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Remove FUSE logic; it's only a sdcardfs wrapper.

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Leaving the FUSE logic intact was confusing to OEMs, who expected
that it would still work and pass CTS.  Remove all the FUSE logic
and leave a comment block about why the wrapper exists.

Also use new Android.bp makefile format.

Test: builds, boots
Bug: 63524725
Change-Id: I8b2a4fa0227109d65689c43302dc6fa40394ff58
This commit is contained in:
Jeff Sharkey 2018-01-08 11:22:38 -07:00
parent 178ede377a
commit 68e1093028
5 changed files with 22 additions and 2001 deletions
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17
sdcard/Android.bp Normal file
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@ -0,0 +1,17 @@
cc_binary {
srcs: ["sdcard.cpp"],
name: "sdcard",
cflags: [
"-Wall",
"-Wno-unused-parameter",
"-Werror",
],
shared_libs: [
"libbase",
"libcutils",
"libminijail",
],
sanitize: {
misc_undefined: ["integer"],
},
}

12
sdcard/Android.mk
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@ -1,12 +0,0 @@
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_SRC_FILES := sdcard.cpp fuse.cpp
LOCAL_MODULE := sdcard
LOCAL_CFLAGS := -Wall -Wno-unused-parameter -Werror
LOCAL_SHARED_LIBRARIES := libbase libcutils libminijail libpackagelistparser
LOCAL_SANITIZE := integer
include $(BUILD_EXECUTABLE)

1476
sdcard/fuse.cpp
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File diff suppressed because it is too large Load diff

209
sdcard/fuse.h
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@ -1,209 +0,0 @@
/*
* 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.
*/
#ifndef FUSE_H_
#define FUSE_H_
#include <dirent.h>
#include <fcntl.h>
#include <linux/fuse.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdlib.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/statfs.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>
#include <map>
#include <string>
#include <android-base/logging.h>
#include <cutils/fs.h>
#include <cutils/multiuser.h>
#include <packagelistparser/packagelistparser.h>
#include <private/android_filesystem_config.h>
#define FUSE_TRACE 0
#if FUSE_TRACE
static constexpr bool kEnableDLog = true;
#else // FUSE_TRACE == 0
static constexpr bool kEnableDLog = false;
#endif
// Use same strategy as DCHECK().
#define DLOG(x) \
if (kEnableDLog) LOG(x)
/* Maximum number of bytes to write in one request. */
#define MAX_WRITE (256 * 1024)
/* Maximum number of bytes to read in one request. */
#define MAX_READ (128 * 1024)
/* Largest possible request.
* The request size is bounded by the maximum size of a FUSE_WRITE request because it has
* the largest possible data payload. */
#define MAX_REQUEST_SIZE (sizeof(struct fuse_in_header) + sizeof(struct fuse_write_in) + MAX_WRITE)
namespace {
struct CaseInsensitiveCompare {
bool operator()(const std::string& lhs, const std::string& rhs) const {
return strcasecmp(lhs.c_str(), rhs.c_str()) < 0;
}
};
}
using AppIdMap = std::map<std::string, appid_t, CaseInsensitiveCompare>;
/* Permission mode for a specific node. Controls how file permissions
* are derived for children nodes. */
typedef enum {
