NaCl(1)

🌸 NaCl(1) — CurveCP 🌸

okay bestie, buckle up, this is the NaCl(1) page from the General Commands Manual and it's literally all about CurveCP — the message-handling programs. it's giving ✨ cryptography ✨ and it's a whole vibe, let's go 💅

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💖 NAME 💖

CurveCP — Message-handling programs

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✨ SYNOPSIS ✨

curvecpserver [-q (optional)]  [-Q (optional)]  [-v (optional)]  [-c
n(optional)]  [sname]  [keydir]  [ip]  [port]  [ext]  [prog]

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🦋 DESCRIPTION 🦋

so this manual page documents, like, briefly, the CurveCP commands. that's the whole job, no cap.

A traditional UNIX-style server such as ftpd handles just one network connection — it reads input from stdin and writes output to stdout. simple era. but a "superserver" such as inetd or tcpserver listens for network connections and starts a separate server process for each connection. multitasking queen behavior 👑

The CurveCP command-line tools have an extra level of modularity, and honestly? it's iconic. The curvecpserver superserver listens for network connections. For each connection, curvecpserver starts the curvecpmessage message handler; curvecpmessage then starts a server such as ftpd. Then ftpd sends a stream of data to curvecpmessage, which in turn sends messages to curvecpserver, which encrypts and authenticates the messages and sends them inside network packets. At the same time curvecpclient receives network packets, verifies and decrypts messages inside the packets, and passes the messages to curvecpmessage; curvecpmessage sends a stream of data to ftpd. The same curvecpmessage tool is also used by curvecpclient. it's a whole relay race and everybody's passing the baton 🏃♀️💨

curvecpserver and curvecpclient can use programs other than curvecpmessage. Those programs can directly generate messages in the CurveCP message format without talking to separate tools such as ftpd; or they can support a completely different protocol that reuses CurveCP's cryptographic layer but transmits different kinds of messages. mix and match, main character energy 🔥

This page explains what programmers have to do to write curvecpmessage replacements that talk to curvecpserver and curvecpclient. so yeah, it's a how-to, bestie 🫶

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🙈 Incoming messagess 🙈

File descriptor 8 is a pipe. Read from this pipe a length byte n, between 1 and 68, and a 16*n-byte message. Repeat. The pipe is set to non-blocking mode; be prepared for EAGAIN and EWOULDBLOCK, even in the middle of a message. 😭 yes, even mid-message. rude but true.

This pipe reading must always be active. The curvecpclient and curvecpserver programs assume that every message is read immediately. If you can't handle a message immediately, read it and put it onto a queue. If you don't have queue space, throw the message away; this shouldn't cause trouble, since you have to be able to handle missing messages in any case. so like, dropping messages is fine?? ok periodt, that's just the design 💀

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🎀 Outgoing messagess 🎀

File descriptor 9 is a pipe. Write to this pipe a length byte n, between 1 and 68, and a 16*n-byte message. Repeat. The pipe is set to non-blocking mode; be prepared for EAGAIN and EWOULDBLOCK, even in the middle of a message. same energy, different pipe 🦋

As a client, do not use length bytes above 40 until a message has arrived from the server. (The messages inside CurveCP Initiate packets are limited to 640 bytes.) okay so that's a real limit, respect it bestie 🙏

The CurveCP server does not start until it has received a message from the client. Furthermore, the CurveCP server must receive this message within 60 seconds of the client starting up. (The CurveCP Initiate packet is valid for only 60 seconds after the corresponding CurveCP Cookie packet.) This does not mean that the client must start sending messages immediately, but it does mean that waiting for more than a second to send a message is a bad idea. ⏰ girl the clock is ticking

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💅 OPTIONS 💅

How to use curvecpserver:

• -q — optional. no error messages. 🤫
• -Q — optional. print error messages (default). 🗣️
• -v — optional. print extra information. 🤓
• -c n — optional. allow at most n clients at once (default 100). 👯♀️
• sname — server's name.
• keydir — use this public-key directory. 🔑
• ip — server's IP address.
• port — server's UDP port.
• ext — server's extension.
• prog — run this server.

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👑 SEE ALSO 👑

curvecpmessage (1), curvecpclient (1), inetd (8), tcpserver (1).

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🌈 AUTHOR 🌈

This manual page was written by Sergiusz Pawlowicz debian@pawlowicz.name for the Debian system (and may be used by others). The source of this page is a webpage https://curvecp.org/messageapi.html. Permission is granted to copy, distribute and/or modify this document under public domain. ✨

This manual page was rewritten for the Debian distribution because the original program does not have a manual page. (iconic of us, honestly 💖)

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and that's the whole page, bestie!! 🫶 you now know CurveCP's message API better than like 90% of people. go write that curvecpmessage replacement, you've got this 💪💜

NaCl(1) 🎀⭐💖