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Clarify which part of the path name is considered for substitution.

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Also use "name" instead of "file name" is some places since the
result could be either a file or a directory.  Work done with jmc@
This commit is contained in:
millert 2024-03-03 15:24:45 +00:00
parent 43503d760f
commit 80249bc85e
1 changed files with 24 additions and 24 deletions
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48
usr.bin/mktemp/mktemp.1
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@ -1,4 +1,4 @@
.\" $OpenBSD: mktemp.1,v 1.33 2024/03/01 23:37:42 millert Exp $ .\" $OpenBSD: mktemp.1,v 1.34 2024/03/03 15:24:45 millert Exp $
.\" .\"
.\" Copyright (c) 1996, 2000, 2001, 2003, 2010, 2013, 2024 .\" Copyright (c) 1996, 2000, 2001, 2003, 2010, 2013, 2024
.\" Todd C. Miller <millert@openbsd.org> .\" Todd C. Miller <millert@openbsd.org>
@ -15,12 +15,12 @@
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\" .\"
.Dd $Mdocdate: March 1 2024 $ .Dd $Mdocdate: March 3 2024 $
.Dt MKTEMP 1 .Dt MKTEMP 1
.Os .Os
.Sh NAME .Sh NAME
.Nm mktemp .Nm mktemp
.Nd make temporary filename (unique) .Nd make temporary file or directory (unique)
.Sh SYNOPSIS .Sh SYNOPSIS
.Nm mktemp .Nm mktemp
.Op Fl dqtu .Op Fl dqtu
@ -29,14 +29,14 @@
.Sh DESCRIPTION .Sh DESCRIPTION
The The
.Nm mktemp .Nm mktemp
utility takes the given filename utility takes the specified file name
.Ar template .Ar template
and overwrites a portion of it to create a unique filename. and overwrites a portion of it to create a unique file name.
The The
.Ar template .Ar template
may be any filename with at least six may be any file name containing at least six
.Ql X Ns s .Ql X Ns s
in the last component of the filename, for example in the last component of the path, for example
.Pa /tmp/tfile.XXXXXXXXXX .Pa /tmp/tfile.XXXXXXXXXX
or or
.Pa /tmp/editor.XXXXXXXXXX.txt . .Pa /tmp/editor.XXXXXXXXXX.txt .
@ -47,7 +47,7 @@ in the
only the last one will be considered. only the last one will be considered.
If no If no
.Ar template .Ar template
is specified, a default of is specified, a default value of
.Pa tmp.XXXXXXXXXX .Pa tmp.XXXXXXXXXX
is used and the is used and the
.Fl t .Fl t
@ -60,8 +60,8 @@ The name chosen depends both on the number of
.Ql X Ns s .Ql X Ns s
in the in the
.Ar template .Ar template
and the number of collisions with pre-existing files. and the number of collisions with pre-existing entries.
The number of unique filenames The number of unique names
.Nm .Nm
can return depends on the number of can return depends on the number of
.Ql X Ns s .Ql X Ns s
@ -74,19 +74,19 @@ testing roughly 26 ** 10 combinations.
.Pp .Pp
If If
.Nm .Nm
can successfully generate a unique filename, the file (or directory) successfully generates a unique name, the file (or directory)
is created with file permissions such that it is only readable and writable is created with permissions such that it is only readable and writable
by its owner (unless the by its owner (unless the
.Fl u .Fl u
flag is given) and the filename is printed to standard output. flag is given) and the name is printed to the standard output.
.Pp .Pp
.Nm mktemp .Nm mktemp
is provided to allow shell scripts to safely use temporary files. is provided to allow shell scripts to safely use temporary files.
Traditionally, many shell scripts take the name of the program with Traditionally, many shell scripts take the name of the program with
the PID as a suffix and use that as a temporary filename. the PID as a suffix and use that as a temporary file name.
This kind of naming scheme is predictable and the race condition it creates This kind of naming scheme is predictable and the race condition it creates
is easy for an attacker to win. is easy for an attacker to win.
A safer, though still inferior approach A safer, though still inferior approach,
is to make a temporary directory using the same naming scheme. is to make a temporary directory using the same naming scheme.
