使用 Python Paramiko SSH 服务器实现 SCP 服务器

Question

我想用 Paramiko 伪造一个 SCP 服务器。 我写了以下代码：

import base64
 
import time
from binascii import hexlify
import os
import socket
import sys
import threading
import traceback
import interactive
# from warnings import cls
import logging
logging.basicConfig(level='DEBUG')

import paramiko
from paramiko import SFTPClient
from paramiko.py3compat import b, u, decodebytes
 
dir_local='/tmp'
# setup logging
paramiko.util.log_to_file("demo_server.log")
 
host_key = paramiko.RSAKey(filename="test_rsa.key")
# host_key = paramiko.DSSKey(filename='test_dss.key')
 
print("Read key: " + u(hexlify(host_key.get_fingerprint())))
 
 
class Server(paramiko.ServerInterface):
    # 'data' is the output of base64.b64encode(key)
    # (using the "user_rsa_key" files)
    data = (
        b"AAAAB3NzaC1yc2EAAAABIwAAAIEAyO4it3fHlmGZWJaGrfeHOVY7RWO3P9M7hp"
        b"fAu7jJ2d7eothvfeuoRFtJwhUmZDluRdFyhFY/hFAh76PJKGAusIqIQKlkJxMC"
        b"KDqIexkgHAfID/6mqvmnSJf0b5W8v5h2pI/stOSwTQ+pxVhwJ9ctYDhRSlF0iT"
        b"UWT10hcuO4Ks8="
    )
    good_pub_key = paramiko.RSAKey(data=decodebytes(data))
 
    def __init__(self):
        logging.info('__init__')
        self.event = threading.Event()
 
    def check_channel_request(self, kind, chanid):
        logging.info('check_channel_request')
        if kind == "session":
            return paramiko.OPEN_SUCCEEDED
        return paramiko.OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED
 
    def check_auth_password(self, username, password):
        logging.info('check_auth_password')
        # Here you can add couple user/password
        if (username == "root") and (password == "password"):
            return paramiko.AUTH_SUCCESSFUL
        return paramiko.AUTH_FAILED
 
    def check_auth_publickey(self, username, key):
        logging.info('check_auth_publickey')
        print("Auth attempt with key: " + u(hexlify(key.get_fingerprint())))
        if (username == "micki") and (key == self.good_pub_key):
            return paramiko.AUTH_SUCCESSFUL
        return paramiko.AUTH_FAILED
 
    def check_auth_gssapi_with_mic(
        self, username, gss_authenticated=paramiko.AUTH_FAILED, cc_file=None
    ):
        logging.info('check_auth_gssapi_with_mic')
        """
        .. note::
            We are just checking in `AuthHandler` that the given user is a
            valid krb5 principal! We don't check if the krb5 principal is
            allowed to log in on the server, because there is no way to do that
            in python. So if you develop your own SSH server with paramiko for
            a certain platform like Linux, you should call ``krb5_kuserok()`` in
            your local kerberos library to make sure that the krb5_principal
            has an account on the server and is allowed to log in as a user.
        .. seealso::
            `krb5_kuserok() man page
            <http://www.unix.com/man-page/all/3/krb5_kuserok/>`_
        """
        if gss_authenticated == paramiko.AUTH_SUCCESSFUL:
            return paramiko.AUTH_SUCCESSFUL
        return paramiko.AUTH_FAILED
 
    def check_auth_gssapi_keyex(
        self, username, gss_authenticated=paramiko.AUTH_FAILED, cc_file=None
    ):
        logging.info('check_auth_gssapi_keyex')
        if gss_authenticated == paramiko.AUTH_SUCCESSFUL:
            return paramiko.AUTH_SUCCESSFUL
        return paramiko.AUTH_FAILED
 
    def enable_auth_gssapi(self):
        logging.info('enable_auth_gssapi')
        return True
 
    def get_allowed_auths(self, username):
        logging.info('get_allowed_auths')
        return "gssapi-keyex,gssapi-with-mic,password,publickey"
 
    def check_channel_shell_request(self, channel):
        logging.info('check_channel_shell_request')
        self.event.set()
        return True
 
    def check_channel_pty_request(
        self, channel, term, width, height, pixelwidth, pixelheight, modes
    ):
        logging.info('check_channel_pty_request')
        return True
 
