Kerberos Support In OpenSSH 122
Dan writes "Marshall Vale writes on behalf of the MIT Kerberos team and several other parties interested in the availability of Kerberos authentication for the SSH protocol. Kerberos is a network authentication protocol. It is designed to provide strong authentication for client/server applications by using secret-key cryptography. Marshall says that Kerberos support within OpenSSH may be incomplete and needs more work. In particular, implementing draft-ietf-secsh-gsskeyex in addition to any other Kerberos mechanisms will better serve the needs of Kerberos community. Secondly, he says that they would like to reduce user confusion associated with all of the different options for Kerberos and SSH. He suggests adoption of the GSSAPI key exchange mechanism in the IETF draft (which uses Kerberos to authenticate both parties to each other), in order to avoid man-in-the-middle attacks."
sad. (Score:1, Funny)
RSA? (Score:3, Insightful)
Re:RSA? (Score:5, Insightful)
Re:RSA? (Score:3, Insightful)
Depends what you means by "accounts". Any way you look at it, you'll want to set up something like LDAP for distributing the equivalent of /etc/passwd data. Kerberos gives you user authentication, and the ability to disable user accounts globally -- though not within the ticket lifetime! Kerberos doesn't give you much in the way of provisioning accounts, whic
Re:RSA? (Score:5, Informative)
old key offered by the server the first time they connect. This common behavior exposes the user to the risk of man-in-the-middle attacks. If I've tricked your stack into connecting to me instead of the host you thought you were getting, I can spoof both ends of the connection and intercept your traffic in the clear. Also, Kerberos authentication is two-way (server to client AND client to server)
Re:RSA? (Score:3, Interesting)
Sadly, recent implementations of MIT Kerberos au
Re:RSA? (Score:2, Informative)
But what does that buy you? I assume that a KDC must encrypt part of it's reply with the host principal's secret key that must also be stored and read from a local keytab file that typically only root can update. How can you spoof this part
Re:RSA? (Score:2)
Sure, so the blackhat machine must have a host principal. That might be secure enough in a small environment. In an enterprise, it's not. You can't guarantee that the trustworthiness of every machine in an enterprise. If you could, you would need Kerberos much less.
Re:RSA? (Score:1)
Re:RSA? (Score:3, Informative)
SSH is great for what it does, but it really doesn't do that much. Most people don't notice this since they don't need it to do much - for them it's just a better telnet.
But it scales horribly, look at the other comments.
Worse, SSH drops authentication information. This doesn't sound like much until you've worked in an environment where clients and servers can perform mutual authentication "beneath the surface," but once you have going back is painful.
Re:RSA? (Score:4, Informative)
If you're deploying SSH in an environment that already uses Kerberos, there absolutely is an advantage. GSSAPI external key exchange means that, if you're authenticated to the Kerberos realm, you have tickets that will let you connect to any other machine in the realm (or in a trusted realm) without having to do out-of-band verification of the RSA key's fingerprint.
With traditional RSA key authentication in SSH, the security of the SSH connection requires that either the user is diligent enough to check every new RSA fingerprint when it pops up, or that the site admin has stored all of the machine fingerprints in /etc/ssh/ssh_known_hosts. With Kerberos, mutual authentication is done for you. This is a very big advantage for anyone with a lot of machines, particularly if Kerberos is in use anyway.
Re:RSA? (Score:2, Informative)
At MIT, at least a year or two back, we had people using a mixture of ssh and kerberized rlogin just to deal with the ticket-forwarding iss
ssh and telnet (Score:3, Interesting)
Re:ssh and telnet (Score:2, Insightful)
Re:ssh and telnet (Score:5, Insightful)
Re:ssh and telnet (Score:2, Informative)
Re:ssh and telnet (Score:3, Informative)
Re:ssh and telnet - POP3 (Score:4, Informative)
I have my own SMTP & pop3 server, and I have compiled my POP3 daemon with ssl support, and I use outlook to connect, securely on pop3, at least no cleartext password exchange there.
Althought it doesn't change anything in the man-in-the-middle problem.
One problem only, as the SSL certificate has been signed by myself, when outlook reconnect to the server first time it is run, it says the certificate is unknown.
Re:ssh and telnet - POP3 (Score:2)
Re:ssh and telnet - POP3 (Score:2)
Re:ssh and telnet (Score:2)
Re:ssh and telnet (Score:5, Insightful)
I still use telnet, ftp and even rsh as well and I don't feel insecure about it. Transport-mode IPSec between hosts really helps a lot here...
The "moronic passwords"-issue comes mainly from pop3 and different web-sessions these days. What the world really needs is opportunistic IPSec.
