As a personal research project I wanted to add post-quantum crypto KEM (key encapsulation) algorithms and new symmetric crypto session algorithms to openssh. I found the openssh code and its channel/context management extremely complex.
Concurrently, I was learning Go. It occurred to me that Go's excellent standard library, including crypto libraries, plus its much safer memory model and string/buffer handling would be better suited to a secure remote shell solution. So I started from scratch, writing a clean-room Go-based solution, without regard for ssh compatibility. Interactive and token-based login, secure copy and tunnels.
Of course, it needs a proper security audit for side channel attacks, protocol vulnerabilities and so on -- but I was impressed by how much simpler a client-server application with crypto and complex terminal handling was in Go.
<pre> $ sloc openssh-portable Languages Files Code Comment Blank Total CodeLns Total 502 112982 14327 15705 143014 100.0% C 389 105938 13349 14416 133703 93.5% Shell 92 6118 937 1129 8184 5.7% Make 16 468 37 131 636 0.4% AWK 1 363 0 7 370 0.3% C++ 3 79 4 18 101 0.1% Conf 1 16 0 4 20 0.0% $ sloc xs Languages Files Code Comment Blank Total CodeLns Total 34 3658 1231 655 5544 100.0% Go 19 3230 1199 507 4936 89.0% Markdown 2 181 0 76 257 4.6% Make 7 148 4 50 202 3.6% YAML 1 39 0 5 44 0.8% Text 1 30 0 7 37 0.7% Modula 1 16 0 2 18 0.3% Shell 3 14 28 8 50 0.9% </pre>