/* Nothing special; this node should just inherit from its parent. */
PERM_INHERIT,
/* This node is one level above a normal root; used for legacy layouts
* which use the first level to represent user_id. */
PERM_PRE_ROOT,
/* This node is "/" */
PERM_ROOT,
/* This node is "/Android" */
PERM_ANDROID,
/* This node is "/Android/data" */
PERM_ANDROID_DATA,
/* This node is "/Android/obb" */
PERM_ANDROID_OBB,
/* This node is "/Android/media" */
PERM_ANDROID_MEDIA,
} perm_t;
struct handle {
int fd;
};
struct dirhandle {
DIR *d;
};
struct node {
__u32 refcount;
__u64 nid;
__u64 gen;
/*
* The inode number for this FUSE node. Note that this isn't stable across
* multiple invocations of the FUSE daemon.
*/
__u32 ino;
/* State derived based on current position in hierarchy. */
perm_t perm;
userid_t userid;
uid_t uid;
bool under_android;
struct node *next; /* per-dir sibling list */
struct node *child; /* first contained file by this dir */
struct node *parent; /* containing directory */
size_t namelen;
char *name;
/* If non-null, this is the real name of the file in the underlying storage.
* This may differ from the field "name" only by case.
* strlen(actual_name) will always equal strlen(name), so it is safe to use
* namelen for both fields.
*/
char *actual_name;
/* If non-null, an exact underlying path that should be grafted into this
* position. Used to support things like OBB. */
char* graft_path;
size_t graft_pathlen;
bool deleted;
};
/* Global data for all FUSE mounts */
struct fuse_global {
pthread_mutex_t lock;
uid_t uid;
gid_t gid;
bool multi_user;
char source_path[PATH_MAX];
char obb_path[PATH_MAX];
AppIdMap* package_to_appid;
__u64 next_generation;
struct node root;
/* Used to allocate unique inode numbers for fuse nodes. We use
* a simple counter based scheme where inode numbers from deleted
* nodes aren't reused. Note that inode allocations are not stable
* across multiple invocation of the sdcard daemon, but that shouldn't
* be a huge problem in practice.
*
* Note that we restrict inodes to 32 bit unsigned integers to prevent
* truncation on 32 bit processes when unsigned long long stat.st_ino is
* assigned to an unsigned long ino_t type in an LP32 process.
*
* Also note that fuse_attr and fuse_dirent inode values are 64 bits wide
* on both LP32 and LP64, but the fuse kernel code doesn't squash 64 bit
* inode numbers into 32 bit values on 64 bit kernels (see fuse_squash_ino
* in fs/fuse/inode.c).
*
* Accesses must be guarded by |lock|.
*/
__u32 inode_ctr;
struct fuse* fuse_default;
struct fuse* fuse_read;
struct fuse* fuse_write;
};
/* Single FUSE mount */
struct fuse {
struct fuse_global* global;
char dest_path[PATH_MAX];
int fd;
gid_t gid;
mode_t mask;
};
/* Private data used by a single FUSE handler */
struct fuse_handler {
struct fuse* fuse;
int token;
/* To save memory, we never use the contents of the request buffer and the read
* buffer at the same time. This allows us to share the underlying storage. */
union {
__u8 request_buffer[MAX_REQUEST_SIZE];
__u8 read_buffer[MAX_READ + PAGE_SIZE];
};
};
void handle_fuse_requests(struct fuse_handler* handler);
void derive_permissions_recursive_locked(struct fuse* fuse, struct node *parent);
#endif /* FUSE_H_ */

