Joints 2018 Final - Crypto & Reversing

#!/usr/bin/env python
import hashlib
from Crypto.Cipher import AES
import os
import sys

BLOCK_SIZE = 16
LIMIT_LEN_BAWAH = 16
LIMIT_LEN_ATAS = 48
key = os.urandom(16)
iv = os.urandom(16)

flag = open('flag.txt').read()

len_pad = lambda tes : (BLOCK_SIZE - (len(tes) % BLOCK_SIZE))
pad = lambda tes : chr(len_pad(tes))*len_pad(tes) + tes
unpad = lambda tes : tes[ord(tes[0]):]

def encrypt(plain,ivs,key):
    obj = AES.new(key,AES.MODE_CBC,ivs)
    paded_plaintext = pad(plain)
    return obj.encrypt(paded_plaintext)

def decrypts(ciphers,ivs,key):
    obj = AES.new(key,AES.MODE_CBC,ivs)
    unpad_plaintext = unpad(obj.decrypt(ciphers))
    return unpad_plaintext

if __name__ == "__main__":
    encrypted_flag = encrypt(flag,iv,key)
    decrypted_flag = decrypts(encrypted_flag,iv,key)
    sys.stdout.write('--WELCOME TO EZ CHALLENGE---\n')
    sys.stdout.write('\nIni hasil enkripsi flag-nya : ')
    sys.stdout.write(encrypted_flag.encode('hex') + '\n')
    sys.stdout.write("\nBuka Jasa Dekrip Gan\n")
    sys.stdout.flush()
    for i in range(300):
        sys.stdout.write("\nMasukin Cipher : ")
        sys.stdout.flush()
        enc = raw_input()
        try:
            enc = enc.decode('hex')
        except:
            sys.stdout.write("\nMasukin dalam bentuk hex gan\n")
            sys.stdout.flush()
            break
    sys.stdout.write("\nMasukan indeks IV yang mau diganti nilainya : ")
    sys.stdout.flush()
    IV_lamaa = raw_input()

    sys.stdout.write("\nMasukan nilai IV yang baru (hex) : ")
    sys.stdout.flush()
    IV_baruu = raw_input()
    try:
        IV_lamaa = int(IV_lamaa)
        IV_baruu = IV_baruu.decode('hex')
    except:
        sys.stdout.write("\nJangan aneh2 gan!\n")
        sys.stdout.flush()
        break
        if len(enc) > LIMIT_LEN_ATAS:
            sys.stdout.write("\nMelewati batas gan !")
            sys.stdout.flush()
            break
        elif len(enc) < LIMIT_LEN_BAWAH:
            sys.stdout.write("\nKurang gan len-nya")
            sys.stdout.flush()
            break
        else:
            iv_baru = iv[:IV_lamaa] + IV_baruu + iv[IV_lamaa+1:]
            dec_str = decrypts(enc,iv_baru,key)
            dec_str_wrap = hashlib.sha256(dec_str).hexdigest()
            sys.stdout.write("Hasil dekrip : " + dec_str_wrap + '\n')
            sys.stdout.flush()

sys.stdout.write("\nMasukan indeks IV yang mau diganti nilainya : ")
sys.stdout.flush()
IV_lamaa = raw_input()

sys.stdout.write("\nMasukan nilai IV yang baru (hex) : ")
sys.stdout.flush()
IV_baruu = raw_input()

#!/usr/bin/env python
# socat TCP-LISTEN:5000,reuseaddr,fork EXEC:./go-block.py
import hashlib
from Crypto.Cipher import AES
import os
import sys

BLOCK_SIZE = 16
LIMIT_LEN_BAWAH = 16
LIMIT_LEN_ATAS = 48
key = os.urandom(16)
iv = os.urandom(16)

