使用twisted.conch作为客户端使用ssh接收扩展数据

时间:2011-10-29 07:50:22

标签: python ssh twisted twisted.conch

我目前正在通过蛮力学习ssh /只是继续黑客攻击,直到我理解它为止。经过一些试验和错误,我已经能够成功发送“pty-req”后跟“shell”请求,我可以获得登录前导码,发送命令和接收标准输出但是我不确定如何告诉SSH服务我想收到stderr和状态消息。通过其他SSH实现(paramiko,Net :: SSH)阅读目前还不是很多指南。

也就是说,看一下用于SSH的RFC之一,我相信列出的请求中的一个可能就是我想要的:http://tools.ietf.org/html/rfc4250#section-4.9.3

#!/usr/bin/env python


from twisted.conch.ssh import transport
from twisted.conch.ssh import userauth
from twisted.conch.ssh import connection
from twisted.conch.ssh import common
from twisted.conch.ssh.common import NS
from twisted.conch.ssh import keys
from twisted.conch.ssh import channel
from twisted.conch.ssh import session
from twisted.internet import defer

from twisted.internet import defer, protocol, reactor
from twisted.python import log
import struct, sys, getpass, os
log.startLogging(sys.stdout)


USER = 'dward'  
HOST = '192.168.0.19' # pristine.local
PASSWD = "password"
PRIVATE_KEY = "~/id_rsa"

class SimpleTransport(transport.SSHClientTransport):
    def verifyHostKey(self, hostKey, fingerprint):
        print 'host key fingerprint: %s' % fingerprint
        return defer.succeed(1) 

    def connectionSecure(self):
        self.requestService(
            SimpleUserAuth(USER,
                SimpleConnection()))

class SimpleUserAuth(userauth.SSHUserAuthClient):
    def getPassword(self):
        return defer.succeed(PASSWD)

    def getGenericAnswers(self, name, instruction, questions):
        print name
        print instruction
        answers = []
        for prompt, echo in questions:
            if echo:
                answer = raw_input(prompt)
            else:
                answer = getpass.getpass(prompt)
            answers.append(answer)
        return defer.succeed(answers)

    def getPublicKey(self):
        path = os.path.expanduser(PRIVATE_KEY) 
        # this works with rsa too
        # just change the name here and in getPrivateKey
        if not os.path.exists(path) or self.lastPublicKey:
            # the file doesn't exist, or we've tried a public key
            return
        return keys.Key.fromFile(filename=path+'.pub').blob()

    def getPrivateKey(self):
        path = os.path.expanduser(PRIVATE_KEY)
        return defer.succeed(keys.Key.fromFile(path).keyObject)



class SimpleConnection(connection.SSHConnection):
    def serviceStarted(self):
        self.openChannel(SmartChannel(2**16, 2**15, self))        




class SmartChannel(channel.SSHChannel):
    name = "session"


    def getResponse(self, timeout = 10):
        self.onData = defer.Deferred()
        self.timeout = reactor.callLater( timeout, self.onData.errback, Exception("Timeout") )
        return self.onData

    def openFailed(self, reason):
        print "Failed", reason

    @defer.inlineCallbacks    
    def channelOpen(self, ignoredData):
        self.data = ''
        self.oldData = ''
        self.onData = None
        self.timeout = None
        term = os.environ.get('TERM', 'xterm')
        #winsz = fcntl.ioctl(fd, tty.TIOCGWINSZ, '12345678')
        winSize = (25,80,0,0) #struct.unpack('4H', winsz)
        ptyReqData = session.packRequest_pty_req(term, winSize, '')

        try:
            result = yield self.conn.sendRequest(self, 'pty-req', ptyReqData, wantReply = 1 )
        except Exception as e:
            print "Failed with ", e

        try:
            result = yield self.conn.sendRequest(self, "shell", '', wantReply = 1)
        except Exception as e:
            print "Failed shell with ", e


