1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#define LOG_TAG "cutils"
18
19/* These defines are only needed because prebuilt headers are out of date */
20#define __USE_XOPEN2K8 1
21#define _ATFILE_SOURCE 1
22#define _GNU_SOURCE 1
23
24#include <cutils/fs.h>
25#include <cutils/log.h>
26
27#include <sys/types.h>
28#include <sys/stat.h>
29#include <fcntl.h>
30#include <unistd.h>
31#include <errno.h>
32#include <string.h>
33#include <limits.h>
34#include <stdlib.h>
35#include <dirent.h>
36
37#define ALL_PERMS (S_ISUID | S_ISGID | S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO)
38#define BUF_SIZE 64
39
40static int fs_prepare_path_impl(const char* path, mode_t mode, uid_t uid, gid_t gid,
41        int allow_fixup, int prepare_as_dir) {
42    // Check if path needs to be created
43    struct stat sb;
44    int create_result = -1;
45    if (TEMP_FAILURE_RETRY(lstat(path, &sb)) == -1) {
46        if (errno == ENOENT) {
47            goto create;
48        } else {
49            ALOGE("Failed to lstat(%s): %s", path, strerror(errno));
50            return -1;
51        }
52    }
53
54    // Exists, verify status
55    int type_ok = prepare_as_dir ? S_ISDIR(sb.st_mode) : S_ISREG(sb.st_mode);
56    if (!type_ok) {
57        ALOGE("Not a %s: %s", (prepare_as_dir ? "directory" : "regular file"), path);
58        return -1;
59    }
60
61    int owner_match = ((sb.st_uid == uid) && (sb.st_gid == gid));
62    int mode_match = ((sb.st_mode & ALL_PERMS) == mode);
63    if (owner_match && mode_match) {
64        return 0;
65    } else if (allow_fixup) {
66        goto fixup;
67    } else {
68        if (!owner_match) {
69            ALOGE("Expected path %s with owner %d:%d but found %d:%d",
70                    path, uid, gid, sb.st_uid, sb.st_gid);
71            return -1;
72        } else {
73            ALOGW("Expected path %s with mode %o but found %o",
74                    path, mode, (sb.st_mode & ALL_PERMS));
75            return 0;
76        }
77    }
78
79create:
80    create_result = prepare_as_dir
81        ? TEMP_FAILURE_RETRY(mkdir(path, mode))
82        : TEMP_FAILURE_RETRY(open(path, O_CREAT | O_CLOEXEC | O_NOFOLLOW | O_RDONLY));
83    if (create_result == -1) {
84        if (errno != EEXIST) {
85            ALOGE("Failed to %s(%s): %s",
86                    (prepare_as_dir ? "mkdir" : "open"), path, strerror(errno));
87            return -1;
88        }
89    } else if (!prepare_as_dir) {
90        // For regular files we need to make sure we close the descriptor
91        if (close(create_result) == -1) {
92            ALOGW("Failed to close file after create %s: %s", path, strerror(errno));
93        }
94    }
95fixup:
96    if (TEMP_FAILURE_RETRY(chmod(path, mode)) == -1) {
97        ALOGE("Failed to chmod(%s, %d): %s", path, mode, strerror(errno));
98        return -1;
99    }
100    if (TEMP_FAILURE_RETRY(chown(path, uid, gid)) == -1) {
101        ALOGE("Failed to chown(%s, %d, %d): %s", path, uid, gid, strerror(errno));
102        return -1;
103    }
104
105    return 0;
106}
107
108int fs_prepare_dir(const char* path, mode_t mode, uid_t uid, gid_t gid) {
109    return fs_prepare_path_impl(path, mode, uid, gid, /*allow_fixup*/ 1, /*prepare_as_dir*/ 1);
110}
111
112int fs_prepare_dir_strict(const char* path, mode_t mode, uid_t uid, gid_t gid) {
113    return fs_prepare_path_impl(path, mode, uid, gid, /*allow_fixup*/ 0, /*prepare_as_dir*/ 1);
114}
115
116int fs_prepare_file_strict(const char* path, mode_t mode, uid_t uid, gid_t gid) {
117    return fs_prepare_path_impl(path, mode, uid, gid, /*allow_fixup*/ 0, /*prepare_as_dir*/ 0);
118}
119
120int fs_read_atomic_int(const char* path, int* out_value) {
121    int fd = TEMP_FAILURE_RETRY(open(path, O_RDONLY));
122    if (fd == -1) {
123        ALOGE("Failed to read %s: %s", path, strerror(errno));
124        return -1;
125    }
126
127    char buf[BUF_SIZE];
128    if (TEMP_FAILURE_RETRY(read(fd, buf, BUF_SIZE)) == -1) {
129        ALOGE("Failed to read %s: %s", path, strerror(errno));
130        goto fail;
131    }
132    if (sscanf(buf, "%d", out_value) != 1) {
133        ALOGE("Failed to parse %s: %s", path, strerror(errno));