309
sdcard/sdcard.cpp
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@ -38,164 +38,18 @@
#include <cutils/multiuser.h>
#include <cutils/properties.h>
#include <packagelistparser/packagelistparser.h>
#include <libminijail.h>
#include <scoped_minijail.h>
#include <private/android_filesystem_config.h>
// README
//
// What is this?
//
// sdcard is a program that uses FUSE to emulate FAT-on-sdcard style
// directory permissions (all files are given fixed owner, group, and
// permissions at creation, owner, group, and permissions are not
// changeable, symlinks and hardlinks are not createable, etc.
//
// See usage() for command line options.
//
// It must be run as root, but will drop to requested UID/GID as soon as it
// mounts a filesystem. It will refuse to run if requested UID/GID are zero.
//
// Things I believe to be true:
//
// - ops that return a fuse_entry (LOOKUP, MKNOD, MKDIR, LINK, SYMLINK,
// CREAT) must bump that node's refcount
// - don't forget that FORGET can forget multiple references (req->nlookup)
// - if an op that returns a fuse_entry fails writing the reply to the
// kernel, you must rollback the refcount to reflect the reference the
// kernel did not actually acquire
//
// This daemon can also derive custom filesystem permissions based on directory
// structure when requested. These custom permissions support several features:
//
// - Apps can access their own files in /Android/data/com.example/ without
// requiring any additional GIDs.
// - Separate permissions for protecting directories like Pictures and Music.
// - Multi-user separation on the same physical device.
#include "fuse.h"
#define PROP_SDCARDFS_DEVICE "ro.sys.sdcardfs"
#define PROP_SDCARDFS_USER "persist.sys.sdcardfs"
// 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 bool package_parse_callback(pkg_info *info, void *userdata) {
struct fuse_global *global = (struct fuse_global *)userdata;
bool res = global->package_to_appid->emplace(info->name, info->uid).second;
packagelist_free(info);
return res;
}
static bool read_package_list(struct fuse_global* global) {
pthread_mutex_lock(&global->lock);
global->package_to_appid->clear();
bool rc = packagelist_parse(package_parse_callback, global);
DLOG(INFO) << "read_package_list: found " << global->package_to_appid->size() << " packages";
// Regenerate ownership details using newly loaded mapping.
derive_permissions_recursive_locked(global->fuse_default, &global->root);
pthread_mutex_unlock(&global->lock);
return rc;
}
static void watch_package_list(struct fuse_global* global) {
struct inotify_event *event;
char event_buf[512];
int nfd = inotify_init();
if (nfd == -1) {
PLOG(ERROR) << "inotify_init failed";
return;
}
bool active = false;
while (1) {
if (!active) {
int res = inotify_add_watch(nfd, PACKAGES_LIST_FILE, IN_DELETE_SELF);
if (res == -1) {
if (errno == ENOENT || errno == EACCES) {
/* Framework may not have created the file yet, sleep and retry. */
LOG(ERROR) << "missing \"" << PACKAGES_LIST_FILE << "\"; retrying...";
sleep(3);
continue;
} else {
PLOG(ERROR) << "inotify_add_watch failed";
return;
}
}
/* Watch above will tell us about any future changes, so
* read the current state. */
if (read_package_list(global) == false) {
LOG(ERROR) << "read_package_list failed";
return;
}
active = true;
}
int event_pos = 0;
ssize_t res = TEMP_FAILURE_RETRY(read(nfd, event_buf, sizeof(event_buf)));
if (res == -1) {
PLOG(ERROR) << "failed to read inotify event";
return;
} else if (static_cast<size_t>(res) < sizeof(*event)) {
LOG(ERROR) << "failed to read inotify event: read " << res << " expected "
<< sizeof(event_buf);
return;
}
while (res >= static_cast<ssize_t>(sizeof(*event))) {
int event_size;
event = reinterpret_cast<struct inotify_event*>(event_buf + event_pos);
DLOG(INFO) << "inotify event: " << std::hex << event->mask << std::dec;
if ((event->mask & IN_IGNORED) == IN_IGNORED) {
/* Previously watched file was deleted, probably due to move
* that swapped in new data; re-arm the watch and read. */
active = false;
}
event_size = sizeof(*event) + event->len;
res -= event_size;
event_pos += event_size;
}
}
}
static int fuse_setup(struct fuse* fuse, gid_t gid, mode_t mask) {
char opts[256];
fuse->fd = TEMP_FAILURE_RETRY(open("/dev/fuse", O_RDWR | O_CLOEXEC));
if (fuse->fd == -1) {
PLOG(ERROR) << "failed to open fuse device";
return -1;
}
umount2(fuse->dest_path, MNT_DETACH);
snprintf(opts, sizeof(opts),
"fd=%i,rootmode=40000,default_permissions,allow_other,user_id=%d,group_id=%d",
fuse->fd, fuse->global->uid, fuse->global->gid);
if (mount("/dev/fuse", fuse->dest_path, "fuse", MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_NOATIME,
opts) == -1) {
PLOG(ERROR) << "failed to mount fuse filesystem";
return -1;
}
fuse->gid = gid;
fuse->mask = mask;
return 0;
}
static void drop_privs(uid_t uid, gid_t gid) {
ScopedMinijail j(minijail_new());
