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April 14, 2017 12:45
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Finds the Function's Load Address
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| #!/usr/bin/env python | |
| #Taken from http://uaf.io/exploitation/misc/2016/04/02/Finding-Functions.html | |
| from pwn import * | |
| import sys, os | |
| wordSz = 4 | |
| hwordSz = 2 | |
| bits = 32 | |
| PIE = 0 | |
| def leak(address, size): | |
| with open('/proc/%s/mem' % pid) as mem: | |
| mem.seek(address) | |
| return mem.read(size) | |
| def findModuleBase(pid, mem): | |
| name = os.readlink('/proc/%s/exe' % pid) | |
| with open('/proc/%s/maps' % pid) as maps: | |
| for line in maps: | |
| if name in line: | |
| addr = int(line.split('-')[0], 16) | |
| mem.seek(addr) | |
| if mem.read(4) == "\x7fELF": | |
| bitFormat = u8(leak(addr + 4, 1)) | |
| if bitFormat == 2: | |
| global wordSz | |
| global hwordSz | |
| global bits | |
| wordSz = 8 | |
| hwordSz = 4 | |
| bits = 64 | |
| return addr | |
| log.failure("Module's base address not found.") | |
| sys.exit(1) | |
| def findIfPIE(addr): | |
| e_type = u8(leak(addr + 0x10, 1)) | |
| if e_type == 3: | |
| return addr | |
| else: | |
| return 0 | |
| def findPhdr(addr): | |
| if bits == 32: | |
| e_phoff = u32(leak(addr + 0x1c, wordSz).ljust(4, '\0')) | |
| else: | |
| e_phoff = u64(leak(addr + 0x20, wordSz).ljust(8, '\0')) | |
| return e_phoff + addr | |
| def findDynamic(Elf32_Phdr, moduleBase, bitSz): | |
| if bitSz == 32: | |
| i = -32 | |
| p_type = 0 | |
| while p_type != 2: | |
| i += 32 | |
| p_type = u32(leak(Elf32_Phdr + i, wordSz).ljust(4, '\0')) | |
| return u32(leak(Elf32_Phdr + i + 8, wordSz).ljust(4, '\0')) + PIE | |
| else: | |
| i = -56 | |
| p_type = 0 | |
| while p_type != 2: | |
| i += 56 | |
| p_type = u64(leak(Elf32_Phdr + i, hwordSz).ljust(8, '\0')) | |
| return u64(leak(Elf32_Phdr + i + 16, wordSz).ljust(8, '\0')) + PIE | |
| def findDynTable(Elf32_Dyn, table, bitSz): | |
| p_val = 0 | |
| if bitSz == 32: | |
| i = -8 | |
| while p_val != table: | |
| i += 8 | |
| p_val = u32(leak(Elf32_Dyn + i, wordSz).ljust(4, '\0')) | |
| return u32(leak(Elf32_Dyn + i + 4, wordSz).ljust(4, '\0')) | |
| else: | |
| i = -16 | |
| while p_val != table: | |
| i += 16 | |
| p_val = u64(leak(Elf32_Dyn + i, wordSz).ljust(8, '\0')) | |
| return u64(leak(Elf32_Dyn + i + 8, wordSz).ljust(8, '\0')) | |
| def getPtr(addr, bitSz): | |
| with open('/proc/%s/maps' % sys.argv[1]) as maps: | |
| for line in maps: | |
| if 'libc-' in line and 'r-x' in line: | |
| libc = line.split(' ')[0].split('-') | |
| i = 3 | |
| while True: | |
| if bitSz == 32: | |
| gotPtr = u32(leak(addr + i*4, wordSz).ljust(4, '\0')) | |
| else: | |
| gotPtr = u64(leak(addr + i*8, wordSz).ljust(8, '\0')) | |
| if (gotPtr > int(libc[0], 16)) and (gotPtr < int(libc[1], 16)): | |
| return gotPtr | |
| else: | |
| i += 1 | |
| continue | |
| def findLibcBase(ptr): | |
| ptr &= 0xfffffffffffff000 | |
| while leak(ptr, 4) != "\x7fELF": | |
| ptr -= 0x1000 | |
| return ptr | |
| def findSymbol(strtab, symtab, symbol, bitSz): | |
| if bitSz == 32: | |
| i = -16 | |
| while True: | |
| i += 16 | |
| st_name = u32(leak(symtab + i, 2).ljust(4, '\0')) | |
| if leak( strtab + st_name, len(symbol)+1 ).lower() == (symbol.lower() + '\0'): | |
| return u32(leak(symtab + i + 4, 4).ljust(4, '\0')) | |
| else: | |
| i = -24 | |
| while True: | |
| i += 24 | |
| st_name = u64(leak(symtab + i, 4).ljust(8, '\0')) | |
| if leak( strtab + st_name, len(symbol)).lower() == (symbol.lower()): | |
| return u64(leak(symtab + i + 8, 8).ljust(8, '\0')) | |
| def lookup(pid, symbol): | |
| with open('/proc/%s/mem' % pid) as mem: | |
| moduleBase = findModuleBase(pid, mem) | |
| log.info("Module's base address:................. " + hex(moduleBase)) | |
| global PIE | |
| PIE = findIfPIE(moduleBase) | |
| if PIE: | |
| log.info("Binary is PIE enabled.") | |
| else: | |
| log.info("Binary is not PIE enabled.") | |
| modulePhdr = findPhdr(moduleBase) | |
| log.info("Module's Program Header:............... " + hex(modulePhdr)) | |
| moduleDynamic = findDynamic(modulePhdr, moduleBase, bits) | |
| log.info("Module's _DYNAMIC Section:............. " + hex(moduleDynamic)) | |
| moduleGot = findDynTable(moduleDynamic, 3, bits) | |
| log.info("Module's GOT:.......................... " + hex(moduleGot)) | |
| libcPtr = getPtr(moduleGot, bits) | |
| log.info("Pointer from GOT to a function in libc: " + hex(libcPtr)) | |
| libcBase = findLibcBase(libcPtr) | |
| log.info("Libc's base address:................... " + hex(libcBase)) | |
| libcPhdr = findPhdr(libcBase) | |
| log.info("Libc's Program Header:................. " + hex(libcPhdr)) | |
| PIE = findIfPIE(libcBase) | |
| libcDynamic = findDynamic(libcPhdr, libcBase, bits) | |
| log.info("Libc's _DYNAMIC Section:............... " + hex(libcDynamic)) | |
| libcStrtab = findDynTable(libcDynamic, 5, bits) | |
| log.info("Libc's DT_STRTAB Table:................ " + hex(libcStrtab)) | |
| libcSymtab = findDynTable(libcDynamic, 6, bits) | |
| log.info("Libc's DT_SYMTAB Table:................ " + hex(libcSymtab)) | |
| symbolAddr = findSymbol(libcStrtab, libcSymtab, symbol, bits) | |
| log.success("%s loaded at address:.............. %s" % (symbol, hex(symbolAddr + libcBase))) | |
| if __name__ == "__main__": | |
| log.info("Manual usage of pwnlib.dynelf") | |
| if len(sys.argv) == 3: | |
| pid = sys.argv[1] | |
| symbol = sys.argv[2] | |
| lookup(pid, symbol) | |
| else: | |
| log.failure("Usage: %s PID SYMBOL" % sys.argv[0]) |
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