When SSHing to a server with encrypted home directories doesn't automatically mount the encrypted directory

[Jon "The Nice Guy" Spriggs]

Binary package hint: ecryptfs-utils

As per http://ubuntuforums.org/showthread.php?p=9931173 I have noticed that when logging in to my home server, which has encrypted directories (using ecryptfs-mount-home), it doesn't always auto-mount these directories. I am using SSH keys to authenticate with the server.

This behaviour *typically* occur after a reboot of the server, and will usually persist until the next time I SSH to the server without using the private key, but is not every time.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: ecryptfs-utils 83-0ubuntu3
ProcVersionSignature: Ubuntu 2.6.32-25.44-generic 2.6.32.21+drm33.7
Uname: Linux 2.6.32-25-generic i686
NonfreeKernelModules: nvidia
Architecture: i386
Date: Wed Oct 6 14:32:53 2010
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Release i386 (20091028.5)
ProcEnviron:
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: ecryptfs-utils

[Tuomas Heino (iheino+ub)]

Maybe this could be reworded as a wishlist bug for a feature to keep some carefully selected subset of files synchronized both in ecrypts and unencrypted forms? Or should some union-mount like feature be needed to store such exceptional files only in unencrypted form?

Workaround:

In order for the keys to be used, authorized-keys should also exist in unencrypted form (this approach implies exposing some known-plaintext, consequences of which should be analyzed further).

In order to achieve this, you can use the following commands when logged in:

sudo mount -o bind /home /mnt
mkdir -m 700 /mnt${HOME#/home}/.ssh
cp -ia ${HOME}/.ssh/authorized_keys /mnt${HOME#/home}/.ssh/
sudo umount /mnt

[Tuomas Heino (iheino+ub)]

**Or some union-mount like feature could...

Unencrypted home directories are typically write-protected. Amended workaround with temporary permissions (if used in any script, it should save original permissions (by using touch -r on $(mktemp -d) for example)):

sudo mount -o bind /home /mnt
chmod u+w /mnt${HOME#/home}
mkdir -m 700 /mnt${HOME#/home}/.ssh
cp -ia ${HOME}/.ssh/authorized_keys /mnt${HOME#/home}/.ssh/
chmod u-w /mnt${HOME#/home}
sudo umount /mnt