T09 · Insecure Skill Coding Practices
Warning
- Location
- scripts/save_paper.py:97
- Finding
- Insufficient Validation of Remote PDF URLs Enables Arbitrary Network Requests## Vulnerability Details **File Location**: `scripts/save_paper.py`, lines 97–125 **Vulnerability Type**: Improper URL validation and unrestricted remote file retrieval **Risk Level**: Medium ### Vulnerable Code ```python # 下载并附加 PDF if 'arxiv.org' in args.url: try: import urllib.request import tempfile # 将摘要链接转换为 PDF 链接 pdf_url = args.url.replace('/abs/', '/pdf/') if not pdf_url.endswith('.pdf'): pdf_url += '.pdf' print(f"正在下载 PDF...") # 设置 User-Agent 以支持下载 opener = urllib.request.build_opener() opener.addheaders = [('User-agent', 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) Chrome/120.0.0.0')] urllib.request.install_opener(opener) # 创建安全的文件名 safe_title = "".join(c for c in args.title if c.isalnum() or c in (" ", "-", "_")).strip() safe_title = safe_title[:50] # 限制长度 safe_filename = f"{safe_title}.pdf" # 使用临时目录，但指定文件名 with tempfile.TemporaryDirectory() as td: pdf_path = os.path.join(td, safe_filename) urllib.request.urlretrieve(pdf_url, pdf_path) print(f"正在上传 PDF 附件（{safe_filename}）...") zot.attachment_simple([pdf_path], item_key) ``` ### Technical Analysis The code determines whether a URL is an arXiv URL by checking whether the untrusted string contains the substring `arxiv.org`. This does not validate the URL's parsed hostname, scheme, port, or redirect destination. For example, both of the following attacker-controlled URLs pass the check even though their effective hosts are not arXiv: ```text https://arxiv.org.attacker.example/payload https://attacker.example/files/arxiv.org/payload ``` ...[truncated 1518 chars]
- Remediation
- ## Remediation Suggestions - Parse the URL using `urllib.parse.urlparse` rather than performing a substring check. - Require the `https` scheme. - Allow only the exact hostname `arxiv.org` and explicitly approved arXiv subdomains. - Reject embedded credentials, unexpected ports, malformed URLs, and non-HTTP schemes. - Derive the PDF URL from a validated arXiv identifier instead of modifying an arbitrary URL. - Disable redirects or validate the hostname, scheme, and port after every redirect. - Stream downloads while enforcing a strict maximum response size. - Require an expected PDF content type and validate the downloaded file signature before uploading it. - Apply connection and read timeouts and delete rejected downloads immediately.