There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
329 lines
7.5 KiB
Groff
329 lines
7.5 KiB
Groff
.\" $NetBSD: mktemp.3,v 1.28 2010/05/14 03:22:49 joerg Exp $
|
|
.\"
|
|
.\" Copyright (c) 1989, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)mktemp.3 8.1 (Berkeley) 6/4/93
|
|
.\"
|
|
.Dd April 29, 2010
|
|
.Dt MKTEMP 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm mktemp ,
|
|
.Nm mkstemp ,
|
|
.Nm mkdtemp
|
|
.Nd make unique temporary file or directory name
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In stdlib.h
|
|
.Ft char *
|
|
.Fn mktemp "char *template"
|
|
.Ft int
|
|
.Fn mkstemp "char *template"
|
|
.Ft char *
|
|
.Fn mkdtemp "char *template"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn mktemp
|
|
function
|
|
takes the given file name template and overwrites a portion of it
|
|
to create a file name.
|
|
This file name is unique and suitable for use
|
|
by the application.
|
|
The template may be any file name with some number of
|
|
.So Li X
|
|
.Sc Ns s
|
|
appended
|
|
to it, for example
|
|
.Pa /tmp/temp.XXXXXX .
|
|
The trailing
|
|
.So Li X
|
|
.Sc Ns s
|
|
are replaced with the current process number and/or a
|
|
unique letter combination.
|
|
The number of unique file names
|
|
.Fn mktemp
|
|
can return depends on the number of
|
|
.So Li X
|
|
.Sc Ns s
|
|
provided.
|
|
Although the
|
|
.Nx
|
|
implementation of the functions will accept any number of trailing
|
|
.So Li X
|
|
.Sc Ns s ,
|
|
for portability reasons one should use only six.
|
|
Using six
|
|
.So Li X
|
|
.Sc Ns s
|
|
will result in
|
|
.Fn mktemp
|
|
testing roughly 26 ** 6 (308915776) combinations.
|
|
.Pp
|
|
The
|
|
.Fn mkstemp
|
|
function
|
|
makes the same replacement to the template and creates the template file,
|
|
mode 0600, returning a file descriptor opened for reading and writing.
|
|
This avoids the race between testing for a file's existence and opening it
|
|
for use.
|
|
.Pp
|
|
The
|
|
.Fn mkdtemp
|
|
function
|
|
is similar to
|
|
.Fn mkstemp ,
|
|
but it creates a mode 0700 directory instead and returns the path.
|
|
.Pp
|
|
Please note that the permissions of the file or directory being created are
|
|
subject to the restrictions imposed by the
|
|
.Xr umask 2
|
|
system call.
|
|
It may thus happen that the created file is unreadable and/or unwritable.
|
|
.Sh RETURN VALUES
|
|
The
|
|
.Fn mktemp
|
|
and
|
|
.Fn mkdtemp
|
|
functions
|
|
return a pointer to the template on success and
|
|
.Dv NULL
|
|
on failure.
|
|
The
|
|
.Fn mkstemp
|
|
function
|
|
returns \-1 if no suitable file could be created.
|
|
If either call fails an error code is placed in the global variable
|
|
.Va errno .
|
|
.Sh EXAMPLES
|
|
Quite often a programmer will want to replace a use of
|
|
.Fn mktemp
|
|
with
|
|
.Fn mkstemp ,
|
|
usually to avoid the problems described above.
|
|
Doing this correctly requires a good understanding of the code in question.
|
|
.Pp
|
|
For instance, code of this form:
|
|
.Bd -literal -offset indent
|
|
char sfn[15] = "";
|
|
FILE *sfp;
|
|
|
|
strlcpy(sfn, "/tmp/ed.XXXXXX", sizeof sfn);
|
|
if (mktemp(sfn) == NULL || (sfp = fopen(sfn, "w+")) == NULL) {
|
|
fprintf(stderr, "%s: %s\en", sfn, strerror(errno));
|
|
return (NULL);
|
|
}
|
|
return (sfp);
|
|
.Ed
|
|
.Pp
|
|
should be rewritten like this:
|
|
.Bd -literal -offset indent
|
|
char sfn[15] = "";
|
|
FILE *sfp;
|
|
int fd = -1;
|
|
|
|
strlcpy(sfn, "/tmp/ed.XXXXXX", sizeof sfn);
|
|
if ((fd = mkstemp(sfn)) == -1 ||
|
|
(sfp = fdopen(fd, "w+")) == NULL) {
|
|
if (fd != -1) {
|
|
unlink(sfn);
|
|
close(fd);
|
|
}
|
|
fprintf(stderr, "%s: %s\en", sfn, strerror(errno));
|
|
return (NULL);
|
|
}
|
|
return (sfp);
|
|
.Ed
|
|
.Pp
|
|
Often one will find code which uses
|
|
.Fn mktemp
|
|
very early on, perhaps to globally initialize the template nicely, but the
|
|
code which calls
|
|
.Xr open 2
|
|
or
|
|
.Xr fopen 3
|
|
on that filename will occur much later.
