Access violation using gpgme

[Daniel Lo Nigro]

Hey Andre, I was just wondering if you had any other ideas about this? I
tried to use WinDbg to debug it, which showed this error message:

> Attempt to execute non-executable address 004fef7c

Full output:
https://gist.github.com/Daniel15/c8c31b9e46d8c2eea6385d7dd1ba6c40

I've been stepping through the code and haven't been able to work out why
this happens, particularly since it happens after the passphrase callback
has returned (so gpgme is calling the callback fine). However, I've never
written any C code, so I'm not familiar with debugging it. The thing I'm
not sure how to determine is where that pointer 0x004fef7c is coming from,
and whether it's inside the gpgme library or in my app.

Thanks!

--
Regards,
Daniel Lo Nigro
https://d.sb/ | Twitter <http://twitter.com/Daniel15> | Facebook
<http://www.facebook.com/daaniel>


On Tue, Feb 5, 2019 at 10:59 AM Daniel Lo Nigro <d at d.sb> wrote:

> The code was using gpgme_io_write to write the passphrase followed by a
> null byte:
> https://github.com/wget/gpgme-sharp/blob/master/gpgme-sharp/Context.cs#L353-L354.
> I changed it to gpgme_io_writen and newline. That code was written by
> someone else way back in 2013 so I wonder if it's been broken this entire
> time. Here's the changes I've made so far:
> https://github.com/wget/gpgme-sharp/compare/master...Daniel15:pinentry
>
> Now I'm getting closer, but there's still some odd behaviour. The first
> time I run my test app, I get an access violation. However, it does spawn
> gpg-agent correctly, and the second time I run it, it works fine! I guess
> gpg-agent is properly receiving/caching the passphrase.
>
> --
> Regards,
> Daniel Lo Nigro
> https://d.sb/ | Twitter <http://twitter.com/Daniel15> | Facebook
> <http://www.facebook.com/daaniel>
>
>
> On Tue, Feb 5, 2019 at 10:32 AM Andre Heinecke <aheinecke at gnupg.org>
> wrote:
>
>> Hi,
>>
>> On Tuesday, February 5, 2019 6:21:45 PM GMT Daniel Lo Nigro wrote:
>> > I'm using gpgme_set_pinentry_mode to set the pinentry mode to
>> "loopback",
>> > and the access violation is being encountered after my pinentry callback
>> > returns. It works fine if I don't use loopback, and instead use the
>> > system's pinentry mechanism.
>>
>> This sounds like your passphrase callback returns invalid data. I would
>> have
>> to look how the PassphraseResult is mapped in the C# bindings but from
>> the C
>> API:
>>
>> The user must write the passphrase, followed by a newline character,
>> to the file descriptor @var{fd}.  The function @code{gpgme_io_writen}
>> should be used for the write operation.  Note that if the user returns
>> 0 to indicate success, the user must at least write a newline
>> character before returning from the callback.
>>
>>
>> I do not think that you need to post your full code, but I would be
>> interested
>> in seeing your Passphrase callback.
>> (Sorry If I'm  the only one answering here but in the GnuPG Team I'm the
>> Guy
>> for "all things windows" ;-) )
>>
>>
>> Regards,
>> Andre
>>
>> --
>> GnuPG e.V., Rochusstr. 44, D-40479 Düsseldorf.  VR 11482 Düsseldorf
>> Vorstand: W.Koch, M.Gollowitzer, A.Heinecke.    Mail: board at gnupg.org
>> Finanzamt D-Altstadt, St-Nr: 103/5923/1779.   Tel: +49-2104-4938799
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.gnupg.org/pipermail/gnupg-devel/attachments/20190207/d7ce5506/attachment-0001.html>