Add optional screenshots to bug reports

2026-09-15 21:16:06 +02:00
parent 39af9ecdb4
commit 5d3ae10036
10 changed files with 263 additions and 12 deletions
@@ -0,0 +1,65 @@
+"""Decode and re-encode small raster uploads before they leave MetalCircle."""
+from io import BytesIO
+import warnings
+
+from PIL import Image, ImageOps
+
+
+MAX_SCREENSHOT_BYTES = 4 * 1024 * 1024
+MAX_SCREENSHOT_PIXELS = 16_000_000
+MAX_SCREENSHOT_OUTPUT_BYTES = 8 * 1024 * 1024
+
+
+class ScreenshotError(ValueError):
+    """Stable validation code; never includes the uploaded filename or bytes."""
+    def __init__(self, code):
+        self.code = code
+        super().__init__(code)
+
+
+def sanitize_screenshot(contents):
+    if not contents:
+        raise ScreenshotError('empty')
+    if len(contents) > MAX_SCREENSHOT_BYTES:
+        raise ScreenshotError('too_large')
+
+    try:
+        with warnings.catch_warnings():
+            warnings.simplefilter('error', Image.DecompressionBombWarning)
+            with Image.open(BytesIO(contents)) as candidate:
+                if candidate.format not in {'JPEG', 'PNG', 'WEBP'}:
+                    raise ScreenshotError('unsupported')
+                if candidate.width * candidate.height > MAX_SCREENSHOT_PIXELS:
+                    raise ScreenshotError('too_large')
+                if getattr(candidate, 'n_frames', 1) != 1:
+                    raise ScreenshotError('unsupported')
+                candidate.verify()
+            with Image.open(BytesIO(contents)) as candidate:
+                if candidate.width * candidate.height > MAX_SCREENSHOT_PIXELS:
+                    raise ScreenshotError('too_large')
+                image = ImageOps.exif_transpose(candidate)
+                image.load()
+                has_alpha = image.mode in {'RGBA', 'LA'} or (
+                    image.mode == 'P' and 'transparency' in image.info
+                )
+                if image.mode not in {'RGB', 'RGBA'}:
+                    image = image.convert('RGBA' if has_alpha else 'RGB')
+                image.thumbnail((1600, 1600))
+                output = BytesIO()
+                if image.mode == 'RGBA':
+                    image.save(output, format='PNG', optimize=True)
+                    extension, media_type = 'png', 'image/png'
+                else:
+                    image.save(output, format='JPEG', quality=85, optimize=True)
+                    extension, media_type = 'jpg', 'image/jpeg'
+                safe_contents = output.getvalue()
+    except ScreenshotError:
+        raise
+    except Exception:
+        # Decoders may raise different exception types for malformed inputs.
+        # Fail closed without exposing decoder details to the caller.
+        raise ScreenshotError('invalid') from None
+
+    if len(safe_contents) > MAX_SCREENSHOT_OUTPUT_BYTES:
+        raise ScreenshotError('too_large')
+    return safe_contents, extension, media_type