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From: "J. Bruce Fields" <bfields@fieldses.org>
To: Kees Cook <keescook@chromium.org>
Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 08/16] nfsd: escape high characters in binary data
Date: Sat, 22 Jun 2019 15:00:58 -0400
Message-ID: <20190622190058.GD5343@fieldses.org> (raw)
In-Reply-To: <201906211431.E6552108@keescook>

On Fri, Jun 21, 2019 at 03:26:00PM -0700, Kees Cook wrote:
> On Fri, Jun 21, 2019 at 01:45:44PM -0400, J. Bruce Fields wrote:
> > I'm not sure who to get review from for this kind of thing.
> > 
> > Kees, you seem to be one of the only people to touch string_helpers.c
> > at all recently, any ideas?
> 
> Hi! Yeah, I'm happy to take a look. Notes below...

Thanks!

> > On Thu, Jun 20, 2019 at 10:51:07AM -0400, J. Bruce Fields wrote:
> > > From: "J. Bruce Fields" <bfields@redhat.com>
> > > 
> > > I'm exposing some information about NFS clients in pseudofiles.  I
> > > expect to eventually have simple tools to help read those pseudofiles.
> > > 
> > > But it's also helpful if the raw files are human-readable to the extent
> > > possible.  It aids debugging and makes them usable on systems that don't
> > > have the latest nfs-utils.
> > > 
> > > A minor challenge there is opaque client-generated protocol objects like
> > > state owners and client identifiers.  Some clients generate those to
> > > include handy information in plain ascii.  But they may also include
> > > arbitrary byte sequences.
> > > 
> > > I think the simplest approach is to limit to isprint(c) && isascii(c)
> > > and escape everything else.
> 
> Can you get the same functionality out of sprintf's %pE (escaped
> string)? If not, maybe we should expand the flags available?

Nothing against it, I just didn't want it to do that for one user,
but...

> 
>  * - 'E[achnops]' For an escaped buffer, where rules are defined by
>  * combination
>  *                of the following flags (see string_escape_mem() for
>  *                the
>  *                details):
>  *                  a - ESCAPE_ANY
>  *                  c - ESCAPE_SPECIAL
>  *                  h - ESCAPE_HEX
>  *                  n - ESCAPE_NULL
>  *                  o - ESCAPE_OCTAL
>  *                  p - ESCAPE_NP
>  *                  s - ESCAPE_SPACE
>  *                By default ESCAPE_ANY_NP is used.
> 
> This doesn't cover escaping >0x7f and " and \
> 
> And perhaps I should rework kstrdup_quotable() to have that flag? It's
> not currently escaping non-ascii and it probably should. Maybe
> "ESCAPE_QUOTABLE" as "q"?

... but if you think there's a lot of existing users that really want
this behavior, then great.

I'll look into that.

The logic around ESCAPE_NP and the "only" string is really confusing.  I
started assuming I could just add an ESCAPE_NONASCII flag and stick "
and \ into the "only" string, but it doesn't work that way.

---b.

  reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-20 14:50 [PATCH 00/16] exposing knfsd client state to userspace J. Bruce Fields
2019-06-20 14:51 ` [PATCH 01/16] nfsd: persist nfsd filesystem across mounts J. Bruce Fields
2019-06-20 14:51 ` [PATCH 02/16] nfsd: rename cl_refcount J. Bruce Fields
2019-06-20 14:51 ` [PATCH 03/16] nfsd4: use reference count to free client J. Bruce Fields
2019-06-20 14:51 ` [PATCH 04/16] nfsd: add nfsd/clients directory J. Bruce Fields
2019-06-20 14:51 ` [PATCH 05/16] nfsd: make client/ directory names small ints J. Bruce Fields
2019-06-20 14:51 ` [PATCH 06/16] nfsd4: add a client info file J. Bruce Fields
2019-06-20 14:51 ` [PATCH 07/16] nfsd: copy client's address including port number to cl_addr J. Bruce Fields
2019-06-20 14:51 ` [PATCH 08/16] nfsd: escape high characters in binary data J. Bruce Fields
2019-06-21 17:45   ` bfields
2019-06-21 22:26     ` Kees Cook
2019-06-22 19:00       ` J. Bruce Fields [this message]
2019-06-22 20:22         ` Kees Cook
2019-06-24 21:05           ` J. Bruce Fields
2019-06-26 16:21             ` J. Bruce Fields
2019-06-27  4:16               ` Kees Cook
2019-06-27 15:23                 ` J. Bruce Fields
2019-06-27 20:21               ` J. Bruce Fields
2019-06-28  3:58                 ` Kees Cook
2019-06-28 16:33                   ` J. Bruce Fields
2019-07-10 22:09                     ` J. Bruce Fields
2019-07-11  1:54                       ` Kees Cook
2019-08-06 12:19   ` Andy Shevchenko
2019-08-06 18:50     ` J. Bruce Fields
2019-08-07  9:00       ` Andy Shevchenko
2019-08-08 11:28         ` bfields
2019-08-27 13:36           ` Andy Shevchenko
2019-06-20 14:51 ` [PATCH 09/16] nfsd: add more information to client info file J. Bruce Fields
2019-06-20 14:51 ` [PATCH 10/16] nfsd4: add file to display list of client's opens J. Bruce Fields
2019-06-20 14:51 ` [PATCH 11/16] nfsd: show lock and deleg stateids J. Bruce Fields
2019-06-20 14:51 ` [PATCH 12/16] nfsd4: show layout stateids J. Bruce Fields
2019-06-20 14:51 ` [PATCH 13/16] nfsd: create get_nfsdfs_clp helper J. Bruce Fields
2019-06-20 14:51 ` [PATCH 14/16] nfsd: allow forced expiration of NFSv4 clients J. Bruce Fields
2019-06-20 14:51 ` [PATCH 15/16] nfsd: create xdr_netobj_dup helper J. Bruce Fields
2019-06-20 14:51 ` [PATCH 16/16] nfsd: decode implementation id J. Bruce Fields
2019-06-21 18:13 ` [PATCH 00/16] exposing knfsd client state to userspace bfields
2019-06-21 19:25   ` Anna Schumaker
2019-06-21 22:08     ` J. Bruce Fields

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