information leakage by kdecache when using encrypted home

Binary package hint: kdebase

KDE uses several directories outside $HOME to store "temporary" files. This may unpleasantly surprise users who choose to encrypt their home directory (using ecryptfs) and expect their data to be protected.

According to http://techbase.kde.org/KDE_System_Administration/KDE_Filesystem_Hierarchy there are at least three user-specific directories placed by default outside $HOME (see the doc for KDE's motivation):
1. /var/tmp/kdecache-$USER/
2. /tmp/kde-$USER/
3. /tmp/ksocket-$USER/

#1 is particularly problematic since /var/tmp is not cleaned upon reboot and stores HTTP cache, thumbnails of viewed images, etc. However, fixing it is quite easy: just set KDEVARTMP to $XDG_CACHE_HOME (or $HOME/.cache/ if $XDG_CACHE_HOME is unset). This probably is only needed for users who encrypt their home directories.

I don't know how #2 is used. It's empty on my system. Probably, leaving it as is is OK because it provides the same guaranties to user as a standard /tmp (e.g. cleanup upon normal boot, but allowing external examination, e.g. from live cd). At least if some decision is made regarding #2 it should expand to whole /tmp, not just KDE's files.

#3 is probably safe since it should only contain named sockets.