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I'm not sure why you condescend me by writing my name in responses to me, but it bugs me to death. That's the second time you've done it to me (you did it when

I'm not sure why you condescend me by writing my name in responses to me, but it bugs me to death. That's the second time you've done it to me (you did it when I took the unpopular side in the Square credit card bonanza, too), and I am capable of communicating with you from the same level. I don't see you naming other people you're communicating with to add emphasis, so I must assume it's me. > to save $15, uses a self-signed certificate. Valid SSL can be had from StartSSL for no charge. Money is not the issue, it's browsers completely flipping their shit at a self-signed. > How does my browser know if I've agreed with your server for a key, or with the man-in-the-middle proxy I've transparently been redirected to? It doesn't. Which is why, quoting myself and adding emphasis: > if I offer a self-signed certificate, perhaps the better UI experience would be to inform the user in that "Page Info" that their connection is encrypted, but they have no idea if the other end is who they say they are This is the function of the big red warning, but it's the implementation of that very warning that I disagree with. However, the traffic in between you and the other end (the other end that you cannot verify, remember) is still encrypted from completely unrelated third parties, so there is still a negligible benefit. It limits "opened Wireshark and watched you work" to "need to know specifically what I'm after and generate a certificate and poison DNS and ..." A self-signed alone raises the barrier to entry at Starbucks significantly from "really, really easy" to "need to reconnoiter the target and have significant control over the network".

tptacek 16y ago
I'm sorry you find that condescending. I don't mean it to be. The distinction you're trying to draw between "attacks that can be carried out with Wireshark" and "attacks that can be carried out with Wireshark and a Perl script" aren't meaningful to me, so I'm obviously the wrong person to try to persuade you about this. Sorry for wasting your time.
- jedsmith 16y ago
  Fair enough -- text is hard to parse. No hard feelings. I don't see why it's a meaningless distinction. To pull off a MITM, you need quite a bit more than a Perl script, and you're pretty much not going to do it on a network that you do not control. I'm speaking from a basic knowledge of networking theory (I've unintentionally avoided dark arts), so I'm willing to be corrected if I'm wrong. That's the value I see: I don't think I'm going to walk into Starbucks with Perl and successfully MITM even my theoretical browser that doesn't care about self-signed certificates. The value is that in that scenario, even a self-signed makes reading traffic that doesn't belong to you harder. I'm here to discuss, though, and I'm willing to learn; don't give up so easily.
  - mukyu 16y ago
    There are multiple software packages that make it trivial to set up a rogue ap or attack a physical network (with say, arp spoofing). The same is true for proxies that will attack ssl by replacing any certs that it needs to. These are not theoretical attacks. Any 16 year old with a $300 netbook can download software written by others and perform these attacks at your local Starbucks in a few hours. They would be able to see all traffic (even https) and without self-signed warnings the only outward sign would be the lack of the green url bar associated with EV certs.
    - mnutt 16y ago
      But what is the resource cost to spoof a connection? Very cheap for a teenager to sit at Starbucks and spoof your connection, but how much would it cost when using a fiber splitter at AT&T in order to MITM billions of connections per day?
      - tptacek 16y ago
        It would cost more to proxy a billion connections a day than to read them off the wire. But it would not cost so much more as to change the feasibility of the attack. At Internet scale, you may be talking about doubling the cost. Meanwhile, the proxy attack is the gold standard on the actual Internet we all use. Sniffers are obsolete.
kronusaturn 16y ago
DNS spoofing on a Wi-Fi network is quite simple, the whole MITM process including certificate generation is already automated with a wireshark-like tool. http://monkey.org/~dugsong/dsniff/faq.html http://monkey.org/~dugsong/dsniff/faq.html

tptacek 16y ago

I'm sorry you find that condescending. I don't mean it to be. The distinction you're trying to draw between "attacks that can be carried out with Wireshark" and "attacks that can be carried out with Wireshark and a Perl script" aren't meaningful to me, so I'm obviously the wrong person to try to persuade you about this. Sorry for wasting your time.

jedsmith 16y ago
Fair enough -- text is hard to parse. No hard feelings. I don't see why it's a meaningless distinction. To pull off a MITM, you need quite a bit more than a Perl script, and you're pretty much not going to do it on a network that you do not control. I'm speaking from a basic knowledge of networking theory (I've unintentionally avoided dark arts), so I'm willing to be corrected if I'm wrong. That's the value I see: I don't think I'm going to walk into Starbucks with Perl and successfully MITM even my theoretical browser that doesn't care about self-signed certificates. The value is that in that scenario, even a self-signed makes reading traffic that doesn't belong to you harder. I'm here to discuss, though, and I'm willing to learn; don't give up so easily.
- mukyu 16y ago
  There are multiple software packages that make it trivial to set up a rogue ap or attack a physical network (with say, arp spoofing). The same is true for proxies that will attack ssl by replacing any certs that it needs to. These are not theoretical attacks. Any 16 year old with a $300 netbook can download software written by others and perform these attacks at your local Starbucks in a few hours. They would be able to see all traffic (even https) and without self-signed warnings the only outward sign would be the lack of the green url bar associated with EV certs.
  - mnutt 16y ago
    But what is the resource cost to spoof a connection? Very cheap for a teenager to sit at Starbucks and spoof your connection, but how much would it cost when using a fiber splitter at AT&T in order to MITM billions of connections per day?
    - tptacek 16y ago
      It would cost more to proxy a billion connections a day than to read them off the wire. But it would not cost so much more as to change the feasibility of the attack. At Internet scale, you may be talking about doubling the cost. Meanwhile, the proxy attack is the gold standard on the actual Internet we all use. Sniffers are obsolete.

kronusaturn 16y ago

DNS spoofing on a Wi-Fi network is quite simple, the whole MITM process including certificate generation is already automated with a wireshark-like tool. http://monkey.org/~dugsong/dsniff/faq.html http://monkey.org/~dugsong/dsniff/faq.html