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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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8
fs/nfsd/nfs3proc.c
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@@ -63,7 +63,8 @@ nfsd3_proc_getattr(struct svc_rqst *rqstp, struct nfsd_fhandle *argp,
SVCFH_fmt(&argp->fh));
fh_copy(&resp->fh, &argp->fh);
nfserr = fh_verify(rqstp, &resp->fh, 0, NFSD_MAY_NOP);
nfserr = fh_verify(rqstp, &resp->fh, 0,
NFSD_MAY_NOP | NFSD_MAY_BYPASS_GSS_ON_ROOT);
if (nfserr)
RETURN_STATUS(nfserr);
@@ -530,7 +531,7 @@ nfsd3_proc_fsstat(struct svc_rqst * rqstp, struct nfsd_fhandle *argp,
dprintk("nfsd: FSSTAT(3) %s\n",
SVCFH_fmt(&argp->fh));
nfserr = nfsd_statfs(rqstp, &argp->fh, &resp->stats);
nfserr = nfsd_statfs(rqstp, &argp->fh, &resp->stats, 0);
fh_put(&argp->fh);
RETURN_STATUS(nfserr);
}
@@ -558,7 +559,8 @@ nfsd3_proc_fsinfo(struct svc_rqst * rqstp, struct nfsd_fhandle *argp,
resp->f_maxfilesize = ~(u32) 0;
resp->f_properties = NFS3_FSF_DEFAULT;
nfserr = fh_verify(rqstp, &argp->fh, 0, NFSD_MAY_NOP);
nfserr = fh_verify(rqstp, &argp->fh, 0,
NFSD_MAY_NOP | NFSD_MAY_BYPASS_GSS_ON_ROOT);
/* Check special features of the file system. May request
* different read/write sizes for file systems known to have