While this does allow one to guarantee that a temporary file will not be While this does allow one to guarantee that a temporary file will not be
subverted, it still allows a simple denial of service attack. subverted, it still allows a simple denial of service attack.
@ -101,7 +101,7 @@ Make a directory instead of a file.
.It Fl p Ar directory .It Fl p Ar directory
Use the specified Use the specified
.Ar directory .Ar directory
as a prefix when generating the temporary filename. as a prefix when generating the temporary name.
The The
.Ar directory .Ar directory
will be overridden by the user's will be overridden by the user's
@ -163,7 +163,7 @@ The following
fragment illustrates a simple use of fragment illustrates a simple use of
.Nm .Nm
where the script should quit if it cannot get a safe where the script should quit if it cannot get a safe
temporary file. temporary file:
.Bd -literal -offset indent .Bd -literal -offset indent
TMPFILE=`mktemp /tmp/example.XXXXXXXXXX` || exit 1 TMPFILE=`mktemp /tmp/example.XXXXXXXXXX` || exit 1
echo "program output" >> $TMPFILE echo "program output" >> $TMPFILE
@ -171,7 +171,7 @@ echo "program output" >> $TMPFILE
.Pp .Pp
The same fragment with support for a user's The same fragment with support for a user's
.Ev TMPDIR .Ev TMPDIR
environment variable can be written as follows. environment variable can be written as follows:
.Bd -literal -offset indent .Bd -literal -offset indent
TMPFILE=`mktemp -t example.XXXXXXXXXX` || exit 1 TMPFILE=`mktemp -t example.XXXXXXXXXX` || exit 1
echo "program output" >> $TMPFILE echo "program output" >> $TMPFILE
@ -181,7 +181,7 @@ This can be further simplified if we don't care about the actual name of
the temporary file. the temporary file.
In this case the In this case the
.Fl t .Fl t
flag is implied. flag is implied:
.Bd -literal -offset indent .Bd -literal -offset indent
TMPFILE=`mktemp` || exit 1 TMPFILE=`mktemp` || exit 1
echo "program output" >> $TMPFILE echo "program output" >> $TMPFILE
@ -194,7 +194,7 @@ In this example the temporary file will be created in
.Pa /extra/tmp .Pa /extra/tmp
unless the user's unless the user's
.Ev TMPDIR .Ev TMPDIR
environment variable specifies otherwise. environment variable specifies otherwise:
.Bd -literal -offset indent .Bd -literal -offset indent
TMPFILE=`mktemp -p /extra/tmp example.XXXXXXXXXX` || exit 1 TMPFILE=`mktemp -p /extra/tmp example.XXXXXXXXXX` || exit 1
echo "program output" >> $TMPFILE echo "program output" >> $TMPFILE
@ -202,10 +202,10 @@ echo "program output" >> $TMPFILE
.Pp .Pp
In other cases, we want the script to catch the error. In other cases, we want the script to catch the error.
For instance, if we attempt to create two temporary files and For instance, if we attempt to create two temporary files and
the second one fails we need to remove the first before exiting. the second one fails we need to remove the first before exiting:
.Bd -literal -offset indent .Bd -literal -offset indent
TMP1=`mktemp -t example.1.XXXXXXXXXX` || exit 1 TMP1=`mktemp -t example.XXXXXXXXXX.1` || exit 1
TMP2=`mktemp -t example.2.XXXXXXXXXX` TMP2=`mktemp -t example.XXXXXXXXXX.2`
if [ $? -ne 0 ]; then if [ $? -ne 0 ]; then
rm -f $TMP1 rm -f $TMP1
exit 1 exit 1
@ -215,7 +215,7 @@ fi
Or perhaps you don't want to exit if Or perhaps you don't want to exit if
.Nm .Nm
is unable to create the file. is unable to create the file.
In this case you can protect that part of the script thusly. In this case you can protect that part of the script thusly:
.Bd -literal -offset indent .Bd -literal -offset indent
TMPFILE=`mktemp -q -t example.XXXXXXXXXX` && { TMPFILE=`mktemp -q -t example.XXXXXXXXXX` && {
# Safe to use $TMPFILE in this block # Safe to use $TMPFILE in this block