minijail_set_supplementary_gids(j.get(), arraysize(kGroups), kGroups);
@ -205,120 +59,6 @@ static void drop_privs(uid_t uid, gid_t gid) {
minijail_enter(j.get());
}
static void* start_handler(void* data) {
struct fuse_handler* handler = static_cast<fuse_handler*>(data);
handle_fuse_requests(handler);
return NULL;
}
static void run(const char* source_path, const char* label, uid_t uid,
gid_t gid, userid_t userid, bool multi_user, bool full_write) {
struct fuse_global global;
struct fuse fuse_default;
struct fuse fuse_read;
struct fuse fuse_write;
struct fuse_handler handler_default;
struct fuse_handler handler_read;
struct fuse_handler handler_write;
pthread_t thread_default;
pthread_t thread_read;
pthread_t thread_write;
memset(&global, 0, sizeof(global));
memset(&fuse_default, 0, sizeof(fuse_default));
memset(&fuse_read, 0, sizeof(fuse_read));
memset(&fuse_write, 0, sizeof(fuse_write));
memset(&handler_default, 0, sizeof(handler_default));
memset(&handler_read, 0, sizeof(handler_read));
memset(&handler_write, 0, sizeof(handler_write));
pthread_mutex_init(&global.lock, NULL);
global.package_to_appid = new AppIdMap;
global.uid = uid;
global.gid = gid;
global.multi_user = multi_user;
global.next_generation = 0;
global.inode_ctr = 1;
memset(&global.root, 0, sizeof(global.root));
global.root.nid = FUSE_ROOT_ID; /* 1 */
global.root.refcount = 2;
global.root.namelen = strlen(source_path);
global.root.name = strdup(source_path);
global.root.userid = userid;
global.root.uid = AID_ROOT;
global.root.under_android = false;
// Clang static analyzer think strcpy potentially overwrites other fields
// in global. Use snprintf() to mute the false warning.
snprintf(global.source_path, sizeof(global.source_path), "%s", source_path);
if (multi_user) {
global.root.perm = PERM_PRE_ROOT;
snprintf(global.obb_path, sizeof(global.obb_path), "%s/obb", source_path);
} else {
global.root.perm = PERM_ROOT;
snprintf(global.obb_path, sizeof(global.obb_path), "%s/Android/obb", source_path);
}
fuse_default.global = &global;
fuse_read.global = &global;
fuse_write.global = &global;
global.fuse_default = &fuse_default;
global.fuse_read = &fuse_read;
global.fuse_write = &fuse_write;
snprintf(fuse_default.dest_path, PATH_MAX, "/mnt/runtime/default/%s", label);
snprintf(fuse_read.dest_path, PATH_MAX, "/mnt/runtime/read/%s", label);
snprintf(fuse_write.dest_path, PATH_MAX, "/mnt/runtime/write/%s", label);
handler_default.fuse = &fuse_default;
handler_read.fuse = &fuse_read;
handler_write.fuse = &fuse_write;
handler_default.token = 0;
handler_read.token = 1;
handler_write.token = 2;
umask(0);
if (multi_user) {
/* Multi-user storage is fully isolated per user, so "other"
* permissions are completely masked off. */
if (fuse_setup(&fuse_default, AID_SDCARD_RW, 0006)
|| fuse_setup(&fuse_read, AID_EVERYBODY, 0027)
|| fuse_setup(&fuse_write, AID_EVERYBODY, full_write ? 0007 : 0027)) {
PLOG(FATAL) << "failed to fuse_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 (fuse_setup(&fuse_default, AID_SDCARD_RW, 0006)
|| fuse_setup(&fuse_read, AID_EVERYBODY, full_write ? 0027 : 0022)
|| fuse_setup(&fuse_write, AID_EVERYBODY, full_write ? 0007 : 0022)) {
PLOG(FATAL) << "failed to fuse_setup";
}
}
// Will abort if priv-dropping fails.
drop_privs(uid, gid);
if (multi_user) {
fs_prepare_dir(global.obb_path, 0775, uid, gid);
}
if (pthread_create(&thread_default, NULL, start_handler, &handler_default)
|| pthread_create(&thread_read, NULL, start_handler, &handler_read)
|| pthread_create(&thread_write, NULL, start_handler, &handler_write)) {
LOG(FATAL) << "failed to pthread_create";
}
watch_package_list(&global);
LOG(FATAL) << "terminated prematurely";
}
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) {
@ -407,41 +147,6 @@ static void run_sdcardfs(const std::string& source_path, const std::string& labe
exit(0);
}
static bool supports_sdcardfs(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("sdcardfs") != 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 supports_sdcardfs();
} else if (!strcmp(property, "force_off")) {
LOG(WARNING) << "User explicitly disabled sdcardfs";
return false;
}
// Fall back to device opinion about state
if (property_get_bool(PROP_SDCARDFS_DEVICE, true)) {
LOG(WARNING) << "Device explicitly enabled sdcardfs";
return supports_sdcardfs();
} else {
LOG(WARNING) << "Device explicitly disabled sdcardfs";
return false;
}
}
static int usage() {
LOG(ERROR) << "usage: sdcard [OPTIONS] <source_path> <label>"
<< " -u: specify UID to run as"
@ -536,11 +241,7 @@ int main(int argc, char **argv) {
sleep(1);
}
if (should_use_sdcardfs()) {
run_sdcardfs(source_path, label, uid, gid, userid, multi_user, full_write, derive_gid,
default_normal);
} else {
run(source_path, label, uid, gid, userid, multi_user, full_write);
}
run_sdcardfs(source_path, label, uid, gid, userid, multi_user, full_write, derive_gid,
default_normal);
return 1;
}