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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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
fs/nfsd/nfs3proc.c
View File

@ -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

30
fs/nfsd/nfsfh.c
View File

@ -302,17 +302,27 @@ fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, int access)
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);

6
fs/nfsd/nfsproc.c
View File

@ -65,7 +65,8 @@ nfsd_proc_getattr(struct svc_rqst *rqstp, struct nfsd_fhandle *argp,
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 @@ nfsd_proc_statfs(struct svc_rqst * rqstp, struct nfsd_fhandle *argp,
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;
}

4
fs/nfsd/vfs.c
View File

@ -1866,9 +1866,9 @@ out:
* 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;

3
include/linux/nfsd/nfsd.h
View File

@ -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 *,