Zhang Jing Xuan
0841b1a103
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131 lines
4.2 KiB
Python
131 lines
4.2 KiB
Python
"""文件上传安全校验。
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提供 validate_upload() 对上传文件做：
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1. 文件名清洗（去除路径、危险字符、控制长度）
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2. 扩展名白名单校验
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3. MIME 与扩展名一致性校验
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4. 文件魔数（magic bytes）校验，防止伪装
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5. 文件大小校验
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"""
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from __future__ import annotations
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import re
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from dataclasses import dataclass
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from typing import Optional
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from fastapi import HTTPException, UploadFile
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# 允许的扩展名 → 期望的 MIME 前缀（; 前部分）
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ALLOWED_TYPES: dict[str, str] = {
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"txt": "text/",
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"md": "text/",
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"csv": "text/",
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"json": "application/json",
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"docx": "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
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"pptx": "application/vnd.openxmlformats-officedocument.presentationml.presentation",
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"pdf": "application/pdf",
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"xlsx": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
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"xls": "application/vnd.ms-excel",
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"png": "image/png",
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"jpg": "image/jpeg",
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"jpeg": "image/jpeg",
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"gif": "image/gif",
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"webp": "image/webp",
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"bmp": "image/bmp",
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}
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# 魔数签名（前若干字节）
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MAGIC_SIGNATURES: dict[str, list[bytes]] = {
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"pdf": [b"%PDF-"],
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"png": [b"\x89PNG\r\n\x1a\n"],
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"jpg": [b"\xff\xd8\xff"],
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"jpeg": [b"\xff\xd8\xff"],
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"gif": [b"GIF87a", b"GIF89a"],
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"bmp": [b"BM"],
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"webp": [b"RIFF"],
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# Office 文件均为 ZIP 容器（PK\x03\x04）
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"docx": [b"PK\x03\x04"],
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"pptx": [b"PK\x03\x04"],
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"xlsx": [b"PK\x03\x04"],
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"xls": [b"\xd0\xcf\x11\xe0"], # OLE 复合文档
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}
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MAX_FILENAME_LEN = 200
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@dataclass
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class UploadCheck:
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filename: str
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suffix: str
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media_type: str
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size: int
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_FILENAME_BAD = re.compile("[\x00-\x1f<>:\"/\\|?*]")
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def sanitize_filename(name: str) -> str:
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"""清洗文件名：去路径、去控制/危险字符、限长。"""
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# 仅保留文件名部分
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name = re.split(r"[\\/]", name)[-1].strip()
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name = _FILENAME_BAD.sub("_", name)
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name = name.strip(". ")
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if not name:
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name = "upload"
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if len(name) > MAX_FILENAME_LEN:
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stem, dot, ext = name.rpartition(".")
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if dot:
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name = stem[: MAX_FILENAME_LEN - len(ext) - 1] + "." + ext
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else:
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name = name[:MAX_FILENAME_LEN]
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return name
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def _check_magic(suffix: str, head: bytes) -> bool:
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sigs = MAGIC_SIGNATURES.get(suffix)
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if not sigs:
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return True # 无签名要求（文本类）默认放行
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return any(head.startswith(sig) for sig in sigs)
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def validate_upload(
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file: UploadFile,
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*,
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content: bytes,
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max_size: Optional[int] = None,
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) -> UploadCheck:
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"""校验上传文件，失败抛出 HTTPException。
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参数 content 为已读取的字节内容（用于魔数校验）。
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"""
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if max_size is not None and len(content) > max_size:
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raise HTTPException(status_code=413, detail=f"文件不能超过 {max_size // (1024 * 1024)}MB")
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if not content:
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raise HTTPException(status_code=400, detail="上传文件为空")
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raw_name = file.filename or "material"
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filename = sanitize_filename(raw_name)
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suffix = filename.rsplit(".", 1)[-1].lower() if "." in filename else ""
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media_type = (file.content_type or "").split(";")[0].strip().lower()
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if suffix not in ALLOWED_TYPES:
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raise HTTPException(
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status_code=415,
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detail="暂不支持该文件类型，请上传 txt、md、csv、json、docx、pptx、pdf、xlsx 或图片",
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)
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# MIME 一致性：图片/office/pdf 必须匹配；文本类型放宽
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expected_mime = ALLOWED_TYPES[suffix]
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if expected_mime != "text/" and media_type and not media_type.startswith(expected_mime.split("/")[0]):
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# 宽松：只校验主类型一致（image/* application/* 等）
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if media_type.split("/")[0] != expected_mime.split("/")[0]:
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raise HTTPException(status_code=415, detail="文件类型与扩展名不一致")
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# 魔数校验
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head = content[:16]
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if not _check_magic(suffix, head):
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raise HTTPException(status_code=415, detail="文件内容与声明类型不符")
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return UploadCheck(filename=filename, suffix=suffix, media_type=media_type or expected_mime, size=len(content))
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