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Annotation of embedaddon/pimd/libite/tempfile.c, revision 1.1

1.1     ! misho       1: /* A secure tmpfile() replacement.
        !             2:  *
        !             3:  * Copyright (c) 2015  Joachim Nilsson <troglobit@gmail.com>
        !             4:  *
        !             5:  * Permission to use, copy, modify, and/or distribute this software for any
        !             6:  * purpose with or without fee is hereby granted, provided that the above
        !             7:  * copyright notice and this permission notice appear in all copies.
        !             8:  *
        !             9:  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
        !            10:  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
        !            11:  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
        !            12:  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
        !            13:  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
        !            14:  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
        !            15:  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
        !            16:  */
        !            17: 
        !            18: #include <paths.h>
        !            19: #include <fcntl.h>             /* O_TMPFILE requires -D_GNU_SOURCE */
        !            20: #include <linux/version.h>
        !            21: #include <stdlib.h>            /* mkstemp() */
        !            22: #include <stdio.h>             /* fdopen() */
        !            23: #include <sys/stat.h>          /* umask() */
        !            24: 
        !            25: #ifndef  O_TMPFILE             /* Too old GLIBC or kernel */
        !            26: #warning O_TMPFILE missing on your system, tempfile() may not work!
        !            27: #define  __O_TMPFILE 020000000
        !            28: #define  O_TMPFILE (__O_TMPFILE | O_DIRECTORY) /* Define and let it fail at runtime */
        !            29: #endif
        !            30: 
        !            31: /**
        !            32:  * tempfile - A secure tmpfile() replacement
        !            33:  *
        !            34:  * This is the secure replacement for tmpfile() that does not exist in
        !            35:  * GLIBC.  The function uses the Linux specific %O_TMPFILE and %O_EXCL
        !            36:  * for security.  When the %FILE is fclose()'ed the file contents is
        !            37:  * lost.  The file is hidden in the %_PATH_TMP directory on the system.
        !            38:  *
        !            39:  * This function requires Linux 3.11, or later, due to %O_TMPFILE.
        !            40:  *
        !            41:  * Returns:
        !            42:  * An open %FILE pointer, or %NULL on error.
        !            43:  */
        !            44: FILE *tempfile(void)
        !            45: {
        !            46: #if LINUX_VERSION_CODE >= KERNEL_VERSION(3,11,0)
        !            47:        int fd;
        !            48:        mode_t oldmask;
        !            49: 
        !            50:        oldmask = umask(0077);
        !            51:        fd = open(_PATH_TMP, O_TMPFILE | O_RDWR | O_EXCL | O_CLOEXEC, S_IRUSR | S_IWUSR);
        !            52:        umask(oldmask);
        !            53:        if (-1 == fd)
        !            54:                return NULL;
        !            55: 
        !            56:        return fdopen(fd, "rw");
        !            57: #else
        !            58: #warning Too old kernel, reverting to wrap unsafe tmpfile() ...
        !            59:        return tmpfile();
        !            60: #endif
        !            61: }
        !            62: 
        !            63: #ifdef UNITTEST
        !            64: int main(void)
        !            65: {
        !            66:        FILE *fp = tempfile(); system("ls -lrt "
        !            67:        _PATH_TMP " | tail -10"); return fclose(fp);
        !            68: }
        !            69: #endif
        !            70: 
        !            71: /**
        !            72:  * Local Variables:
        !            73:  *  compile-command: "make V=1 -f tempfile.mk"
        !            74:  *  version-control: t
        !            75:  *  indent-tabs-mode: t
        !            76:  *  c-file-style: "linux"
        !            77:  * End:
        !            78:  */