1 /*
2  * Copyright (C) 2007 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 /* This file is used to define the properties of the filesystem
18 ** images generated by build tools (mkbootfs and mkyaffs2image) and
19 ** by the device side of adb.
20 */
21 
22 #define LOG_TAG "fs_config"
23 
24 #define _GNU_SOURCE
25 
26 #include <errno.h>
27 #include <fcntl.h>
28 #include <stdbool.h>
29 #include <stdint.h>
30 #include <stdio.h>
31 #include <stdlib.h>
32 #include <string.h>
33 #include <sys/stat.h>
34 #include <sys/types.h>
35 
36 #include <log/log.h>
37 #include <private/android_filesystem_config.h>
38 #include <utils/Compat.h>
39 
40 #ifndef O_BINARY
41 #define O_BINARY 0
42 #endif
43 
44 /* The following structure is stored little endian */
45 struct fs_path_config_from_file {
46     uint16_t len;
47     uint16_t mode;
48     uint16_t uid;
49     uint16_t gid;
50     uint64_t capabilities;
51     char prefix[];
52 } __attribute__((__aligned__(sizeof(uint64_t))));
53 
54 /* My kingdom for <endian.h> */
get2LE(const uint8_t * src)55 static inline uint16_t get2LE(const uint8_t* src)
56 {
57     return src[0] | (src[1] << 8);
58 }
59 
get8LE(const uint8_t * src)60 static inline uint64_t get8LE(const uint8_t* src)
61 {
62     uint32_t low, high;
63 
64     low = src[0] | (src[1] << 8) | (src[2] << 16) | (src[3] << 24);
65     high = src[4] | (src[5] << 8) | (src[6] << 16) | (src[7] << 24);
66     return ((uint64_t) high << 32) | (uint64_t) low;
67 }
68 
69 #define ALIGN(x, alignment) ( ((x) + ((alignment) - 1)) & ~((alignment) - 1) )
70 
71 /* Rules for directories.
72 ** These rules are applied based on "first match", so they
73 ** should start with the most specific path and work their
74 ** way up to the root.
75 */
76 
77 static const struct fs_path_config android_dirs[] = {
78     { 00770, AID_SYSTEM, AID_CACHE,  0, "cache" },
79     { 00771, AID_SYSTEM, AID_SYSTEM, 0, "data/app" },
80     { 00771, AID_SYSTEM, AID_SYSTEM, 0, "data/app-private" },
81     { 00771, AID_ROOT,   AID_ROOT,   0, "data/dalvik-cache" },
82     { 00771, AID_SYSTEM, AID_SYSTEM, 0, "data/data" },
83     { 00771, AID_SHELL,  AID_SHELL,  0, "data/local/tmp" },
84     { 00771, AID_SHELL,  AID_SHELL,  0, "data/local" },
85     { 01771, AID_SYSTEM, AID_MISC,   0, "data/misc" },
86     { 00770, AID_DHCP,   AID_DHCP,   0, "data/misc/dhcp" },
87     { 00771, AID_SHARED_RELRO, AID_SHARED_RELRO, 0, "data/misc/shared_relro" },
88     { 00775, AID_MEDIA_RW, AID_MEDIA_RW, 0, "data/media" },
89     { 00775, AID_MEDIA_RW, AID_MEDIA_RW, 0, "data/media/Music" },
90     { 00771, AID_SYSTEM, AID_SYSTEM, 0, "data" },
91     { 00750, AID_ROOT,   AID_SHELL,  0, "sbin" },
92     { 00755, AID_ROOT,   AID_SHELL,  0, "system/bin" },
93     { 00755, AID_ROOT,   AID_SHELL,  0, "system/vendor" },
94     { 00755, AID_ROOT,   AID_SHELL,  0, "system/xbin" },
95     { 00755, AID_ROOT,   AID_ROOT,   0, "system/etc/ppp" },
96     { 00755, AID_ROOT,   AID_SHELL,  0, "vendor" },
97     { 00777, AID_ROOT,   AID_ROOT,   0, "sdcard" },
98     { 00755, AID_ROOT,   AID_ROOT,   0, 0 },
99 };
100 
101 /* Rules for files.
102 ** These rules are applied based on "first match", so they
103 ** should start with the most specific path and work their
104 ** way up to the root. Prefixes ending in * denotes wildcard
105 ** and will allow partial matches.
