VoldNativeService.cpp

/*
 * Copyright (C) 2017 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.
 */

#include "VoldNativeService.h"
#include "VolumeManager.h"

#include <fstream>

#include <android-base/logging.h>
#include <android-base/stringprintf.h>
#include <android-base/strings.h>
#include <private/android_filesystem_config.h>

#ifndef LOG_TAG
#define LOG_TAG "vold"
#endif

using android::base::StringPrintf;
using std::endl;

namespace android {
namespace vold {

namespace {

constexpr const char* kDump = "android.permission.DUMP";

static binder::Status ok() {
    return binder::Status::ok();
}

static binder::Status exception(uint32_t code, const std::string& msg) {
    return binder::Status::fromExceptionCode(code, String8(msg.c_str()));
}

binder::Status checkPermission(const char* permission) {
    pid_t pid;
    uid_t uid;

    if (checkCallingPermission(String16(permission), reinterpret_cast<int32_t*>(&pid),
            reinterpret_cast<int32_t*>(&uid))) {
        return ok();
    } else {
        return exception(binder::Status::EX_SECURITY,
                StringPrintf("UID %d / PID %d lacks permission %s", uid, pid, permission));
    }
}

binder::Status checkUid(uid_t expectedUid) {
    uid_t uid = IPCThreadState::self()->getCallingUid();
    if (uid == expectedUid || uid == AID_ROOT) {
        return ok();
    } else {
        return exception(binder::Status::EX_SECURITY,
                StringPrintf("UID %d is not expected UID %d", uid, expectedUid));
    }
}

#define ENFORCE_UID(uid) {                                  \
    binder::Status status = checkUid((uid));                \
    if (!status.isOk()) {                                   \
        return status;                                      \
    }                                                       \
}

}  // namespace

status_t VoldNativeService::start() {
    IPCThreadState::self()->disableBackgroundScheduling(true);
    status_t ret = BinderService<VoldNativeService>::publish();
    if (ret != android::OK) {
        return ret;
    }
    sp<ProcessState> ps(ProcessState::self());
    ps->startThreadPool();
    ps->giveThreadPoolName();
    return android::OK;
}

status_t VoldNativeService::dump(int fd, const Vector<String16> & /* args */) {
    auto out = std::fstream(StringPrintf("/proc/self/fd/%d", fd));
    const binder::Status dump_permission = checkPermission(kDump);
    if (!dump_permission.isOk()) {
        out << dump_permission.toString8() << endl;
        return PERMISSION_DENIED;
    }

    out << "vold is happy!" << endl;
    out.flush();

    return NO_ERROR;
}

binder::Status VoldNativeService::reset() {
    ENFORCE_UID(AID_SYSTEM);

    LOG(INFO) << "reset() via Binder!";
    VolumeManager::Instance()->reset();
    return ok();
}

}  // namespace vold
}  // namespace android