Fix unexpected errors when decoding truncated QOI images

Tests/test_file_qoi.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from io import BytesIO
 from pathlib import Path
 
 import pytest
@@ -32,6 +33,15 @@ def test_invalid_file() -> None:
         QoiImagePlugin.QoiImageFile(invalid_file)
 
 
+@pytest.mark.parametrize("length", (14, 44, 48, 55))
+def test_truncated(length: int) -> None:
+    with open("Tests/images/pil123rgba.qoi", "rb") as fp:
+        data = fp.read()[:length]
+    with Image.open(BytesIO(data)) as im:
+        with pytest.raises(ValueError, match="not enough image data"):
+            im.load()
+
+
 def test_op_index() -> None:
     # QOI_OP_INDEX as the first chunk
     with Image.open("Tests/images/op_index.qoi") as im:

src/PIL/QoiImagePlugin.py

@@ -61,12 +61,20 @@ def decode(self, buffer: Image.DecoderInput) -> tuple[int, int]:
         bands = Image.getmodebands(self.mode)
         dest_length = self.state.xsize * self.state.ysize * bands
         while len(data) < dest_length:
-            byte = self.fd.read(1)[0]
+            byte_data = self.fd.read(1)
+            if not byte_data:
+                break
+            byte = byte_data[0]
             value: bytes | bytearray
             if byte == 0b11111110 and self._previous_pixel:  # QOI_OP_RGB
-                value = bytearray(self.fd.read(3)) + self._previous_pixel[3:]
+                rgb_data = self.fd.read(3)
+                if len(rgb_data) < 3:
+                    break
+                value = bytearray(rgb_data) + self._previous_pixel[3:]
             elif byte == 0b11111111:  # QOI_OP_RGBA
                 value = self.fd.read(4)
+                if len(value) < 4:
+                    break
             else:
                 op = byte >> 6
                 if op == 0:  # QOI_OP_INDEX
@@ -86,7 +94,10 @@ def decode(self, buffer: Image.DecoderInput) -> tuple[int, int]:
                         )
                     )
                 elif op == 2 and self._previous_pixel:  # QOI_OP_LUMA
-                    second_byte = self.fd.read(1)[0]
+                    second_byte_data = self.fd.read(1)
+                    if not second_byte_data:
+                        break
+                    second_byte = second_byte_data[0]
                     diff_green = (byte & 0b00111111) - 32
                     diff_red = ((second_byte & 0b11110000) >> 4) - 8
                     diff_blue = (second_byte & 0b00001111) - 8