Subject: [secdir] Question about NFSv4/NFSv4.1 crypto support

From: Tim Polk <[email-masked]>
Date: Wed, 3 Dec 2008 09:57:59 -0500

Folks,

After delaying for weeks, I am finally getting into my reviews of
nfsv4.1 and the supporting documents for this Thursday's telechat.

I have encountered one particularly troubling aspect: the mandatory to
implement security mechanisms seem to be rather weak, and some
aspects are unspecified.

The mandatory security mechanisms are Kerberos, LIPKEY and SPKM-3.
REPCSEC_GSS can be used to negotiate other mechanisms, but my
immediate concern is the mandatory to implements.

draft-ietf-nfsv4-minorversion1 provides no information about the  
algorithms
to be used, so I fell back to RFC 3530 (NFSv4) to try to sort this out.

Kerberos is certainly well-specified for an acceptable range of  
algorithms,
but as I understand RFC 3530, the krb5, krb5i and krb5p pseudo flavors
rely on DES and MD5 for security services.  (Perhaps I am misreading
this, and the implication is that DES and MD5 are the mandatory to
implement algorithms, but that still would be unacceptable in my mind.)

The LIPKEY and SPKM-3 mechanisms are only defined with respect to a
small number of algorithms, and most of them are weak.  The  mandatory
to implement for LIPKEY seems to be MD5 and Cast5 (a.k.a., CAST-128)
if  I understand RFC 3530 correctly.  SPKM-3 (and by extension, LIPKEY)
is specified for DES and  CAST5 as encryption algorithms and MD5-RSA,
DES-MAC, DSA-SHA1, HMAC-MD5, and SHA1-RSA are the only integrity
algorithms.  There are also no restrictions or guidance with respect  
to key
sizes for DSA or RSA.

Some of this could probably be handled in the security considerations
(e.g., RSA and DSA key sizes), but some of the issues strike me as
fundamental.

As I have interpreted the text, there is no mandatory to implement  
security
mechanism in nfsv4.1 that provides a reasonable level of cryptographic
security.  Am I missing something?

Any feedback would be appreciated!

Thanks,

Tim Polk

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From: Love Hörnquist Åstrand <[email-masked]>
Date: Wed, 3 Dec 2008 10:10:53 -0800

3 dec 2008 kl. 06.57 skrev Tim Polk:

> The LIPKEY and SPKM-3

LIPKEY and SPKM-3 is close to impossible to implement in a interopable  
way and is way underspecified.

Just forget about them.

Love