Re: pgcrypto: PGP signatures

On Wed, Sep 3, 2014 at 2:13 PM, Marko Tiikkaja <marko(at)joh(dot)to> wrote:

> On 2014-09-03 10:33 PM, Jeff Janes wrote:
>
>> On Wed, Sep 3, 2014 at 12:43 PM, Marko Tiikkaja <marko(at)joh(dot)to> wrote:
>>
>>> Right. This patch only adds support for signing data when encrypting it
>>> at the same time. There's no support for detached signatures, nor is
>>> there
>>> support for anything other than signatures of encrypted data. I should
>>> have been more clear on that in my initial email. :-(
>>>
>>>
>>> OK, thanks. How hard do you think it would to allow NULL (or empty
>> string?) passwords to gpg_sym_signatures and gpg_sym_decrypt_verify to
>> accommodate this?
>>
>
> To sign without encrypting?

To verify signatures of things that are not encrypted. I'm not really
interested in storing private keys in PostgreSQL, just things that can be
done with public keys. (But I will make a dummy private key for testing if
I get that far.)

...

> Once I wrap it in dearmor, I get the ERROR: No signature matching the key
>> id present in the message
>>
>> The public key block I am giving it is for the keyid that is reported
>> by pgp_sym_signatures, so I don't know what the problem might be.
>>
>
> Have you tried with the debug=1 option? (It's undocumented, but it was
> like that before this patch and I didn't touch it).

I have now, but it didn't produce any output for this situation. I have
two theories for the problem. My test signed message was signed with a
keyring that had a signing subkey, so it was signed with that, not with the
master. Maybe it doesn't like that. Also, I created the signed message in
gpg, then imported it to PostgreSQL, and maybe it doesn't like that.

I've never used the pgp functions of pgcrypto before, so I decided to take
a step back and try some of the functions that predate the proposed patch.
And I can't get them to work well, either.

If I use pgp_sym_encrypt to encrypt a message with AES, then
pgp_sym_decrypt will decrypt, and so will gpg command line tool. But if I
use gpg to encrypt a message, pgp_sym_decrypt will not decrypt it.

select pgp_sym_decrypt(dearmor('-----BEGIN PGP MESSAGE-----
Version: GnuPG v2.0.14 (GNU/Linux)
Password: foobar

jA0EBwMCqywsAv/hXJ7D0j8BWsD+9H7DY4KhrIIw2oV/6tBueVQ28+VDjBw9rGiy
3JRPmyXNN4wRTZXIyTVzK3LylWLomD9pQkao4hrQwSs=
=02RI
-----END PGP MESSAGE-----
'),'foobar','debug=1');
NOTICE: dbg: parse_literal_data: data type=b
ERROR: Not text data

So I don't know if I am doing something wrong, or if the PostgreSQL
implementation of pgp is just not interoperable with other implementations.
That makes it hard to test the new features if I can't make the old ones
work.

The two messages I am working with are:

Created: echo -n 'a message'|gpg -c --armor --cipher-algo AES -
-----BEGIN PGP MESSAGE-----
Version: GnuPG v2.0.14 (GNU/Linux)
Password: foobar

jA0EBwMCqywsAv/hXJ7D0j8BWsD+9H7DY4KhrIIw2oV/6tBueVQ28+VDjBw9rGiy
3JRPmyXNN4wRTZXIyTVzK3LylWLomD9pQkao4hrQwSs=
=02RI
-----END PGP MESSAGE-----

and

Created: select armor(pgp_sym_encrypt('a message','foobar'));
-----BEGIN PGP MESSAGE-----

ww0EBwMCYzgp4dU3zCJ30joBViH28prwc9jIHhzUyXt31omiHao7NeOuLhCR0/uhAB6GRfYAXWVa
x+FTsW27F46/W7dlRjxCuzcu
=jQGZ
-----END PGP MESSAGE-----

Cheers,

Jeff