On Sun, Dec 28, 2014 at 6:02 PM, Robert Drake <rdrake@direcpath.com> wrote:
Picking back up where this left off last year, because I apparently only work on TACACS during the holidays :)
avoiding relatives? :)
On 12/30/2013 7:28 PM, Jimmy Hess wrote:
Even 5 seconds extra for each command may hinder operators, to the extent it would be intolerable; shell commands should run almost instantaneously.... this is not a GUI, with an hourglass. Real-time responsiveness in a shell is crucial --- which remote auth should not change. Sometimes operators paste a buffer with a fair number of commands, not expecting a second delay between each command --- a repeated delay, may also break a pasted sequence.
It is very possible for two of three auth servers to be unreachable, in case of a network break, but that isn't necessary. The "response timeout" might be 5 seconds, but in reality, there are cases where you would wait longer, and that is tragic, since there are some obvious alternative approaches that would have had results that would be more 'friendly' to the interactive user.
(Like remembering which server is working for a while, or remembering that all servers are down -- for a while, and having a 50ms timeout, with all servers queried in parallel, instead of a 5 seconds timeout)
I think this needs to be part of the specification.
I'm sure the reason they didn't do parallel queries was because of both network and CPU load back when the protocol was drafted. But it might be good to have local caching of authentication so that can happen even when servers are down or slow. Authorization could be updated to send the permissions to the router for local handling. Then if the server dies while a session is open only accounting would be affected.
Juniper, at least, does the authorization cache on the device trick... (or really scoping of commands/areas a user is permitted via a local cache file in /var/tmp)
That does increase the vendors/implementors work but it might be doable in phases and with partial support with the clients and servers negotiating what is possible. The biggest drawback to making things like this better is you don't gain much except during outages and if you increase complexity too much you make it wide open for bugs.
and I wonder what percentage of 'users' a vendor has actually USE tac+ (or even radius). I bet it's shockingly low...
Maybe there is a simpler solution that keeps you happy about redundancy but doesn't increase complexity that much (possibly anycast tacacs, but the session basis of the protocol has always made that not feasible). It's
does it really? :)
possible that one of the L4 protocols Saku Ytti mentioned, QUIC or MinimaLT would address these problems too. It's possible that if we did the transport with BEEP it would also provide this, but I'm reading the docs and I don't think it goes that far in terms of connection assurance.
So, here is my TACACS RFC christmas list:
1. underlying crypto
juniper, cisco, arista, sun, linux, freebsd still can't get TCP-AO working... they don't all have ssl libraries in their "os" either... Getting to some answer other than: "F-it, put it i clear text" for new protocols on routers really is a bit painful... not to mention ITARs sorts of problems that arise. -chris
2. ssh host key authentication - having the router ask tacacs for an authorized_keys list for rdrake. I'm willing to let this go because many vendors are finding ways to do key distribution, but I'd still like to have a standard (https://code.google.com/p/openssh-lpk/ for how to do this over LDAP in UNIX) 3. authentication and authorization caching and/or something else