About
tcplay is a free (BSD-licensed), pretty much fully featured (including multiple keyfiles, cipher cascades, etc) and stable TrueCrypt implementation.
This implementation supports mapping (opening) both system and normal TrueCrypt volumes, as well as opening hidden volumes and opening an outer volume while protecting a hidden volume. There is also support to create volumes, including hidden volumes, etc. Since version 1.1, there is also support for restoring from the backup header (if present), change passphrase, keyfile and PBKDF2 PRF function.
Since tcplay uses dm-crypt (or dm_target_crypt on DragonFly) it makes full use of any available hardware encryption/decryption support once the volume has been mapped.
It is based solely on the documentation available on the TrueCrypt website, many hours of trial and error and the output of the Linux' TrueCrypt client. As it turns out, most technical documents on TrueCrypt contain mistakes, hence the trial and error approach.
Implementation notes
DragonFly BSD uses the hybrid OpenSSL + cryptodev(9) approach that can be found in crypto-dev.c. OpenSSL is only used for the hash/pbkdf2. The encryption/decryption is performed via cryptodev(9) with enabled cryptosoft.
On Linux gcrypt is used for the encryption and decryption. For the hash/pbkdf2 either gcrypt or OpenSSL can be used. gcrypt only supports pbkdf2 since its July 2011 release (1.5.0), while OpenSSL has had pbkdf2 since around December 2010, so its easier to find in most distros.
The crypto options can be chosen with make/Makefile parameters. Building on Linux is as easy as doing
make -f Makefile.classic SYSTEM=linux
you can even skip the SYSTEM=linux, since that's the default. To choose the PBKDF backend, you can use either,
make -f Makefile.classic PBKDF_BACKEND=openssl
or
make -f Makefile.classic PBKDF_BACKEND=gcrypt
The interface to device mapper is libdevmapper on Linux and libdm on DragonFly. libdm is a BSD-licensed version of libdevmapper that I hacked together in a few hours.
On Ubuntu, the following dev packages are needed to build tcplay:
apt-get install libdevmapper-dev libgcrypt11-dev uuid-dev
cmake
New in version 1.0 is a cmake build system. tcplay can now be built using:
mkdir objdir
cd objdir
cmake ..
make
NOTE: building inside the source directory is discouraged, so please do build inside an "objdir" directory. If you happen to do it anyway, you can clean up behind cmake using:
make -f Makefile.classic clean_cmake_mess
This process will check for dependencies and automatically select whether to use OpenSSL or gcrypt as PBKDF backend.
In addition, this process will also generate a .pc file (pkg-config) for the tcplay library.
The classic single-file Makefile can still be used for building, however, using
make -f Makefile.classic
Or, if you only want the command line tool:
make -f Makefile.classic tcplay
Documentation
Please refer to the man pages bundled with tcplay.
Download for packaging
Latest release can be found as a (source) tarball at:
https://github.com/bwalex/tc-play/archive/v1.1.tar.gz
Bugs
Please report all bugs on the github issue tracker. If appropriate, please attach a small test volume which you think tcplay isn't handling correctly. The reduce_test_vol.sh script in test/ can significantly reduce the size of a volume when compressed by stripping out all the unnecessary data, leaving only the headers. After that, just bzip2 it and it should be fairly tiny.
What would be even better is if you could write a small test case to reproduce the issue. The README in the test/ directory has information on how to write tests for tcplay.
OS Support
tcplay is now available for both DragonFly BSD and Linux. It is a core part of the DragonFly BSD operating system and is available in a number of linux distros.
Licensing
The project is under a two-clause BSD license. I would consider dual-licensing it if required. Drop me an email to discuss the options.
Development
tcplay is pretty much stable, but if you find a bug, please report it. If anyone wants to add new features or port it to another OS, I'll gladly merge your changes into this repository so that there is a single point of contact.
I've noticed that sometimes bugs are only reported downstream (e.g. in the distro's bugtracker). Please make sure those bugs are also reported upstream on github, otherwise odds are they will never reach me.
Bugs in the TrueCrypt documentation
The TrueCrypt documentation is pretty bad and does not really represent the actual on-disk format nor the encryption/decryption process.
Some notable differences between actual implementation and documentation:
- PBKDF using RIPEMD160 only uses 2000 iterations if the volume isn't a system volume.
- The keyfile pool is not XOR'ed with the passphrase but modulo-256 summed.
- Every field except the minimum version field of the volume header are in big endian.
- Some volume header fields (creation time of volume and header) are missing in the documentation.
- All two-way cipher cascades are the wrong way round in the documentation, but all three-way cipher cascades are correct.