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What nonsense. If I'm on an unsecured wireless network at the local Starbucks, untrusted TLS means I know nobody else in the coffee shop is snooping on it or i

What nonsense. If I'm on an unsecured wireless network at the local Starbucks, untrusted TLS means I know nobody else in the coffee shop is snooping on it or injecting anything into it. Why is this so difficult for people to grasp?

mikeash 10y ago
Doesn't it just mean that they'd have to MITM you to snoop or inject? It's better, since it raises the bar some, but it doesn't really change what's possible there.
- bandrami 10y ago
  So, we agree: it's strictly better
  - jedberg 10y ago
    It's not strictly better -- it gives a false sense of security. As you plainly showed by believing that having https at a Starbucks with an untrusted cert is safe, which it is clearly not. Security involve both a technical and social aspect. While the unsigned cert may offer better security (but there is no way for you to know) it most certainly offers a worse social aspect, that being a false sense of security. So I'd say you're wrong -- it is strictly worse, because it offers no better security but a worse sense of security.
- daxorid 10y ago
  For non-CA certs, you either manually verify hashes or install the self-signed root cert. So no, the attacker would have to at minimum find a SHA1 hash collision, otherwise the client will know they're being MitM'ed.
strommen 10y ago
Untrusted TLS does not mean that nobody else in the coffee shop is snooping on it. That Starbucks access point you've connected to might actually be the Pineapple belonging to the guy at the corner table, and he's injecting his own untrusted SSL certs into your HTTPS traffic and snooping/injecting into all your traffic. EDIT - and to clarify what others have said: HTTPS implies a trusted connection (unlike plain HTTP). And a self-signed certificate cannot be trusted under any circumstances.
- jessaustin 10y ago
  A self-signed certificate can be trusted when my client recognizes it as one that I already trust. E.g., maybe it's for a server in my home, to which I have previously connected via my wired home network.
byuu 10y ago
This part is wrong, sorry. An attacker can sign his own certificate for your domain, and send you that. Then he can communicate with the real site on your behalf. Your only protection would be if you pre-installed said self-signed certificate before going to the coffee shop. Your warning would be that the certificate was suddenly untrusted again. It also wouldn't prevent an attack by someone that could forge a certificate from a trusted intermediate CA. HPKP could help there; but if you have someone like that targeting you in a coffee shop, you have much bigger problems. The important thing though is that this is still not worse than plain HTTP. And in fact, it's better: it makes the attacker's job a lot more difficult. Especially when done at large scale (eg ISP ad injection.)

mikeash 10y ago

Doesn't it just mean that they'd have to MITM you to snoop or inject? It's better, since it raises the bar some, but it doesn't really change what's possible there.

bandrami 10y ago
So, we agree: it's strictly better
- jedberg 10y ago
  It's not strictly better -- it gives a false sense of security. As you plainly showed by believing that having https at a Starbucks with an untrusted cert is safe, which it is clearly not. Security involve both a technical and social aspect. While the unsigned cert may offer better security (but there is no way for you to know) it most certainly offers a worse social aspect, that being a false sense of security. So I'd say you're wrong -- it is strictly worse, because it offers no better security but a worse sense of security.
daxorid 10y ago
For non-CA certs, you either manually verify hashes or install the self-signed root cert. So no, the attacker would have to at minimum find a SHA1 hash collision, otherwise the client will know they're being MitM'ed.

strommen 10y ago

Untrusted TLS does not mean that nobody else in the coffee shop is snooping on it. That Starbucks access point you've connected to might actually be the Pineapple belonging to the guy at the corner table, and he's injecting his own untrusted SSL certs into your HTTPS traffic and snooping/injecting into all your traffic. EDIT - and to clarify what others have said: HTTPS implies a trusted connection (unlike plain HTTP). And a self-signed certificate cannot be trusted under any circumstances.

jessaustin 10y ago
A self-signed certificate can be trusted when my client recognizes it as one that I already trust. E.g., maybe it's for a server in my home, to which I have previously connected via my wired home network.

byuu 10y ago

This part is wrong, sorry. An attacker can sign his own certificate for your domain, and send you that. Then he can communicate with the real site on your behalf. Your only protection would be if you pre-installed said self-signed certificate before going to the coffee shop. Your warning would be that the certificate was suddenly untrusted again. It also wouldn't prevent an attack by someone that could forge a certificate from a trusted intermediate CA. HPKP could help there; but if you have someone like that targeting you in a coffee shop, you have much bigger problems. The important thing though is that this is still not worse than plain HTTP. And in fact, it's better: it makes the attacker's job a lot more difficult. Especially when done at large scale (eg ISP ad injection.)