fix: Make sure split_chunks doesn’t get 0 as chunk size

secret_handshake/util.py

@@ -44,14 +44,17 @@ def inc_nonce(nonce: bytes) -> bytes:
     return bnum
 
 
-def split_chunks(seq: Sequence[T], n: int) -> Generator[Sequence[T], None, None]:
+def split_chunks(seq: Sequence[T], chunk_size: int) -> Generator[Sequence[T], None, None]:
     """Split sequence in equal-sized chunks.
 
     The last chunk is not padded."""
 
+    if chunk_size <= 0:
+        raise ValueError("chunk_size must be greater than zero")
+
     while seq:
-        yield seq[:n]
+        yield seq[:chunk_size]
-        seq = seq[n:]
+        seq = seq[chunk_size:]
 
 
 def long_to_bytes(n: int, blocksize: int = 0) -> bytes:

tests/test_util.py

@@ -49,6 +49,16 @@ def test_split_chunks_is_generator() -> None:
     assert isinstance(split_chunks([], 1), GeneratorType)
 
 
+@pytest.mark.parametrize("size", (-123, -1, 0))
+def test_nonpositive_chunk_size(size: int) -> None:
+    """Test if split_chunks() with non-positive chunk sizes raise an error"""
+
+    with pytest.raises(ValueError) as ctx:
+        list(split_chunks(b"", size))
+
+    assert str(ctx.value) == "chunk_size must be greater than zero"
+
+
 @pytest.mark.parametrize(
     "in_,chunksize,out",
     (