// Copyright (C) 2016 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#define LOG_TAG "sdcard"
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <linux/fuse.h>
#include <pthread.h>
#include <stdlib.h>
#include <string.h>
#include <sys/inotify.h>
#include <sys/mount.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/macros.h>
#include <android-base/stringprintf.h>
#include <android-base/strings.h>
#include <cutils/fs.h>
#include <cutils/multiuser.h>
#include <cutils/properties.h>
#include <libminijail.h>
#include <scoped_minijail.h>
#include <private/android_filesystem_config.h>
#define PROP_SDCARDFS_DEVICE "ro.sys.sdcardfs"
#define PROP_SDCARDFS_USER "persist.sys.sdcardfs"
static bool supports_esdfs(void) {
std::string filesystems;
if (!android::base::ReadFileToString("/proc/filesystems", &filesystems)) {
PLOG(ERROR) << "Could not read /proc/filesystems";
return false;
}
for (const auto& fs : android::base::Split(filesystems, "\n")) {
if (fs.find("esdfs") != std::string::npos) return true;
}
return false;
}
static bool should_use_sdcardfs(void) {
char property[PROPERTY_VALUE_MAX];
// Allow user to have a strong opinion about state
property_get(PROP_SDCARDFS_USER, property, "");
if (!strcmp(property, "force_on")) {
LOG(WARNING) << "User explicitly enabled sdcardfs";
return true;
} else if (!strcmp(property, "force_off")) {
LOG(WARNING) << "User explicitly disabled sdcardfs";
return !supports_esdfs();
}
// Fall back to device opinion about state
if (property_get_bool(PROP_SDCARDFS_DEVICE, true)) {
LOG(WARNING) << "Device explicitly enabled sdcardfs";
return true;
} else {
LOG(WARNING) << "Device explicitly disabled sdcardfs";
return !supports_esdfs();
}
}
// NOTE: This is a vestigial program that simply exists to mount the in-kernel
// sdcardfs filesystem. The older FUSE-based design that used to live here has
// been completely removed to avoid confusion.
/* Supplementary groups to execute with. */
static const gid_t kGroups[1] = { AID_PACKAGE_INFO };
static void drop_privs(uid_t uid, gid_t gid) {
ScopedMinijail j(minijail_new());
minijail_set_supplementary_gids(j.get(), arraysize(kGroups), kGroups);
minijail_change_gid(j.get(), gid);
minijail_change_uid(j.get(), uid);
/* minijail_enter() will abort if priv-dropping fails. */
minijail_enter(j.get());
}
static bool 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 use_esdfs) {
// Try several attempts, each time with one less option, to gracefully
// handle older kernels that aren't updated yet.
for (int i = 0; i < 4; i++) {
std::string new_opts;
if (multi_user && i < 3) new_opts += "multiuser,";
if (derive_gid && i < 2) new_opts += "derive_gid,";
if (default_normal && i < 1) new_opts += "default_normal,";
auto opts = android::base::StringPrintf("fsuid=%d,fsgid=%d,%smask=%d,userid=%d,gid=%d",
fsuid, fsgid, new_opts.c_str(), mask, userid, gid);
if (mount(source_path.c_str(), dest_path.c_str(), use_esdfs ? "esdfs" : "sdcardfs",
MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_NOATIME, opts.c_str()) == -1) {
PLOG(WARNING) << "Failed to mount sdcardfs with options " << opts;
} else {
return true;
}
}
return false;
}
static bool sdcardfs_setup_bind_remount(const std::string& source_path, const std::string& dest_path,
gid_t gid, mode_t mask) {
std::string opts = android::base::StringPrintf("mask=%d,gid=%d", mask, gid);
if (mount(source_path.c_str(), dest_path.c_str(), nullptr,
MS_BIND, nullptr) != 0) {
PLOG(ERROR) << "failed to bind mount sdcardfs filesystem";
return false;
}
if (mount(source_path.c_str(), dest_path.c_str(), "none",
MS_REMOUNT | MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_NOATIME, opts.c_str()) != 0) {
PLOG(ERROR) << "failed to mount sdcardfs filesystem";
if (umount2(dest_path.c_str(), MNT_DETACH))
PLOG(WARNING) << "Failed to unmount bind";
return false;
}
return true;
}
static bool 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 use_esdfs) {
if (use_esdfs) {
return sdcardfs_setup(source_path, dest_path, fsuid, fsgid, multi_user, userid, gid, mask,
derive_gid, default_normal, use_esdfs);
} else {
return sdcardfs_setup_bind_remount(default_path, dest_path, gid, mask);
}
}
static void 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 use_esdfs) {
std::string dest_path_default = "/mnt/runtime/default/" + label;
std::string dest_path_read = "/mnt/runtime/read/" + label;
std::string dest_path_write = "/mnt/runtime/write/" + label;
umask(0);
if (multi_user) {
// Multi-user storage is fully isolated per user, so "other"
// permissions are completely masked off.
