solve_oracle_of_blair.py

from sock import Sock
from string import printable
so = Sock('crypto.2021.chall.actf.co:21112')
len_flag=25
def recv(x):
	so.read_until(b"give input: ")
	so.send_line(x)
	res = so.read_line().strip()
	return res

flag=''
while True:
	i=1
	len_flag=len_flag-i
	res=recv((b'a'*(23+len_flag)+b'{}').hex())[32:96] 	
	for char in printable:	
		#print(char)
		ans=recv((b'a'*(23+len_flag)+flag.encode()+char.encode()+b'{}').hex())[32:96]
		if ans==res:
			flag+=char
			print(flag)
			i+=1
			break
	if len(flag)==25:
		break
print(flag)