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#!/usr/bin/env python3
# behave_agent.py - a simple agent to execute command
# NO AUTHENTICATIONS. It should only be used in behave test.
import io
import os
import pwd
import socket
import struct
import subprocess
import typing
MSG_EOF = 0
MSG_USER = 1
MSG_CMD = 2
MSG_OUT = 4
MSG_ERR = 5
MSG_RC = 6
class Message:
@staticmethod
def write(output, type: int, data: bytes):
output.write(struct.pack('!ii', type, len(data)))
output.write(data)
@staticmethod
def read(input):
buf = input.read(8)
type, length = struct.unpack('!ii', buf)
if length > 0:
buf = input.read(length)
else:
buf = b''
return type, buf
class SocketIO(io.RawIOBase):
def __init__(self, s: socket.socket):
self._socket = s
def readable(self) -> bool:
return True
def writable(self) -> bool:
return True
def read(self, __size: int = -1) -> bytes:
return self._socket.recv(__size)
def readinto(self, __buffer) -> int:
return self._socket.recv_into(__buffer)
def readall(self) -> bytes:
raise NotImplementedError
def write(self, __b) -> int:
return self._socket.send(__b)
def call(host: str, port: int, cmdline: str, user: typing.Optional[str] = None):
family, type, proto, _, sockaddr = socket.getaddrinfo(host, port, type=socket.SOCK_STREAM)[0]
with socket.socket(family, type, proto) as s:
s.connect(sockaddr)
sout = io.BufferedWriter(SocketIO(s), 4096)
Message.write(sout, MSG_USER, user.encode('utf-8') if user else _getuser().encode('utf-8'))
Message.write(sout, MSG_CMD, cmdline.encode('utf-8'))
Message.write(sout, MSG_EOF, b'')
sout.flush()
s.shutdown(socket.SHUT_WR)
rc = None
stdout = []
stderr = []
sin = io.BufferedReader(SocketIO(s), 4096)
while True:
type, buf = Message.read(sin)
if type == MSG_OUT:
stdout.append(buf)
elif type == MSG_ERR:
stderr.append(buf)
elif type == MSG_RC:
rc, = struct.unpack('!i', buf)
elif type == MSG_EOF:
assert rc is not None
return rc, b''.join(stdout), b''.join(stderr)
else:
raise ValueError(f"Unknown message type: {type}")
def serve(stdin, stdout, stderr):
# This is an xinetd-style service.
assert os.geteuid() == 0
user = None
cmd = None
sin = io.BufferedReader(stdin)
while True:
type, buf = Message.read(sin)
if type == MSG_USER:
user = buf.decode('utf-8')
elif type == MSG_CMD:
cmd = buf.decode('utf-8')
elif type == MSG_EOF:
assert user is not None
assert cmd is not None
break
else:
raise ValueError(f"Unknown message type: {type}")
if user == 'root':
args = ['/bin/sh']
else:
args = ['/bin/su', '-', user, '-c', '/bin/sh']
result = subprocess.run(
args,
input=cmd.encode('utf-8'),
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
)
sout = io.BufferedWriter(stdout)
Message.write(sout, MSG_RC, struct.pack('!i', result.returncode))
Message.write(sout, MSG_OUT, result.stdout)
Message.write(sout, MSG_ERR, result.stderr)
Message.write(sout, MSG_EOF, b'')
stdout.flush()
def _getuser():
return pwd.getpwuid(os.geteuid()).pw_name
if __name__ == '__main__':
with open(0, 'rb') as stdin, \
open(1, 'wb') as stdout, \
open(2, 'wb') as stderr:
serve(stdin, stdout, stderr)
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