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

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