1 // Copyright (C) 2016 The Android Open Source Project
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #define LOG_TAG "sdcard"
16
17 #include <dirent.h>
18 #include <errno.h>
19 #include <fcntl.h>
20 #include <linux/fuse.h>
21 #include <pthread.h>
22 #include <stdlib.h>
23 #include <string.h>
24 #include <sys/inotify.h>
25 #include <sys/mount.h>
26 #include <sys/resource.h>
27 #include <sys/stat.h>
28 #include <sys/types.h>
29 #include <unistd.h>
30 #include <vector>
31
32 #include <android-base/file.h>
33 #include <android-base/logging.h>
34 #include <android-base/macros.h>
35 #include <android-base/stringprintf.h>
36 #include <android-base/strings.h>
37
38 #include <cutils/fs.h>
39 #include <cutils/multiuser.h>
40 #include <cutils/properties.h>
41
42 #include <libminijail.h>
43 #include <scoped_minijail.h>
44
45 #include <private/android_filesystem_config.h>
46
47 #define PROP_SDCARDFS_DEVICE "ro.sys.sdcardfs"
48 #define PROP_SDCARDFS_USER "persist.sys.sdcardfs"
49
supports_esdfs(void)50 static bool supports_esdfs(void) {
51 std::string filesystems;
52 if (!android::base::ReadFileToString("/proc/filesystems", &filesystems)) {
53 PLOG(ERROR) << "Could not read /proc/filesystems";
54 return false;
55 }
56 for (const auto& fs : android::base::Split(filesystems, "\n")) {
57 if (fs.find("esdfs") != std::string::npos) return true;
58 }
59 return false;
60 }
61
should_use_sdcardfs(void)62 static bool should_use_sdcardfs(void) {
63 char property[PROPERTY_VALUE_MAX];
64
65 // Allow user to have a strong opinion about state
66 property_get(PROP_SDCARDFS_USER, property, "");
67 if (!strcmp(property, "force_on")) {
68 LOG(WARNING) << "User explicitly enabled sdcardfs";
69 return true;
70 } else if (!strcmp(property, "force_off")) {
71 LOG(WARNING) << "User explicitly disabled sdcardfs";
72 return !supports_esdfs();
73 }
74
75 // Fall back to device opinion about state
76 if (property_get_bool(PROP_SDCARDFS_DEVICE, true)) {
77 LOG(WARNING) << "Device explicitly enabled sdcardfs";
78 return true;
79 } else {
80 LOG(WARNING) << "Device explicitly disabled sdcardfs";
81 return !supports_esdfs();
82 }
83 }
84
85 // NOTE: This is a vestigial program that simply exists to mount the in-kernel
86 // sdcardfs filesystem. The older FUSE-based design that used to live here has
87 // been completely removed to avoid confusion.
88
89 /* Supplementary groups to execute with. */
90 static const gid_t kGroups[1] = { AID_PACKAGE_INFO };
91
drop_privs(uid_t uid,gid_t gid)92 static void drop_privs(uid_t uid, gid_t gid) {
93 ScopedMinijail j(minijail_new());
94 minijail_set_supplementary_gids(j.get(), arraysize(kGroups), kGroups);
95 minijail_change_gid(j.get(), gid);
96 minijail_change_uid(j.get(), uid);
97 /* minijail_enter() will abort if priv-dropping fails. */
98 minijail_enter(j.get());
99 }
100
sdcardfs_setup(const std::string & source_path,const std::string & dest_path,uid_t fsuid,gid_t fsgid,bool multi_user,userid_t userid,gid_t gid,mode_t mask,bool derive_gid,bool default_normal,bool unshared_obb,bool use_esdfs)101 static bool sdcardfs_setup(const std::string& source_path, const std::string& dest_path,
102 uid_t fsuid, gid_t fsgid, bool multi_user, userid_t userid, gid_t gid,
103 mode_t mask, bool derive_gid, bool default_normal, bool unshared_obb,
104 bool use_esdfs) {
105 // Add new options at the end of the vector.
106 std::vector<std::string> new_opts_list;
107 if (multi_user) new_opts_list.push_back("multiuser,");
108 if (derive_gid) new_opts_list.push_back("derive_gid,");
109 if (default_normal) new_opts_list.push_back("default_normal,");
110 if (unshared_obb) new_opts_list.push_back("unshared_obb,");
111 // Try several attempts, each time with one less option, to gracefully
112 // handle older kernels that aren't updated yet.
