSettings(UINT256_T, zero_value),
+        "code_offset": KwargSettings(UINT256_T, IRnode.from_list(3, typ=UINT256_T)),
     }
     _has_varargs = True
 

vyper/compiler/phases.py

@@ -16,6 +16,7 @@
 from vyper.semantics.types.function import ContractFunctionT
 from vyper.semantics.types.module import ModuleT
 from vyper.typing import StorageLayout
+from vyper.utils import ERC5202_PREFIX
 from vyper.venom import generate_assembly_experimental, generate_ir
 
 DEFAULT_CONTRACT_PATH = PurePath("VyperContract.vy")
@@ -228,8 +229,7 @@ def bytecode_runtime(self) -> bytes:
 
     @cached_property
     def blueprint_bytecode(self) -> bytes:
-        blueprint_preamble = b"\xFE\x71\x00"  # ERC5202 preamble
-        blueprint_bytecode = blueprint_preamble + self.bytecode
+        blueprint_bytecode = ERC5202_PREFIX + self.bytecode
 
         # the length of the deployed code in bytes
         len_bytes = len(blueprint_bytecode).to_bytes(2, "big")

vyper/utils.py

@@ -398,6 +398,7 @@ class SizeLimits:
 
 
 EIP_170_LIMIT = 0x6000  # 24kb
+ERC5202_PREFIX = b"\xFE\x71\x00"  # default prefix from ERC-5202
 
 SHA3_BASE = 30
 SHA3_PER_WORD = 6