ssh protocol 1

jonfa · 01-23-2007, 03:11 PM

Hi All,

I just installed Centos 4.4 and have a question reagrding ssh. I see in /etc/ssh/sshd_config that protocol 2 and 1 are listed. Am I correct in assuming that the default is protocol 2 and the server will stepdown to protocol 1 if a client is using protocol 1? I understand I can uncomment the line and just use protocol 2. However, I thought protocol 1 was vulnerable to man-in-the-middle attacks so why even bother putting it in as an option?

Thanks for the help.

blackhole54 · 01-23-2007, 04:44 PM

If both are listed, the preference will be in the order listed. If you want to force protocol 2, remove the "1" from the line. If the client insists on protocol 1, then no connection will be established. Protocol two is more secure, but I forget the details.

tredegar · 01-23-2007, 04:45 PM

Quote:

However, I thought protocol 1 was vulnerable to man-in-the-middle attacks so why even bother putting it in as an option?

This is historical. Most people (perhaps using ancient systems) would rather get an insecure connection than no connection at all: that way they can upgrade and secure their software (perhaps remotely). If you are unhappy about your ssh falling back to protocol 1 then you can disable this. It is, as you say, an option.