Getting Firefox and KeePassXC flatpaks to talk!

Fix to get KeepassXC and Firefox to communicate via native messaging when running both as flatpak and using the KeePassXC browser extension.

IMPORTANT CAVEAT: For this fix to work KeePassXC has to be launched before Firefox.

On e.g. KDE you can facilitate that with an autostart entry that uses the --minimized flag. E.g. by putting a file keepass.desktop inside ~/.config/autostart which contains

[Desktop Entry]
Type=Application
Name=KeePassXC (Flatpak, minimiert)
Exec=flatpak run org.keepassxc.KeePassXC --minimized
X-GNOME-Autostart-enabled=true

The actual script:

#!/bin/bash

# IMPORTANT CAVEAT: For this fix to work KeePassXC has to be launched before Firefox.
# Taken and translated from https://linuxnews.de/keepassxc-2-7-10/

# Set flatpak-override, to connect KeePassXC and Firefox
echo "Set Flatpak-Override, to connect KeePassXC to Firefox..."
flatpak override --user \
--filesystem={/var/lib,xdg-data}/flatpak/{app/org.keepassxc.KeePassXC,runtime/org.kde.Platform}:ro \
--filesystem=xdg-run/app/org.keepassxc.KeePassXC:create \
org.mozilla.firefox
echo "Flatpak-Override set."

# Create wrapper-script for keepassxc-proxy...
echo "Create Wrapper-Script for keepassxc-proxy..."
WRAPPER_DIR="$HOME/.var/app/org.mozilla.firefox/.local/bin"
WRAPPER_SCRIPT="$WRAPPER_DIR/keepassxc-proxy-wrapper.sh"
mkdir -p "$WRAPPER_DIR"

echo "writing wrapper-script..."
cat << 'EOF' > "$WRAPPER_SCRIPT"
#!/bin/bash
APP_REF="org.keepassxc.KeePassXC/x86_64/stable"
for inst in "$HOME/.local/share/flatpak" "/var/lib/flatpak"; do
    if [ -d "$inst/app/$APP_REF" ]; then
        FLATPAK_INST="$inst"
        break
    fi
done
[ -z "$FLATPAK_INST" ] && exit 1
APP_PATH="$FLATPAK_INST/app/$APP_REF/active"
RUNTIME_REF=$(awk -F'=' '$1=="runtime" { print $2 }' < "$APP_PATH/metadata")
RUNTIME_PATH="$FLATPAK_INST/runtime/$RUNTIME_REF/active"
exec flatpak-spawn \
    --env=LD_LIBRARY_PATH=/app/lib \
    --app-path="$APP_PATH/files" \
    --usr-path="$RUNTIME_PATH/files" \
    -- keepassxc-proxy "$@"
EOF
echo "wrapper-script created"

# Make wrapper-script executable
echo "Setze Berechtigungen für Wrapper-Skript..."
chmod +x "$WRAPPER_SCRIPT"
echo "Wrapper-Skript ist nun ausführbar."

# Create native messaging host JSON
echo "Create native messaging host JSON-File for Firefox..."
NATIVE_MESSAGING_DIR="$HOME/.var/app/org.mozilla.firefox/.mozilla/native-messaging-hosts"
NATIVE_MESSAGING_FILE="$NATIVE_MESSAGING_DIR/org.keepassxc.keepassxc_browser.json"
mkdir -p "$NATIVE_MESSAGING_DIR"

echo "Writing native messaging JSON-File..."
cat <<EOF > "$NATIVE_MESSAGING_FILE"
{
    "allowed_extensions": [
        "keepassxc-browser@keepassxc.org"
    ],
    "description": "KeePassXC integration with native messaging support",
    "name": "org.keepassxc.keepassxc_browser",
    "path": "$WRAPPER_SCRIPT",
    "type": "stdio"
}
EOF
echo "Native messaging JSON-File created"

echo "Setup completed. Please restart KeePassXC and Firefox to apply the changes."