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/* $OpenBSD: shm_open.c,v 1.8 2015/12/10 13:03:22 tedu Exp $ */
/*
* Copyright (c) 2013 Ted Unangst <tedu@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <sha2.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
/* SHA256_DIGEST_STRING_LENGTH includes nul */
/* "/tmp/" + sha256 + ".shm" */
#define SHM_PATH_SIZE (5 + SHA256_DIGEST_STRING_LENGTH + 4)
/* O_CLOEXEC and O_NOFOLLOW are extensions to POSIX */
#define OK_FLAGS (O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC | O_NOFOLLOW)
static void
makeshmpath(const char *origpath, char *shmpath, size_t len)
{
char buf[SHA256_DIGEST_STRING_LENGTH];
SHA256Data(origpath, strlen(origpath), buf);
snprintf(shmpath, len, "/tmp/%s.shm", buf);
}
int
shm_open(const char *path, int flags, mode_t mode)
{
char shmpath[SHM_PATH_SIZE];
struct stat sb;
int fd;
if (((flags & O_ACCMODE) != O_RDONLY && (flags & O_ACCMODE) != O_RDWR)
|| (flags & ~(O_ACCMODE | OK_FLAGS))) {
errno = EINVAL;
return -1;
}
flags |= O_CLOEXEC | O_NOFOLLOW;
mode = mode & 0600;
makeshmpath(path, shmpath, sizeof(shmpath));
fd = open(shmpath, flags, mode);
if (fd == -1)
return -1;
if (fstat(fd, &sb) == -1 || !S_ISREG(sb.st_mode)) {
close(fd);
errno = EINVAL;
return -1;
}
if (sb.st_uid != geteuid()) {
close(fd);
errno = EPERM;
return -1;
}
return fd;
}
DEF_WEAK(shm_open);
int
shm_unlink(const char *path)
{
char shmpath[SHM_PATH_SIZE];
makeshmpath(path, shmpath, sizeof(shmpath));
return unlink(shmpath);
}
int
shm_mkstemp(char *template)
{
size_t templatelen;
char *t;
int i, fd;
templatelen = strlen(template);
t = malloc(templatelen + 1);
if (!t)
return -1;
t[templatelen] = '\0';
fd = -1;
for (i = 0; i < INT_MAX; i++) {
memcpy(t, template, templatelen);
if (!_mktemp(t))
break;
fd = shm_open(t, O_RDWR | O_EXCL | O_CREAT, 0600);
if (fd != -1) {
memcpy(template, t, templatelen);
break;
}
}
free(t);
return fd;
}
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