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Hack your way through Stripe's Capture the Flag

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Re: Hack your way through Stripe's Capture the Flag

#91

Post by jetsnoc »

sdfjkl wrote: post #3
pavel_lishin wrote: post #2

I keep getting this: level01@ctf:/tmp/tmp.c6PoABNv99$ ls bash: fork: retry: Resource temporarily unavailable

Someone set us up the (fork)bomb. That didn't take long. Sadly it's a bit silly and ruins all the fun for the rest of us :-/

I think people must be brute-forcing level03 instead of figuring out how to calculate the index they need?! That could work but you won't know how address math/pointer math actually works. This isn't really fair to yourself, you'll be skipping out on understanding what a word size is.

But, for those uninterested in the minutiae of how it actually works if you are going to brute force this please compile this application on your OWN 64-bit system (gcc -g -o level03 level03.c) and run your nasty for() loop there so you aren't hosing the processes on this system!

Re: Hack your way through Stripe's Capture the Flag

#92

Post by gdb »

[deleted] wrote: post #89

[deleted]

I think the machine was actually hosed due to fork bomb. (I kept bumping the rlimits as more people logged in and ran up against nprocs, but the last time I clearly just bumped nprocs way too high. Live and learn....)

You certainly should be able to solve all of the levels without tons of brute force though.

Re: Hack your way through Stripe's Capture the Flag

#93

Post by lftl »

gqwo wrote: post #88

Am i just too stupid or is there a problem with level2, i can open files like /etc/passwd but not /home/level03/.password

Pretty sure it's broken right now. It was working earlier, but it returns nothing now, and the password that was in place doesn't work any more.

Re: Hack your way through Stripe's Capture the Flag

#94

Post by gravitronic »

lftl wrote: post #93
gqwo wrote: post #88

Am i just too stupid or is there a problem with level2, i can open files like /etc/passwd but not /home/level03/.password

Pretty sure it's broken right now. It was working earlier, but it returns nothing now, and the password that was in place doesn't work any more.

For a second I thought it was a brilliant trick and the password for level03 was blank.. but no. haha.

Re: Hack your way through Stripe's Capture the Flag

#95

Post by chrisacky »

gdb wrote: post #90
heywire wrote: post #69

Earlier quoted context omitted.

Must be fun watching all of the attempts... Do you have any way to monitor progress?

We don't have an exposed way. We'll probably do a summary blog post in the future with stats though!

I've been trying to read $ history

Failed. :) I figured that would of been an easy way to progress through the levels. Read bash history from other users.

Re: Hack your way through Stripe's Capture the Flag

#96

Post by gdb »

lftl wrote: post #93
gqwo wrote: post #88

Am i just too stupid or is there a problem with level2, i can open files like /etc/passwd but not /home/level03/.password

Pretty sure it's broken right now. It was working earlier, but it returns nothing now, and the password that was in place doesn't work any more.

We're taking a look! (Bleh, spinup scripts not working as well as you'd like....)

Re: Hack your way through Stripe's Capture the Flag

#97

Post by gqwo »

gdb wrote: post #96
lftl wrote: post #93

Earlier quoted context omitted.

Pretty sure it's broken right now. It was working earlier, but it returns nothing now, and the password that was in place doesn't work any more.

We're taking a look! (Bleh, spinup scripts not working as well as you'd like....)

ah, now it works thanks

Re: Hack your way through Stripe's Capture the Flag

#98

Post by jessepollak »

gdb wrote: post #96
lftl wrote: post #93

Earlier quoted context omitted.

Pretty sure it's broken right now. It was working earlier, but it returns nothing now, and the password that was in place doesn't work any more.

We're taking a look! (Bleh, spinup scripts not working as well as you'd like....)

It's working now! Before it wasn't even printing my user agent and info though.

Re: Hack your way through Stripe's Capture the Flag

#99

Post by jessepollak »

olalonde wrote: post #71
jessepollak wrote: post #30

anyone have any good resources for understanding the basics of all of this?

For level 1 to 3, Google those: system() exploit, never trust user input, buffer overflow

thanks! I got 1 and 2 before I saw this, but we'll see how I do on 3.

Re: Hack your way through Stripe's Capture the Flag

#100

Post by unixpickle »

gue5t wrote: post #36
jc4p wrote: post #28

Earlier quoted context omitted.

Same, the only thing I can think of is doing something with the pointers in the fns variable in main, but I can't quite figure out what to do.

I've been playing with nm, but without a hex editor I feel crippled :/

You could also use objdump -d to decompile the binary.
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