Replay recorded fds and binders in fuzzers

Save object offsets in RecordedTransaction and generate seed
corpus so that objects will be replaced by random binders and
random fds. Adding tests to replay fds and binders in
binderRecordReplayTests.

Test: m binderRecordReplayTest && adb sync && atest -c  binderRecordReplayTest
Bug: 299650657
Change-Id: Ib9e1827b31194d8ea85def5dd3089a98b207da25

11 files changed, 377 insertions, 69 deletions

diff --git a/libs/binder/RecordedTransaction.cpp b/libs/binder/RecordedTransaction.cpp
index 525ba2e9b9..de2a69f7cf 100644
--- a/libs/binder/RecordedTransaction.cpp
+++ b/libs/binder/RecordedTransaction.cpp
@@ -114,8 +114,8 @@ static_assert(PADDING8(8) == 0);
 
 RecordedTransaction::RecordedTransaction(RecordedTransaction&& t) noexcept {
     mData = t.mData;
-    mSent.setData(t.getDataParcel().data(), t.getDataParcel().dataSize());
-    mReply.setData(t.getReplyParcel().data(), t.getReplyParcel().dataSize());
+    mSentDataOnly.setData(t.getDataParcel().data(), t.getDataParcel().dataSize());
+    mReplyDataOnly.setData(t.getReplyParcel().data(), t.getReplyParcel().dataSize());
 }
 
 std::optional<RecordedTransaction> RecordedTransaction::fromDetails(
@@ -136,12 +136,21 @@ std::optional<RecordedTransaction> RecordedTransaction::fromDetails(
         return std::nullopt;
     }
 
-    if (t.mSent.setData(dataParcel.data(), dataParcel.dataBufferSize()) != android::NO_ERROR) {
+    if (const auto* kernelFields = dataParcel.maybeKernelFields()) {
+        for (size_t i = 0; i < kernelFields->mObjectsSize; i++) {
+            uint64_t offset = kernelFields->mObjects[i];
+            t.mData.mSentObjectData.push_back(offset);
+        }
+    }
+
+    if (t.mSentDataOnly.setData(dataParcel.data(), dataParcel.dataBufferSize()) !=
+        android::NO_ERROR) {
         ALOGE("Failed to set sent parcel data.");
         return std::nullopt;
     }
 
-    if (t.mReply.setData(replyParcel.data(), replyParcel.dataBufferSize()) != android::NO_ERROR) {
+    if (t.mReplyDataOnly.setData(replyParcel.data(), replyParcel.dataBufferSize()) !=
+        android::NO_ERROR) {
         ALOGE("Failed to set reply parcel data.");
         return std::nullopt;
     }
@@ -154,6 +163,7 @@ enum {
     DATA_PARCEL_CHUNK = 2,
     REPLY_PARCEL_CHUNK = 3,
     INTERFACE_NAME_CHUNK = 4,
+    DATA_PARCEL_OBJECT_CHUNK = 5,
     END_CHUNK = 0x00ffffff,
 };
 
@@ -265,21 +275,30 @@ std::optional<RecordedTransaction> RecordedTransaction::fromFile(const unique_fd
                 break;
             }
             case DATA_PARCEL_CHUNK: {
-                if (t.mSent.setData(reinterpret_cast<const unsigned char*>(payloadMap),
-                                    chunk.dataSize) != android::NO_ERROR) {
+                if (t.mSentDataOnly.setData(reinterpret_cast<const unsigned char*>(payloadMap),
+                                            chunk.dataSize) != android::NO_ERROR) {
                     ALOGE("Failed to set sent parcel data.");
                     return std::nullopt;
                 }
                 break;
             }
             case REPLY_PARCEL_CHUNK: {
-                if (t.mReply.setData(reinterpret_cast<const unsigned char*>(payloadMap),
-                                     chunk.dataSize) != android::NO_ERROR) {
+                if (t.mReplyDataOnly.setData(reinterpret_cast<const unsigned char*>(payloadMap),
+                                             chunk.dataSize) != android::NO_ERROR) {
                     ALOGE("Failed to set reply parcel data.");
                     return std::nullopt;
                 }
                 break;
             }
+            case DATA_PARCEL_OBJECT_CHUNK: {
+                const uint64_t* objects = reinterpret_cast<const uint64_t*>(payloadMap);
+                size_t metaDataSize = (chunk.dataSize / sizeof(uint64_t));
+                ALOGI("Total objects found in saved parcel %zu", metaDataSize);
+                for (size_t index = 0; index < metaDataSize; ++index) {
+                    t.mData.mSentObjectData.push_back(objects[index]);
+                }
+                break;
+            }
             case END_CHUNK:
                 break;
             default:
@@ -343,14 +362,26 @@ android::status_t RecordedTransaction::dumpToFile(const unique_fd& fd) const {
         return UNKNOWN_ERROR;
     }
 
