1 /*-
2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33 #include <errno.h>
34 #include <fcntl.h>
35 #include <signal.h>
36 #include <stdio.h>
37 #include <stdlib.h>
38 #include <sys/stat.h>
39 #include <sys/types.h>
40 #include <unistd.h>
41
42 #include "private/ErrnoRestorer.h"
43
__fd_to_fp(int fd)44 static FILE* __fd_to_fp(int fd) {
45 FILE* fp = fdopen(fd, "w+");
46 if (fp != nullptr) return fp;
47
48 ErrnoRestorer errno_restorer;
49 close(fd);
50 return nullptr;
51 }
52
__tmpfile_dir_legacy(const char * tmp_dir)53 static FILE* __tmpfile_dir_legacy(const char* tmp_dir) {
54 char* path = nullptr;
55 if (asprintf(&path, "%s/tmp.XXXXXXXXXX", tmp_dir) == -1) {
56 return nullptr;
57 }
58
59 int fd = mkstemp(path);
60 if (fd == -1) {
61 free(path);
62 return nullptr;
63 }
64
65 // Unlink the file now so that it's removed when closed.
66 unlink(path);
67 free(path);
68
69 // Can we still use the file now it's unlinked?
70 // File systems without hard link support won't have the usual Unix semantics.
71 struct stat sb;
72 if (fstat(fd, &sb) == -1) {
73 ErrnoRestorer errno_restorer;
74 close(fd);
75 return nullptr;
76 }
77
78 return __fd_to_fp(fd);
79 }
80
__tmpfile_dir(const char * tmp_dir)81 static FILE* __tmpfile_dir(const char* tmp_dir) {
82 int fd = open(tmp_dir, O_TMPFILE | O_RDWR, S_IRUSR | S_IWUSR);
83 if (fd == -1) return __tmpfile_dir_legacy(tmp_dir);
84 return __fd_to_fp(fd);
85 }
86
tmpfile()87 FILE* tmpfile() {
88 // TODO: get this app's temporary directory from the framework ("/data/data/app/cache").
89
90 // $EXTERNAL_STORAGE turns out not to be very useful because it doesn't support hard links.
91 // This means we can't do the usual trick of calling unlink before handing the file back.
92
93 FILE* fp = __tmpfile_dir("/data/local/tmp");
94 if (fp == nullptr) {
95 // P_tmpdir is "/tmp/", but POSIX explicitly says that tmpdir(3) should try P_tmpdir before
96 // giving up. This is potentially useful for bionic on the host anyway.
97 fp = __tmpfile_dir(P_tmpdir);
98 }
99 return fp;
100 }
101 __strong_alias(tmpfile64, tmpfile);
102