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nfsd: permit unauthenticated stat of export root

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RFC 2623 section 2.3.2 permits the server to bypass gss authentication
checks for certain operations that a client may perform when mounting.
In the case of a client that doesn't have some form of credentials
available to it on boot, this allows it to perform the mount unattended.
(Presumably real file access won't be needed until a user with
credentials logs in.)

Being slightly more lenient allows lots of old clients to access
krb5-only exports, with the only loss being a small amount of
information leaked about the root directory of the export.

This affects only v2 and v3; v4 still requires authentication for all
access.

Thanks to Peter Staubach testing against a Solaris client, which
suggesting addition of v3 getattr, to the list, and to Trond for noting
that doing so exposes no additional information.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Cc: Peter Staubach <staubach@redhat.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
This commit is contained in:
J. Bruce Fields
2008-08-07 13:00:20 -04:00
parent 5dd248f6f1
commit 04716e6621
5 changed files with 33 additions and 18 deletions
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3
include/linux/nfsd/nfsd.h
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@ -38,6 +38,7 @@
#define NFSD_MAY_LOCK 32
#define NFSD_MAY_OWNER_OVERRIDE 64
#define NFSD_MAY_LOCAL_ACCESS 128 /* IRIX doing local access check on device special file*/
#define NFSD_MAY_BYPASS_GSS_ON_ROOT 256
#define NFSD_MAY_CREATE (NFSD_MAY_EXEC|NFSD_MAY_WRITE)
#define NFSD_MAY_REMOVE (NFSD_MAY_EXEC|NFSD_MAY_WRITE|NFSD_MAY_TRUNC)
@ -125,7 +126,7 @@ int nfsd_truncate(struct svc_rqst *, struct svc_fh *,
__be32 nfsd_readdir(struct svc_rqst *, struct svc_fh *,
loff_t *, struct readdir_cd *, filldir_t);
__be32 nfsd_statfs(struct svc_rqst *, struct svc_fh *,
struct kstatfs *);
struct kstatfs *, int access);
int nfsd_notify_change(struct inode *, struct iattr *);
__be32 nfsd_permission(struct svc_rqst *, struct svc_export *,