RFC: pefs - stacked cryptographic filesystem

Gleb Kurtsou gleb.kurtsou at gmail.com
Mon Sep 6 19:09:40 UTC 2010


I would like to ask for feedback on a kernel level stacked cryptographic
filesystem. It has started as Summer Of Code'2009 project and matured a
lot since then. I've recently added support for sparse files and
switched to XTS encryption mode.

I've been using it to encrypt my home directory for almost a year
already, and use fsx, dbench and blogbench for testing. So it should be
fairly stable.

Tested on top of ZFS, UFS and tmpfs on amd64 and i386; both 9-CURRENT
and 8-STABLE supported.

Please email me separately if you're willing to help testing on big
endian machine, XTS code doesn't look endian correct.

At this point all of the project goals complete and I'd like it to get
wider coverage in terms of tests and reviews and hope to see it commited
to HEAD soon.

Installation instructions:

1a. Clone git repository:
# git clone git://github.com/glk/pefs.git pefs
# cd pefs

1b. Or download latest snapshot from github:

2. Build and install:
# make obj all
# make install

3. Mount pefs filesystem:
# pefs mount ~/Private ~/Private

4. Enter passphrase:
# pefs addkey ~/Private

5. Test it and report back. There is also a man page available.

6. Example how to save your key in keychain database.

pefs has to be mounted and key specified to make fs writable, create
keychain with single entry (keychain -Z option):
# pefs addchain -Z ~/Private
Don't encrypt .pefs.db:
# mv ~/Private/.pefs.db /tmp
# umount ~/Private
# mv /tmp/.pefs.db ~/Private
# pefs mount ~/Private ~/Private
Use -c option to verify key is in database
# pefs addkey -c ~/Private

7. You can setup pam_pefs (not compiled by default) to add key to home
directory and authenticate against keychain database on login, e.g. by
adding the following line to /etc/pam.d/system before pam_unix.so:

auth	sufficient	pam_pefs.so	try_first_pass

The following is a list of its most important features:

*   Kernel level file system, no user level daemons needed.
    Transparently runs on top of existing file systems.
*   Random per file tweak value used for encryption, which guaranties
    different cipher texts for the same encrypted files.
*   Saves metadata only in encrypted file name, but not in file itself.
*   Supports arbitrary number of keys per file system, default directory
    key, mixing files encrypted with different keys in same directory.
*   Allows defining key chains, can be used to add/delete several keys
    by specifying only master key.
*   Uses modern cryptographic algorithms: AES and Camellia in XTS mode,
    PKCS#5v2 and HKDF for key generation.

Github repository: http://github.com/glk/pefs

More details on my blog: http://glebkurtsou.blogspot.com/search/label/pefs


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