syntax: default highlighting for OpenSSH client/server config (ssh_config, sshd_config)

[tredondo]

Is there an existing request for this?

• I have searched the existing issues

Is your feature request related to a problem?

When opening /etc/ssh/sshd_config (or /etc/ssh/ssh_config, and their *.d/*.conf drop-ins) in mcedit, no syntax highlighting is applied and Options -> Syntax Highlighting shows unknown. These are among the most commonly edited system files on any Linux host, and editing them with highlighting would be nice.

The reason is that misc/syntax/Syntax.in only maps files whose name ends in .cfg, .cnf, or .conf to conf.syntax:

file ..\*\\.(?i:cfg|cnf|conf)$ Config\sfile
include conf.syntax

Since sshd_config and ssh_config use an underscore and have no extension, they fall through to the final file .\* unknown rule and get unknown.syntax.

Describe the solution you'd like

Map OpenSSH's canonical config filenames to a syntax definition by default. Two reasonable options:

1. Minimal (preferred for a first step) — reuse the existing generic conf.syntax. In misc/syntax/Syntax.in, before the unknown catch-all, add:

   file (.*/)?ssh(d)?_config(\\..*)?$ OpenSSH\sconfig\sfile
   include conf.syntax
   

   This covers ssh_config, sshd_config, and drop-ins under ssh_config.d/ / sshd_config.d/ (e.g. 50-cloud-init.conf users typically also have a parent ssh_config to edit). It immediately fixes the "unknown" status and gives #-comments, quoted strings, numbers, and = highlighting from conf.syntax.

2. Nicer (optional follow-up) — ship a dedicated misc/syntax/sshd.syntax (or openssh.syntax) that additionally highlights the well-known OpenSSH keywords as defined in sshd_config(5) and ssh_config(5) — e.g. Host, Match, Port, ListenAddress, PermitRootLogin, PasswordAuthentication, PubkeyAuthentication, AuthorizedKeysFile, AllowUsers, Ciphers, MACs, KexAlgorithms, HostKey, Subsystem, Include, etc., and the yes/no/prohibit-password value tokens. Then point the Syntax.in rule above at it instead of conf.syntax.

Either way, the user-visible improvement is: opening sshd_config in mcedit no longer shows "unknown" and gets at least baseline coloring out of the box.

Describe alternatives you've considered

• Temporarily tenaming/symlinking system files to sshd.conf so the existing *.conf rule kicks is
• Relying on the first-line regex in Syntax.in. sshd_config typically starts with # $OpenBSD: sshd_config,v ... but it's not unique enough to safely key off, so a filename rule is the right place.

Additional context

Happy to send a PR for option 1 (one-liner in Syntax.in) and if desired, a follow-up PR adding a dedicated sshd.syntax.

[zyv]

Hey, I was cautious about commenting on the built-in syntax enhancements in view of #5067, but apparently first it will take me a lot of time to deal with that, and second it might result in keeping our built-in system (alone or in parallel) anyways.

So yes, we would be interested in a dedicated sshd.syntax. I think the one-liner PR wouldn't help much, because the second PR is likely to land before we release.