[RFC] /etc/shells management (fish, mksh, posh, tcsh, zsh)

[Warren Young]

On May 12, 2016, at 3:36 PM, Yaakov Selkowitz <yselkowitz@cygwin.com> wrote:
> 
> What are the consequences of having shells listed in /etc/shells which aren't on the system?

That file is a security feature, but the typical way Cygwin works — i.e. that normal users are allowed to install software, modify /etc/*, and so forth — nullifies its value.

But, if you do somehow lock down /etc/shells so that normal users can’t write to it, you’re also presumably locking down /bin, so a malicious user couldn’t drop in a bogus /bin/fish file and convince other software to run it as a shell.

Too bad there is no /etc/shells.d.  Then non-Base shells could just add themselves there.