Subject: Re: OpenPGP vs. OpenPGP/MIME

From: [email-masked]
Date: Wed, 13 Feb 2002 09:44:05 +0200

PGP/MIME is evil.

can not save message to disk and decrypt and/or verify later outside MUA,
some virus checking software removes attachments,
does not work with many mailing lists (that are configured to remove attachments),
does not work with web archives of mailing lists (for example http://www.imc.org/ietf-openpgp/mail-archive/msg03690.html),
does not work with newsgroups.

__
Disastry  http://disastry.dhs.org/
http://disastry.dhs.org/pgp <----PGP plugins for Netscape and MDaemon
 ^----PGP 2.6.3ia-multi05 (supports IDEA, CAST5, BLOWFISH, TWOFISH,
      AES, 3DES ciphers and MD5, SHA1, RIPEMD160, SHA2 hashes)

---

From: Marc Mutz <[email-masked]>
Date: Wed, 13 Feb 2002 10:53:17 +0100

> PGP/MIME is evil.

I disagree. pgp/miem isn't evil at all. It's the broken mail software 
out there that is the problem. And I restate that deprecating pgp/mime 
(or whatever this should lead to) will take the strain off of those 
"vendors" to fix their "products"...

> can not save message to disk and decrypt and/or verify later outside

For "decrypt", this is usually wrong, since exactly one part contains 
the encrypted data, the other only contains metadata, which is either 
superfluous or could be translated into options for the OpenPGP backend 
when decrypting...

So the real problem is signing:
The MUA could offer to convert the multipart/signed part to a 
file/detached sig pair of files on save.

Remember: You can't also view asian text/plain, wihc is usually encoded 
in base64, without the help of the MUA.

> some virus checking software removes attachments,

which is broken behaviour...

> does not work with many mailing lists (that are configured to remove

those ml's are broken (since multipart/signed is _not_ an attachment).

> does not work with web archives of mailing lists (for
> example http://www.imc.org/ietf-openpgp/mail-archive/msg03690.html),

broken software used there, too.

> does not work with newsgroups.

Care to explain what's the problem there?

So why are all those packages broken? Because pgp/mime is so rare that 
they don't need to fix their stuff.

Marc

- -- 
Marc Mutz <[email-masked]>

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From: Thomas Roessler <[email-masked]>
Date: Wed, 13 Feb 2002 10:50:05 +0100

>can not save message to disk and decrypt and/or verify later 

Where do you get the expectation from that you can handle e-mail 
messages without software able to parse their format?

(And, BTW, you can certainly do all you desire outside the MUA. You 
just have to do some _very_ basic MIME parsing yourself.

>some virus checking software removes attachments,

Such virus checking software is broken.

>does not work with many mailing lists (that are configured to 

Such mailing lists are broken.

>does not work with web archives of mailing lists (for example 
>http://www.imc.org/ietf-openpgp/mail-archive/msg03690.html),

That's not an example for PGP/MIME, but an example for mailing list 
archiving software not being able to cope with RFC announcements as 
sent out by the RFC editor.  This is another instance of broken 
software.  Nice try, though.

>does not work with newsgroups.

Why not?

-- 
Thomas Roessler                        <[email-masked]>

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From: Ian Bell <[email-masked]>
Date: Wed, 13 Feb 2002 11:35:54 +0000

>PGP/MIME is evil.

It is the only sensible way to properly secure an entire MIME message
with PGP.

In the case of signed messages, it allows the recipient to be sure that
the sender signed _all_ of the message, including attachments: it allows
arbitrarily complex messages to be signed successfully: in principle it
allows the sender to send a signed message to a group of people, some of
whom are not interested in PGP at all since the act of signing does not
pollute the actual message in any way.

Of course the last point depends on basic MIME compliance of users'
MUAs, and there are some common clients that treat multipart/unknown
differently to multipart/mixed :-((

In the case of encrypted messages, it allows the sender to be sure that
no-one intercepting the message can know if any attachments are present
and what types of attachments there are. It allows encryption of
arbitrarily complex messages.

>can not save message to disk and decrypt

the decryption is easy; but you will be left with a MIME message which
will need to be interpreted (by munpack etc) which is a barrier. Best
thing is to encourage PGP/MIME support in MUAs.

>and/or verify later outside MUA,

verify is easy if the message source is available.

>some virus checking software removes attachments,

some virus checking software removes/quarantines _all_ PGP encrypted
material.

>does not work with many mailing lists (that are configured to remove

Best thing is to encourage PGP/MIME support in mailing-lists.