-    if (NO_ERROR != writeChunk(fd, DATA_PARCEL_CHUNK, mSent.dataBufferSize(), mSent.data())) {
+    if (NO_ERROR !=
+        writeChunk(fd, DATA_PARCEL_CHUNK, mSentDataOnly.dataBufferSize(), mSentDataOnly.data())) {
         ALOGE("Failed to write sent Parcel to fd %d", fd.get());
         return UNKNOWN_ERROR;
     }
-    if (NO_ERROR != writeChunk(fd, REPLY_PARCEL_CHUNK, mReply.dataBufferSize(), mReply.data())) {
+
+    if (NO_ERROR !=
+        writeChunk(fd, REPLY_PARCEL_CHUNK, mReplyDataOnly.dataBufferSize(),
+                   mReplyDataOnly.data())) {
         ALOGE("Failed to write reply Parcel to fd %d", fd.get());
         return UNKNOWN_ERROR;
     }
+
+    if (NO_ERROR !=
+        writeChunk(fd, DATA_PARCEL_OBJECT_CHUNK, mData.mSentObjectData.size() * sizeof(uint64_t),
+                   reinterpret_cast<const uint8_t*>(mData.mSentObjectData.data()))) {
+        ALOGE("Failed to write sent parcel object metadata to fd %d", fd.get());
+        return UNKNOWN_ERROR;
+    }
+
     if (NO_ERROR != writeChunk(fd, END_CHUNK, 0, NULL)) {
         ALOGE("Failed to write end chunk to fd %d", fd.get());
         return UNKNOWN_ERROR;
@@ -384,10 +415,14 @@ uint32_t RecordedTransaction::getVersion() const {
     return mData.mHeader.version;
 }
 
+const std::vector<uint64_t>& RecordedTransaction::getObjectOffsets() const {
+    return mData.mSentObjectData;
+}
+
 const Parcel& RecordedTransaction::getDataParcel() const {
-    return mSent;
+    return mSentDataOnly;
 }
 
 const Parcel& RecordedTransaction::getReplyParcel() const {
-    return mReply;
+    return mReplyDataOnly;
 }
diff --git a/libs/binder/include/binder/Parcel.h b/libs/binder/include/binder/Parcel.h
index 09da6e3c4a..d7096d8a75 100644
--- a/libs/binder/include/binder/Parcel.h
+++ b/libs/binder/include/binder/Parcel.h
@@ -55,6 +55,9 @@ class String8;
 class TextOutput;
 namespace binder {
 class Status;
+namespace debug {
+class RecordedTransaction;
+}
 }
 
 class Parcel {
@@ -1443,6 +1446,9 @@ private:
     // TODO(b/202029388): Remove 'getBlobAshmemSize' once no prebuilts reference
     // this
     size_t getBlobAshmemSize() const;
+
+    // Needed so that we can save object metadata to the disk
+    friend class android::binder::debug::RecordedTransaction;
 };
 