if (!sdcardfs_setup(source_path, dest_path_default, uid, gid, multi_user, userid,
AID_SDCARD_RW, 0006, derive_gid, default_normal, use_esdfs) ||
!sdcardfs_setup_secondary(dest_path_default, source_path, dest_path_read, uid, gid,
multi_user, userid, AID_EVERYBODY, 0027, derive_gid,
default_normal, use_esdfs) ||
!sdcardfs_setup_secondary(dest_path_default, source_path, dest_path_write, uid, gid,
multi_user, userid, AID_EVERYBODY, full_write ? 0007 : 0027,
derive_gid, default_normal, use_esdfs)) {
LOG(FATAL) << "failed to sdcardfs_setup";
}
} else {
// Physical storage is readable by all users on device, but
// the Android directories are masked off to a single user
// deep inside attr_from_stat().
if (!sdcardfs_setup(source_path, dest_path_default, uid, gid, multi_user, userid,
AID_SDCARD_RW, 0006, derive_gid, default_normal, use_esdfs) ||
!sdcardfs_setup_secondary(dest_path_default, source_path, dest_path_read, uid, gid,
multi_user, userid, AID_EVERYBODY, full_write ? 0027 : 0022,
derive_gid, default_normal, use_esdfs) ||
!sdcardfs_setup_secondary(dest_path_default, source_path, dest_path_write, uid, gid,
multi_user, userid, AID_EVERYBODY, full_write ? 0007 : 0022,
derive_gid, default_normal, use_esdfs)) {
LOG(FATAL) << "failed to sdcardfs_setup";
}
}
// Will abort if priv-dropping fails.
drop_privs(uid, gid);
if (multi_user) {
std::string obb_path = source_path + "/obb";
fs_prepare_dir(obb_path.c_str(), 0775, uid, gid);
}
exit(0);
}
static int usage() {
LOG(ERROR) << "usage: sdcard [OPTIONS] <source_path> <label>"
<< " -u: specify UID to run as"
<< " -g: specify GID to run as"
<< " -U: specify user ID that owns device"
<< " -m: source_path is multi-user"
<< " -w: runtime write mount has full write access"
<< " -P preserve owners on the lower file system";
return 1;
}
int main(int argc, char **argv) {
const char *source_path = NULL;
const char *label = NULL;
uid_t uid = 0;
gid_t gid = 0;
userid_t userid = 0;
bool multi_user = false;
bool full_write = false;
bool derive_gid = false;
bool default_normal = false;
int i;
struct rlimit rlim;
int fs_version;
setenv("ANDROID_LOG_TAGS", "*:v", 1);
android::base::InitLogging(argv, android::base::LogdLogger(android::base::SYSTEM));
int opt;
while ((opt = getopt(argc, argv, "u:g:U:mwGi")) != -1) {
switch (opt) {
case 'u':
uid = strtoul(optarg, NULL, 10);
break;
case 'g':
gid = strtoul(optarg, NULL, 10);
break;
case 'U':
userid = strtoul(optarg, NULL, 10);
break;
case 'm':
multi_user = true;
break;
case 'w':
full_write = true;
break;
case 'G':
derive_gid = true;
break;
case 'i':
default_normal = true;
break;
case '?':
default:
return usage();
}
}
for (i = optind; i < argc; i++) {
char* arg = argv[i];
if (!source_path) {
source_path = arg;
} else if (!label) {
label = arg;
} else {
LOG(ERROR) << "too many arguments";
return usage();
}
}
if (!source_path) {
LOG(ERROR) << "no source path specified";
return usage();
}
if (!label) {
LOG(ERROR) << "no label specified";
return usage();
}
if (!uid || !gid) {
LOG(ERROR) << "uid and gid must be nonzero";
return usage();
}
rlim.rlim_cur = 8192;
rlim.rlim_max = 8192;
if (setrlimit(RLIMIT_NOFILE, &rlim) == -1) {
PLOG(ERROR) << "setting RLIMIT_NOFILE failed";
}
while ((fs_read_atomic_int("/data/.layout_version", &fs_version) == -1) || (fs_version < 3)) {
LOG(ERROR) << "installd fs upgrade not yet complete; waiting...";
sleep(1);
}
run_sdcardfs(source_path, label, uid, gid, userid, multi_user, full_write, derive_gid,
default_normal, !should_use_sdcardfs());
return 1;
}