liballium: A C Tor Pluggable Transports Utility Library Yawning Angel

liballium attempts to reduce the amount of boilerplate code required to implement pluggable transports for Tor in C or C++.

Features:

• Handles the runtime configuration of PT clients and servers
• (TODO) Routines for talking to the transport control port
• (TODO) Routines for talking to the extended OR port (including a traffic shaper)

liballium embeds the following third party codebases:

• Better String Library (safer string manipulation routines)
• sput (unit test framework, included in tests only)

Specs implemented:

• https://gitweb.torproject.org/torspec.git/blob/HEAD:/pt-spec.txt
• (TODO) https://gitweb.torproject.org/torspec.git/blob/HEAD:/proposals/196-transport-control-ports.txt

Notes:

• Basic familiarity with the relevant Tor specs is assumed.
• The code should work on Windows, however it is untested on that platform and most likely requires changes. Patches accepted.
• The Tor Pluggable Transport spec does not currently specify the format for IPv6 addresses. liballium assumes that the standard [addr]:port form is to be used.

Known gotchas:

• allium_ptcfg_state_dir()/allium_ptcfg_auth_cookie_file() will probably misbehave if the paths are non-ASCII. This behavior is not considered a bug as environment variable values are NULL terminated by definition (See IEEE Std. 1003.1 8.1).
• liballium is slightly more strict than pt-spec.txt for the contents of PTCFG_SERVER_TRANSPORT_OPTIONS. In particular, the "k" string is not unescaped when doing processing, so things like "foo:arg\=bleah=123" will cause a ENV-ERROR to be returned to Tor (As of the date of writing this library, that functionality is still rather experimental in Tor anyway).
• tests/ptcfg_test.c depends on inet_pton so it won't run on ancient systems. A notable one would be WinXP. This probably won't be fixed.

See the COPYING file for licence related information.