Tails OpenPGP applet should not empty the clipboard after a bad decryption passphrase was entered

Initial bug report

When decrypting a text encrypted using passphrase encryption with Tails gpgApplet, if you enter a wrong passphrase you have to copy the text again to try another passphrase. The encrypted text should be kept in the clipboard even if the given passphrase is wrong.

Bug description

Investigating this bug, I found that the issue is that gpgApplet recieves "owner-change" signal on X clipboard, with an empty clipboard content each time it is called. It used to update freshest clipboard as a consequence, thus not accessing the encrypted data anymore.

1st fix

In bugfix/gpgapplet_do_not_erase_clipboard now update the clipboard only if it is not empty. This keeps the content of the CLIPBOARD clipboard. Shipped in Tails 0.19.

Left to do

The X clipboard is still filled with empty data, replacing its old content. If it was the X clipboard that contained the data to be decrypted, the initial bug report would still apply.

Related issues

• Blocked by #7711 (closed)

Original created by @tails on 5967 (Redmine)