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diff --git a/posts/redpwn2021.md b/posts/redpwn2021.md index aaf29d0..9ac8e29 100644 --- a/posts/redpwn2021.md +++ b/posts/redpwn2021.md @@ -665,18 +665,22 @@ remaining possibilities until it got longer output from the program, but laziness took over and I decided that spending 45 minutes doing very dull work was more worth it instead. -### Willem's part in the CTF +## Willem's part in the CTF Hi, Willem here. + In this part I will talk about my experience during the CTF and The collaboration between me and Loek. -This was also my first CTF, just like Loek, because of this was quite -uncertain about my skill level. For example, I have no experience using Linux -systems, but from what I learned before the CTF it is quite essential. My fear of -not being able to do any off the challenge disappear quickly after we had completely -the beginner challenges. -With a simple sql injection I got my first real flag. +### web/orm-bad + +This was also my first CTF, just like Loek, because of this was quite uncertain +about my skill level. For example, I have no experience using Linux systems, +but from what I learned before the CTF it is quite essential. My fear of not +being able to do any of the challenges disappeared quickly after we had +completed the beginner challenges. With a simple sql injection I got my first +real flag: + ``` username: admin';-- password: @@ -688,55 +692,63 @@ when you're actually doing a challenge it's the last thing you think about. So, we didn't really know who was doing which challenge, but because we're a team of two this wasn't a big problem. -The most challenge were a bit to hard for me. Some I would get pretty far, but needed -Loek's help to solve it. Others I didn't even attempt to begin on. +The most challenge were a bit to hard for me. Some I would get pretty far, but +needed Loek's help to solve it. Others I didn't even attempt to begin on. + +### misc/the-substitution-game + +One challenge I spend a lot of time on was __The substitution game__. In the +substitution game you had to substitute certain parts of the input string to +get the desired output string. I got to level for of 6. Level 1 and 2 to were +really simple, but at level 3 you started to need to really understand the +game. -One challenge I spend a lot of time on was __The substitution game__. -In the substitution game you had to substitute certain parts of the input string -to get the desired output string. I got to level for of 6. -level 1 and 2 to were really simple, but at level 3 you started to need to -really understand the game. ``` level 3: initial: aaaaaaaaaaaaaa (the amount of a's varied) target: a ``` -The solution is really simple, but it's pretty hard to get to it. -You want to remove 'a's so I started with ```a => ``` , this turn all 'a's -to None and left you with an empty string. The problem is you can't substitute anything in -an empty string. The solution was ```aa => a```, this removed an 'a' every time -the initial string got checked. To get this solution you had to realize, -that the program would always substitute the first instance it would come -across, and the program was set to do way more than needed substitutions. -This would come handy in the next level. + +The solution is really simple, but it's pretty hard to get to it. You want to +remove 'a's so I started with `a => `, this turn all 'a's to None and left you +with an empty string. The problem is you can't substitute anything in an empty +string. The solution was `aa => a`, this removed an 'a' every time the initial +string got checked. To get this solution you had to realize, that the program +would always substitute the first instance it would come across, and the +program was set to do way more than needed substitutions. This would come handy +in the next level. + ``` level 4: initial: ggggggggggg (the amount of g's varied) target: ginkoid ``` + After completing level 3 this level looks very easy, just substitute the g's -like before ```gg => g``` and turn the last g into ginkoid ```g => ginkoid``` -, but this didn't work because of the way the program worked, after getting to a +like before `gg => g` and turn the last g into ginkoid `g => ginkoid` , but +this didn't work because of the way the program worked, after getting to a valid solution I didn't stop and the single g in ginkoid would also change to -ginkoid. You would get infinite ginkoid. -The solution was: -```gg => ginkoid; ginkoidginkoid => ginkoid; ginkoidg => ginkoid``` +ginkoid. You would get infinite ginkoid. The solution was: + +``` +gg => ginkoid; ginkoidginkoid => ginkoid; ginkoidg => ginkoid +``` + I began with noticing you couldn't just change the g, because that would also change the g in ginkoid. so double gg becomes ginkoid. We have to use the same -trick as in level 3 to gain only one ginkoid ```ginkoidginkoid => ginkoid``` -because of the way we changed the single g's to ginkoid it would only work -with an even amount of g's. In the case there was an uneven amount of g's -we would be left with ginkoidg, so we remove it ```ginkoidg => ginkoid```. +trick as in level 3 to gain only one ginkoid `ginkoidginkoid => ginkoid` +because of the way we changed the single g's to ginkoid it would only work with +an even amount of g's. In the case there was an uneven amount of g's we would +be left with ginkoidg, so we remove it `ginkoidg => ginkoid`. I found this challenge really enjoyable and during this challenge I noticed -that I most enjoy the puzzle aspect of computer science, puzzling for hours -to fix a bug and then finally finding a solution. - -I didn't complete many challenges and wasn't really able to help Loek, but -I really enjoyed the CTF. It's a really fun way to test your skills and -knowledge. In the end I'm really happy with the score we (mostly Loek) got -and I think I’ll take part in other CTFs in the future. +that I most enjoy the puzzle aspect of computer science, puzzling for hours to +fix a bug and then finally finding a solution. +I didn't complete many challenges and wasn't really able to help Loek, but I +really enjoyed the CTF. It's a really fun way to test your skills and +knowledge. In the end I'm really happy with the score we (mostly Loek) got and +I think I’ll take part in other CTFs in the future. ## Epilogue |