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purr-c

This repository holds some loosely related networking projects of mine. This is mainly a learning exercise for network, crypto and SSL programming, and all of the programs inside should be treated as such.

The BearSSL library was chosen as the crypto and SSL implementation.

The code has a few instances of // TODO: remove hack comments and the like, which I hope to get to someday.

Building

The only external dependency is BearSSL - on Void Linux, this can be obtained with the bearssl-devel package. GNU Make and a C99 compiler, such as cproc, are required for building.

You can build and install the project with the commands below:

$ ./configure # creates config.mk
$ make
$ make install PREFIX=$HOME/.local

Alternatively, you can use the Meson build system:

$ meson build --prefix $HOME/.local
$ ninja -C build
$ ninja -C install

Programs

purr

This is a pure C client for the PurritoBin pastebin server, and uses PurritoBin's author's instance in https://bsd.ac by default.

It supports symmetric paste encryption (as supported by PurritoBin's online interface and its suggested clients). This makes it possible to share paste links that can only be decrypted by someone who has the keys to them. The key and IV are stored in the url's hash property, and are never sent to the server.

It can also work as a very limited curl alternative, due to its support of both HTTP and HTTPS. It uses HTTP/1.0 for communication, but requires the Content-Length field in the response header - this is done because I have found servers that don't send notify_close when their transmission is done, instead relying on the Content-Length field to provide enough information for the client to determine if the transmission was sucessful or if the connection was terminated before it should have been.

This program can use either Linux's getrandom(2) system call or BSD's arc4random_buf(3) function for key generation.

Usage

Usage information can be viewed with purr -h. There are two symlinks to the purr executable, meow and meowd, which are used as shortcuts to send and receive encrypted pastes, respectively.

gemi

This is a (not so dumb anymore) Gemini client. It doesn't support TOFU (Trust On First Use) yet, so it isn't fully compliant with the Gemini spec, but it can talk to any server, not being limited to those whose certificates can be verified by the local trust anchors.

It has a built-in "navigation" mechanism via the -b command line flag, which parses the received page, finds links, asks the user to select one, and execs into itself with the new link.

It supports parsing server messages, including redirects, and can deal with "complex" links, such as ../../docs. It is now in the process of being submitted to the browser torture test.

Usage

Usage information can be viewed with gemi -h.

Acknowledgements

  • Thomas Pornin for BearSSL
  • Laurent Bercot for s6-networking (even though it's no longer in use here)
  • epsilon-0 for PurritoBin (and the valuable help while I was testing this program)
  • paolostivanin for libbaseencode (also no longer used here)