Friday, June 5, 2020

ASIS CTF Quals 2015 - Sawthis Writeup - Srand Remote Prediction


The remote service ask for a name, if you send more than 64 bytes, a memory leak happens.
The buffer next to the name's is the first random value used to init the srand()


If we get this value, and set our local srand([leaked] ^ [luckyNumber]) we will be able to predict the following randoms and win the game, but we have to see few details more ;)

The function used to read the input until the byte \n appears, but also up to 64 bytes, if we trigger this second condition there is not 0x00 and the print shows the random buffer :)

The nickname buffer:



The seed buffer:



So here it is clear, but let's see that the random values are computed with several gpu instructions which are decompiled incorrectly:







We tried to predict the random and aply the gpu divisions without luck :(



There was a missing detail in this predcitor, but there are always other creative ways to do the things.
We use the local software as a predictor, we inject the leaked seed on the local binary of the remote server and got a perfect syncronization, predicting the remote random values:




The process is a bit ugly becouse we combined automated process of leak exctraction and socket interactive mode, with the manual gdb macro.




The macro:



















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Why Should you take care of Day by Day Pregnancy?


Taking care of your baby and your body on Day by Day Pregnancy

If you're pregnant now, you should know how important is to take care of yourself and your future baby. Well, pregnant is something that every married girl dream of. Sooner or later, after you married and settle down, your husband and yourself will love to have a new comer in your house, especially if only both of you living together without living with your other family members like your parents, grandparents or any other sibling

It is extremely important to take care of your baby and yourself on day by day pregnancy. You must eat the right food and make sure that the food you ate will not harm your baby and yourself.

Yes, pregnant is great, eating right and good nutrition food for your baby is a must! but how about the excessive pounds you will get when you're pregnant and after you delivered? is it something that you must consider of? as a woman, it is extremely important to take care of our weight, fat means ugly, and what happen when we're fat? of course, we will lost our self confident at first. And what happen when we lost our self confident?

If you're not even dare to look at yourself in the mirror, do you think that your belove husband will like to hug you, kiss you and look at you like before? even if your husband looks at you like before, you might probably think, "what's wrong with him, he look at my fat meat all the time!"

well, dont' let this happens to you. It is Extremely important to get rid of the excessive fat during and after pregnancy.

Here at Pregnancy Without Pounds, I found an absolutely great course and guide for your day by day pregnancy course, free of charge. They'll send you article and some guide several times a week for you to learn how to take care of yourself and your baby.

This is what they claim: