1 /*
2 * Copyright (C) 2016 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <cutils/android_get_control_file.h>
30
31 #include <ctype.h>
32 #include <errno.h>
33 #include <fcntl.h>
34 #include <limits.h>
35 #include <stdio.h>
36 #include <stdlib.h>
37 #include <string.h>
38 #include <sys/stat.h>
39 #include <sys/types.h>
40 #include <unistd.h>
41
42 #include <string>
43
44 #include <android-base/file.h>
45 #include <android-base/stringprintf.h>
46
47 #include "android_get_control_env.h"
48
__android_get_control_from_env(const char * prefix,const char * name)49 int __android_get_control_from_env(const char* prefix, const char* name) {
50 if (!prefix || !name) return -1;
51
52 char *key = NULL;
53 if (asprintf(&key, "%s%s", prefix, name) < 0) return -1;
54 if (!key) return -1;
55
56 char *cp = key;
57 while (*cp) {
58 if (!isalnum(*cp)) *cp = '_';
59 ++cp;
60 }
61
62 const char* val = getenv(key);
63 free(key);
64 if (!val) return -1;
65
66 errno = 0;
67 long fd = strtol(val, NULL, 10);
68 if (errno) return -1;
69
70 // Since we are inheriting an fd, it could legitimately exceed _SC_OPEN_MAX
71 if ((fd < 0) || (fd > INT_MAX)) return -1;
72
73 // Still open?
74 if (TEMP_FAILURE_RETRY(fcntl(fd, F_GETFD)) < 0) return -1;
75
76 return static_cast<int>(fd);
77 }
78
android_get_control_file(const char * path)79 int android_get_control_file(const char* path) {
80 std::string given_path;
81 if (!android::base::Realpath(path, &given_path)) return -1;
82
83 // Try path, then realpath(path), as keys to get the fd from env.
84 auto fd = __android_get_control_from_env(ANDROID_FILE_ENV_PREFIX, path);
85 if (fd < 0) {
86 fd = __android_get_control_from_env(ANDROID_FILE_ENV_PREFIX, given_path.c_str());
87 if (fd < 0) return fd;
88 }
89
90 // Find file path from /proc and make sure it is correct
91 auto proc = android::base::StringPrintf("/proc/self/fd/%d", fd);
92 std::string fd_path;
93 if (!android::base::Realpath(proc, &fd_path)) return -1;
94
95 if (given_path != fd_path) return -1;
96 // It is what we think it is
97
98 return fd;
99 }
100