Re:ssh and telnet (Score:3, Informative)
Re:ssh and telnet (Score:3, Informative)
One must understand the rationale for developing opportunistic encryption. It is not to provide for secure communication. It exists to clog the spooks' sniffers with as much un
Re:ssh and telnet (Score:5, Insightful)
"No matter what security measures you implement, the end users are still the weakest link in the chain."
I think it speaks for itself. Passwords can be brute forced via secure protocols as well. Passwords can be copied from stick-it notes on people's monitors, or from knowing their maiden name.
While cleartext protocols should be disabled, many places use them... a LOT. And while I know SSH can replace most of their functionality, many places have scripts that have been running for years that would need man power to rewrite (even if changing only one line) which makes it difficult for many organizations decide this is a priority.
Heck, I had a hell of a time convincing our organization to move from SSHv1 to SSHv2 due to the man-in-the-middle attacks.
Re:ssh and telnet (Score:2)
I tell you, I have no stick-it notes on my monitor, and I am not married. Now you tell me, what is the new password I got from
Re:ssh and telnet (Score:2)
However when it comes to passwords most of the people on a corporate network will be, and it doesn't have to be *your* password I crack, just *a* password.
Re:ssh and telnet (Score:3, Funny)
"Ritz.. now with more crackability."
Re:ssh and telnet, sftp and ftp (Score:3, Insightful)
I would agree 100% with this, some *NIX flavours do this already, notable NetBSD and OpenBSD, and I suspect FreeBSD does also, though TBH that's guessing. With SSH available there really is no need that I can think of off hand (I'm sure someone can think up a counter argument) for telnet to still exist, and the only reason for plain ftp to
Re:ssh and telnet, sftp and ftp (Score:3, Interesting)
The telnet client can also be used as a diagnostic tool, though netcat is better.
Re:ssh and telnet (Score:2, Informative)
From what I've seen, the main reason people use telnet etc. is simply because it's enabled by default. They are too clueless to install SSH (and often too clueless to enable telnet if it were disabled), sometimes they haven't even heard of it.
Many open source OS distributions (at least the *BSDs, probably most if not all Linux distributions) already include SSH and disable almost everything in inetd.conf by default.
MacOS X also includes (but doesn't enable) SSH and disables everything
Re:ssh and telnet (Score:1)
Re:ssh and telnet (Score:3, Insightful)
Where I work, we allow kerberized telnet, but not cleartext telnet. Same for ftp.
-ave
Re:ssh and telnet (Score:4, Insightful)
I find it odd that systems package together telnet (a nice wrapper for TCP, with a few extra features; very useful for a number of things, including getting the weather) with telnetd (a program for providing shell access to attackers, simply based on the few extra features over TCP. Similarly ssh and sshd. Programs that make connections are very different from programs that provide shell access.
Personally, I think Linux distros should have remote login disabled by default. Anyone who actually wants it will know how to enable it, and will hopefully pick a sane protocol to use to do so.
A use for telnet (Score:2)
I use the telnet client to test connectability to various ports...
telnet somehost 25
is a nice way to make sure that the SMTP server is running.
Other than that, I agree that telnet servers should be disabled by default (RH8 and up no longer install it by default). If I have to login to a machine with telnet, the first things I do on it are install SSH and ask permission to change passwords.
FTP servers are OK if t
Re:ssh and telnet (Score:1)
The i
Re:Well that's a start ... but ... (Score:3, Informative)
Globus Grid Support too! (Score:3, Informative)
Windows 2K/XP and KErberos (Score:5, Interesting)
Re:Windows 2K/XP and KErberos (Score:3, Informative)
MIT has single-signon working (the conversion happens automatically) but I don't know if they released the code.
Re:Windows 2K/XP and KErberos (Score:1)
Re:Windows 2K/XP and KErberos (Score:2)
Re:Windows 2K/XP and KErberos (Score:2, Informative)
Other parties? (Score:5, Funny)
There are other parties interested in Kerberos?
Comment removed (Score:4, Informative)
Re:Other parties? (Score:1)
Re:Other parties? (Score:3, Insightful)
Yes SCO now owns Kerberos (Score:2, Funny)
kerberos+ssh+putty (Score:5, Informative)
we're beta testing (or will start soon) but it works!
respond if you're interested...
Re:kerberos+ssh+putty (Score:1)
hello, this would be awesome! Definately interested.
Re:kerberos+ssh+putty (Score:1)
-ave
Re:kerberos+ssh+putty (Score:1)
Sorry!
-ave
Re:kerberos+ssh+putty (Score:2, Interesting)
kputty@jaccard.us
Thanks!
AFS token forwarding for SSHV2? (Score:3, Interesting)
Or with Kerberos authentication does token forwarding no longer matter, because it's not needed?
Re:Binary-only restrictions (Score:2, Informative)
The problem is that the current version of OpenSSH does an aklog with krb4, which may or may not work without additional patching (i.e. changing the aklog code to use krb5) depending on how your sshd handles the krb libs.
