Expletive#
oh no! it seems like only some of the characters on my keyboard are working…
Given this file
blacklist = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
def security_check(s):
return any(c in blacklist for c in s) or s.count('_') > 50
BUFFER_SIZE = 36
while True:
cmds = input("> ")
if security_check(cmds):
print("invalid input")
else:
if len(cmds) > BUFFER_SIZE:
print(open("flag.txt", "r").read())
break
else:
print("nope")So, to get the flag, you need to provide an input that satisfies three conditions:
- It must not contain any alphanumeric characters (a-z, A-Z, 0-9).
- The number of underscore characters (
_) must not exceed 50. - The total length of the input string must be greater than 36 characters.
python3 -c "print('_' * 37)" | nc challs.bcactf.com 38421 ─╯
> bcactf{fudG3_5hOo7_d4rn100}Flag: bcactf{fudG3_5hOo7_d4rn100}