106 */
107 static const char conf_dir[] = "/system/etc/fs_config_dirs";
108 static const char conf_file[] = "/system/etc/fs_config_files";
109 
110 static const struct fs_path_config android_files[] = {
111     { 00440, AID_ROOT,      AID_SHELL,     0, "system/etc/init.goldfish.rc" },
112     { 00550, AID_ROOT,      AID_SHELL,     0, "system/etc/init.goldfish.sh" },
113     { 00550, AID_ROOT,      AID_SHELL,     0, "system/etc/init.ril" },
114     { 00550, AID_DHCP,      AID_SHELL,     0, "system/etc/dhcpcd/dhcpcd-run-hooks" },
115     { 00555, AID_ROOT,      AID_ROOT,      0, "system/etc/ppp/*" },
116     { 00555, AID_ROOT,      AID_ROOT,      0, "system/etc/rc.*" },
117     { 00444, AID_ROOT,      AID_ROOT,      0, conf_dir + 1 },
118     { 00444, AID_ROOT,      AID_ROOT,      0, conf_file + 1 },
119     { 00644, AID_SYSTEM,    AID_SYSTEM,    0, "data/app/*" },
120     { 00644, AID_MEDIA_RW,  AID_MEDIA_RW,  0, "data/media/*" },
121     { 00644, AID_SYSTEM,    AID_SYSTEM,    0, "data/app-private/*" },
122     { 00644, AID_APP,       AID_APP,       0, "data/data/*" },
123 
124     /* the following five files are INTENTIONALLY set-uid, but they
125      * are NOT included on user builds. */
126     { 04750, AID_ROOT,      AID_SHELL,     0, "system/xbin/su" },
127     { 06755, AID_ROOT,      AID_ROOT,      0, "system/xbin/librank" },
128     { 06755, AID_ROOT,      AID_ROOT,      0, "system/xbin/procrank" },
129     { 06755, AID_ROOT,      AID_ROOT,      0, "system/xbin/procmem" },
130     { 04770, AID_ROOT,      AID_RADIO,     0, "system/bin/pppd-ril" },
131 
132     /* the following files have enhanced capabilities and ARE included in user builds. */
133     { 00750, AID_ROOT,      AID_SHELL,     (1ULL << CAP_SETUID) | (1ULL << CAP_SETGID), "system/bin/run-as" },
134     { 00700, AID_SYSTEM,    AID_SHELL,     (1ULL << CAP_BLOCK_SUSPEND), "system/bin/inputflinger" },
135 
136     { 00750, AID_ROOT,      AID_ROOT,      0, "system/bin/uncrypt" },
137     { 00750, AID_ROOT,      AID_ROOT,      0, "system/bin/install-recovery.sh" },
138     { 00755, AID_ROOT,      AID_SHELL,     0, "system/bin/*" },
139     { 00755, AID_ROOT,      AID_ROOT,      0, "system/lib/valgrind/*" },
140     { 00755, AID_ROOT,      AID_ROOT,      0, "system/lib64/valgrind/*" },
141     { 00755, AID_ROOT,      AID_SHELL,     0, "system/xbin/*" },
142     { 00755, AID_ROOT,      AID_SHELL,     0, "system/vendor/bin/*" },
143     { 00755, AID_ROOT,      AID_SHELL,     0, "vendor/bin/*" },
144     { 00750, AID_ROOT,      AID_SHELL,     0, "sbin/*" },
145     { 00755, AID_ROOT,      AID_ROOT,      0, "bin/*" },
146     { 00750, AID_ROOT,      AID_SHELL,     0, "init*" },
147     { 00750, AID_ROOT,      AID_SHELL,     0, "sbin/fs_mgr" },
148     { 00640, AID_ROOT,      AID_SHELL,     0, "fstab.*" },
149     { 00644, AID_ROOT,      AID_ROOT,      0, 0 },
150 };
151 
fs_config_open(int dir,const char * target_out_path)152 static int fs_config_open(int dir, const char *target_out_path)
153 {
154     int fd = -1;
155 
156     if (target_out_path && *target_out_path) {
157         /* target_out_path is the path to the directory holding content of system partition
158            but as we cannot guaranty it ends with '/system' we need this below skip_len logic */
159         char *name = NULL;
160         int target_out_path_len = strlen(target_out_path);
161         int skip_len = strlen("/system");
162 
163         if (target_out_path[target_out_path_len] == '/') {
164             skip_len++;
165         }
166         asprintf(&name, "%s%s", target_out_path, (dir ? conf_dir : conf_file) + skip_len);
167         if (name) {
168             fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_BINARY));
169             free(name);
170         }
171     }
172     if (fd < 0) {
173         fd = TEMP_FAILURE_RETRY(open(dir ? conf_dir : conf_file, O_RDONLY | O_BINARY));
174     }
175     return fd;
176 }
177 
fs_config_cmp(bool dir,const char * prefix,size_t len,const char * path,size_t plen)178 static bool fs_config_cmp(bool dir, const char *prefix, size_t len,
