diff options
| -rw-r--r-- | sdcard/fuse.cpp | 3 | ||||
| -rw-r--r-- | sdcard/sdcard.cpp | 106 |
2 files changed, 105 insertions, 4 deletions
diff --git a/sdcard/fuse.cpp b/sdcard/fuse.cpp index 6a972ea76..f549606a9 100644 --- a/sdcard/fuse.cpp +++ b/sdcard/fuse.cpp @@ -23,9 +23,6 @@ /* FUSE_CANONICAL_PATH is not currently upstreamed */ #define FUSE_CANONICAL_PATH 2016 -#define PROP_SDCARDFS_DEVICE "ro.sys.sdcardfs" -#define PROP_SDCARDFS_USER "persist.sys.sdcardfs" - #define FUSE_UNKNOWN_INO 0xffffffff /* Pseudo-error constant used to indicate that no fuse status is needed diff --git a/sdcard/sdcard.cpp b/sdcard/sdcard.cpp index 3481ec300..70bbf2641 100644 --- a/sdcard/sdcard.cpp +++ b/sdcard/sdcard.cpp @@ -28,11 +28,16 @@ #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 <packagelistparser/packagelistparser.h> #include <libminijail.h> @@ -73,6 +78,9 @@ #include "fuse.h" +#define PROP_SDCARDFS_DEVICE "ro.sys.sdcardfs" +#define PROP_SDCARDFS_USER "persist.sys.sdcardfs" + /* Supplementary groups to execute with. */ static const gid_t kGroups[1] = { AID_PACKAGE_INFO }; @@ -307,6 +315,98 @@ static void run(const char* source_path, const char* label, uid_t uid, 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) { + std::string opts = android::base::StringPrintf("fsuid=%d,fsgid=%d,%smask=%d,userid=%d,gid=%d", + fsuid, fsgid, multi_user?"multiuser,":"", mask, userid, gid); + + if (mount(source_path.c_str(), dest_path.c_str(), "sdcardfs", + MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_NOATIME, opts.c_str()) != 0) { + PLOG(ERROR) << "failed to mount sdcardfs filesystem"; + return false; + } + + return true; +} + +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) { + 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) + || !sdcardfs_setup(source_path, dest_path_read, uid, gid, multi_user, userid, + AID_EVERYBODY, 0027) + || !sdcardfs_setup(source_path, dest_path_write, uid, gid, multi_user, userid, + AID_EVERYBODY, full_write ? 0007 : 0027)) { + 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) + || !sdcardfs_setup(source_path, dest_path_read, uid, gid, multi_user, userid, + AID_EVERYBODY, full_write ? 0027 : 0022) + || !sdcardfs_setup(source_path, dest_path_write, uid, gid, multi_user, userid, + AID_EVERYBODY, full_write ? 0007 : 0022)) { + 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 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, false)) { + 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" @@ -389,6 +489,10 @@ int main(int argc, char **argv) { sleep(1); } - run(source_path, label, uid, gid, userid, multi_user, full_write); + if (should_use_sdcardfs()) { + run_sdcardfs(source_path, label, uid, gid, userid, multi_user, full_write); + } else { + run(source_path, label, uid, gid, userid, multi_user, full_write); + } return 1; } |