|
|
(In almost all cases, the use of
|
|
.Xr fopen 3
|
|
will mean that the flags
|
|
.Dv O_CREAT
|
|
|
|
|
.Dv O_EXCL
|
|
are not given to
|
|
.Xr open 2 ,
|
|
and thus a symbolic link race becomes possible, hence making
|
|
necessary the use of
|
|
.Xr fdopen 3
|
|
as seen above).
|
|
Furthermore, one must be careful about code which opens, closes, and then
|
|
re-opens the file in question.
|
|
Finally, one must ensure that upon error the temporary file is
|
|
removed correctly.
|
|
.Pp
|
|
There are also cases where modifying the code to use
|
|
.Fn mktemp ,
|
|
in concert with
|
|
.Xr open 2
|
|
using the flags
|
|
.Dv O_CREAT
|
|
|
|
|
.Dv O_EXCL ,
|
|
is better, as long as the code retries a new template if
|
|
.Xr open 2
|
|
fails with an
|
|
.Va errno
|
|
of
|
|
.Er EEXIST .
|
|
.Sh ERRORS
|
|
The
|
|
.Fn mktemp ,
|
|
.Fn mkstemp
|
|
and
|
|
.Fn mkdtemp
|
|
functions
|
|
may set
|
|
.Va errno
|
|
to one of the following values:
|
|
.Bl -tag -width Er
|
|
.It Bq Er ENOTDIR
|
|
The pathname portion of the template is not an existing directory.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn mktemp ,
|
|
.Fn mkstemp
|
|
and
|
|
.Fn mkdtemp
|
|
functions
|
|
may also set
|
|
.Va errno
|
|
to any value specified by the
|
|
.Xr stat 2
|
|
function.
|
|
.Pp
|
|
The
|
|
.Fn mkstemp
|
|
function
|
|
may also set
|
|
.Va errno
|
|
to any value specified by the
|
|
.Xr open 2
|
|
function.
|
|
.Pp
|
|
The
|
|
.Fn mkdtemp
|
|
function
|
|
may also set
|
|
.Va errno
|
|
to any value specified by the
|
|
.Xr mkdir 2
|
|
function.
|
|
.Sh SEE ALSO
|
|
.Xr chmod 2 ,
|
|
.Xr getpid 2 ,
|
|
.Xr open 2 ,
|
|
.Xr stat 2 ,
|
|
.Xr umask 2
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn mktemp
|
|
conforms to
|
|
.St -p1003.1-2001 .
|
|
It was however removed from the specification in the
|
|
.St -p1003.1-2008
|
|
revision.
|
|
The
|
|
.Fn mkstemp
|
|
and
|
|
.Fn mkdtemp
|
|
functions conform to
|
|
.St -p1003.1-2004
|
|
and
|
|
.St -p1003.1-2008 ,
|
|
respectively.
|
|
.Sh HISTORY
|
|
A
|
|
.Fn mktemp
|
|
function appeared in
|
|
.At v7 .
|
|
.Pp
|
|
The
|
|
.Fn mkstemp
|
|
function appeared in
|
|
.Bx 4.4 .
|
|
.Pp
|
|
The
|
|
.Fn mkdtemp
|
|
function appeared in
|
|
.Nx 1.4 .
|
|
.Sh BUGS
|
|
For
|
|
.Fn mktemp
|
|
there is an obvious race between file name selection and file
|
|
creation and deletion: the program is typically written to call
|
|
.Xr tmpnam 3 ,
|
|
.Xr tempnam 3 ,
|
|
or
|
|
.Fn mktemp .
|
|
Subsequently, the program calls
|
|
.Xr open 2
|
|
or
|
|
.Xr fopen 3
|
|
and erroneously opens a file (or symbolic link, fifo or other
|
|
device) that the attacker has created in the expected file location.
|
|
Hence
|
|
.Fn mkstemp
|
|
is recommended, since it atomically creates the file.
|
|
An attacker can guess the filenames produced by
|
|
.Fn mktemp .
|
|
Whenever it is possible,
|
|
.Fn mkstemp
|
|
or
|
|
.Fn mkdtemp
|
|
should be used instead.
|
|
.Pp
|
|
For this reason,
|
|
.Xr ld 1
|
|
will output a warning message whenever it links code that uses
|
|
.Fn mktemp .
|
|
.Pp
|
|
The
|
|
.Fn mkdtemp
|
|
function is nonstandard and should not be used if portability is required.
|
|
.Sh SECURITY CONSIDERATIONS
|
|
The use of
|
|
.Fn mktemp
|
|
should generally be avoided, as a hostile process can exploit a race
|
|
condition in the time between the generation of a temporary filename by
|
|
.Fn mktemp
|
|
and the invoker's use of the temporary name.
|
|
A link-time warning will be issued advising the use of
|
|
.Fn mkstemp
|
|
or
|
|
.Fn mkdtemp
|
|
instead.
|