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Zcentric

The old blog

Posts

Notes on iPhone development, Linux, Django and infrastructure, written between 2008 and 2016.

  1. SPF DNS Lookup check for Nagios

    Did you know that there is a max number of DNS lookups that can be done for an SPF lookup. The number is 10 and that includes any a or mx records along with includes to different hosts. I noticed this when I ran a SPF …

  2. No more apt-get prompts

    Sometimes you might be installing a package and don’t want it to prompt at all. Apt will prompt you a lot sometimes if you just do an apt-get install packageName. For example If you want to install, if there are …

  3. grep only stderr from a command

    So sometimes you have a command where you want to only grep stderr. For example I use Cronic to manage all my cronjobs. It’s really nice since it sends a nicely formatted email back to you if a command returns …

  4. Remove internal hosts in postfix

    A proper way to setup your network is to have a postfix relay server sitting somewhere on your network that every other server has access to via port 25. Now your relay server(s) are the only ones that should have …

  5. How many bits per point in a whisper file in graphite

    Tweet This is an easy one. You do an ls over a whisper file and get something like 1.1M -rwxr-xr-x  1 root root 1.1M Aug  9 11:06 Active.wsp Now you are planning to save more metrics in your graphite server or …

  6. Google Authenticator with OpenVPN for 2 factor auth

    Tweet This post will describe how to get it working with Ubuntu 12.04. It should work with other versions along with other Linux distros. The only difference is the package names might change. Install the packages Run …

  7. Stripe CTF 2.0 Level 2

    Tweet About This is another PHP level where they emulate a little social network where you can upload a image of to use for your profile. This level goes into what is wrong if you don’t force an output file type …

  8. Stripe CTF 2.0 Level 3

    Tweet About Here is a python level. They claim this one is more secure and it is a bit more but not really. Hint Given There really is no hint given other then in the code Problem in the code So take a look at line #86 …

  9. Stripe CTF 2.0 Level 0

    Tweet About This is the first level of Stripe’s challenge. You start off in an app that stores secret passwords for users and you have an option to store a password or retrive a password. Hint Given So the …

  10. Stripe CTF 2.0 Level 1

    Tweet About In this level you are given a form where you have to “guess” the secret password to get the password to the next level. This level is in PHP and requires you to really looking at the code to …

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