Selection decryption

[Jacques Le Malade]

Hello,
I am going to look at this. That's most interesting !

> Going to download gpgme and gpa :-)

Merci beaucoup !

Jacques le Fou

2010/2/2, Werner Koch <wk at gnupg.org>:
> Hi,
>
> here is some code to see how the UI-server works.
>
>   /*
>    *  file.c
>    *  This file is part of Mousepad
>    [...]
>
>   #include <gpgme.h>
>
> You need gpgme of course.  Here is the code to write out teh encrypted
> data:
>
>   /* Encrypt or sign the string PLAINTEXT and write it to FP.  MODE
>    * controls whether encrypt, signing or both are used.  The function
>    * employs an external UI server and requires that gpgme has been
>    * initialized at startup.  Returns 0 on success.  */
>   static int crypt_write (const char *plaintext, CryptMode mode, FILE *fp)
>   {
>        gpg_error_t err;
>        gpgme_ctx_t ctx;
>        gpgme_data_t in, out;
>
>        err = gpgme_new (&ctx);
>        if (err) {
>             g_debug ("error creating gpgme context: %s", gpg_strerror
> (err));
>             return -1;
>        }
>
>        /* Tell GPGME to use the "UI-Server protocol".  */
>        err = gpgme_set_protocol (ctx, GPGME_PROTOCOL_UISERVER);
>        if (err) {
>             g_debug ("gpgme does not support the UI protocol: %s",
>                      gpg_strerror (err));
>             gpgme_release (ctx);
>             return -1;
>        }
>
>        /* We want the UI server to use the best encryption protocol around.
> */
>        err = gpgme_set_sub_protocol (ctx, GPGME_PROTOCOL_OpenPGP);
>        if (err) {
>             g_debug ("error asking the UI server to use the %s protocol:
> %s",
>                      "OpenPGP", gpg_strerror (err));
>             gpgme_release (ctx);
>             return -1;
>        }
>
>        /* Wrap the data into an GPGME object.  */
>        err = gpgme_data_new_from_mem (&in, plaintext, strlen (plaintext),
> 0);
>        if (err) {
>             g_debug ("error creating gpgme data object: %s",
>                      gpg_strerror (err));
>             gpgme_release (ctx);
>             return -1;
>        }
>
> There are several other methods how to create a gpgme data objects, but
> this one will probably also fit your requirements.
>
>        /* Wrap the output stream into an GPGME object.  */
>        err = gpgme_data_new_from_stream (&out, fp);
>        if (err) {
>             g_debug ("error creating gpgme stream data object: %s",
>                      gpg_strerror (err));
>             gpgme_data_release (in);
>             gpgme_release (ctx);
>             return -1;
>        }
>
> MODE below comes from a selector in the file dialog.
>
>        /* Do whatever has been requested.  */
>        if (mode == CRYPT_ENCRYPT) {
>             err = gpgme_op_encrypt (ctx, NULL, 0, in, out);
>             if (err)
>                  g_debug ("error encrypting file: %s <%s>",
>                           gpg_strerror (err), gpg_strsource (err));
>        }
>        else if (mode == CRYPT_SIGN) {
>             err = gpgme_op_sign (ctx, in, out, GPGME_SIG_MODE_NORMAL);
>             if (err)
>                  g_debug ("error signing file: %s <%s>",
>                           gpg_strerror (err), gpg_strsource (err));
>        }
>        else if (mode == CRYPT_SIGNENCRYPT) {
>             err = gpgme_op_encrypt_sign (ctx, NULL, 0, in, out);
>             if (err)
>                  g_debug ("error signing and encrypting file: %s <%s>",
>                           gpg_strerror (err), gpg_strsource (err));
>        }
>        else
>             err = gpg_error (GPG_ERR_BUG);
>
>        /* Cleanup.  */
>        gpgme_data_release (out);
>        gpgme_data_release (in);
>        gpgme_release (ctx);
>
>        return err? -1:0;
>   }
>
> The rest of the code in file.c erely adds the mentioned selector widget
> and hooks into the saving procedure.  I leave that out.
>
> Now, to test this you need to start gpa as a server:
>
>   gpa --server
>
> and it should just work; i.e. you get a selection dialog etc.  As I said
> in my last mail you need the latest gpa version, the latest gpgme
> version and thus also the latest libassuan version.  Old GnuPG versions
> should do fine.  Note that you can also S/MIME encrypt if you like
> (cf. gpgme_set_sub_protocol).
>
> Decryption is similar, but I don't think I tested it.  The reason why we
> have this UI-server thing is that we use it in the Windows version to do
> all key selection and actual encryption stuff in our Outlook and
> Explorer plugins within a usable GUI framework (GTK+ or Qt).  Thus there
> is no reason not to use it in other software as well.
>
> I'd really love to see that feature in real use.  Thus if there are any
> problems, I is likely that I can help you.  if something needs to be
> added to GPA, this can be done pretty quicker - or do it yourself (we
> don't need copyright assignments for GPA).
>
>
> Salam-Shalom,
>
>    Werner
>
>
> --
> Die Gedanken sind frei.  Ausnahmen regelt ein Bundesgesetz.
>
>