install-sh -s on readonly file

install-sh -s on readonly file

[Karl Berry]

Hi - I sent this possible patch for install-sh to bug-automake
(https://debbugs.gnu.org/cgi/bugreport.cgi?bug=36966, appended below for
convenience).  My fix seems clunky to me, but neither Jim nor I could
think of a better way and there were no replies on the list.  I just
thought I'd send it here to see if anyone had any ideas before we
install it ... --thanks, karl.


From: Karl Berry <karl@freefriends.org>
To: bug-automake@gnu.org
Subject: install-sh -s on 555 executable fails

(I'm not on this list, so please keep me in cc if need be.)

It seems that install-sh -s (what automake's install-strip target can
end up doing) fails if the original file doesn't have the owner-write
bit set:

cp /bin/cp /tmp/rx            # any binary will do
chmod 555 /tmp/rx             # make unwritable to owner
install-sh -s /tmp/rx /tmp/sx # try to install, with strip
-> strip: unable to copy file '/tmp/_inst.31092_'; reason: Permission denied
echo $?
-> 1

Although install-sh (version 2018-03-11.20, lines 224ff.) does some
stuff to ensure that umask will not clear an owner-writable bit in the
destination, that's not enough to make it owner-writable if it's not
already.

The only less-than-wonderful fix I could come up with is to explicitly
do chmod u+w if strip is being executed. I thought maybe it would be
worth trying the strip even if the chmod failed, hence the ; instead of
&&, but it's not something I feel strongly about. And maybe there is
some nicer way to do it altogether.

--- a/build-aux/install-sh
+++ b/build-aux/install-sh
@@ -461,7 +461,7 @@ do
     #
     { test -z "$chowncmd" || $doit $chowncmd "$dsttmp"; } &&
     { test -z "$chgrpcmd" || $doit $chgrpcmd "$dsttmp"; } &&
-    { test -z "$stripcmd" || $doit $stripcmd "$dsttmp"; } &&
+    { test -z "$stripcmd" || ($doit $chmodcmd u+w "$dsttmp"; $doit $stripcmd "$dsttmp") } &&
     { test -z "$chmodcmd" || $doit $chmodcmd $mode "$dsttmp"; } &&
 
     # If -C, don't bother to copy if it wouldn't change the file.


Wdyt? --thanks, karl.

Re: install-sh -s on readonly file

[Paul Eggert]

[-- Attachment #1: Type: text/plain, Size: 287 bytes --]

Karl Berry wrote:
> -    { test -z "$stripcmd" || $doit $stripcmd "$dsttmp"; } &&
> +    { test -z "$stripcmd" || ($doit $chmodcmd u+w "$dsttmp"; $doit $stripcmd "$dsttmp") } &&

How about the attached Automake patch instead? It avoids the extra forks and 
exec. Admittedly it's longer.

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-install-sh-support-s-with-read-only-source.patch --]
[-- Type: text/x-patch; name="0001-install-sh-support-s-with-read-only-source.patch", Size: 1281 bytes --]

From c50db415f06d3a29780fe9650654165f6fa28bf0 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Sun, 25 Aug 2019 18:51:26 -0700
Subject: [PATCH] install-sh: support -s with read-only source
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Problem reported by Karl Berry in:
https://lists.gnu.org/r/bug-gnulib/2019-08/msg00067.html
* lib/install-sh: If -s is given, create the temporary file
with $cp_umask so that ‘strip’ can write to it.
---
 lib/install-sh | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/lib/install-sh b/lib/install-sh
index 8175c640f..1f5cdccc7 100755
--- a/lib/install-sh
+++ b/lib/install-sh
@@ -451,7 +451,16 @@ do
     trap 'ret=$?; rm -f "$dsttmp" "$rmtmp" && exit $ret' 0
 
     # Copy the file name to the temp name.
-    (umask $cp_umask && $doit_exec $cpprog "$src" "$dsttmp") &&
+    (umask $cp_umask &&
+     { test -z "$stripcmd" || {
+	 if test -z "$doit"; then
+	   : >"$dsttmp" # No need to fork-exec 'touch'.
+	 else
+	   $doit touch "$dsttmp"
+	 fi
+       }
+     } &&
+     $doit_exec $cpprog "$src" "$dsttmp") &&
 
     # and set any options; do chmod last to preserve setuid bits.
     #
-- 
2.21.0

Re: install-sh -s on readonly file

[Karl Berry]

Hi Paul,

    How about the attached Automake patch instead? 

Thanks much. Clever. Seems good to me. Can you install it in am, please?

Perhaps it is worth a comment that it's desired to create the file with
$cp_umask (not just cp-ing it), in order in ensure $dsttmp is writable,
else strip can fail. Otherwise there is no obvious reason for the
complicated sequence.  At least if I'm understanding correctly what you
are doing ... --thanks, karl.

Re: install-sh -s on readonly file

[Paul Eggert]

Karl Berry wrote:
> Can you install it in am, please?
> 
> Perhaps it is worth a comment

Thanks for checking. I installed it into Automake master, with a comment.