I read somewhere that SSH can be MITM'ed by a global adversary on the first visit (before it establishes the secure connection). Is that true?
Why aren’t we using SSH for everything?
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Re: Why aren’t we using SSH for everything?
#12Why aren’t we using SSH for everything?
Because "Use X for everything" is a terrible design decision? SSH uses flexible transport with some desirable features and may be underutilized in practice.
This question is starting to feel like people who want to staple every pie in the sky idea to the bitcoin blockchain because it too has a set of desirable properties.
Re: Why aren’t we using SSH for everything?
#13I read somewhere that SSH can be MITM'ed by a global adversary on the first visit (before it establishes the secure connection). Is that true?
It can be MITM-ed on any connection. Whether you approve the host fingerprint is, and has always been, entirely up to you.
Re: Why aren’t we using SSH for everything?
#14I read somewhere that SSH can be MITM'ed by a global adversary on the first visit (before it establishes the secure connection). Is that true?
You get shown a key fingerprint at first connection. If you verify that with a secure source you can confirm the host you are communicating with.
Actually bothering and having a secure way to verify the fingerprint are exercises left to the reader.
Re: Why aren’t we using SSH for everything?
#15I read somewhere that SSH can be MITM'ed by a global adversary on the first visit (before it establishes the secure connection). Is that true?
If you don't actually check the fingerprint of the key matches the fingerprint you were given (in some other secure way, such as walking over to the server), then yes, a first-visit MITM is possible.
Re: Why aren’t we using SSH for everything?
#16Why aren’t we using SSH for everything? Because "Use X for everything" is a terrible design decision? SSH uses flexible transport with some desirable features and may be underutilized in practice. This question is starting to feel like people who want to staple every pie in the sky idea to the bitcoin blockchain because it too has a set of desirable properties.
You're right, we probably shouldn't use SSH to microwave our food.
But a lot of things where we use HTTP today, we could be using SSH if we had better library support. Some more ideas towards the end of the post.
Re: Why aren’t we using SSH for everything?
#17I read somewhere that SSH can be MITM'ed by a global adversary on the first visit (before it establishes the secure connection). Is that true?
Yes. It does not have any centralized certificate system like HTTPS so unless you can manually verify the host's public key, you will not know whether your first visit is being proxied. Of course, if the first one is proxied, so may subsequent ones, and you would only get a warning if the proxy was removed or if it's key changed.
Re: Why aren’t we using SSH for everything?
#18I read somewhere that SSH can be MITM'ed by a global adversary on the first visit (before it establishes the secure connection). Is that true?
It can be MITM-ed on any connection. Whether you approve the host fingerprint is, and has always been, entirely up to you.
Default configuration on all of the system's I have used (mostly Ubuntu) is that you cannot just approve it. You have to actually remove it from the known hosts table, in effect starting a new "first session". You can set it to allow override without deleting the entry though and some system may have this as the default.
Re: Why aren’t we using SSH for everything?
#19I read somewhere that SSH can be MITM'ed by a global adversary on the first visit (before it establishes the secure connection). Is that true?
Yes. It does not have any centralized certificate system like HTTPS so unless you can manually verify the host's public key, you will not know whether your first visit is being proxied. Of course, if the first one is proxied, so may subsequent ones, and you would only get a warning if the proxy was removed or if it's key changed.
SSH supports CA-style key signing, and it also supports server fingerprint validation over DNSSEC (search for SSHFP DNS).
Unfortunately neither of these things are commonly used yet. Cloudflare is adding DNSSEC support soon, so hopefully that will change.
Re: Why aren’t we using SSH for everything?
#20If you believe Jacob Appelbaum, we probably should not be using SSH for anything http://media.ccc.de/browse/congress/2014/31c3_-_6258_-_en_-_...
This link 404's for me; can you give a summary?
That's weird all the CCC videos were returning 404. The link appears to be working again now. It's a few days since I watched but I inferred that SSH may have some undisclosed vulnerabilities.