134 lines
4.5 KiB
Python
134 lines
4.5 KiB
Python
"""安全工具 — 文件上传校验和 URL 安全校验。"""
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import ipaddress
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import io
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import logging
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import os
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import socket
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logger = logging.getLogger(__name__)
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# PDF 文件头魔数
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PDF_MAGIC = b"%PDF"
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# 文件大小限制（默认 30MB）
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MAX_FILE_SIZE = int(os.environ.get("MAX_UPLOAD_SIZE_MB", "30")) * 1024 * 1024
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# PDF 页数限制（默认 200 页）
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MAX_PDF_PAGES = int(os.environ.get("MAX_PDF_PAGES", "200"))
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# 私网/保留 IP 前缀
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_PRIVATE_NETWORKS = [
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ipaddress.ip_network("127.0.0.0/8"), # loopback
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ipaddress.ip_network("10.0.0.0/8"), # 私网 A
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ipaddress.ip_network("172.16.0.0/12"), # 私网 B
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ipaddress.ip_network("192.168.0.0/16"), # 私网 C
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ipaddress.ip_network("169.254.0.0/16"), # 链路本地
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ipaddress.ip_network("0.0.0.0/8"), # 当前网络
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ipaddress.ip_network("::1/128"), # IPv6 loopback
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ipaddress.ip_network("fc00::/7"), # IPv6 私网
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ipaddress.ip_network("fe80::/10"), # IPv6 链路本地
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]
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def prepare_pdf_upload(file_storage, password: str = "") -> tuple[bool, str, bytes | None]:
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"""校验 PDF；加密文件解密后返回可供解析的 PDF 字节。
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密码不会写入数据库或日志。空密码可自动处理仅限制复制/打印的 PDF。
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返回 (is_valid, error_message, pdf_bytes)。
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"""
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file_storage.seek(0)
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original_bytes = file_storage.read()
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file_storage.seek(0)
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# 1. 检查文件大小
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size = len(original_bytes)
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if size == 0:
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return False, "文件为空", None
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if size > MAX_FILE_SIZE:
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return False, f"文件大小 {size // (1024*1024)}MB 超过限制 {MAX_FILE_SIZE // (1024*1024)}MB", None
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# 2. 检查 PDF 魔数
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if not original_bytes[:8].startswith(PDF_MAGIC):
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return False, "文件不是有效的 PDF 格式", None
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# 3. 解密并检查页数
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try:
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import pypdf
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reader = pypdf.PdfReader(io.BytesIO(original_bytes))
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pdf_bytes = original_bytes
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if reader.is_encrypted:
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decrypt_result = reader.decrypt(password or "")
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if decrypt_result == 0:
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message = "PDF 密码错误，请重新输入" if password else "该 PDF 需要打开密码，请填写密码后重试"
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return False, message, None
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writer = pypdf.PdfWriter()
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writer.append_pages_from_reader(reader)
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output = io.BytesIO()
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writer.write(output)
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pdf_bytes = output.getvalue()
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# 4. 检查页数
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if len(reader.pages) > MAX_PDF_PAGES:
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return False, f"PDF 页数 {len(reader.pages)} 超过限制 {MAX_PDF_PAGES} 页", None
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except ImportError:
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# pypdf 不可用时跳过加密和页数检查
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pdf_bytes = original_bytes
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except Exception as e:
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logger.warning(f"PDF 解析检查失败: {e}")
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return False, "PDF 文件内容损坏、密码错误或格式无效", None
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finally:
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file_storage.seek(0)
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return True, "", pdf_bytes
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def validate_pdf_upload(file_storage, password: str = "") -> tuple[bool, str]:
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"""兼容旧调用：只返回 PDF 校验结果。"""
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is_valid, error_message, _ = prepare_pdf_upload(file_storage, password)
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return is_valid, error_message
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def is_safe_base_url(url: str) -> tuple[bool, str]:
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"""检查 Base URL 是否安全（拒绝私网、环回、元数据地址）。
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返回 (is_safe, error_message)。
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"""
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if not url:
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return True, ""
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# 只允许 http/https
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if not url.startswith(("http://", "https://")):
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return False, "仅支持 http/https 协议"
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# 解析主机名
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from urllib.parse import urlparse
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try:
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parsed = urlparse(url)
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except Exception:
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return False, "URL 格式无效"
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hostname = parsed.hostname
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if not hostname:
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return False, "URL 缺少主机名"
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# 拒绝明确的 localhost
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if hostname in ("localhost", "0.0.0.0"):
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return False, f"不允许访问 {hostname}"
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# DNS 解析后检查 IP
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try:
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for info in socket.getaddrinfo(hostname, None, socket.AF_UNSPEC, socket.SOCK_STREAM):
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ip_str = info[4][0]
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ip = ipaddress.ip_address(ip_str)
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for network in _PRIVATE_NETWORKS:
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if ip in network:
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return False, f"不允许访问私网/保留地址 ({ip_str})"
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except socket.gaierror:
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pass # DNS 解析失败不阻止，让后续调用报错
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except Exception as e:
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logger.warning(f"URL 安全检查异常: {e}")
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return True, ""
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