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| import threading
from pwn import *
from base64 import b64decode
from Crypto.Cipher import AES
from Crypto.Util.number import *
p = 217534615279223294476101434763509239207
g = 2
state = False
q = None
io = remote("121.40.247.133", "28419")
def adapt_message(message):
return message.ljust(16 - len(message) % 16 + len(message), b'\x00')
def get_encrypted_flag():
print("[++++++++++++++++] Enc_flag generating [++++++++++++++++]")
io.recvuntil("encrypted flag: b'")
encrypted_flag = b64decode(io.recvuntil("'"))
print("Enc_flag:", encrypted_flag)
print("[++++++++++++++++] Enc_flag generating completed [++++++++++++++++]")
return encrypted_flag
def gen_RSA_key():
print("[++++++++++++++++] RSA key generating [++++++++++++++++]")
io.recvuntil("e = ")
e = int(io.recvline())
print("e:", str(e))
io.recvuntil("n = ")
n = int(io.recvline())
print("n:", str(n))
io.recvuntil("partial d: ")
d0 = int(io.recvline())
print("d0:", str(d0))
print("[++++++++++++++++] RSA key generating completed [++++++++++++++++]")
return (e, n, d0)
def MITM_connect():
print("[++++++++++++++++] MITM connecting [++++++++++++++++]")
gamma = 1551
keyG = pow(g, gamma, p)
io.recvuntil("A: ")
keyA = int(io.recvline())
print(keyA)
io.sendlineafter("A: ", str(keyG))
io.recvuntil("B: ")
keyB = int(io.recvline())
io.sendlineafter("B: ", str(keyG))
keyC = pow(keyB, gamma, p)
keyS = pow(keyA, gamma, p)
keyC = long_to_bytes(keyC).rjust(16, b'\x00')
keyS = long_to_bytes(keyS).rjust(16, b'\x00')
cipherC = AES.new(keyC, AES.MODE_ECB)
cipherS = AES.new(keyS, AES.MODE_ECB)
print("keyC:", keyC)
print("keyS:", keyS)
print("[++++++++++++++++] MITM connecting completed [++++++++++++++++]")
return (cipherC, cipherS)
def MITM_conversation(cipherC, cipherS):
print("[++++++++++++++++] MITM conversation [++++++++++++++++]")
for i in range(5):
io.recvuntil("A: ")
messageA = io.recvline().strip()
messageA = long_to_bytes(int(messageA, 16))
messageA = cipherS.decrypt(messageA.rjust((16 - len(messageA) % 16) % 16 + len(messageA), b'\x00'))
print("A:", messageA)
randnum_begin = messageA.find(b'stamp:') + 6
randnum_end = messageA.find(b'\x00')
randnum = bytes(str((int(messageA[randnum_begin:randnum_end]) + 1) % 256), encoding="utf8")
new_messageA = messageA[:randnum_begin] + randnum
new_messageA = adapt_message(new_messageA)
print("G:", new_messageA)
s = cipherC.encrypt(new_messageA)
s = hex(bytes_to_long(s))[2:]
io.sendlineafter("A: ", s)
io.recvuntil("B: ")
messageB = io.recvline().strip()
messageB = long_to_bytes(int(messageB, 16))
messageB = cipherC.decrypt(messageB.rjust((16 - len(messageB) % 16) % 16 + len(messageB), b'\x00'))
print("B:", messageB)
randnum_begin = messageB.find(b'stamp:') + 6
randnum_end = messageB.find(b'\x00')
randnum = bytes(str((int(messageB[randnum_begin:randnum_end]) + 1) % 256), encoding="utf8")
if i == 4:
new_messageB = b'I want to get my AES-key.\ntimestamp:' + randnum
else:
new_messageB = messageB[:randnum_begin] + randnum
new_messageB = adapt_message(new_messageB)
print("G:", new_messageB)
s = cipherS.encrypt(new_messageB)
s = hex(bytes_to_long(s))[2:]
io.sendlineafter("B: ", s)
io.recvuntil("A: ")
res = io.recvline().strip()
res = long_to_bytes(int(res, 16))
res = cipherS.decrypt(res.rjust((16 - len(res) % 16) % 16 + len(res), b'\x00'))
print(res)
enc_begin = res.find(b'key: ') + 5
enc_end = res.find(b'\ntimestamp')
enc = res[enc_begin:enc_end]
print('enc:', enc)
print("[++++++++++++++++] MITM conversation completed [++++++++++++++++]")
io.close()
return bytes_to_long(enc)
def partial_p(p0, kbits, n):
global state
global q
PR.<x> = PolynomialRing(Zmod(n))
f = 2^kbits*x + p0
f = f.monic()
roots = f.small_roots(X=2^(1400-kbits), beta=0.65)
if roots:
x0 = roots[0]
p = gcd(2^kbits*x0 + p0, n)
if ZZ(p):
q = int(p)
state = True
def find_p(d0, kbits, e, n):
global state
global q
X = var('X')
for k in range(1, e+1):
print("\r{}/{}".format(k, e), end="")
if state == True:
return
results = solve_mod([e*d0*X - k*X*(n-X+1) + k*n == X], 2^kbits)
for x in results:
p0 = ZZ(x[0])
if p0 > 1 and n % p0 == 0:
q = int(p0)
state = True
return
daemon_thread = threading.Thread(target=partial_p, args=(p0,kbits,n,), daemon=True)
daemon_thread.start()
def main():
encrypted_flag = get_encrypted_flag()
(e, n, d0) = gen_RSA_key()
(cipherC, cipherS) = MITM_connect()
c = MITM_conversation(cipherC, cipherS)
print("RSA_enc_key:", c)
d0 = Integer(d0)
kbits = d0.nbits()
find_p(d0, kbits, e, n)
p = n // q
d = inverse(e, (p-1)*(q-1))
print("[+] d = {}".format(d))
key = long_to_bytes(pow(c, d, n))
aes = AES.new(key, AES.MODE_ECB)
print(aes.decrypt(encrypted_flag))
if __name__ == "__main__":
main()
|
