openssh unix dev - May 2001 - RSARhosts / Hostbased auth and euid=0 requirement

I'm not happy with ssh being setuid root. I know that the long-term goal is 
to have a seperate host-key-management process, but that is a ways off.

Until then, I'd like to propose the following:

- Allow ssh to read alternate key files.

This would allow the ssh client to use keyfiles different from the ones 
sshd uses. I know that this can be done now by changing the ones sshd uses, 
but I'd rather make ssh the special case.

- Allow said key files to be group readable

Changing authfile.c:key_perm_ok() to allow group readable keys would allow 
us to make ssh setgid instead of setuid. Yes, this is insecure if someone 
is stupid enough to export their key files via NFS or some other such 
sillyness, but is safe for sane admins.

If we do both of the above, ssh can be setgid ssh, and optionally use 
different keys for client and server identification. Host-based auth now 
works without a root-priveledged client. Damage from a security issue in 
ssh is limited to spoofing a trusted host, instead of total system 
compromise.

I'm happy to write the code changes, but wanted to run this up the flagpole 
first to see if there was strong resistance.

-- 
Carson

On Fri, May 04, 2001 at 02:18:10AM -0700, Carson Gaspar
wrote:
> - Allow ssh to read alternate key files.
i'm not sure about this one.
you want to force ssh to read arbitraty key files
and produce valid signatures with random files.
> - Allow said key files to be group readable
we've been discussion a setgid ssh earlier, but
decided that it's not the way to go.

however, i think about moving the client side of
hostbased authentication out of ssh, to a setuid binary
	/usr/libexec/ssh-keysign
and remove the sbit from ssh.
ssh-keysign will read the hostkeys and generate a valid
signature.

this won't work for rhosts-rsa, but there is no need
to use rhosts-rsa if hostbased authentication works.
if you really need to support protocol 1 with rhosts-rsa,
you can turn on the sbit again for ssh.

-m