扭曲的网络代理

Question

我一直在运行此代码（来自： http://blog.somethingaboutcode.com/?p=155 ）：

from twisted.internet import reactor
from twisted.web import http
from twisted.web.proxy import Proxy, ProxyRequest, ProxyClientFactory, ProxyClient
from ImageFile import Parser
from StringIO import StringIO

class InterceptingProxyClient(ProxyClient):
    def __init__(self, *args, **kwargs):
        ProxyClient.__init__(self, *args, **kwargs)
        self.image_parser = None

    def handleHeader(self, key, value):
        if key == "Content-Type" and value in ["image/jpeg", "image/gif", "image/png"]:
            self.image_parser = Parser()
        if key == "Content-Length" and self.image_parser:
            pass
        else:
            ProxyClient.handleHeader(self, key, value)

    def handleEndHeaders(self):
        if self.image_parser:
            pass #Need to calculate and send Content-Length first
        else:
            ProxyClient.handleEndHeaders(self)

    def handleResponsePart(self, buffer):
        print buffer
        if self.image_parser:
            self.image_parser.feed(buffer)
        else:
            ProxyClient.handleResponsePart(self, buffer)

    def handleResponseEnd(self):
        if self.image_parser:
            image = self.image_parser.close()
            try:
                format = image.format
                image = image.rotate(180)
                s = StringIO()
                image.save(s, format)
                buffer = s.getvalue()
            except:
                buffer = ""
            ProxyClient.handleHeader(self, "Content-Length", len(buffer))
            ProxyClient.handleEndHeaders(self)
            ProxyClient.handleResponsePart(self, buffer)
        ProxyClient.handleResponseEnd(self)

class InterceptingProxyClientFactory(ProxyClientFactory):
    protocol = InterceptingProxyClient

class InterceptingProxyRequest(ProxyRequest):
    protocols = {'http': InterceptingProxyClientFactory}
    ports = {"http" : 80}

class InterceptingProxy(Proxy):
    requestFactory = InterceptingProxyRequest

factory = http.HTTPFactory()
factory.protocol = InterceptingProxy

reactor.listenTCP(8000, factory)
reactor.run()

每当我得到这个并转到 127.0.0.1:8000 我得到这个：

Traceback (most recent call last):
  File "C:\Program Files\Python 2.6.2\lib\site-packages\twisted\python\log.py",
line 84, in callWithLogger
    return callWithContext({"system": lp}, func, *args, **kw)
  File "C:\Program Files\Python 2.6.2\lib\site-packages\twisted\python\log.py",
line 69, in callWithContext
    return context.call({ILogContext: newCtx}, func, *args, **kw)
  File "C:\Program Files\Python 2.6.2\lib\site-packages\twisted\python\context.p
y", line 59, in callWithContext
    return self.currentContext().callWithContext(ctx, func, *args, **kw)
  File "C:\Program Files\Python 2.6.2\lib\site-packages\twisted\python\context.p
y", line 37, in callWithContext
    return func(*args,**kw)
--- <exception caught here> ---
  File "C:\Program Files\Python 2.6.2\lib\site-packages\twisted\internet\selectr
eactor.py", line 146, in _doReadOrWrite
    why = getattr(selectable, method)()
  File "C:\Program Files\Python 2.6.2\lib\site-packages\twisted\internet\tcp.py"
, line 460, in doRead
    return self.protocol.dataReceived(data)
  File "C:\Program Files\Python 2.6.2\lib\site-packages\twisted\protocols\basic.
py", line 251, in dataReceived
    why = self.lineReceived(line)
  File "C:\Program Files\Python 2.6.2\lib\site-packages\twisted\web\http.py", li
ne 1573, in lineReceived
    self.allContentReceived()
  File "C:\Program Files\Python 2.6.2\lib\site-packages\twisted\web\http.py", li
ne 1641, in allContentReceived
    req.requestReceived(command, path, version)
  File "C:\Program Files\Python 2.6.2\lib\site-packages\twisted\web\http.py", li
ne 807, in requestReceived
    self.process()
  File "C:\Program Files\Python 2.6.2\lib\site-packages\twisted\web\proxy.py", l
ine 147, in process
    port = self.ports[protocol]
exceptions.KeyError: ''

每当我设置 firefox 或 chrome 或 opera 在 localhost:8000 上使用代理时，都没有与代理建立连接（并且我可以不再连接到任何页面，尽管这可能是因为它没有连接到代理）。

---

好吧，它仍然失败，并且通过日志记录，当我将 Firefox 设置为使用 localhost:8000 处的代理并且不直接从 Web 浏览器访问代理时（例如通过在 Firefox 的地址栏中键入 localhost:8000），我会得到此输出

2010-08-04 12:31:18-0400 [-] Log opened.
2010-08-04 12:31:29-0400 [-] twisted.web.http.HTTPFactory starting on 8000
2010-08-04 12:31:29-0400 [-] Starting factory <twisted.web.http.HTTPFactory inst
ance at 0x010B3EE0>
2010-08-04 12:33:55-0400 [-] Received SIGINT, shutting down.
2010-08-04 12:33:55-0400 [twisted.web.http.HTTPFactory] (Port 8000 Closed)
2010-08-04 12:33:55-0400 [twisted.web.http.HTTPFactory] Stopping factory <twiste
d.web.http.HTTPFactory instance at 0x010B3EE0>
2010-08-04 12:33:55-0400 [-] Main loop terminated.

但是当我直接访问代理我收到关键错误。

我也不能嗅； Wireshark 似乎没有嗅探本地主机流量，如果我使用 fiddler 2，它会将自己设置为代理（因此我不再使用代理服务器），然后工作（因为它使用 fiddler 2 的代理）。

Answer 1

直接连接时看到的 KeyError 异常是由于对代理的请求必须包含绝对 URL 而不是相对 URL 造成的。如果您的浏览器不知道它正在与代理通信，它将请求类似 /foo/bar 的 URL。如果它确实知道自己正在与代理通信，它将改为请求类似 http://example.com/foo/bar 的内容。 http://example.com/ 部分很重要，因为它是代理知道它应该发出和检索什么的唯一方式。

至于为什么 Firefox、Chrome 或 Opera 在配置后都不会连接到代理，这有点难以解释。确保您配置的是“HTTP 代理”，而不是任何其他受支持类型的代理。仔细检查后，您可能需要使用 Wireshark 等工具来更好地了解网络层上发生的情况。

有可能确实与代理建立了连接，但出现了其他问题，导致连接无法完成。在这种情况下，如果没有启用日志记录，您可能无法仅通过查看代理的输出来判断代理正在接收连接。要启用日志记录，请尝试：

from sys import stdout
from twisted.python.log import startLogging
startLogging(stdout)