On 3/1/15 3:34 PM, Daniel Kahn Gillmor wrote:
On Sun 2015-03-01 20:01:05 +0100, Werner Koch wrote:
On Sun, 1 Mar 2015 15:32, rp...@kcore.de said:
is there a command line utility that takes a PGP/MIME encrypted message
(a plain RFC 2822 text file) and outputs an unencrypted copy? The
Not really. MIME is a structured format and as such it may result in a
bunch of encrypted, non-nencrypted, signed, unsigned,
message/alternative sub-documents. Thus it is not easy to write a
general purpose command line tool.
python's email module is quite good for programmatically handling mime
parts if you want to manipulate an e-mail (though it may not be so good
for reconstructing it in some sort of bytewise exact fashion).
You may start with gpgparsemail which is not installed bald build as
part of gnupg in the tools directory. It returns an annotated format
which might be easier for further processing steps than plain MIME.
If you only want to decrypt a standard MIME encrypted mail, it is easy.
Simply pipe the entire mail through gpg and you will get the decrypted
MIME container.
You should also note that any decryption like this is likely to remove
any OpenPGP signature as well, for those MUAs that do the
encryption+signing step all in one OpenPGP piece (i believe that the
gpgtools mail.app plugin places the OpenPGP signature inside a
multipart/signed MIME message, which is then itself encrypted, rather
than placing encryption and signatures all in the OpenPGP part
directly).
A tool that transforms an OpenPGP encrypted+signed MIME message into an
OpenPGP-signed MIME message while retaining the original signature would
be a really nice tool to have.
The signature is an attachment on a PGP/MIME message of course, so you'd
have to preserve the two files separately.
My (Al)pine PGP filters are shell scripts that (amongst other things)
will verify and decrypt PGP/MIME messages. You could easily adapt that
code to output the canonical version of the message to a file, along
with the corresponding signature.
hope this helps,
Doug
https://dougbarton.us/PGP/ppf/index.html
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