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使用存在响应中的消息总数作为获取 uid 的方法是否安全？

7.3.1. 存在响应

内容：无

  The EXISTS response reports the number of messages in the mailbox.
  This response occurs as a result of a SELECT or EXAMINE command,
  and if the size of the mailbox changes (e.g., new messages).

  The update from the EXISTS response MUST be recorded by the
  client.

示例：S: * 23 EXISTS

应用内输出

2013-02-02 01:24:42-0500 [IMAP4Client (TLSMemoryBIOProtocol),client] C: '0005 IDLE'
2013-02-02 01:24:42-0500 [IMAP4Client (TLSMemoryBIOProtocol),client] S: '+ idling'
2013-02-02 01:25:17-0500 [IMAP4Client (TLSMemoryBIOProtocol),client] S: '* 6 EXISTS'
2013-02-02 01:25:47-0500 [IMAP4Client (TLSMemoryBIOProtocol),client] S: '* 7 EXISTS'

twisted 的 IMAP 客户端协议的修改版本

class IMAP4Client(imap4.IMAP4Client):
    """
        A client with callbacks for greeting messages from an IMAP server and new messages.
        """
    greetDeferred = None

    def __init__(self, *args, **kw):

        # is IDLE active
        self.idle_active = False
        # do we want to support IDLE
        self.idle_enabled = False
        imap4.IMAP4Client.__init__(self, *args, **kw)

    def serverGreeting(self, caps):
        self.serverCapabilities = caps
        if self.greetDeferred is not None:
            d, self.greetDeferred = self.greetDeferred, None
            d.callback(self)

    def enable_IDLE(self):
        print "Enabling Idle...."
        self.idle_enabled = True
        if self.queued == []:# if there is no current command
            # issue the idle command
            cmd = Command("IDLE", continuation = self.idle_continuation)
            d = self.sendCommand(cmd)
            # THEN mark it active NOT BEFORE as, if IDLE is active when a command is sent (such as the above IDLE command) it stops IDLE by sending the DONE line
            self.idle_active = True
            d.addCallback(self.idle_done)
            return d
        else:
            pass # IDLE will be enables when queued commands in waiting are done

    def lineReceived(self, line):
        print "S: %s" % str(repr(line))
        return imap4.IMAP4Client.lineReceived(self, line)

    def sendLine(self, line):
        print "C: %s" % str(repr(line))
        return imap4.IMAP4Client.sendLine(self, line)

    def idle_continuation(self, *args, **kw):
        pass# ignore for now

    def sendCommand(self, cmd):
        cmd.defer = Deferred()

        # checks to see if IDLE command can be enabled when this command is done
        cmd.defer.addCallback(self.command_done)

        if self.idle_active: # if we are waiting for IDLE
            self.sendLine("DONE")
            # append it to the queue and wait for the idle deferred callback
            self.queued.append(cmd)
            return cmd.defer

        if self.waiting:
            self.queued.append(cmd)
            return cmd.defer

        t = self.makeTag()
        self.tags[t] = cmd
        self.sendLine(cmd.format(t))
        self.waiting = t
        self._lastCmd = cmd
        return cmd.defer

    def command_done(self, result):
        print "A command was finished"
        print "Waiting %s" % self.waiting
        print self.queued
        print "IDLE Enabled %s" % self.idle_enabled

        # cannot use if not self.waiting so check if the command queue is empty 
        empty_queue = (self.queued == [])

        if empty_queue and self.idle_enabled: # yay no commands enable IDLE
            print "Enabling idle"
            self.idle_active = True
            # issue the command
            self.idle_active = True
            cmd = Command("IDLE", continuation = self.idle_continuation)
            d = self.sendCommand(cmd)
            d.addCallback(self.idle_done)
            return d
        return result

    def idle_done(self, result):
        print "IDLE Done"
        self.idle_active = False
        # twisted's own handling of the command queue should handle sending the next command
        # so there is no need to grab the next command as when the OK Response after DONE 
        # trigger it
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2 回答 2

1

我认为使用邮箱中的邮件数量是“足够安全的”，只要您立即采取行动并准备好在您需要显示邮箱时突然不同时回退到 SEARCH（也许一条消息已被删除）由另一个客户）。这实际上仅适用于非破坏性操作，因此如果您确实需要使用 EXPUNGE，请谨慎使用它。

于 2013-02-02T06:46:32.733 回答
1

呃……“安全”？如果您不控制核电站，那么可能。这是一条经验法则：当您的软件出现故障时，会不会有人受伤？如果没有，无论做什么都是安全的。

“正确”怎么说？不，这是不正确的，因为EXISTS响应告诉您邮箱中存在多少邮件。它不会告诉您其中任何一个的UID。

于 2013-02-02T17:07:01.543 回答