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/* $OpenBSD: shm_open.c,v 1.9 2017/09/10 18:20:00 guenther Exp $ */ |
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/* |
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* Copyright (c) 2013 Ted Unangst <tedu@openbsd.org> |
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* |
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* Permission to use, copy, modify, and distribute this software for any |
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* purpose with or without fee is hereby granted, provided that the above |
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* copyright notice and this permission notice appear in all copies. |
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* |
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR |
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN |
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF |
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
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*/ |
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#include <sys/types.h> |
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#include <sys/mman.h> |
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#include <sys/stat.h> |
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#include <errno.h> |
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#include <fcntl.h> |
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#include <limits.h> |
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#include <sha2.h> |
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#include <stdio.h> |
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#include <stdlib.h> |
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#include <string.h> |
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#include <unistd.h> |
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/* SHA256_DIGEST_STRING_LENGTH includes nul */ |
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/* "/tmp/" + sha256 + ".shm" */ |
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#define SHM_PATH_SIZE (5 + SHA256_DIGEST_STRING_LENGTH + 4) |
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/* O_CLOEXEC and O_NOFOLLOW are extensions to POSIX */ |
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#define OK_FLAGS (O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC | O_NOFOLLOW) |
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static void |
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makeshmpath(const char *origpath, char *shmpath, size_t len) |
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{ |
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char buf[SHA256_DIGEST_STRING_LENGTH]; |
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SHA256Data(origpath, strlen(origpath), buf); |
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snprintf(shmpath, len, "/tmp/%s.shm", buf); |
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} |
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int |
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shm_open(const char *path, int flags, mode_t mode) |
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{ |
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char shmpath[SHM_PATH_SIZE]; |
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struct stat sb; |
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int fd; |
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if (((flags & O_ACCMODE) != O_RDONLY && (flags & O_ACCMODE) != O_RDWR) |
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|| (flags & ~(O_ACCMODE | OK_FLAGS))) { |
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errno = EINVAL; |
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return -1; |
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} |
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flags |= O_CLOEXEC | O_NOFOLLOW; |
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mode = mode & 0600; |
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makeshmpath(path, shmpath, sizeof(shmpath)); |
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fd = HIDDEN(open)(shmpath, flags, mode); |
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if (fd == -1) |
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return -1; |
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if (fstat(fd, &sb) == -1 || !S_ISREG(sb.st_mode)) { |
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HIDDEN(close)(fd); |
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errno = EINVAL; |
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return -1; |
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} |
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if (sb.st_uid != geteuid()) { |
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HIDDEN(close)(fd); |
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errno = EPERM; |
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return -1; |
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} |
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return fd; |
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} |
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DEF_WEAK(shm_open); |
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int |
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shm_unlink(const char *path) |
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{ |
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char shmpath[SHM_PATH_SIZE]; |
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makeshmpath(path, shmpath, sizeof(shmpath)); |
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return unlink(shmpath); |
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} |
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int |
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shm_mkstemp(char *template) |
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{ |
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size_t templatelen; |
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char *t; |
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int i, fd; |
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templatelen = strlen(template); |
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t = malloc(templatelen + 1); |
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if (!t) |
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return -1; |
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t[templatelen] = '\0'; |
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fd = -1; |
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for (i = 0; i < INT_MAX; i++) { |
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memcpy(t, template, templatelen); |
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if (!_mktemp(t)) |
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break; |
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fd = shm_open(t, O_RDWR | O_EXCL | O_CREAT, 0600); |
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if (fd != -1) { |
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memcpy(template, t, templatelen); |
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break; |
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} |
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} |
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free(t); |
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return fd; |
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} |
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