stronger ciphers support for NFS on RHEL5 (Secure NFS under Red Hat Enterprise Linux 4)

[Mikhail T.]

Hello!

The message at

http://mailman.mit.edu/pipermail/kerberos/2008-March/013398.html

warns about using anything but des-cbc-crc for NFS-access on Linux, but
ends with:

RHEL 5 has MIT 1.6, so the problem shouldn't exist there.

I'm currently struggling to make the KRB5-secured NFS-mounts work
between RHEL-5.4 client and a Solaris-8 server. The mounts succeed:

apdevl:/krbexport on /mnt type nfs (rw,intr,sec=krb5,addr=x.x.x.x)

but any attempt to access the mounted share (/mnt) is denied. All such
attempts also result in the following messages logged by rpc.gssd on the
client:

WARNING: Failed to create krb5 context for user with uid 18039 for
server apdevl.dev.pathfinder.com

Am I right thinking, the problem is due to des-cbc-crc being disabled
realm-wide here? (The DES cipher is deemed too insecure by the network
admins.) Should I still have this problem -- despite running RHEL-5.4?
Any chance, support for stronger ciphers was added to Linux NFS-clients
since RHEL-5.4 was released?

Thanks a lot! Yours,

-mi

[Kevin Coffman]

Yes, if des-cbc-crc is disabled realm-wide then I think you will have
problems with Linux NFS. This is not a Kerberos problem.

The "problem" I was referring to with the note, "RHEL 5 has MIT 1.6,
so the problem shouldn't exist there.", was the necessity of limiting
all applications on the client to des-cbc-crc by specifying
"default_tgs_enctypes = des-cbc-crc" in /etc/krb5.conf. There is no
need to do this for RHEL 5 machines since linux's rpc.gssd and
Kerberos have the code to limit the negotiation to only des-cbc-crc
for NFS.

Unfortunately, the code to support stronger ciphers has not made it
into the Linux kernel yet, and I don't have any idea when it will
finally make it in.

Let me know if you have other questions...

K.C.