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| #!/usr/bin/env python
import re
import string
import sock as s
def parse_line(line):
stack = []
while len(line) > 0:
match = re.search("(^\d+)(.+)", line)
if match:
num, line = match.group(1), match.group(2)
stack.append(num)
elif line[0] in "*+^":
op = line[0]
if len(stack) > 1:
stack, a, b = stack[:-2], stack[-2], stack[-1]
else:
stack, a, b = stack[:-1], stack[-1], "0"
stack.append("{}{}{}".format(a, op, b))
line = line[1:]
if op == "+" and all(c.isdigit() for c in b):
result, line = line[0], line[1:]
stack, a = stack[:-1], stack[-1]
stack.append("{}{}{}".format(a, "=", result))
else:
stack.append(line[0])
line = line[1:]
assert len(stack) == 1
return stack[0]
def solve(x, coeffs, mod):
ret = 0
assert(len(coeffs) == 12)
for e in range(len(coeffs)):
ret += coeffs[e]*pow(x,len(coeffs)-e-1)
ret %= mod
return ret % mod
def get_coeffs(term):
ret = []
term += "*x^0"
summands = term.split("+")
i = 11
for summand in summands:
coeff, rest = summand.split("*")
x, exp = rest.split("^")
while i > int(exp):
ret.append(0)
i -= 1
ret.append(int(coeff))
i -= 1
while i >= 0:
ret.append(0)
i -= 1
return ret
def calc(term, x, mod):
coeffs = get_coeffs(term)
for i in range(mod):
result = solve(i, coeffs, mod) % mod
if result == x:
return i
f = s.Sock("asis-ctf.ir", 65433, timeout=10)
print f.read_until("START")
while True:
line = f.read_until("END")[:-4]
stack = [parse_line(term) for term in line.split(",")[:32]]
num_count = len([item.split("=")[1] for item in stack if item.split("=")[1].isdigit()])
res = []
for item in stack:
term,var = item.split("=")
if var.isdigit():
charset = string.digits
else:
charset = string.ascii_lowercase
new = calc(term, (charset.find(var)), len(charset))
res.append(charset[new])
f.send("".join(res))
f.read_until("OK\n")
print f.read_all()
print "finished"
|