/*
 * Copyright (C) 2022 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 <fuzzbinder/libbinder_driver.h>

#include <fuzzbinder/random_parcel.h>

#include <android-base/logging.h>
#include <binder/IPCThreadState.h>
#include <binder/ProcessState.h>

namespace android {

void fuzzService(const sp<IBinder>& binder, FuzzedDataProvider&& provider) {
    fuzzService(std::vector<sp<IBinder>>{binder}, std::move(provider));
}

void fuzzService(const std::vector<sp<IBinder>>& binders, FuzzedDataProvider&& provider) {
    RandomParcelOptions options{
            .extraBinders = binders,
            .extraFds = {},
    };

    // Always take so that a perturbation of just the one ConsumeBool byte will always
    // take the same path, but with a different UID. Without this, the fuzzer needs to
    // guess both the change in value and the shift at the same time.
    int64_t maybeSetUid = provider.ConsumeIntegral<int64_t>();
    if (provider.ConsumeBool()) {
        // set calling uid
        IPCThreadState::self()->restoreCallingIdentity(maybeSetUid);
    }

    while (provider.remaining_bytes() > 0) {
        provider.PickValueInArray<std::function<void()>>({
                [&]() {
                    // Most of the AIDL services will have small set of transaction codes.
                    uint32_t code = provider.ConsumeBool()
                            ? provider.ConsumeIntegral<uint32_t>()
                            : provider.ConsumeIntegralInRange<uint32_t>(0, 100);
                    uint32_t flags = provider.ConsumeIntegral<uint32_t>();
                    Parcel data;
                    // for increased fuzz coverage
                    data.setEnforceNoDataAvail(false);
                    data.setServiceFuzzing();

                    sp<IBinder> target = options.extraBinders.at(
                            provider.ConsumeIntegralInRange<size_t>(0,
                                                                    options.extraBinders.size() -
                                                                            1));
                    options.writeHeader = [&target](Parcel* p, FuzzedDataProvider& provider) {
                        // most code will be behind checks that the head of the Parcel
                        // is exactly this, so make it easier for fuzzers to reach this
                        if (provider.ConsumeBool()) {
                            p->writeInterfaceToken(target->getInterfaceDescriptor());
                        }
                    };

                    std::vector<uint8_t> subData = provider.ConsumeBytes<uint8_t>(
                            provider.ConsumeIntegralInRange<size_t>(0, provider.remaining_bytes()));
                    fillRandomParcel(&data, FuzzedDataProvider(subData.data(), subData.size()),
                                     &options);

                    Parcel reply;
                    // for increased fuzz coverage
                    reply.setEnforceNoDataAvail(false);
                    reply.setServiceFuzzing();
                    (void)target->transact(code, data, &reply, flags);

                    // feed back in binders and fds that are returned from the service, so that
                    // we can fuzz those binders, and use the fds and binders to feed back into
                    // the binders
                    auto retBinders = reply.debugReadAllStrongBinders();
                    options.extraBinders.insert(options.extraBinders.end(), retBinders.begin(),
                                                retBinders.end());
                    auto retFds = reply.debugReadAllFileDescriptors();
                    for (size_t i = 0; i < retFds.size(); i++) {
                        options.extraFds.push_back(base::unique_fd(dup(retFds[i])));
                    }
                },
                [&]() {
                    if (options.extraFds.size() == 0) {
                        return;
                    }
                    uint32_t toDelete =
                            provider.ConsumeIntegralInRange<uint32_t>(0,
                                                                      options.extraFds.size() - 1);
                    options.extraFds.erase(options.extraFds.begin() + toDelete);
                },
                [&]() {
                    if (options.extraBinders.size() <= 1) {
                        return;
                    }
                    uint32_t toDelete =
                            provider.ConsumeIntegralInRange<uint32_t>(0,
                                                                      options.extraBinders.size() -
                                                                              1);
                    options.extraBinders.erase(options.extraBinders.begin() + toDelete);
                },
        })();
    }

    // invariants
    auto ps = ProcessState::selfOrNull();
    if (ps) {
        CHECK_EQ(0, ps->getThreadPoolMaxTotalThreadCount())
                << "Binder threadpool should not be started by fuzzer because coverage can only "
                   "cover in-process calls.";
    }
}

} // namespace android
