nfsd: permit unauthenticated stat of export root
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>
diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
index 4d617ea..9dbd2eb 100644
--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -63,7 +63,8 @@
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 @@
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 @@
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
diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index ea37c96..cd25d91 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -302,17 +302,27 @@
if (error)
goto out;
- if (!(access & NFSD_MAY_LOCK)) {
- /*
- * pseudoflavor restrictions are not enforced on NLM,
- * which clients virtually always use auth_sys for,
- * even while using RPCSEC_GSS for NFS.
- */
- error = check_nfsd_access(exp, rqstp);
- if (error)
- goto out;
- }
+ /*
+ * pseudoflavor restrictions are not enforced on NLM,
+ * which clients virtually always use auth_sys for,
+ * even while using RPCSEC_GSS for NFS.
+ */
+ if (access & NFSD_MAY_LOCK)
+ goto skip_pseudoflavor_check;
+ /*
+ * Clients may expect to be able to use auth_sys during mount,
+ * even if they use gss for everything else; see section 2.3.2
+ * of rfc 2623.
+ */
+ if (access & NFSD_MAY_BYPASS_GSS_ON_ROOT
+ && exp->ex_path.dentry == dentry)
+ goto skip_pseudoflavor_check;
+ error = check_nfsd_access(exp, rqstp);
+ if (error)
+ goto out;
+
+skip_pseudoflavor_check:
/* Finally, check access permissions. */
error = nfsd_permission(rqstp, exp, dentry, access);
diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
index 0766f95..5cffeca 100644
--- a/fs/nfsd/nfsproc.c
+++ b/fs/nfsd/nfsproc.c
@@ -65,7 +65,8 @@
dprintk("nfsd: GETATTR %s\n", 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);
return nfsd_return_attrs(nfserr, resp);
}
@@ -521,7 +522,8 @@
dprintk("nfsd: STATFS %s\n", SVCFH_fmt(&argp->fh));
- nfserr = nfsd_statfs(rqstp, &argp->fh, &resp->stats);
+ nfserr = nfsd_statfs(rqstp, &argp->fh, &resp->stats,
+ NFSD_MAY_BYPASS_GSS_ON_ROOT);
fh_put(&argp->fh);
return nfserr;
}
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 18060be..1319e80 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1866,9 +1866,9 @@
* N.B. After this call fhp needs an fh_put
*/
__be32
-nfsd_statfs(struct svc_rqst *rqstp, struct svc_fh *fhp, struct kstatfs *stat)
+nfsd_statfs(struct svc_rqst *rqstp, struct svc_fh *fhp, struct kstatfs *stat, int access)
{
- __be32 err = fh_verify(rqstp, fhp, 0, NFSD_MAY_NOP);
+ __be32 err = fh_verify(rqstp, fhp, 0, NFSD_MAY_NOP | access);
if (!err && vfs_statfs(fhp->fh_dentry,stat))
err = nfserr_io;
return err;