Stop ssh client from offering all the public keys it can find?

Question

Like most sysadmins I use openssh all the time. I have about a dozen ssh keys, I like to have a different ssh key for each host. However this causes a problem when I am connecting to a host for the first time, and all I have is a password. I want to just connect to the host using a password, no ssh key in this case. However the ssh client will offer all the public keys in my ~/.ssh/ (I know this from looking at the output of ssh -v). Since I have so many, I will get disconnected for too many authentication failures.

Is there some way to tell my ssh client to not offer all the ssh keys?

Answer 1

Following James Sneeringer's solution, you might just want to set an ssh_config along the lines of:

Host *.mycompany.com
  IdentityFile .ssh/id_dsa_mycompany_main

Host *.mycustomer.com
  IdentityFile .ssh/id_dsa_mycustomer

Host *
  RSAAuthentication no #this should be up top, avoid ssh1 at all costs
  PubkeyAuthentication no

If you connect with a particular key to many machines not in a common domain, consider giving them all CNAMEs in your own DNS. I do this with all customer systems.

Answer 2

Similar to user23413's solution, you can disable public key authentication altogether for a particular host (or wildcard pattern):

Host *.example.org
RSAAuthentication no        # SSHv1
PubkeyAuthentication no     # SSHv2

Answer 3

If you point to a particular key file with ssh -i /path/to/key it'll only use that one even if others are loaded into the agent, and you won't be prompted for the password. You can also edit you ~/.ssh/config and ad something like this...

Host foo.example.com
IdentityFile .ssh/id_rsa_foo.example.com

you can also do...

Host *.example.org
IdentityFile .ssh/id_rsa_example.org