eCryptfs: what if I remove ~/.ecryptfs

Question

I'm learning how to use eCryptfs: https://wiki.archlinux.org/index.php/ECryptfs

I get things as below from the link:

This is used to derive the actual file encryption master key. Thus, you should not enter a custom one unless you know what you are doing - instead press Enter to let it auto-generate a secure random one. It will be encrypted using the login passphrase and stored in this encrypted form in ~/.ecryptfs/wrapped-passphrase. Later it will automatically be decrypted ("unwrapped") again in RAM when needed, so you never have to enter it manually. Make sure this file does not get lost, otherwise you can never access your encrypted folder again!

So I did a simple test:

ecryptfs-setup-private
mkdir -p ~/test
mount -t ecryptfs ~/test ~/test
cd ~/test && vim data
umount -t ecryptfs ~/test

For now, I did get an encrypted file, which means that ~/test/data was unreadable. Of course, if I mount it again, I can read it.

Now, I delete ~/.ecryptfs: rm -rf ~/.ecryptfs. Then I try to mount it: mount -t ecryptfs ~/test ~/test

To my surprise, I can still mount it and read the ~/test/data.

Now I'm confused. I thought I could move ~/.encryptfs into some USB to keep my secret data secure. But it doesn't seem to work because I can still mount it even if I delete ~/.encryptfs. Am I doing something wrong?

Answer 1

A reading of the manpage and a quick skim of the source to confirm indicates that (among other things) ecryptfs-setup-private creates a directory with encrypted data at ~/.Private, creates a mountpoint for decrypted data at ~/Private, and encrypts the encryption key with the login passphrase at ~/.ecryptfs/wrapped-passphrase. These paths are not configurable.

What you've done is create an ecryptfs directory at ~/.Private with a wrapped passphrase, then created a separate ecryptfs directory at ~/test using your passphrase directly as the key (bad idea). If you want to test that wrapped passphrases work properly you will need to use the ~/Private directory instead of trying to create your own.