134        goto fail;
135    }
136    close(fd);
137    return 0;
138
139fail:
140    close(fd);
141    *out_value = -1;
142    return -1;
143}
144
145int fs_write_atomic_int(const char* path, int value) {
146    char temp[PATH_MAX];
147    if (snprintf(temp, PATH_MAX, "%s.XXXXXX", path) >= PATH_MAX) {
148        ALOGE("Path too long");
149        return -1;
150    }
151
152    int fd = TEMP_FAILURE_RETRY(mkstemp(temp));
153    if (fd == -1) {
154        ALOGE("Failed to open %s: %s", temp, strerror(errno));
155        return -1;
156    }
157
158    char buf[BUF_SIZE];
159    int len = snprintf(buf, BUF_SIZE, "%d", value) + 1;
160    if (len > BUF_SIZE) {
161        ALOGE("Value %d too large: %s", value, strerror(errno));
162        goto fail;
163    }
164    if (TEMP_FAILURE_RETRY(write(fd, buf, len)) < len) {
165        ALOGE("Failed to write %s: %s", temp, strerror(errno));
166        goto fail;
167    }
168    if (close(fd) == -1) {
169        ALOGE("Failed to close %s: %s", temp, strerror(errno));
170        goto fail_closed;
171    }
172
173    if (rename(temp, path) == -1) {
174        ALOGE("Failed to rename %s to %s: %s", temp, path, strerror(errno));
175        goto fail_closed;
176    }
177
178    return 0;
179
180fail:
181    close(fd);
182fail_closed:
183    unlink(temp);
184    return -1;
185}
186
187#ifndef __APPLE__
188
189int fs_mkdirs(const char* path, mode_t mode) {
190    int res = 0;
191    int fd = 0;
192    struct stat sb;
193    char* buf = strdup(path);
194
195    if (*buf != '/') {
196        ALOGE("Relative paths are not allowed: %s", buf);
197        res = -EINVAL;
198        goto done;
199    }
200
201    if ((fd = open("/", 0)) == -1) {
202        ALOGE("Failed to open(/): %s", strerror(errno));
203        res = -errno;
204        goto done;
205    }
206
207    char* segment = buf + 1;
208    char* p = segment;
209    while (*p != '\0') {
210        if (*p == '/') {
211            *p = '\0';
212
213            if (!strcmp(segment, "..") || !strcmp(segment, ".") || !strcmp(segment, "")) {
214                ALOGE("Invalid path: %s", buf);
215                res = -EINVAL;
216                goto done_close;
217            }
218
219            if (fstatat(fd, segment, &sb, AT_SYMLINK_NOFOLLOW) != 0) {
220                if (errno == ENOENT) {
221                    /* Nothing there yet; let's create it! */
222                    if (mkdirat(fd, segment, mode) != 0) {
223                        if (errno == EEXIST) {
224                            /* We raced with someone; ignore */
225                        } else {
226                            ALOGE("Failed to mkdirat(%s): %s", buf, strerror(errno));
227                            res = -errno;
228                            goto done_close;
229                        }
230                    }
231                } else {
232                    ALOGE("Failed to fstatat(%s): %s", buf, strerror(errno));
233                    res = -errno;
234                    goto done_close;
235                }
236            } else {
237                if (S_ISLNK(sb.st_mode)) {
238                    ALOGE("Symbolic links are not allowed: %s", buf);
239                    res = -ELOOP;
240                    goto done_close;
241                }
242                if (!S_ISDIR(sb.st_mode)) {
243                    ALOGE("Existing segment not a directory: %s", buf);
244                    res = -ENOTDIR;
245                    goto done_close;
246                }
247            }
248
249            /* Yay, segment is ready for us to step into */
250            int next_fd;
251            if ((next_fd = openat(fd, segment, O_NOFOLLOW | O_CLOEXEC)) == -1) {
252                ALOGE("Failed to openat(%s): %s", buf, strerror(errno));
253                res = -errno;
254                goto done_close;
255            }
256
257            close(fd);
258            fd = next_fd;
259
260            *p = '/';
261            segment = p + 1;
262        }
263        p++;
264    }
265
266done_close:
267    close(fd);
268done:
269    free(buf);
270    return res;
271}
272
273#endif
274