Re: [PATCH] nfsd: permit unauthenticated stat of export root

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On Thu, Aug 07, 2008 at 02:23:40PM -0400, Peter Staubach wrote:
> J. Bruce Fields wrote:
>> From: J. Bruce Fields <bfields@xxxxxxxxxxxxxx>
>>
>> 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 on v2 and v3; v4 still requires authentication for all
>> access.
>>
>> Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxxxxxx>
>> ---
>>  fs/nfsd/nfs3proc.c        |    5 +++--
>>  fs/nfsd/nfsfh.c           |   30 ++++++++++++++++++++----------
>>  fs/nfsd/nfsproc.c         |    6 ++++--
>>  fs/nfsd/vfs.c             |    4 ++--
>>  include/linux/nfsd/nfsd.h |    3 ++-
>>  5 files changed, 31 insertions(+), 17 deletions(-)
>>
>> I intend to submit this for 2.6.28
>>
>> diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
>> index 4d617ea..1419142 100644
>> --- a/fs/nfsd/nfs3proc.c
>> +++ b/fs/nfsd/nfs3proc.c
>> @@ -530,7 +530,7 @@ 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 +558,8 @@ 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
>>   
>
> I would think that you might want to have nfsd3_proc_getattr()
> in this list too.  Some clients may need to generate a GETATTR
> if they need the attributes for the root node.

Do you know of any? rfc 2623 makes it sound like those clients are out
of luck.  And testing confirms that this patch is sufficient for the
linux client, at least.

--b.
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