Flag: `ctfzone{2e71b73d355eac0ce5a90b53bf4c03b2}`
```from pwn import *
s = remote('crypto-01.v7frkwrfyhsjtbpfcppnu.ctfz.one', 1337)
s.sendafter('Login: ', 'A' * 7 + 'B' * 16 + 'C')s.sendafter('$ ', 'session --get')
iv, ct = s.recvline().strip().split(':')
# _ = unknown character# pt[0:16]  = '_________AAAAAAA'# pt[16:32] = 'BBBBBBBBBBBBBBBB'# pt[32:48] = 'C_______regular\x01'
mask = xor('regular\x01', 'root\x04\x04\x04\x04')ct = b64d(ct)ct = ct[:24] + xor(ct[24:32], mask) + ct[32:]
s.sendafter('$ ', 'session --set {}:{}'.format(iv, b64e(ct)))s.sendafter('$ ', 'cat flag.txt')
print s.recvline().strip()```