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tiprotd

An implementation of multiple trivial and abadoned network protocols, with a twist. It is written in Rust, using the low-level async library mio.

Implemented protocols

  • echo (TCP, UDP and UDPlite port 7, unix stream, seqpacket and datagram socket)
  • discard (TCP, SCTP, UDP and UDPlite port 9, unix stream, seqpacket and datagram socket, posix message queue, pipe)
  • daytime (TCP, UDP and UDPlite port 13, unix stream, seqpacket and datagram socket)
  • QOTD (TCP, UDP and UDPlite port 17, unix stream, seqpacket and datagram socket)
  • chargen (TCP, UDP and UDPlite port 17, unix stream, seqpacket and datagram socket)
  • time (TCP, UDP and UDPlite port 37, unix stream, seqpacket and datagram socket)

To prevent being used for UDP amplification DDoS attacks, UDP replies are limited to 1 MiB per IPv4 address or IPv6 /64 network within a 10 minute window unless a TCP connection has been made from that IP. Some protocols also send less data or don't respond to unverified clients.

The unix domain protocols listen to abstract addresses in addition to path-based addresses in the current directory.

I plan to eventually also implement TCPMUX (port 1), TFTP (port 69) and Modbus TCP (port 502) and want to also support the transport layer protocols DCCP and SCTP fully.

Invocation

Command line arguments are ignored and there is no way to select which protocols to enable or where they listen. Quotes to send from QOTD are read from quotes.txt in the current directory. Quotes are separated by lines starting with three or more dashes. The content used for chargen is read from LICENSE.md.

If binding to the first port fails due to permission error, it will add 10000 to the port numbers and try again. (so echo becomes port 10007 and time becomes port 10037) It does not drop root privileges after setting up the listening sockets, so for security it should be given the CAP_NET_BIND_SERVICE capability and then run as a normal user:

cargo build --release
sudo setcap CAP_NET_BIND_SERVICE=+eip target/release/tiprotd
sudo -u nobody target/release/tiprotd

Clients

For most protocols, netcat or socat is all you need; For example use nc -u localhost 10007 for UDP echo running on an unprivileged port or socat - TCP6:[::1]:10017 for TCP QOTD.

Tip: to make netcat terminate after receiving the TCP response, pass it the -N flag and redirect stdin to /dev/null: nc -N 127.0.0.1 10017 </dev/null

To find the listening sockets, (on Linux) run ss --listening --query inet --numeric -processes or sudo netstat --listening --numeric-ports --inet --inet6 --programs.

In clients/ there are protocol-specific clients and simple programs I wrote to get familiar with the transport layer protocols and sockets programming in general.

License

Copyright 2019, 2021 Torbjørn Birch Moltu

This program can be redistributed and/or modified under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License along with this program. If not, see https://www.gnu.org/licenses/

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, shall be licensed as above, without any additional terms or conditions.