NUCLEAR LAUNCH CODE (1000 points)

History and task

You have just landed a job with the ISP TRUSTWORTHY INTERNET, who has important customers, such as the American government. The company does thorough background checks of all employees, you included. However, they found out that you're a CHINESE SPY!

At work, you have access to TRUSTWORTHY INTERNET's infrastructure, especially the software bridge.py, which routes packages between the customers.

Through your contacts in the Chinese government, you have the following information:

Public RSA-keys for several persons/organizations.
Private keys for an international Chinese company.
That Obama is very eager to know the latest NUCLEAR LAUNCH CODE, and thus presses F5 in his browser repeatedly.
The American government uses RSA with PKCS1_OAEP for Public Key Encryption.
The launch code is XOR'ed with some secret information.

Your mission: GET THE NUCLEAR LAUNCH CODE!

Connect to the VPN to access the servers.

bridge.py

import struct, socket, sys
from select import select

TCP_Mr_OBAMA = ('10.20.9.100', 2000)
TCP_WWW_NSAx = ('10.20.10.100', 2000)

def main():
    sock_a = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock_a.connect(TCP_Mr_OBAMA)

    sock_b = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock_b.connect(TCP_WWW_NSAx)

    socks = [sock_a, sock_b]

    route_table = { "Mr_OBAMA": sock_a,
                    "WWW_NSAx": sock_b}
    while socks:
        (rlist, _, _) = select(socks, [], [])

        for s in rlist:
            pkg = PackageFromSocket(s)
            print pkg
            if pkg.receiver in route_table:
                pkg.send(route_table[pkg.receiver])
            else:
                print "Dropper pakke fra ukjent mottaker:", pkg

class Package:
    def __init__(self, sender, receiver, proto, length, payload):
        self.sender = sender
        self.receiver = receiver
        self.proto = proto
        self.length = len(payload)
        self.payload = payload

    def send(self, sock):
        self.length = len(self.payload)
        data = struct.pack("!8s8s5sL%ds" % self.length,
            self.sender, self.receiver, self.proto,
            self.length, self.payload)
        sock.sendall(data)

    def __repr__(self):
        items = [self.sender, self.receiver, self.proto, self.payload]
        return "SRC=%s DST=%s PROTO=%s CONTENT=%s" %\
            tuple([x.__repr__() for x in items])

def PackageFromSocket(sock):
    def recv_all(sock, size):
        data = ""
        while len(data) < size:
            tmp = sock.recv(size - len(data))
            if not tmp:
                print "recv returned without data. Exiting."
                sys.exit(1)
            data += tmp
        return data

    header = recv_all(sock, 25)
    pkg = struct.unpack_from("!8s8s5sL", header)
    payload = recv_all(sock, pkg[3])
    return Package(*(pkg + (payload,)))


if __name__ == "__main__":
    main()

RSA-keys

INTRUDER.private

INTRUDER.public

Mr_OBAMA.public

WWW_NSAx.public

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Required assignments

Stream cipher bit flipping