Merge pull request from GHSA-ph9x-4vc9-m39g

the routine for aligning call-site posargs and kwargs in
`vyper.codegen.context.lookup_internal_function` was incorrect in cases
where the internal function had more than one default argument - it
consumed default args at the call site from the end instead of the
beginning of the defaults list. this commit fixes and adds some tests
for the alignment routine.

tests/parser/features/test_internal_call.py

@@ -1,6 +1,9 @@
+import string
 from decimal import Decimal
 
+import hypothesis.strategies as st
 import pytest
+from hypothesis import given, settings
 
 from vyper.compiler import compile_code
 from vyper.exceptions import ArgumentException, CallViolation
@@ -642,3 +645,62 @@ def bar() -> String[6]:
     c = get_contract_with_gas_estimation(contract)
 
     assert c.bar() == "hello"
+
+
+# TODO probably want to refactor these into general test utils
+st_uint256 = st.integers(min_value=0, max_value=2**256 - 1)
+st_string65 = st.text(max_size=65, alphabet=string.printable)
+st_bytes65 = st.binary(max_size=65)
+st_sarray3 = st.lists(st_uint256, min_size=3, max_size=3)
+st_darray3 = st.lists(st_uint256, max_size=3)
+
+internal_call_kwargs_cases = [
+    ("uint256", st_uint256),
+    ("String[65]", st_string65),
+    ("Bytes[65]", st_bytes65),
+    ("uint256[3]", st_sarray3),
+    ("DynArray[uint256, 3]", st_darray3),
+]
+
+
+@pytest.mark.parametrize("typ1,strategy1", internal_call_kwargs_cases)
+@pytest.mark.parametrize("typ2,strategy2", internal_call_kwargs_cases)
+def test_internal_call_kwargs(get_contract, typ1, strategy1, typ2, strategy2):
+    # GHSA-ph9x-4vc9-m39g
+
+    @given(kwarg1=strategy1, default1=strategy1, kwarg2=strategy2, default2=strategy2)
+    @settings(deadline=None, max_examples=5)  # len(cases) * len(cases) * 5 * 5
+    def fuzz(kwarg1, kwarg2, default1, default2):
+        code = f"""
+@internal
+def foo(a: {typ1} = {repr(default1)}, b: {typ2} = {repr(default2)}) -> ({typ1}, {typ2}):
+    return a, b
+
+@external
+def test0() -> ({typ1}, {typ2}):
+    return self.foo()
+
+@external
+def test1() -> ({typ1}, {typ2}):
+    return self.foo({repr(kwarg1)})
+
+@external
+def test2() -> ({typ1}, {typ2}):
+    return self.foo({repr(kwarg1)}, {repr(kwarg2)})
+
+@external
+def test3(x1: {typ1}) -> ({typ1}, {typ2}):
+    return self.foo(x1)
+
+@external
+def test4(x1: {typ1}, x2: {typ2}) -> ({typ1}, {typ2}):
+    return self.foo(x1, x2)
+        """
+        c = get_contract(code)
+        assert c.test0() == [default1, default2]
+        assert c.test1() == [kwarg1, default2]
+        assert c.test2() == [kwarg1, kwarg2]
+        assert c.test3(kwarg1) == [kwarg1, default2]
+        assert c.test4(kwarg1, kwarg2) == [kwarg1, kwarg2]
+
+    fuzz()

vyper/codegen/context.py

@@ -267,10 +267,8 @@ def _check(cond, s="Unreachable"):
         # _check(all(l.typ == r.typ for (l, r) in zip(args_ir, sig.args))
 
         num_provided_kwargs = len(args_ir) - len(sig.base_args)
-        num_kwargs = len(sig.default_args)
-        kwargs_needed = num_kwargs - num_provided_kwargs
 
-        kw_vals = list(sig.default_values.values())[:kwargs_needed]
+        kw_vals = list(sig.default_values.values())[num_provided_kwargs:]
 
         return sig, kw_vals