[[ Actually, best thing is to encourage MIME support in mailing lists
(some lists append text material to the end of messages - which in the
case of multipart/* messages gets hidden by MIME MUAs!) ]]

>does not work with newsgroups.

have a look at alt.security.pgp and see how much PGP clear-signed
material is quoted/requoted etc Many messages consist mainly of
redundant fragments of quoted ascii-armor. This seems to me to be a
serious barrier to the routine use of PGP in newsgroups/mailing-lists.

How about the opposite contention:

"Clear-signed messages are evil"

    The ascii-armor is intrusive, so that the use of PGP is restricted
    to arenas where people will put up with such material "in their
    faces".

    The ascii-armor breaks the UseNet signature convention ("-- "
    becomes "- -- "): another barrier to routine use of PGP in UseNet.

    Clear signing is often done "behind the MUAs back" - leading to
    wrapping problems (how many users have to be told how to balance the
    wrapping action of their MUAs against the wrapping action of their
    PGP settings?)

    Clear-signing starts breaking when messages are not simple us-ascii
    and can't be used to properly secure messages with attachments.

    [As an example of the first case, I will clear sign this message via
    the clipboard. The signature will fail. because the '€' character
    will be signed by PGP as a Windows-1252 character (which is what the
    clipboard will contain), but my MUA will send it utf-8.]

In practice, clear-signing can be made to interoperate for simple us-
ascii messages, and PGP/MIME support is indeed patchy, but I hope
PGP/MIME support does grow because of its inherent advantages.

And if it doesn't, the "world's most popular clients" can still sign and
encrypt arbitrary MIME messages securely - they include seamless S/MIME
support.

- --
Ian Bell                                           T U R N P I K E

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From: Jon Callas <[email-masked]>
Date: Wed, 13 Feb 2002 11:09:45 -0800

>Such mailing lists are broken.

As someone who runs a number of such "broken" mailing lists, I "broke" them
because I consider the security risk of my list being use to spread the
latest Outlook thingie to be much higher than the damage caused by breaking
them. It also prevents the inevitable newbie who sends a picture or movie
as an attachment, causing a dozen people to go over their mail quotas. My
message to my users is that if it's important, put it somewhere and provide
a URL. If it's important, I'll even provide disk space for it.

I must respectfully disagree with this assessment. People who maintain
computer systems used by a number of people have a responsibility to
protect that shared resource. Stopping attachments on mailing lists is not
any more "broken" than putting up a firewall is.

	Jon

---

From: Marc Mutz <[email-masked]>
Date: Wed, 13 Feb 2002 23:09:53 +0100

> >Such mailing lists are broken.
<snip>
> I must respectfully disagree with this assessment. People who
> maintain computer systems used by a number of people have a
> responsibility to protect that shared resource. Stopping attachments
> on mailing lists is not any more "broken" than putting up a firewall
> is.
<snip>

A mailing list software isn't broken because it filters out attachments, 
but because it can't distinguish pgp/mime signed plain text messages 
from attachments. Not everything consisting of a mulitpart contains an 
attachment.
In fact, it would be totally legal for me to always send multipart 
messages, where, for instance, the first nested body part contains the 
text of the mail and the secons one my signature.

I can't speak for Thomas, but that's probably what he meant: That 
mailing list software needs to be able to distinguish between 
attachments and signed messages.

(Though I can understand why Thomas could find ml's which filter all 
"attachments" broken: You can't even forward a message to them (needs a 
multipart/mixed with nested message/rfc822 - eek)).

Marc

- -- 
Marc Mutz <[email-masked]>

---

From: Ian Bell <[email-masked]>
Date: Thu, 14 Feb 2002 09:23:22 +0000

>>Such mailing lists are broken.
[]
>any more "broken" than putting up a firewall is.

Yes, but there is no reason why mailing-list software should regard 
application/pgp-signature as an "attachment" when protecting 
mailing-lists against misplaced or dangerous attachments.

(This sent PGP/MIME signed, just to see what happens on this list!)

-- 
Ian Bell                                           T U R N P I K E

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From: [email-masked] (Bodo Moeller)
Date: Sun, 17 Feb 2002 01:21:14 +0100 (CET)

> them.

So it's not about multipart messages, but about dangerous Content-Types?
Dangerous Content-Type values have nothing to do with whether a
message is a multipart message or not.  Any Content-Type can be named
directly in the main message headers, and completely harmless
Content-Types can be named in the individual body parts of a multipart
message.

>       It also prevents the inevitable newbie who sends a picture or movie
> as an attachment, causing a dozen people to go over their mail quotas.

Again, this has nothing to do with multiparts.  If you want to prevent
huge messages, set an appropriate message size limit.