mdw@git.distorted.org.uk Git - checkpath/blob - tmpdir.1

   1 .\" -*-nroff-*-
   2 .TH tmpdir 1 "6 April 1999" "Local tools"
   3 .SH NAME
   4 tmpdir \- choose, or check a choice of, temporary directory
   5 .SH SYNOPSIS
   6 .B tmpdir
   7 .RB [ \-bc ]
   8 .RB [ \-v
   9 .IR dir ]
  10 .SH USAGE
  11 The
  12 .B tmpdir
  13 program creates a secure place for temporary files to be stored, and
  14 outputs an assignment to the
  15 .B TMPDIR
  16 variable suitable for execution by a shell.
  17 .PP
  18 Many programs aren't sufficiently careful about how they handle
  19 temporary files.  For example, if a program which creates files in
  20 .B /tmp
  21 without making careful checks beforehand, a malicious user who can
  22 predict the name that the program will use can create a symbolic link
  23 with that name: when run, the program will then overwrite some file
  24 using your current privileges.  Similarly, many programs create
  25 temporary files using generous default permissions, which may well be a
  26 mistake.
  27 .PP
  28 The
  29 .B tmpdir
  30 program finds a secure place for temporary files, creating one if
  31 necessary.  The criteria it uses to choose a place are as follows:
  32 .IP "   1."
  33 The temporary directory must be owned by the user, and have mode 700
  34 (i.e., readable, writable and searchable only by the owner).
  35 .IP "   2."
  36 The path through the filesystem to the temporary directory must be
  37 secure against modifications by other malicious users.  See the
  38 .BR chkpath (1)
  39 manual page for a description of how this is done: the two programs work
  40 in the same way.
  41 .PP
  42 First,
  43 .B tmpdir
  44 checks to see whether the current value of the
  45 .B TMPDIR
  46 environment variable is a secure place for temporary files.  If so, it
  47 is accepted immediately.  Otherwise, it tries to find or create a
  48 directory in
  49 .B /tmp
  50 (on the assumption that this is a fast disk suitable for temporary
  51 files), with the name
  52 .BI /tmp/ user \- suffix
  53 for some
  54 .IR suffix .
  55 If that fails, it tries to create a directory in your home directory,
  56 with the name
  57 .BI ~/tmp\- suffix\fR.
  58 If
  59 .I that
  60 fails too, then
  61 .B tmpdir
  62 gives up: if your home directory's not secure (or full) than a secure
  63 temporary directory is the least of your worries.
  64 .SS Options
  65 The following options are supported:
  66 .TP
  67 .B "\-b, \-\-bourne"
  68 Output an assignment using Bourne shell syntax.  The default is to
  69 examine the user's shell and decide which syntax to use based on that.
  70 .TP
  71 .B "\-c, \-\-cshell"
  72 Output an assignment using C shell syntax.
  73 .TP
  74 .BI "\-v, --verify " dir
  75 Don't try to find a temporary directory; just see whether
  76 .I dir
  77 is secure, and exit successfully if it is (and unsuccessfully if it
  78 isn't).
  79 .SH BUGS
  80 None known.
  81 .SH SEE ALSO
  82 .BR chkpath (1),
  83 .BR tmpnam (3),
  84 .BR tmpfile (3).
  85 .SH AUTHOR
  86 Mark Wooding (mdw@nsict.org).