        #fetch preample    
        data = yield self.getResponse()
        """
        Welcome to Ubuntu 11.04 (GNU/Linux 2.6.38-8-server x86_64)

            * Documentation:  http://www.ubuntu.com/server/doc

             System information as of Sat Oct 29 13:09:50 MDT 2011

             System load:  0.0               Processes:           111
             Usage of /:   48.0% of 6.62GB   Users logged in:     1
             Memory usage: 39%               IP address for eth1: 192.168.0.19
             Swap usage:   3%

             Graph this data and manage this system at https://landscape.canonical.com/
           New release 'oneiric' available.
           Run 'do-release-upgrade' to upgrade to it.

           Last login: Sat Oct 29 01:23:16 2011 from 192.168.0.17
        """
        print data
        while data != "" and data.strip().endswith("~$") == False:
            try:
                data = yield self.getResponse()
                print repr(data)
                """
                \x1B]0;dward@pristine: ~\x07dward@pristine:~$ 
                """
            except Exception as e:
                print e
                break

        self.write("false\n")
        #fetch response
        try:
            data = yield self.getResponse()
        except Exception as e:
            print "Failed to catch response?", e
        else:
            print data
            """
                false
                \x1B]0;dward@pristine: ~\x07dward@pristine:~$ 
            """

        self.write("true\n")
        #fetch response
        try:
            data = yield self.getResponse()
        except Exception as e:
            print "Failed to catch response?", e
        else:
            print data
            """
            true
            \x1B]0;dward@pristine: ~\x07dward@pristine:~$ 
            """

        self.write("echo Hello World\n\x00")
        try:
            data = yield self.getResponse()
        except Exception as e:
            print "Failed to catch response?", e
        else:            
            print data
            """
            echo Hello World
            Hello World
            \x1B]0;dward@pristine: ~\x07dward@pristine:~$ 
            """

        #Close up shop
        self.loseConnection()
        dbgp = 1


    def request_exit_status(self, data):
        status = struct.unpack('>L', data)[0]
        print 'status was: %s' % status    

    def dataReceived(self, data):
        self.data += data
        if self.onData is not None:
            if self.timeout and self.timeout.active():
                self.timeout.cancel()
            if self.onData.called == False:                
                self.onData.callback(data)

    def extReceived(self, dataType, data):
        dbgp = 1
        print "Extended Data recieved! dataType = %s , data = %s " % ( dataType, data, )
        self.extendData = data

    def closed(self):
        print 'got data : %s' % self.data.replace("\\r\\n","\r\n")
        self.loseConnection()
        reactor.stop()



protocol.ClientCreator(reactor, SimpleTransport).connectTCP(HOST, 22)
reactor.run()

此外,我尝试向远程shell添加一个明确的错误命令:

    self.write("ls -alF badPathHere\n\x00")
    try:
        data = yield self.getResponse()
    except Exception as e:
        print "Failed to catch response?", e
    else:            
        print data
        """
        ls -alF badPathHere
        ls: cannot access badPathHere: No such file or directory
        \x1B]0;dward@pristine: ~\x07dward@pristine:~$ 
        """

看起来stderr正在混入stderr

1 个答案:

答案 0 :(得分:0)

通过挖掘OpenSSH的源代码,在session.c处在线处理通道会话逻辑 2227功能 - > session_input_channel_req,如果给出一个pty-req,那么“shell”请求会导致do_exec_pty,最终导致调用session_set_fds(s,ptyfd,fdout,-1,1,1)。第四个参数通常是负责处理stderr的文件描述符,但由于没有提供,因此stderr不会有任何扩展数据。

最终,即使我修改openssh以提供stderr FD,问题仍然存在于shell中。此时完成猜测工作,但我相信类似于通过xterm或putty等终端登录ssh服务,stderr和stdout一起发送,除非通过类似“2> someFile”的内容明确重定向,这超出了SSH服务提供商。