Re: PATCH: compaudit allows owner of executable

[Peter Stephenson <p.w.stephenson@xxxxxxxxxxxx>]

On Wed, 30 Jan 2013 13:40:24 -0800
Danek Duvall <duvall@xxxxxxxxxxxxxx> wrote:
> On Wed, Jan 30, 2013 at 09:11:48PM +0000, Peter Stephenson wrote:
> > I couldn't think of a reasonably safe, standard way of finding out who
> > owns the executable, however.  So I've done it using the /proc file
> > system.  I've also assumed zstat is available from zsh/stat.
> > Suggestions for improvements welcome.
> 
> On Solaris, the path would be /proc/$$/object/a.out.  From the code, I
> think that'll work as far back as Solaris 2.6, but I don't have any old
> machines to verify that on.

Thanks, I now have the following.
 
> Solaris also has a "getexecname()" library call, also introduced in 2.6,
> but that would require writing C code, and making it available from shell
> code, which seems like it's more work (if slightly more stable an
> interface).  There also are ways to get this information on Solaris with
> dlinfo(), which may be more portable on other systems than getexecname().

Unfortunately I can't find those elsewhere.  I'll stick with the /proc
link.

Index: Completion/compaudit
===================================================================
RCS file: /cvsroot/zsh/zsh/Completion/compaudit,v
retrieving revision 1.11
diff -p -u -r1.11 compaudit
--- Completion/compaudit	10 Sep 2011 17:09:51 -0000	1.11
+++ Completion/compaudit	31 Jan 2013 19:43:07 -0000
@@ -82,18 +82,45 @@ fi
 
 [[ $_i_fail == use ]] && return 0
 
+# We will always allow files to be owned by root and the owner of the
+# present process.
+local _i_owners="u0u${EUID}"
+
+# Places we will look for a link to the executable
+local -a _i_exes
+_i_exes=(
+    /proc/$$/exe
+    /proc/$$/object/a.out
+    )
+local _i_exe
+
+# If we can find out who owns the executable, we will allow files to
+# be owned by that user, too.  The argument is that if you don't trust
+# the owner of the executable, it's way too late to worry about it now...
+for _i_exe in _i_exes; do
+  if [[ -e $_i_exe ]] ;then
+    if zmodload -F zsh/stat b:zstat 2>/dev/null; then
+      local -A _i_stathash
+      if zstat -H _i_stathash /proc/$$/exe &&
+	[[ $_i_stathash[uid] -ne 0 ]]; then
+	_i_owners+="u${_i_stathash[uid]}"
+      fi
+    fi
+    break
+  fi
+done
+
 # We search for:
-# - world/group-writable directories in fpath not owned by root and the user
+# - world/group-writable directories in fpath not owned by $_i_owners
 # - parent-directories of directories in fpath that are world/group-writable
-#   and not owned by root and the user (that would allow someone to put a
+#   and not owned by $_i_owners (that would allow someone to put a
 #   digest file for one of the directories into the parent directory)
-# - digest files for one of the directories in fpath not owned by root and
-#   the user
-# - and for files in directories from fpath not owned by root and the user
+# - digest files for one of the directories in fpath not owned by $_i_owners
+# - and for files in directories from fpath not owned by $_i_owners
 #   (including zwc files)
 
-_i_wdirs=( ${^fpath}(N-f:g+w:,-f:o+w:,-^u0u${EUID})
-           ${^fpath:h}(N-f:g+w:,-f:o+w:,-^u0u${EUID}) )
+_i_wdirs=( ${^fpath}(N-f:g+w:,-f:o+w:,-^${_i_owners})
+           ${^fpath:h}(N-f:g+w:,-f:o+w:,-^${_i_owners}) )
 
 # RedHat Linux "per-user groups" check.  This is tricky, because it's very
 # difficult to tell whether the sysadmin has put someone else into your
@@ -111,7 +138,7 @@ if (( $#_i_wdirs )); then
 
   if [[ $GROUP == $LOGNAME && ( -z $GROUPMEM || $GROUPMEM == $LOGNAME ) ]]
   then
-    _i_wdirs=( ${^_i_wdirs}(N-f:g+w:^g:${GROUP}:,-f:o+w:,-^u0u${EUID}) )
+    _i_wdirs=( ${^_i_wdirs}(N-f:g+w:^g:${GROUP}:,-f:o+w:,-^${_i_owners}) )
   fi
 fi
 
@@ -122,8 +149,8 @@ then
   _i_wdirs=( ${_i_wdirs:#/usr/local/*} ${^_i_ulwdirs}(Nf:g+ws:^g:staff:,f:o+w:,^u0) )
 fi
 
-_i_wdirs=( $_i_wdirs ${^fpath}.zwc^([^_]*|*~)(N-^u0u${EUID}) )
-_i_wfiles=( ${^fpath}/^([^_]*|*~)(N-^u0u${EUID}) )
+_i_wdirs=( $_i_wdirs ${^fpath}.zwc^([^_]*|*~)(N-^${_i_owners}) )
+_i_wfiles=( ${^fpath}/^([^_]*|*~)(N-^${_i_owners}) )
 
 case "${#_i_wdirs}:${#_i_wfiles}" in
 (0:0) _i_q= ;;

-- 
Peter Stephenson <p.w.stephenson@xxxxxxxxxxxx>
Web page now at http://homepage.ntlworld.com/p.w.stephenson/