 
DoGSSAPIKeyExchange = True
 
# now connect
try:
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    sock.bind(("192.168.34.10", 22))
except Exception as e:
    print("*** Bind failed: " + str(e))
    traceback.print_exc()
    sys.exit(1)
 
try:
    sock.listen(100)
    print("Listening for connection ...")
    client, addr = sock.accept()
except Exception as e:
    print("*** Listen/accept failed: " + str(e))
    traceback.print_exc()
    sys.exit(1)
 
print("Got a connection!")
 
try:
    t = paramiko.Transport(client, gss_kex=DoGSSAPIKeyExchange)
    t.set_gss_host(socket.getfqdn(""))
    try:
        t.load_server_moduli()
    except:
        print("(Failed to load moduli -- gex will be unsupported.)")
        raise
    t.add_server_key(host_key)
    server = Server()
    try:
        t.start_server(server=server)
    except paramiko.SSHException:
        print("*** SSH negotiation failed.")
        sys.exit(1)
 
    # wait for auth
    chan = t.accept(20)
    if chan is None:
        print("*** No channel.")
        sys.exit(1)
    print("Authenticated!")
 
  
    transport = paramiko.Transport(sock=("192.168.34.10", 22))
    transport.connect(username="root", password="password")
 
    interactive.interactive_shell(chan)

    server.event.wait(450)
    if not server.event.is_set():
        print("*** Client never asked for a shell.")
        sys.exit(1)
 
    chan.send("Success Connect\r\n\r\n")
 
    f = chan.makefile("rU")
 
    while True:
        cmd = f.readline().strip("\r\n")
        myCmd = os.popen(cmd).read()
        print(myCmd)
        # chan.send("\r\nGot The Command, " + myCmd + ".\r\n")

    chan.close()
 
 
except Exception as e:
    print("*** Caught exception: " + str(e.__class__) + ": " + str(e))
    traceback.print_exc()
    try:
        t.close()
    except:
        pass
    sys.exit(1)

在我的客户端上，当我启动scp -v file_to_transfer root@192.168.34.10:/home/user/时，我有以下几行

root@192.168.34.10's password: 
debug1: Authentication succeeded (password).
Authenticated to 192.168.34.10 ([192.168.34.10]:22).
debug1: channel 0: new [client-session]
debug1: Entering interactive session.
debug1: pledge: network
debug1: Sending environment.
debug1: Sending env XMODIFIERS = @im=none
debug1: Sending env LANG = fr_FR.UTF-8
debug1: Sending command: scp -v -t /home/user/
exec request failed on channel 0
lost connection

ssh 连接运行良好。 但是当客户端发送命令scp -v -t /home/user/ ，exec 请求失败。

我已经尝试了很多很多修改，但我不知道该怎么做才能解决我的问题......

你有什么想法可以解决我的问题。

谢谢。

Answer 1

scp使用“exec”通道，而不是“shell”通道。

所以你需要实现ServerInterface.check_channel_exec_request 。

---

但请注意，如果您想创建自定义的“SCP 服务器”，则不需要对 SSH 服务器进行编码。 使用标准 SSH 服务器（如 OpenSSH）并为其实现自定义“SCP 服务器”（使用 Python 或您喜欢的任何语言）。 scp用作服务器。 所以你需要做的就是把你的假scp二进制文件（服务器）放在你的 SSH 服务器上，而不是标准的 OpenSSH scp二进制文件。

---

在任何情况下，研究OpenSSH scp代码以了解它是如何工作的。

也可以看看：

• SCP（安全复制协议）文件传输如何工作？
• JSch库中SCP协议实现说明