113 for (int i = 0; i <= new_opts_list.size(); ++i) {
114 std::string new_opts;
115 for (int j = 0; j < new_opts_list.size() - i; ++j) {
116 new_opts += new_opts_list[j];
117 }
118
119 auto opts = android::base::StringPrintf("fsuid=%d,fsgid=%d,%smask=%d,userid=%d,gid=%d",
120 fsuid, fsgid, new_opts.c_str(), mask, userid, gid);
121 if (mount(source_path.c_str(), dest_path.c_str(), use_esdfs ? "esdfs" : "sdcardfs",
122 MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_NOATIME, opts.c_str()) == -1) {
123 PLOG(WARNING) << "Failed to mount sdcardfs with options " << opts;
124 } else {
125 return true;
126 }
127 }
128
129 return false;
130 }
131
sdcardfs_setup_bind_remount(const std::string & source_path,const std::string & dest_path,gid_t gid,mode_t mask)132 static bool sdcardfs_setup_bind_remount(const std::string& source_path, const std::string& dest_path,
133 gid_t gid, mode_t mask) {
134 std::string opts = android::base::StringPrintf("mask=%d,gid=%d", mask, gid);
135
136 if (mount(source_path.c_str(), dest_path.c_str(), nullptr,
137 MS_BIND, nullptr) != 0) {
138 PLOG(ERROR) << "failed to bind mount sdcardfs filesystem";
139 return false;
140 }
141
142 if (mount(source_path.c_str(), dest_path.c_str(), "none",
143 MS_REMOUNT | MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_NOATIME, opts.c_str()) != 0) {
144 PLOG(ERROR) << "failed to mount sdcardfs filesystem";
145 if (umount2(dest_path.c_str(), MNT_DETACH))
146 PLOG(WARNING) << "Failed to unmount bind";
147 return false;
148 }
149
150 return true;
151 }
152
sdcardfs_setup_secondary(const std::string & default_path,const std::string & source_path,const std::string & dest_path,uid_t fsuid,gid_t fsgid,bool multi_user,userid_t userid,gid_t gid,mode_t mask,bool derive_gid,bool default_normal,bool unshared_obb,bool use_esdfs)153 static bool sdcardfs_setup_secondary(const std::string& default_path,
154 const std::string& source_path, const std::string& dest_path,
155 uid_t fsuid, gid_t fsgid, bool multi_user, userid_t userid,
156 gid_t gid, mode_t mask, bool derive_gid, bool default_normal,
157 bool unshared_obb, bool use_esdfs) {
158 if (use_esdfs) {
159 return sdcardfs_setup(source_path, dest_path, fsuid, fsgid, multi_user, userid, gid, mask,
160 derive_gid, default_normal, unshared_obb, use_esdfs);
161 } else {
162 return sdcardfs_setup_bind_remount(default_path, dest_path, gid, mask);
163 }
164 }
165
run_sdcardfs(const std::string & source_path,const std::string & label,uid_t uid,gid_t gid,userid_t userid,bool multi_user,bool full_write,bool derive_gid,bool default_normal,bool unshared_obb,bool use_esdfs)166 static void run_sdcardfs(const std::string& source_path, const std::string& label, uid_t uid,
167 gid_t gid, userid_t userid, bool multi_user, bool full_write,
168 bool derive_gid, bool default_normal, bool unshared_obb, bool use_esdfs) {
169 std::string dest_path_default = "/mnt/runtime/default/" + label;
170 std::string dest_path_read = "/mnt/runtime/read/" + label;
171 std::string dest_path_write = "/mnt/runtime/write/" + label;
172 std::string dest_path_full = "/mnt/runtime/full/" + label;
173
174 umask(0);
175 if (multi_user) {
176 // Multi-user storage is fully isolated per user, so "other"
177 // permissions are completely masked off.
178 if (!sdcardfs_setup(source_path, dest_path_default, uid, gid, multi_user, userid,
179 AID_SDCARD_RW, 0006, derive_gid, default_normal, unshared_obb,
180 use_esdfs) ||
181 !sdcardfs_setup_secondary(dest_path_default, source_path, dest_path_read, uid, gid,
182 multi_user, userid, AID_EVERYBODY, 0027, derive_gid,
183 default_normal, unshared_obb, use_esdfs) ||
184 !sdcardfs_setup_secondary(dest_path_default, source_path, dest_path_write, uid, gid,
185 multi_user, userid, AID_EVERYBODY, full_write ? 0007 : 0027,
186 derive_gid, default_normal, unshared_obb, use_esdfs) ||
187 !sdcardfs_setup_secondary(dest_path_default, source_path, dest_path_full, uid, gid,
188 multi_user, userid, AID_EVERYBODY, 0007, derive_gid,
189 default_normal, unshared_obb, use_esdfs)) {
190 LOG(FATAL) << "failed to sdcardfs_setup";
191 }
192 } else {
193 // Physical storage is readable by all users on device, but
194 // the Android directories are masked off to a single user
195 // deep inside attr_from_stat().
