Bug#1009890: libqca-qt5: QCA::startDecrypt() doesn't ask for a pass phrase

[Ron Murray <rjmx@rjmx.net>]

Package: libqca-qt5-2
Version: 2.3.4-1
Severity: normal
File: libqca-qt5

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Hash: SHA512

Dear Maintainer,

   I'm writing an app that can use PGP/GPG to encrypt entries, and,
since the rest of the app is written in Qt5, I chose to use QCA for
that part.

   My code (the relevant part, anyway) looks like this:

    QByteArray message = content.toLocal8Bit();

    QCA::OpenPGP gpg;
    QCA::SecureMessage msg(&gpg);

    msg.startDecrypt();
    msg.update(message);
    msg.end();
    msg.waitForFinished(-1);

   When I try to decrypt a GPG entry with this code, it returns
"ErrorUnknown", which I take to indicate that it doesn't have a
passphrase for the secret key. It certainly didn't ask for one.

   It is interesting, however, that if I use the command-line gpg to
decrypt a file using the same secret key (and get asked for a
pass phrase), I can go back to my app, try to decrypt the same PGP
entry again, and it works, because gpg-agent still contains the pass
phrase until it times out.

   So it seems that QCA can access pass phrases in gpg-agent, but it's
unable to request a pinentry from gpg-agent to collect a pass phrase
otherwise. I did manage to catch an invocation of gpg while my app was
decrypting a largish file, and perhaps that's relevant. It's

/usr/bin/gpg --no-tty --pinentry-mode loopback --fixed-list-mode \
- --with-colons --with-fingerprint --with-fingerprint --list-public-keys

   Looking through the documentation, I don't see anything related to
collecting pass phrases for secret keys, but it's possible that I
missed it. Please let me know if that's the case.

 .....Ron

- -- System Information:
Debian Release: bookworm/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 5.17.3.khufu (SMP w/8 CPU threads; PREEMPT)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages libqca-qt5-2:amd64 depends on:
ii  libc6         2.33-7
ii  libgcc-s1     12-20220319-1
ii  libqt5core5a  5.15.2+dfsg-16
ii  libstdc++6    12-20220319-1

Versions of packages libqca-qt5-2:amd64 recommends:
ii  ca-certificates       20211016
ii  libqca-qt5-2-plugins  2.3.4-1

libqca-qt5-2:amd64 suggests no packages.

- -- no debconf information

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