Odo Head Spa offered by Odo Beauty Care Limited

Odo Beauty Care Limited Welcome to our first Odo Head Spa Salon located at 9F Pennington Com Bldg., 17 Pennington Street, Causeway Bay (Near to Regal Hotel, Hong Kong and above 7-11) 香港铜锣湾边寧顿亍 17号 边寧顿商业大厅厦电梯 9字 鄰近香港富豪酒店,7-11 樓上 TEL: 9010-1586 English and Japanese only (英/日语) Email: info@odo.com.hk BY APPOINTMENT ONLY 完全予約制 敬请电約

網頁

Powered By Blogger

2020年6月10日星期三

Defcon 2015 Coding Skillz 1 Writeup

Just connecting to the service, a 64bit cpu registers dump is received, and so does several binary code as you can see:



The registers represent an initial cpu state, and we have to reply with the registers result of the binary code execution. This must be automated becouse of the 10 seconds server socket timeout.

The exploit is quite simple, we have to set the cpu registers to this values, execute the code and get resulting registers.

In python we created two structures for the initial state and the ending state.

cpuRegs = {'rax':'','rbx':'','rcx':'','rdx':'','rsi':'','rdi':'','r8':'','r9':'','r10':'','r11':'','r12':'','r13':'','r14':'','r15':''}
finalRegs = {'rax':'','rbx':'','rcx':'','rdx':'','rsi':'','rdi':'','r8':'','r9':'','r10':'','r11':'','r12':'','r13':'','r14':'','r15':''}

We inject at the beginning several movs for setting the initial state:

for r in cpuRegs.keys():
    code.append('mov %s, %s' % (r, cpuRegs[r]))

The 64bit compilation of the movs and the binary code, but changing the last ret instruction by a sigtrap "int 3"
We compile with nasm in this way:

os.popen('nasm -f elf64 code.asm')
os.popen('ld -o code code.o ')

And use GDB to execute the code until the sigtrap, and then get the registers

fd = os.popen("gdb code -ex 'r' -ex 'i r' -ex 'quit'",'r')
for l in fd.readlines():
    for x in finalRegs.keys():
           ...

We just parse the registers and send the to the server in the same format, and got the key.


The code:

from libcookie import *
from asm import *
import os
import sys

host = 'catwestern_631d7907670909fc4df2defc13f2057c.quals.shallweplayaga.me'
port = 9999

cpuRegs = {'rax':'','rbx':'','rcx':'','rdx':'','rsi':'','rdi':'','r8':'','r9':'','r10':'','r11':'','r12':'','r13':'','r14':'','r15':''}
finalRegs = {'rax':'','rbx':'','rcx':'','rdx':'','rsi':'','rdi':'','r8':'','r9':'','r10':'','r11':'','r12':'','r13':'','r14':'','r15':''}
fregs = 15

s = Sock(TCP)
s.timeout = 999
s.connect(host,port)

data = s.readUntil('bytes:')


#data = s.read(sz)
#data = s.readAll()

sz = 0

for r in data.split('\n'):
    for rk in cpuRegs.keys():
        if r.startswith(rk):
            cpuRegs[rk] = r.split('=')[1]

    if 'bytes' in r:
        sz = int(r.split(' ')[3])



binary = data[-sz:]
code = []

print '[',binary,']'
print 'given size:',sz,'bin size:',len(binary)        
print cpuRegs


for r in cpuRegs.keys():
    code.append('mov %s, %s' % (r, cpuRegs[r]))


#print code

fd = open('code.asm','w')
fd.write('\n'.join(code)+'\n')
fd.close()
Capstone().dump('x86','64',binary,'code.asm')

print 'Compilando ...'
os.popen('nasm -f elf64 code.asm')
os.popen('ld -o code code.o ')

print 'Ejecutando ...'
fd = os.popen("gdb code -ex 'r' -ex 'i r' -ex 'quit'",'r')
for l in fd.readlines():
    for x in finalRegs.keys():
        if x in l:
            l = l.replace('\t',' ')
            try:
                i = 12
                spl = l.split(' ')
                if spl[i] == '':
                    i+=1
                print 'reg: ',x
                finalRegs[x] = l.split(' ')[i].split('\t')[0]
            except:
                print 'err: '+l
            fregs -= 1
            if fregs == 0:
                #print 'sending regs ...'
                #print finalRegs
                
                buff = []
                for k in finalRegs.keys():
                    buff.append('%s=%s' % (k,finalRegs[k]))


                print '\n'.join(buff)+'\n'

                print s.readAll()
                s.write('\n'.join(buff)+'\n\n\n')
                print 'waiting flag ....'
                print s.readAll()

                print '----- yeah? -----'
                s.close()
                



fd.close()
s.close()





Related news


沒有留言:

發佈留言