196 if (!sdcardfs_setup(source_path, dest_path_default, uid, gid, multi_user, userid,
197 AID_SDCARD_RW, 0006, derive_gid, default_normal, unshared_obb,
198 use_esdfs) ||
199 !sdcardfs_setup_secondary(dest_path_default, source_path, dest_path_read, uid, gid,
200 multi_user, userid, AID_EVERYBODY, full_write ? 0027 : 0022,
201 derive_gid, default_normal, unshared_obb, use_esdfs) ||
202 !sdcardfs_setup_secondary(dest_path_default, source_path, dest_path_write, uid, gid,
203 multi_user, userid, AID_EVERYBODY, full_write ? 0007 : 0022,
204 derive_gid, default_normal, unshared_obb, use_esdfs) ||
205 !sdcardfs_setup_secondary(dest_path_default, source_path, dest_path_full, uid, gid,
206 multi_user, userid, AID_EVERYBODY, 0007, derive_gid,
207 default_normal, unshared_obb, use_esdfs)) {
208 LOG(FATAL) << "failed to sdcardfs_setup";
209 }
210 }
211
212 // Will abort if priv-dropping fails.
213 drop_privs(uid, gid);
214
215 if (multi_user) {
216 std::string obb_path = source_path + "/obb";
217 fs_prepare_dir(obb_path.c_str(), 0775, uid, gid);
218 }
219
220 exit(0);
221 }
222
usage()223 static int usage() {
224 LOG(ERROR) << "usage: sdcard [OPTIONS] <source_path> <label>"
225 << " -u: specify UID to run as"
226 << " -g: specify GID to run as"
227 << " -U: specify user ID that owns device"
228 << " -m: source_path is multi-user"
229 << " -w: runtime write mount has full write access"
230 << " -P: preserve owners on the lower file system"
231 << " -o: obb dir doesn't need to be shared between users";
232 return 1;
233 }
234
main(int argc,char ** argv)235 int main(int argc, char **argv) {
236 const char *source_path = NULL;
237 const char *label = NULL;
238 uid_t uid = 0;
239 gid_t gid = 0;
240 userid_t userid = 0;
241 bool multi_user = false;
242 bool full_write = false;
243 bool derive_gid = false;
244 bool default_normal = false;
245 bool unshared_obb = false;
246 int i;
247 struct rlimit rlim;
248 int fs_version;
249
250 setenv("ANDROID_LOG_TAGS", "*:v", 1);
251 android::base::InitLogging(argv, android::base::LogdLogger(android::base::SYSTEM));
252
253 int opt;
254 while ((opt = getopt(argc, argv, "u:g:U:mwGio")) != -1) {
255 switch (opt) {
256 case 'u':
257 uid = strtoul(optarg, NULL, 10);
258 break;
259 case 'g':
260 gid = strtoul(optarg, NULL, 10);
261 break;
262 case 'U':
263 userid = strtoul(optarg, NULL, 10);
264 break;
265 case 'm':
266 multi_user = true;
267 break;
268 case 'w':
269 full_write = true;
270 break;
271 case 'G':
272 derive_gid = true;
273 break;
274 case 'i':
275 default_normal = true;
276 break;
277 case 'o':
278 unshared_obb = true;
279 break;
280 case '?':
281 default:
282 LOG(ERROR) << "Unknown option: '" << opt << "'";
283 return usage();
284 }
285 }
286
287 for (i = optind; i < argc; i++) {
288 char* arg = argv[i];
289 if (!source_path) {
290 source_path = arg;
291 } else if (!label) {
292 label = arg;
293 } else {
294 LOG(ERROR) << "too many arguments";
295 return usage();
296 }
297 }
298
299 if (!source_path) {
300 LOG(ERROR) << "no source path specified";
301 return usage();
302 }
303 if (!label) {
304 LOG(ERROR) << "no label specified";
305 return usage();
306 }
307 if (!uid || !gid) {
308 LOG(ERROR) << "uid and gid must be nonzero";
309 return usage();
310 }
311
312 rlim.rlim_cur = 8192;
313 rlim.rlim_max = 8192;
314 if (setrlimit(RLIMIT_NOFILE, &rlim) == -1) {
315 PLOG(ERROR) << "setting RLIMIT_NOFILE failed";
316 }
317
318 while ((fs_read_atomic_int("/data/.layout_version", &fs_version) == -1) || (fs_version < 3)) {
319 LOG(ERROR) << "installd fs upgrade not yet complete; waiting...";
320 sleep(1);
321 }
322
323 run_sdcardfs(source_path, label, uid, gid, userid, multi_user, full_write, derive_gid,
324 default_normal, unshared_obb, !should_use_sdcardfs());
325 return 1;
326 }
327