Anything to get K5 in the openssh core ... (Score:1)
openssh and kerberos (Score:2)
Add kerberos-over-ssh2 support to ssh(1).
though, reading some openbsd mailing lists, i get the following:
the openssh maintainers would like to have full kerberos support in openssh. however, the mit kerberos code is full of bugs and poorly maintained. the openbsd and openssh developers are sick of dealing with it, and are trying to minimize use of kerberos in the system.
kerberos 4 has been pulled out of openss
Advantage? (Score:3, Interesting)
rlogin -x $HOSTNAME
? I'm talking about the Kerberized rlogin, of course (possibly known as krlogin to some of you linux users). The -x means to force encryption of the entire session.
Re:Advantage? (Score:1)
-ave
Isn't this old? (Score:3, Informative)
There is already a patch (Score:5, Informative)
Kerberos + Windows AD (Score:1, Interesting)
Re:Kerberos + Windows AD (Score:2)
See, the thing most people don't realize about AD, is that while it sort of supports Kerberos, the minute something goes even slightly wrong (some UDP packets get lost, a time skew's detected, m
The previous flamefest over this.. (Score:4, Informative)
Re:The previous flamefest over this.. (Score:1, Interesting)
And has there been any attempt by anyone to either
If not, then Theo's objections still apply, and this whole thing is just more pissing and moaning that "we have a patch and those bastard developers are ignoring us."
Re:The previous flamefest over this.. (Score:1)
I can understand their reluctance, but meeting people half way is needed.
it's been there for a while (Score:5, Informative)
And BTW, kerberos 5 sysadmins can disable non-encrypted services, so rsh/rlogin/telnet/ftp/etc can mandate encryption or fail the connections.
Re:it's been there for a while (Score:1, Informative)
Re:it's been there for a while (Score:1)
The first way is using a rather 'quick but broken' method that ssh.com used. This method cleans up the major problem in sshv1 krb passing (which was sending a TGT before you were verified), but does not do any sort of verification of the server to the client or much vice versa. This was implemented into the CVS of SSH.com last month or so.
The second
next step (Score:3, Informative)
Cussed out in Klingon (Score:4, Funny)
Yeah! Well, your mother!
Ahh, yes.. draft-ietf-secsh-gsskeyex.. (Score:2, Funny)
Ahh yes. draft-ietf-secsh-gsskeyex.
Encryption so secure you need a key just to decipher the name!
:)
Man-in-the-middle (Score:3, Insightful)
Re:Man-in-the-middle (Score:1)
The Confusion (Score:1)
and yet he mentions draft-ietf-secsh-gsskeyex...
Big win for government (Score:2, Interesting)
(e.g. http://kirby.hpcmp.hpc.mil/)
Having Kerberos in the default install should ease one of the many headache's government sysadmins have to endure.
GSSAPI works already (Score:2)
Pardon? (Score:2)
Support OpenSSH development... (Score:1, Interesting)
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Support OpenSSH, have a look at this new Tshirt OpenSSH 2 $20 [openbsd.org] or for Europe EUR 20 [openbsd.org]
thank you.
Broader Kerberos adaption. (Score:2)
Would be very nice if the desktops(KDE/Gnome) had wider support for kerberos.. e.g. (GUI/Nautilus/Konqueror) ftp client with kerberos support and similar to.. After all, why provide username/password every damn time I have to access a resource within the "domain" I'm already logged on to ?
People.. use kerberos... demand kerberos support..
there are rumors... (Score:1)
about a brand new 0day in the OpenSSH krb5 code.
(SSH team did a minor cleanup on the SSH code and introduced some vulnerbility somehow).
now, go figure!
Re:Time for Linux to catch up? (Score:5, Insightful)
Re:Time for Linux to catch up? (Score:3, Informative)
By the way, I've been using Kerberos in Slackware Linux in 1996. Does it fell to your definition of "forever"?
Re:Time for Linux to catch up? (Score:5, Informative)
Unix systems have had Kerberos forever, via both commercial implementations and the MIT reference implementations. Linux DISTRIBUTIONS largely haven't had them, but that's because of the hassles with US export controls in place until recently. Anyone likely to use Kerberos also knew how to build the MIT reference implementation from scratch, if necessary.
Windows is actually a "Johnny-come-lately" - I had been working on unofficial Debian packages of the MIT Krb5 packages for about 3 years when MS announced Windows would use Kerberos in new products, and as usual they attempted to add their own unpublished proprietary crap to it. I (and many other people) didn't mind them adding add'l field specific to the W2K client model, but there was no need for the initial draconian non-disclosure policies.
Re:Time for Linux to catch up? (Score:2, Informative)
Re:Goatse Receiver, ass contortionist, dead at 55 (Score:2, Funny)