# flag = open('flag.txt').read()
flag = 'JOINTS18{abcdefghijklmnoprstuvw}'

len_pad = lambda tes : (BLOCK_SIZE - (len(tes) % BLOCK_SIZE))
pad = lambda tes : chr(len_pad(tes))*len_pad(tes) + tes
unpad = lambda tes : tes[ord(tes[0]):]

def encrypt(plain,ivs,key):
    obj = AES.new(key,AES.MODE_CBC,ivs)
    paded_plaintext = pad(plain)
    return obj.encrypt(paded_plaintext)

def decrypts(ciphers,ivs,key):
    obj = AES.new(key,AES.MODE_CBC,ivs)
    unpad_plaintext = unpad(obj.decrypt(ciphers))
    return unpad_plaintext

if __name__ == "__main__":
    print 'iv:', repr(iv)
    encrypted_flag = encrypt(flag,iv,key)
    decrypted_flag = decrypts(encrypted_flag,iv,key)
    sys.stdout.write('--WELCOME TO EZ CHALLENGE---\n')
    sys.stdout.write('\nIni hasil enkripsi flag-nya : ')
    sys.stdout.write(encrypted_flag.encode('hex') + '\n')
    sys.stdout.write("\nBuka Jasa Dekrip Gan\n")
    sys.stdout.flush()
    for i in range(300):
        sys.stdout.write("\nMasukin Cipher : ")
        sys.stdout.flush()
        enc = raw_input()
        try:
            enc = enc.decode('hex')
        except:
            sys.stdout.write("\nMasukin dalam bentuk hex gan\n")
            sys.stdout.flush()
            break
    sys.stdout.write("\nMasukan indeks IV yang mau diganti nilainya : ")
    sys.stdout.flush()
    IV_lamaa = raw_input()

    sys.stdout.write("\nMasukan nilai IV yang baru (hex) : ")
    sys.stdout.flush()
    IV_baruu = raw_input()
    try:
        IV_lamaa = int(IV_lamaa)
        IV_baruu = IV_baruu.decode('hex')
    except:
        sys.stdout.write("\nJangan aneh2 gan!\n")
        sys.stdout.flush()
        break
        if len(enc) > LIMIT_LEN_ATAS:
            sys.stdout.write("\nMelewati batas gan !")
            sys.stdout.flush()
            break
        elif len(enc) < LIMIT_LEN_BAWAH:
            sys.stdout.write("\nKurang gan len-nya")
            sys.stdout.flush()
            break
        else:
            iv_baru = iv[:IV_lamaa] + IV_baruu + iv[IV_lamaa+1:]
            dec_str = decrypts(enc,iv_baru,key)

            print 'iv_baru:', repr(iv_baru)
            print 'dec_str:', dec_str

            dec_str_wrap = hashlib.sha256(dec_str).hexdigest()
            sys.stdout.write("Hasil dekrip : " + dec_str_wrap + '\n')
            sys.stdout.flush()

hashlib.sha256('').hexdigest() == 'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855'

from pwn import *
import hashlib, string

p = remote('localhost', 5000)

p.recvuntil('flag-nya :')
enc = p.recvline().strip()
print enc

array = []

for i in range(256):
    p.recvuntil('Masukin Cipher : ')
    p.sendline(enc)

    p.recvuntil('yang mau diganti nilainya : ')
    p.sendline('0')

    payload = hex(i)[2:]
    if len(payload) == 1:
        payload = '0' + payload

    p.recvuntil('yang baru (hex) : ')
    p.sendline(payload)

    p.recvuntil('Hasil dekrip : ')
    wow = p.recvline().strip()
    array.append(wow)

z = '\n'.join(array)
print z

flag = ''
sp = string.printable

while 'JOINTS18' not in flag:
    for c in sp:
        pload = c + flag
        check = hashlib.sha256(pload).hexdigest()
        if check in z:
            flag = pload
            print flag
            break

p.close()

kiwo = [34, 28, 8, 29, 54, 45, 0, 5, 8, 2, 6, 7, 0, 54, 39, 12, 2, 54, 27, 8, 54]
# print(len(kiwo))
tengen = [0, 0, 0, 0, 0, 0, 0, 24, 8, 5, 8, 9, 8, 51, 17, 43, 12, 111, 66, 17, 54]
# print(len(tengen))

kiri = ''
kanan = ''
flag = []

for i in kiwo:
  flag.append(i ^ 0x69)
  kiri += chr(i ^ 0x69)

for j in range(len(tengen)):
  kanan += chr(flag[j] ^ tengen[j])

print('Flag: JOINTS18{\%s}' % (kiri+kanan))