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290930Re: Sufficiently locked down?

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  • Stan Hoeppner
    Jan 24, 2013
      On 1/24/2013 8:42 AM, Jeroen Geilman wrote:
      > On 01/24/2013 07:08 AM, Stan Hoeppner wrote:
      >> On 1/23/2013 2:23 PM, Grant wrote:
      >>>>> I thought my postfix setup was configured to send mail on port 587 and
      >>>>> receive mail on port 25, so I was surprised to find that I could send
      >>>>> mail from the local machine on port 25. Is my config OK?
      >>>> Postfix never sends mail *from* TCP 25 or TCP 587. These are receive
      >>>> ports. Outbound connections occur on high ports. You're not properly
      >>>> describing your use case, actually not at all. Would you please?
      >>> You're right, I didn't word that correctly. I thought mail received
      >>> on port 25 could only be delivered locally with my config, but I was
      >>> able to send mail to any destination via port 25. The mail client and
      >>> mail server are on the same machine.
      >> You haven't identified a problem Grant. You've identified standard
      >> Postfix behavior and told us it is confusing to you. We have no idea
      >> why that is confusing to you because you haven't told us exactly how you
      >> are trying to use Postfix. One thing I can tell you up front is that
      >> using authentication between your MUA and Postfix on 587 is useless,
      >> completely unnecessary, because the packets are transferred via machine
      >> memory, never going over the wire. The submission service exists
      >> strictly for accepting authenticated connections over a network. Your
      >> connections exist entirely within on machine.
      >>
      >
      > If he is actually using SMTP submission on the local server, that is
      > obviously untrue.

      So you're saying all interprocess communication should require
      authentication and encryption? Hmm.. how many of the applications you
      run do this Jeroen?

      > The workings of SMTP submission are not dependent on where this happens
      > from.
      >
      > I would recommend submission regardless of goal or purpose, even on
      > localhost.

      That's because you seem to be looking at this backwards.

      smtp over TLS with auth has a single goal: security. What additional
      security is provided by using TLS and auth for interprocess
      communication on a single user PC? I.e. what is the attack vector here,
      and how does 'submission' prevent such an atack? Answer: there is no
      attack vector, thus it doesn't help.

      --
      Stan
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