How to Use flatpak KeepassXC with flatpak Firefox or Chromium based browser.

At the moment January 2023. Flatpak Keepassxc doesn’t connect with Flatpak Firefox or other chromium based browsers. But we will use some tricks to fix this issue.

Firefox

1. Granted the browser access to KeePassXC flatpak app and KDE runtime installations, and to the KeePassXC proxy socket:

   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
   

2. Created a wrapper script that will launch the official keepassxc-proxy from KeePassXC flatpak, at a path accessible by the Firefox flatpak, e.g.

   mkdir -p ~/.var/app/org.mozilla.firefox/.local/bin/

   nano ~/.var/app/org.mozilla.firefox/.local/bin/keepassxc-proxy-wrapper.sh

   #!/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 "$@"
   

   chmod +x ~/.var/app/org.mozilla.firefox/.local/bin/keepassxc-proxy-wrapper.sh

3. Put the native messaging host json manifest to a the path where flatpaked Firefox will look for it, e.g.
   mkdir -p ~/.var/app/org.mozilla.firefox/.mozilla/native-messaging-hosts

   nano ~/.var/app/org.mozilla.firefox/.mozilla/native-messaging-hosts/org.keepassxc.keepassxc_browser.json

   {
       "allowed_extensions": [
           "keepassxc-browser@keepassxc.org"
       ],
       "description": "KeePassXC integration with native messaging support",
       "name": "org.keepassxc.keepassxc_browser",
       "path": "/home/username/.var/app/org.mozilla.firefox/data/bin/keepassxc-proxy-wrapper.sh",
       "type": "stdio"
   }
   

   Restart Keepassxc & Firefox.

Brave

1. put keepassxc-proxy-wrapper.sh to ~/.var/app/com.brave.Browser/config/BraveSoftware/Brave-Browser/keepassxc-proxy-wrapper.sh. make sure keepassxc-proxy-wrapper.sh is executable.

2. Copy Native messaging host from ~/.config/BraveSoftware/Brave-Browser/NativeMessagingHosts/ to ~/.var/app/com.brave.Browser/config/BraveSoftware/Brave-Browser/NativeMessagingHosts/
   and edited the line

   {
       "allowed_origins": [
           "chrome-extension://pdffhmdngciaglkoonimfcmckehcpafo/",
           "chrome-extension://oboonakemofpalcgghocfoadofidjkkk/"
       ],
       "description": "KeePassXC integration with native messaging support",
       "name": "org.keepassxc.keepassxc_browser",
       "path": "/home/username/.var/app/com.brave.Browser/config/BraveSoftware/Brave-Browser/keepassxc-proxy-wrapper.sh",
       "type": "stdio"
   }