diff --git a/sdcard/sdcard.c b/sdcard/sdcard.c index 45efe369e..d8fda676f 100644 --- a/sdcard/sdcard.c +++ b/sdcard/sdcard.c @@ -1894,6 +1894,105 @@ static void run(const char* source_path, const char* label, uid_t uid, exit(1); } +static int sdcardfs_setup(const char *source_path, const char *dest_path, uid_t fsuid, + gid_t fsgid, bool multi_user, userid_t userid, gid_t gid, mode_t mask) { + char opts[256]; + + snprintf(opts, sizeof(opts), + "fsuid=%d,fsgid=%d,%smask=%d,userid=%d,gid=%d", + fsuid, fsgid, multi_user?"multiuser,":"", mask, userid, gid); + + if (mount(source_path, dest_path, "sdcardfs", + MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_NOATIME, opts) != 0) { + ERROR("failed to mount sdcardfs filesystem: %s\n", strerror(errno)); + return -1; + } + + return 0; +} + +static void run_sdcardfs(const char* source_path, const char* label, uid_t uid, + gid_t gid, userid_t userid, bool multi_user, bool full_write) { + char dest_path_default[PATH_MAX]; + char dest_path_read[PATH_MAX]; + char dest_path_write[PATH_MAX]; + char obb_path[PATH_MAX]; + snprintf(dest_path_default, PATH_MAX, "/mnt/runtime/default/%s", label); + snprintf(dest_path_read, PATH_MAX, "/mnt/runtime/read/%s", label); + snprintf(dest_path_write, PATH_MAX, "/mnt/runtime/write/%s", 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)) { + ERROR("failed to fuse_setup\n"); + exit(1); + } + } 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)) { + ERROR("failed to fuse_setup\n"); + exit(1); + } + } + + /* Drop privs */ + if (setgroups(sizeof(kGroups) / sizeof(kGroups[0]), kGroups) < 0) { + ERROR("cannot setgroups: %s\n", strerror(errno)); + exit(1); + } + if (setgid(gid) < 0) { + ERROR("cannot setgid: %s\n", strerror(errno)); + exit(1); + } + if (setuid(uid) < 0) { + ERROR("cannot setuid: %s\n", strerror(errno)); + exit(1); + } + + if (multi_user) { + snprintf(obb_path, sizeof(obb_path), "%s/obb", source_path); + fs_prepare_dir(&obb_path[0], 0775, uid, gid); + } + + exit(0); +} + +static bool supports_sdcardfs(void) { + FILE *fp; + char *buf = NULL; + size_t buflen = 0; + + fp = fopen("/proc/filesystems", "r"); + if (!fp) { + ERROR("Could not read /proc/filesystems, error: %s\n", strerror(errno)); + return false; + } + while ((getline(&buf, &buflen, fp)) > 0) { + if (strstr(buf, "sdcardfs\n")) { + free(buf); + fclose(fp); + return true; + } + } + free(buf); + fclose(fp); + return false; +} + int main(int argc, char **argv) { const char *source_path = NULL; const char *label = NULL; @@ -1966,6 +2065,10 @@ int main(int argc, char **argv) { sleep(1); } - run(source_path, label, uid, gid, userid, multi_user, full_write); + if (supports_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; }