serve.py

#!/usr/bin/python3 -u
import os
import sys
import random
import subprocess
import string
import shutil

class HashCash(object):
    def __init__(self, bits=28):
        import random, string
        self.rand = ''.join(random.choice(string.ascii_lowercase) for _ in range(8))
        self.bits = bits
        self.msg = 'Solve PoW with: hashcash -mqb{} {}'.format(bits, self.rand)

    def check(self, stamp):
        import hashlib
        assert stamp.startswith('1:')
        assert stamp.split(':')[3] == self.rand
        assert int(hashlib.sha1(stamp.encode()).hexdigest(), 16) < 2**(160-self.bits)

    @staticmethod
    def check_stdin(bits=28):
        import sys
        hc = HashCash(bits)
        print(hc.msg)
        sys.stdout.flush()
        hc.check(sys.stdin.readline().strip())


def main():
    # HashCash.check_stdin()
    fsize = int(input("Size of payload in bytes: "))

    MAX_SIZE = 10 * 1024 * 1024
    data = sys.stdin.buffer.read(fsize)[:MAX_SIZE]
    print(f"Read {len(data)} bytes")

    os.makedirs("./home/user/")
    shutil.copyfile("/app/initramfs.cpio.gz", "./initramfs.cpio.gz")
    with open("./home/user/exploit", "wb") as initramfs:
        initramfs.write(data)

    os.system("chmod 755 ./home/user/exploit && echo ./home/user/exploit | cpio -R +1000:+1000 -H newc -o | gzip -9 >> ./initramfs.cpio.gz");
    print("Starting computer...")
    os.execvp("/app/qemu-system-aarch64",
             ["/app/qemu-system-aarch64",
              "-machine", "virt",
              "-cpu", "max",
              "-smp", "2",
              "-kernel", "/app/Image",
              "-initrd", "./initramfs.cpio.gz",
              "-m", "128m",
              "-nographic",
              "-nic", "none",
              "-append", "console=ttyAMA0 oops=panic",
              "-monitor", "/dev/null"]
            )

if __name__ == "__main__":
    main()