T09 · Insecure Skill Coding Practices
Warning
- Location
- scripts/cn_meme_generator.py:140
- Finding
- Unbounded and Unvalidated Remote Image Response<![CDATA[ ## Vulnerability Details **File Location**: `scripts/cn_meme_generator.py`, lines 140-144 **Vulnerability Type**: Unrestricted remote response buffering and missing content validation **Risk Level**: Medium ```python resp = requests.get(url, timeout=30) if resp.status_code == 200: with open(output, 'wb') as f: f.write(resp.content) ``` ### Technical Analysis The AI image generation path retrieves content from an external service and accesses `resp.content`, which buffers the complete response in memory. The configured 30-second timeout limits network waiting periods but does not impose a maximum response size. The program accepts every HTTP 200 response without checking its `Content-Type`, declared length, actual byte count, image format, or whether Pillow can safely decode it. It then writes those bytes directly to the caller-selected output file. Consequently, a compromised, malicious, or malfunctioning external service can return an oversized payload or arbitrary non-image content. Saving arbitrary bytes does not itself execute them, and the remote service cannot independently select the destination path. Exploitation is therefore primarily a resource-exhaustion and content-integrity risk rather than remote code execution. ### Attack Path 1. A user invokes the script in AI mode with a prompt. 2. The script sends the prompt to the Pollinations image endpoint. 3. The endpoint, or a compromised component in its delivery chain, returns HTTP 200 with an excessively large or non-image response. 4. `requests` buffers the complete response through `resp.content`, consuming memory without an application-level size limit. 5. The script writes the entire response to the selected output path, consuming disk space and presenting unverified bytes as an image. 6. The process may become unavailable due to memory or storage exhaustion, or downstream software may later process an invalid or hostile image payload. ### Impact Assessment Exploitatio ...[truncated 628 chars]
- Remediation
- <![CDATA[ ## Remediation Suggestions 1. Use `stream=True` and read the response in fixed-size chunks. 2. Reject responses whose `Content-Length` exceeds a conservative image size limit, while also enforcing the limit during streaming because the header can be absent or dishonest. 3. Require an allowlisted image media type, such as `image/png`, `image/jpeg`, or `image/webp`. 4. Download into a securely created temporary file rather than writing directly to the final destination. 5. Open the temporary file with Pillow and call `verify()` to confirm that it contains a supported image. 6. Enforce image dimension and decompressed-pixel limits to mitigate decompression-bomb payloads. 7. Atomically move the validated file to the requested destination only after all checks succeed. 8. Delete partial temporary files on every failure path and report a concise error. Example hardening pattern: ```python import os import tempfile from PIL import Image, UnidentifiedImageError MAX_DOWNLOAD_BYTES = 10 * 1024 * 1024 ALLOWED_CONTENT_TYPES = {"image/png", "image/jpeg", "image/webp"} Image.MAX_IMAGE_PIXELS = 25_000_000 with requests.get(url, timeout=(5, 30), stream=True) as resp: resp.raise_for_status() content_type = resp.headers.get("Content-Type", "").split(";", 1)[0].lower() if content_type not in ALLOWED_CONTENT_TYPES: raise ValueError("The remote service returned an unsupported content type") declared_size = resp.headers.get("Content-Length") if declared_size and int(declared_size) > MAX_DOWNLOAD_BYTES: raise ValueError("The remote image exceeds the permitted size") output_dir = os.path.dirname(os.path.abspath(output)) fd, temporary_path = tempfile.mkstemp(dir=output_dir, suffix=".download") try: received = 0 with os.fdopen(fd, "wb") as temporary_file: for chunk in resp.iter_content(chunk_size=64 * 1024): if not chunk: continue received += len( ...[truncated 431 chars]