179                                     const char *path, size_t plen)
180 {
181     if (dir) {
182         if (plen < len) {
183             return false;
184         }
185     } else {
186         /* If name ends in * then allow partial matches. */
187         if (prefix[len - 1] == '*') {
188             return !strncmp(prefix, path, len - 1);
189         }
190         if (plen != len) {
191             return false;
192         }
193     }
194     return !strncmp(prefix, path, len);
195 }
196 
fs_config(const char * path,int dir,const char * target_out_path,unsigned * uid,unsigned * gid,unsigned * mode,uint64_t * capabilities)197 void fs_config(const char *path, int dir, const char *target_out_path,
198                unsigned *uid, unsigned *gid, unsigned *mode, uint64_t *capabilities)
199 {
200     const struct fs_path_config *pc;
201     int fd, plen;
202 
203     if (path[0] == '/') {
204         path++;
205     }
206 
207     plen = strlen(path);
208 
209     fd = fs_config_open(dir, target_out_path);
210     if (fd >= 0) {
211         struct fs_path_config_from_file header;
212 
213         while (TEMP_FAILURE_RETRY(read(fd, &header, sizeof(header))) == sizeof(header)) {
214             char *prefix;
215             uint16_t host_len = get2LE((const uint8_t *)&header.len);
216             ssize_t len, remainder = host_len - sizeof(header);
217             if (remainder <= 0) {
218                 ALOGE("%s len is corrupted", dir ? conf_dir : conf_file);
219                 break;
220             }
221             prefix = calloc(1, remainder);
222             if (!prefix) {
223                 ALOGE("%s out of memory", dir ? conf_dir : conf_file);
224                 break;
225             }
226             if (TEMP_FAILURE_RETRY(read(fd, prefix, remainder)) != remainder) {
227                 free(prefix);
228                 ALOGE("%s prefix is truncated", dir ? conf_dir : conf_file);
229                 break;
230             }
231             len = strnlen(prefix, remainder);
232             if (len >= remainder) { /* missing a terminating null */
233                 free(prefix);
234                 ALOGE("%s is corrupted", dir ? conf_dir : conf_file);
235                 break;
236             }
237             if (fs_config_cmp(dir, prefix, len, path, plen)) {
238                 free(prefix);
239                 close(fd);
240                 *uid = get2LE((const uint8_t *)&(header.uid));
241                 *gid = get2LE((const uint8_t *)&(header.gid));
242                 *mode = (*mode & (~07777)) | get2LE((const uint8_t *)&(header.mode));
243                 *capabilities = get8LE((const uint8_t *)&(header.capabilities));
244                 return;
245             }
246             free(prefix);
247         }
248         close(fd);
249     }
250 
251     pc = dir ? android_dirs : android_files;
252     for(; pc->prefix; pc++){
253         if (fs_config_cmp(dir, pc->prefix, strlen(pc->prefix), path, plen)) {
254             break;
255         }
256     }
257     *uid = pc->uid;
258     *gid = pc->gid;
259     *mode = (*mode & (~07777)) | pc->mode;
260     *capabilities = pc->capabilities;
261 }
262 
fs_config_generate(char * buffer,size_t length,const struct fs_path_config * pc)263 ssize_t fs_config_generate(char *buffer, size_t length, const struct fs_path_config *pc)
264 {
265     struct fs_path_config_from_file *p = (struct fs_path_config_from_file *)buffer;
266     size_t len = ALIGN(sizeof(*p) + strlen(pc->prefix) + 1, sizeof(uint64_t));
267 
268     if ((length < len) || (len > UINT16_MAX)) {
269         return -ENOSPC;
270     }
271     memset(p, 0, len);
272     uint16_t host_len = len;
273     p->len = get2LE((const uint8_t *)&host_len);
274     p->mode = get2LE((const uint8_t *)&(pc->mode));
275     p->uid = get2LE((const uint8_t *)&(pc->uid));
276     p->gid = get2LE((const uint8_t *)&(pc->gid));
277     p->capabilities = get8LE((const uint8_t *)&(pc->capabilities));
278     strcpy(p->prefix, pc->prefix);
279     return len;
280 }
281