Linux-Unix

A while back the FileMaker Server (FMS) installer for Ubuntu Linux started checking the currently installed web server versions and giving warnings and an interactive prompt (!) in case of outdated versions. This is rather annoying if you like to install/upgrade your FMS non-interactively. Using ansible, for example, your playbook would just hang and you would start wondering what’s going on. Let’s see what is actually happening, why it’s happening, and how to solve it. ...

Say you want to allow a non-root user on Linux to execute a couple of scripts as root or another user with more privileges. A common way of doing this is to make an entry in the sudoers file. If the scripts are written in Python, it could look something like this: johndoe ALL=(ALL) /usr/bin/python3 /opt/utils/*.py Essentially, this means that the user johndoe can execute /usr/bin/python3 /opt/utils/*.py on any machine (ALL) as any user ((ALL)). ...

This is a write-up for Hack the Box’s just retired Tabby machine. We first find a Directory Traversal vulnerability in a web app and use it to obtain credentials for a Tomcat server running on the same host. Cracking a zip password of a discovered file then gives us access to the first low-priv user. From there, we exploit the fact that our user is part of the lxd group, create a small Alpine Linux image and eventually mount the host’s root file system in a new container. ...

To boot Linux without Data Execution Prevention, so that the OS doesn’t mark certain memory regions as non-executable, we… 1.) … boot and enter the GRUB menu (hold Shift-key on boot*) 2.) … select the OS and press e to edit the commands and kernel parameters 3.) … add noexec=off and/or noexec32=off (depending on what you want) in the linux line 4.) … then boot with Ctrl-x ...

Recently, I needed to transfer a binary over a very limited network connection allowing only small packets to be sent. I ended up splitting the binary into pieces on my Linux box and reassembled the pieces on the target Windows host. If, for some reason, you cannot use easier means like IP fragmentation and work with a smaller maximum transfer unit (MTU), here’s how to do the splitting and re-combining. ...