GPGME export secret subkeys

[Jacob Adams]

On 05/30/2018 02:00 PM, Werner Koch wrote:
> On Wed, 30 May 2018 17:22, tookmund at gmail.com said:
>> GPGME has export and import functions that work well as alternatives to
>> "gpg --import" and "gpg --export". However, looking through the
>> documentation I cannot find an equivalent to "gpg
>> --export-secret-subkeys". Have I missed something, or does such
>> functionality not yet exist?
> 
> GPGME does not support all features of gpg; that is to avoid creating a
> too baroque API.  If you need this you can resort to the gpgme_op_spawn
> API.  

Ah ok thank you. That's definitely more sensible than having a function
for everything.

> For example here is how we make sure in GPA that the gpg-agent is
> started (required for direct smartcard operations).
> 
> 
> --8<---------------cut here---------------start------------->8---
> void
> gpa_start_agent (void)
> {
>   gpg_error_t err;
>   gpgme_ctx_t ctx;
>   char *pgm;
>   const char *argv[3];
> 
>   pgm = get_gpg_connect_agent_path ();
>   if (!pgm)
>     {
>       g_message ("tool to start the agent is not available");
>       return;
>     }
> 
>   ctx = gpa_gpgme_new ();
>   gpgme_set_protocol (ctx, GPGME_PROTOCOL_SPAWN);
>   argv[0] = "";   /* Auto-insert the basename.  */
>   argv[1] = "NOP";
>   argv[2] = NULL;
>   err = gpgme_op_spawn (ctx, pgm, argv, NULL, NULL, NULL, GPGME_SPAWN_DETACHED);
>   if (err)
>     g_message ("error running '%s': %s", pgm, gpg_strerror (err));
>   g_free (pgm);
>   gpgme_release (ctx);
> }
> --8<---------------cut here---------------end--------------->8---
> 
> You need to adjust it for your needs; for example the first fucntion
> call should be get_gpg_path which can be implemented this way:
> 
> --8<---------------cut here---------------start------------->8---
> static const gchar *
> get_gpg_path (void)
> {
>   gpgme_engine_info_t engine;
> 
>   gpgme_get_engine_info (&engine);
>   while (engine)
>     {
>       if (engine->protocol == GPGME_PROTOCOL_OpenPGP)
> 	return engine->file_name;
>       engine = engine->next;
>     }
>   return NULL;
> }
> --8<---------------cut here---------------end--------------->8---
> 

I'm using the python bindings and actually having a bit of trouble with
op_spawn. I've fallen back on setting GNUPGHOME and calling python's
subprocess.run which pretty much does the same thing.

The simple test case attached fails for me with:
Traceback (most recent call last):
  File "/tmp/opspawn.py", line 7, in <module>
    ctx.op_spawn(gpgbin, ['', '--version'], None, out, None, 0)
  File "/usr/local/lib/python3.6/dist-packages/gpg/core.py", line 151,
in wrapper
    return _funcwrap(self, *args)
  File "/usr/local/lib/python3.6/dist-packages/gpg/core.py", line 132,
in _funcwrap
    result = func(slf.wrapped, *args)
  File "/usr/local/lib/python3.6/dist-packages/gpg/gpgme.py", line 2267,
in gpgme_op_spawn
    return _gpgme.gpgme_op_spawn(ctx, file, argv, datain, dataout,
dataerr, flags)
TypeError: in method 'gpgme_op_spawn', argument 5 of type 'gpgme_data_t'

Like I said it's not really a problem since I'm using subprocess but I
thought I should report it nonetheless.

Thanks,
Jacob


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