Replace grep with getent in entrypoint.sh

[nfsec]

Use simpler, native "getent" command to get entries from NSS insead of "grep".

[adfoster-r7]

Thanks for the PR! I'm in favor of the existing grep functionality here as it's a bit more human readable

[nfsec]

Can you please explain how grep is more readable?

[adfoster-r7]

My opinion - everyone knows about grep - someone seeing this for the first time is likely to have to read the getent docs 😄

[nfsec]

Thanks for the opinion. My opinion is that learning commands should not end on grep.

[bwatters-r7]

Honestly, I'd never see this command before, so I looked it up, and this situation seems exactly what this command is for? My only concern is that online someone suggested their zshell implemented this manually rather than using a POSIX executable, though they did not site the OS. Forgive my ignorance of this command, but I know grep is well-supported across a long history of unix/linux/BSD, and from some brief reading it appears getent is as well.
I did see varying opinions on whether or not it was supported on OSX; my assumption is that it would work. Also, since this is to let people run Metasploit in a docker container, I'd expect anything to be relatively recent.

TL;DR: I'm for it, but we should make sure the support is universal to the expected use-cases.

[adfoster-r7]

For my env on OSX with zsh it was a shell script yeah, which just uses grep:

$ which getent
getent () {
	if [[ $1 = hosts ]]
	then
		sed 's/#.*//' /etc/$1 | grep -w $2
	elif [[ $2 = <-> ]]
	then
		grep ":$2:[^:]*$" /etc/$1
	else
		grep "^$2:" /etc/$1
	fi
}

And it wasn't available in OSX's bash:

bash-3.2$ getent
bash: getent: command not found

Since this is only being used in the docker entrypoint though in an environment we control, and if we ever change the base image the test suite will fail if getent isn't available, I'm happy enough to land this 👍

[adfoster-r7]

Release Notes

Updates the docker entrypoint script to use getent instead of grep when detecting user/group details