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Full Discussion: How to set a non-login non-interactive shell for a user?
Homework and Emergencies Homework & Coursework Questions How to set a non-login non-interactive shell for a user? Post 302930026 by cjcox on Monday 29th of December 2014 05:28:27 PM
Old 12-29-2014
Ok... it gets sort of shell specific. Shells will source in certain files if the are "interactive".... however, some shell allow you to override that... With that said, often time trying to override it will break things... so for example if somebody does:

Code:
ssh noninteractiveuser@somemachine.com sh -i

Which is fairly generic and pretty portable... you'd get this weird pseudotty-less interactive session on the remote host. It may error, and of course, it won't work like a true interactive shell... and note, other things won't work right without a tty.... so it's "ok" and a common hackers way to get an almost interactive session going.

But... since Linux has effectively stomped Unix into the ground, we can assume that all shells are bash nowadays :-). If so, the shell variable dash (e.g. $-) will contain attributes enabled on the shell... if it contains an "i" then the shell is interactive. So, in the case of our hack attempt above, you won't get an "i" in the string returned.

So... can you set a user up as a non-interactive user? I hope you can see the answer is yes and if using bash, you may even be able to circumvent typical ways of getting around it (but probably not every way).

The rest is left as an exercise for the reader.... can't give you all the answers!!

---------- Post updated at 04:05 PM ---------- Previous update was at 03:56 PM ----------

I'm feeling generous...

Put this into the .bashrc of the user:

Code:
echo "$-" | grep 'i' && exit 0

---------- Post updated at 04:14 PM ---------- Previous update was at 04:05 PM ----------

aack... it's buggy... not well thought out... the sh -i trick works against it. But anyway, probably will lead you to a solution.

---------- Post updated at 04:28 PM ---------- Previous update was at 04:14 PM ----------

Ok... scrap class... anyone know of a way to circumvent ssh ... sh -i and make that not work? I smell a vulnerability in bash.
 

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LEARN ABOUT DEBIAN

surfraw-update-path

SURFRAW-UPDATE-PATH(1)					User Contributed Perl Documentation				    SURFRAW-UPDATE-PATH(1)

NAME

       surfraw-update-path - updates PATH in shell config files

SYNOPSIS

       surfraw-update-path [-add] [-remove] [-check] [-sys] [-all] [-help] [-shell=SHELL]

DESCRIPTION

       surfraw-update-path adds the surfraw elvi directory (/usr/lib/surfraw) to your PATH in your shell's config file.

       Currently it supports bash, sh, csh, tcsh, ash, dash, ksh, pdksh, zsh, rc, and es

       Don't forget to login again or source your login files for it to take effect.

OPTIONS

       -check
	   Checks to see if the surfraw config code is present.  This is the default.

       -add
	   Adds the surfraw config code.

       -remove
	   Removes the surfraw config code

       -sys
	   Updates the system-wide shell config instead of the user.  Must be done as root.

       -shell=SHELL
	   Selects the shell to configure. Defaults to the value of the $SHELL environment variable.

	   Currently supported shells are:

	   sh, ash, bash, dash, csh, tcsh, ksh, pdksh, zsh, rc, and es.

       -all
	   Attempts to configure the startup files for all known shells

       -help
	   Gives a usage message

RETURN VALUE

       -check returns 0 if the surfraw code is present in the file, 1 if it is not found, or 2 on error.

       All other options return 0 on success, or 2 on error.

ENVIRONMENT

       SHELL
	   Used to determine which shell to configure, if -shell is not given.

       HOME
	   Used to find users config files.

       ENV Used by posix-compliant shells to specify a startup rc file.

       ZDOTDIR
	   Used to find user config files for zsh. If not set, defaults to HOME.

SEE ALSO

       surfraw(1), sh(1), ash(1), bash(1), dash(1), csh(1), tcsh(1), ksh(1), pdksh(1), zsh(1), rc(1), es(1)

AUTHOR

       Ian Beckwith <ianb@erislabs.net>

perl v5.12.4							    2011-07-12						    SURFRAW-UPDATE-PATH(1)
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