Re: Insecure use of file in /tmp by trn

[pfaffben () MSU EDU (Ben Pfaff)]

Rogier Wolff <R.E.Wolff () BITWIZARD NL> writes:

   Creating a tempfile from a C program is possible since we have a
   mkstmp call. It is sufficiently tricky that I wouldn't dare
   replicating the functionality myself. Creating a private directory in
   /tmp and putting the tempfiles in there might be the only solution for
   shell scripts.

Debian uses a program called `mktemp' to create temporary files in
shell scripts.  Other distributions might well adopt this or a similar
solution.  An excerpt from its manpage is enclosed below.

SYNOPSIS
     mktemp [-q] [-u] template

DESCRIPTION
     The mktemp utility takes the given file name template and overwrites a
     portion of it to create a file name.  This file name is unique and suit-
     able for use by the application.  The template is any file name with six
     `Xs' appended to it, for example /tmp/temp.XXXXXX. The `Xs' are replaced
     with the current process number and/or a unique letter combination.
     Roughly 26 ** 6 combinations are tried.

     If mktemp can successfully generate a unique file name, the file is cre-
     ated with mode 0600 (unless the -u flag is given) and the filename is
     printed to standard output.

     Debian packages using mktemp in maintainer scripts must depend on de-
     bianutils >= 1.7.

EXAMPLES
     The following sh(1) fragment illustrates a simple use of mktemp where the
     script should quit if it cannot get a safe temporary file.

           p=`basename $0`
           TMPFILE=`mktemp /tmp/$p.XXXXXX` || exit 1
           echo "program output" >> $TMPFILE