Re: [PATCH] git-quiltimport: fix security risk because of un-sanitized $level.

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 12, 2008, 20:55 UTC
Message-ID: <7v63vr64rn.fsf@gitster.siamese.dyndns.org>
In-Reply-To: <20080312204648.GA28729@artemis.madism.org>

Pierre Habouzit <madcoder@debian.org> writes:

Show 10 quoted lines

> Signed-off-by: Pierre Habouzit <madcoder@debian.org>
> ---
>
>   I assume that nobody will have a series with -p1000 in it :)
>   sorry for this gross mistake in the first place.
>
>   [ for the inattentive readers $level was used without quoting, for
>     good reasons as it's sometime empty and then we don't want to pass
>     an empty argument to git-apply, though someone could use that to run
>     arbitrary commands, not nice ]

A traditional way to deal with that situation in shell scripts is to use this idiom:

	${var_that_may_not_be_set+"$var_that_may_not_be_set"}

You can use :+ in place of + to also reject empty string on modern systems.

#!/bin/sh not_set=t ; unset not_set is_set=t

report () {
	echo "I got $# args"
        i=1
        for it
        do
        	echo "$i: $it"
                i=$(( $i+1 ))
	done
        echo
}

report sending not_set ${not_set:+"$not_set"} string report sending is_set ${is_set:+"$is_set"} string