From b3b5611e046b93fb20aa783d6d11d986f33f91f6 Mon Sep 17 00:00:00 2001

From: Paul Eggert <eggert <at> cs.ucla.edu>

Date: Thu, 3 Oct 2013 21:12:09 -0700

Subject: [PATCH] znew: avoid denial-of-service issue

Reported by Rich Burridge in <http://bugs.gnu.org/15522>.

* znew.in: Rewrite to avoid the need for a temporary file in /tmp.

That way, we avoid the need for set -C

and worrying about denial of service.

Use touch -r and chmod --reference rather than cpmod.

Assume cp -p works, as it's now universal.

Quote 'echo' args better, while we're at it.

(warn, tmp, cpmod, cpmodarg): Remove.

(GZIP): Unset, so that we needn't test for gzip extension.

(ext): Now always '.gz'.

* znew.1: Document the change of implementation assumptions.

---

diff --git a/znew.1 b/znew.1

index dcdf84f..2a7e5e1 100644

--- a/znew.1

+++ b/znew.1

@@ -32,9 +32,16 @@ Keep a .Z file when it is smaller than the .gz file; implies

 .SH "SEE ALSO"

 gzip(1), zmore(1), zdiff(1), zgrep(1), zforce(1), gzexe(1), compress(1)

 .SH BUGS

-.I Znew

-does not maintain the time stamp with the -P option if

-.I cpmod(1)

-is not available and

-.I touch(1)

-does not support the -r option.

+If the

+.B \-P

+option is used,

+.I znew

+does not maintain the time stamp if

+.IR touch (1)

+does not support the

+.B \-r

+option, and does not maintain permissions if

+.IR chmod (1)

+does not support the

+.B \-\-reference

+option.

diff --git a/znew.in b/znew.in

index 9bd3ce9..d16311a 100644

--- a/znew.in

+++ b/znew.in

@@ -58,33 +58,9 @@ new=0

 block=1024

 # block is the disk block size (best guess, need not be exact)

-warn="(does not preserve modes and timestamp)"

-tmp=${TMPDIR-/tmp}/zfoo.$$

-set -C

-echo hi > $tmp || exit

-if test -z "`(${CPMOD-cpmod} $tmp $tmp) 2>&1`"; then

-  cpmod=${CPMOD-cpmod}

-  warn=""

-fi

-

-if test -z "$cpmod" && ${TOUCH-touch} -r $tmp $tmp 2>/dev/null; then

-  cpmod="${TOUCH-touch}"

-  cpmodarg="-r"

-  warn="(does not preserve file modes)"

-fi

-

-# check if GZIP env. variable uses -S or --suffix

-gzip -q $tmp

-ext=`echo $tmp* | sed "s|$tmp||"`

-rm -f $tmp*

-if test -z "$ext"; then

-  echo znew: error determining gzip extension

-  exit 1

-fi

-if test "$ext" = ".Z"; then

-  echo znew: cannot use .Z as gzip extension.

-  exit 1

-fi

+# Beware -s or --suffix in $GZIP.

+unset GZIP

+ext=.gz

 for arg

 do

@@ -116,26 +92,27 @@ if test -n "$opt"; then

 fi

 for i do

-  n=`echo $i | sed 's/.Z$//'`

+  n=`echo "$i" | sed 's/.Z$//'`

   if test ! -f "$n.Z" ; then

-    echo $n.Z not found

+    echo "$n.Z not found"

     res=1; continue

   fi

   test $keep -eq 1 && old=`wc -c < "$n.Z"`

   if test $pipe -eq 1; then

     if gzip -d < "$n.Z" | gzip $opt > "$n$ext"; then

       # Copy file attributes from old file to new one, if possible.

-      test -n "$cpmod" && $cpmod $cpmodarg "$n.Z" "$n$ext" 2> /dev/null

+      touch -r"$n.Z" -- "$n$ext" 2>/dev/null

+      chmod --reference="$n.Z" -- "$n$ext" 2>/dev/null

     else

-      echo error while recompressing $n.Z

+      echo "error while recompressing $n.Z"

       res=1; continue

     fi

   else

     if test $check -eq 1; then

-      if cp -p "$n.Z" "$n.$$" 2> /dev/null || cp "$n.Z" "$n.$$"; then

+      if cp -p "$n.Z" "$n.$$"; then

         :

       else

-        echo cannot backup "$n.Z"

+        echo "cannot backup $n.Z"

         res=1; continue

       fi

     fi

@@ -143,7 +120,7 @@ for i do

       :

     else

       test $check -eq 1 && mv "$n.$$" "$n.Z"

-      echo error while uncompressing $n.Z

+      echo "error while uncompressing $n.Z"

       res=1; continue

     fi

     if gzip $opt "$n"; then

@@ -151,10 +128,10 @@ for i do

     else

       if test $check -eq 1; then

         mv "$n.$$" "$n.Z" && rm -f "$n"

-        echo error while recompressing $n

+        echo "error while recompressing $n"

       else

         # compress $n  (might be dangerous if disk full)

-        echo error while recompressing $n, left uncompressed

+        echo "error while recompressing $n, left uncompressed"

       fi

       res=1; continue

     fi

@@ -175,7 +152,7 @@ for i do

     else

       test $pipe -eq 0 && mv "$n.$$" "$n.Z"

       rm -f "$n$ext"

-      echo error while testing $n$ext, $n.Z unchanged

+      echo "error while testing $n$ext, $n.Z unchanged"

       res=1; continue

     fi

   elif test $pipe -eq 1; then

-- 

1.8.3.1