fix(wechat): sanitize media file_name to block path traversal in _dl_media#609
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kevinchennewbee wants to merge 1 commit into
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fix(wechat): sanitize media file_name to block path traversal in _dl_media#609kevinchennewbee wants to merge 1 commit into
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…media
`_dl_media` takes `file_name` straight from the inbound message payload
(attacker-controllable) and joins it onto `_TEMP_DIR` before writing the
decrypted bytes:
fname = sub.get('file_name') or f'{uuid...}{ext}'
p = os.path.join(_TEMP_DIR, fname); open(p, 'wb').write(pt)
`os.path.join(base, '../../x')` (or an absolute path) escapes `_TEMP_DIR`,
so a remote sender can write attacker-chosen content to an arbitrary path
on the bot host — e.g. drop a file into an autoload location. It is a write
primitive reachable by anyone who can message the bot.
Fix: collapse the inbound name to its basename before use. A normal
filename has no directory component, so basename is the identity for
legitimate names and behavior is unchanged; only `../` / absolute paths
are neutralized. Empty names still fall through to the uuid fallback.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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现象
frontends/wechatapp.py的_dl_media把入站消息里的file_name直接用来落盘解密后的媒体内容。file_name来自对方消息，攻击者可控。根因
os.path.join(base, '../../x')（或绝对路径）会逃出_TEMP_DIR。任何能给 bot 发消息的人，就能把自己控制的内容写到宿主机任意路径——比如丢进自启动目录。这是一个远程可达的任意写原语。修法
落盘前把入站名收敛成 basename。正常文件名没有目录部分，basename 是恒等，合法行为完全不变；只有
..// 绝对路径被中和。空名仍走原来的 uuid 兜底。实测
python3 -m py_compile frontends/wechatapp.py通过../../../../etc/cron.d/evil→evil、/root/.bashrc→.bashrc、photo.jpg→photo.jpg（恒等）、空名 → uuid 兜底单文件单行改动，行为对合法文件名不变。