[PATCH] src_postinst.cygpart: Sanitize binary data in bash command subst

[Eric Blake]

On 12/16/2016 02:40 PM, Eric Blake wrote:
> bash 4.4 now warns about skipping NUL bytes in $(command), since
> command substitution is only well-formed for commands that output
> text, but NUL bytes are not text.  Silence the warning by removing
> NUL bytes from the stream before bash can see them.
> ---
>  lib/src_postinst.cygpart | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/src_postinst.cygpart b/lib/src_postinst.cygpart
> index 30ad90e..2ae26b6 100644
> --- a/lib/src_postinst.cygpart
> +++ b/lib/src_postinst.cygpart
> @@ -967,14 +967,14 @@ __prepstrip() {
>  		# Magic number is at end of file:
>  		# http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=256900#74
>  		# http://cygwin.com/ml/cygwin-apps/2010-10/msg00057.html
> -		case $(tail -c 12 "${exe}") in
> +		case $(tail -c 12 "${exe}" | tr -d '\0') in
>  			Caml1999X0[0-9][0-9])  continue ;;
>  		esac
> 
>  		# Perl Archive (PAR) binaries must not be stripped
>  		# https://rt.cpan.org/Public/Bug/Display.html?id=18536
>  		# http://cygwin.com/ml/cygwin-apps/2012-07/msg00088.html
> -		case $(tail -c 8 "${exe}" | tr '\012' '%') in
> +		case $(tail -c 8 "${exe}" | tr '\012\0' '%') in
>  			%PAR\.pm%)  continue ;;
>  		esac

And of course, reading this in isolation, we could shave a process or
two by merging the two case statements into one, if you want to go one
step further as a micro-optimization:

diff --git i/lib/src_postinst.cygpart w/lib/src_postinst.cygpart
index 2ae26b6..ac045ee 100644
--- i/lib/src_postinst.cygpart
+++ w/lib/src_postinst.cygpart
@@ -967,15 +967,12 @@ __prepstrip() {
 		# Magic number is at end of file:
 		# http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=256900#74
 		# http://cygwin.com/ml/cygwin-apps/2010-10/msg00057.html
-		case $(tail -c 12 "${exe}" | tr -d '\0') in
-			Caml1999X0[0-9][0-9])  continue ;;
-		esac
-
 		# Perl Archive (PAR) binaries must not be stripped
 		# https://rt.cpan.org/Public/Bug/Display.html?id=18536
 		# http://cygwin.com/ml/cygwin-apps/2012-07/msg00088.html
-		case $(tail -c 8 "${exe}" | tr '\012\0' '%') in
-			%PAR\.pm%)  continue ;;
+		case $(tail -c 12 "${exe}" | tr '\012\0' '%') in
+			*%PAR\.pm%)  continue ;;
+			Caml1999X0[0-9][0-9])  continue ;;
 		esac

 		echo "        ${exe}";


-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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