QCA2

[Albert Astals Cid]

El dissabte, 10 de setembre de 2022, a les 5:00:26 (CEST), Ron Murray va 
escriure:
>    I'm working on a project using Qt5, GPG and QCA2, the latter because
> it can encrypt and decrypt PGP messages. This, of course, involves
> using the qca-gnupg plugin.
> 
>    Encryption went fine (there's no need to sign anything (at the
> moment, anyway)). Decryption, however, presented a problem: How to get
> the password into gpg? I tried following the one example that I could
> find (eventhandlerdemo.cpp), but I could never get the PasswordAsker
> to, you know, actually ask for a password. 

Works fine here [1], i do

./bin/qcatool-qt5 message encrypt pgp P:df11

being df11 the short descriptor [2] of my key that has a passphrase, enter 
some 
text on the command line and press Ctrl+D and then run

./bin/qcatool-qt5 message decrypt pgp
paste the text on the command line that the encrypt process entered, press 
Ctrl+D

and feed it that and it ends up in the PassphrasePrompt class code asking my 
passphrase on the command line.

Cheers,
  Albert

[1] Well, it needs a fix in the qcatool code, but that's "irrelevant", the 
library code is fine.
https://invent.kde.org/libraries/qca/-/merge_requests/89/diffs

[2] you can use 
  qcatool-qt5 keystore list-stores
and
  qcatool-qt5 keystore list ID_OF_THE_GPG_KEYRING
to try to find your short id if needed

> I did discover, however,
> that if I first used gpg to decrypt something (and supplying my
> password to the agent in the process), that my program would
> successfully decrypt things until the agent timed out (i.e. ten minutes
> or so).
> 
>    I began to think  that the problem lay in the qca2 library. I went
> through the source code and did a bit of tracing, and I found that QCA
> always supplies "--pinentry-mode loopback" on the gpg command line.
> This will never invoke the pinentry dialog, because that mode forces
> gpg to ask for a password on the command line, which, apart from being
> useless in a GUI application, won't work anyway because QCA also
> supplies "--no-tty" on the command line, and that suppresses console
> output.
> 
>    I managed to modify the qca-gnupg plugin code to replace "--
> pinentry-mode loopback" with "--pinentry-mode default" when it's
> decrypting or signing a message, built the libraries, installed it, and
> now I get a proper pinentry dialog when I want to decrypt a message.
> 
>    So, the questions that I have are these:
> 
> 1. I don't think that QCA, on its own, has any way to supply a password
> to gpg or gpg-agent (apart, I suppose, by supplying it on the command
> line, and nobody wants that), and anyway it's not implemented. But have
> I missed something? Has anyone got QCA to decrypt files with GPG
> lately?
> 
> 2. Would this patch be useful for others? Note that it only affects the
> qca-gnupg plugin: the rest of QCA is untouched.
> 
>    I'm using the current QCA version on Debian testing (2.3.4-1+b1).