 // ---------------------------------------------------------------------------
diff --git a/libs/binder/include/binder/RecordedTransaction.h b/libs/binder/include/binder/RecordedTransaction.h
index 505c1992b9..f0bee7f39e 100644
--- a/libs/binder/include/binder/RecordedTransaction.h
+++ b/libs/binder/include/binder/RecordedTransaction.h
@@ -50,6 +50,7 @@ public:
     uint32_t getVersion() const;
     const Parcel& getDataParcel() const;
     const Parcel& getReplyParcel() const;
+    const std::vector<uint64_t>& getObjectOffsets() const;
 
 private:
     RecordedTransaction() = default;
@@ -75,10 +76,11 @@ private:
     struct MovableData { // movable
         TransactionHeader mHeader;
         std::string mInterfaceName;
+        std::vector<uint64_t> mSentObjectData; /* Object Offsets */
     };
     MovableData mData;
-    Parcel mSent;
-    Parcel mReply;
+    Parcel mSentDataOnly;
+    Parcel mReplyDataOnly;
 };
 
 } // namespace binder::debug
diff --git a/libs/binder/tests/Android.bp b/libs/binder/tests/Android.bp
index dd2be94a76..aba2319485 100644
--- a/libs/binder/tests/Android.bp
+++ b/libs/binder/tests/Android.bp
@@ -69,10 +69,14 @@ cc_test {
 cc_test {
     name: "binderRecordReplayTest",
     srcs: ["binderRecordReplayTest.cpp"],
+    cflags: [
+        "-DBINDER_WITH_KERNEL_IPC",
+    ],
     shared_libs: [
         "libbinder",
         "libcutils",
         "libutils",
+        "liblog",
     ],
     static_libs: [
         "binderRecordReplayTestIface-cpp",
@@ -96,6 +100,9 @@ aidl_interface {
             enabled: true,
             platform_apis: true,
         },
+        ndk: {
+            enabled: false,
+        },
     },
 }
 
diff --git a/libs/binder/tests/IBinderRecordReplayTest.aidl b/libs/binder/tests/IBinderRecordReplayTest.aidl
index bd6b03c6e0..29267e91c6 100644
--- a/libs/binder/tests/IBinderRecordReplayTest.aidl
+++ b/libs/binder/tests/IBinderRecordReplayTest.aidl
@@ -69,4 +69,10 @@ interface IBinderRecordReplayTest {
 
     void setSingleDataParcelableArray(in SingleDataParcelable[] input);
     SingleDataParcelable[] getSingleDataParcelableArray();
+
+    void setBinder(in IBinder binder);
+    IBinder getBinder();
+
+    void setFileDescriptor(in FileDescriptor fd);
+    FileDescriptor getFileDescriptor();
 }
diff --git a/libs/binder/tests/binderRecordReplayTest.cpp b/libs/binder/tests/binderRecordReplayTest.cpp
index 73c0a94ce2..b975fad2c9 100644
--- a/libs/binder/tests/binderRecordReplayTest.cpp
+++ b/libs/binder/tests/binderRecordReplayTest.cpp
@@ -24,7 +24,10 @@
 #include <binder/RecordedTransaction.h>
 #include <binder/unique_fd.h>
 
+#include <cutils/ashmem.h>
+
 #include <fuzzbinder/libbinder_driver.h>
+#include <fuzzbinder/random_binder.h>
 #include <fuzzer/FuzzedDataProvider.h>
 #include <fuzzseeds/random_parcel_seeds.h>
 
@@ -37,6 +40,7 @@
 
 using namespace android;
 using android::generateSeedsFromRecording;
+using android::RandomBinder;
 using android::binder::borrowed_fd;
 using android::binder::Status;
 using android::binder::unique_fd;
@@ -44,6 +48,7 @@ using android::binder::debug::RecordedTransaction;
 using parcelables::SingleDataParcelable;
 
 const String16 kServerName = String16("binderRecordReplay");
+extern std::string kRandomInterfaceName;
 
 #define GENERATE_GETTER_SETTER_PRIMITIVE(name, T) \
     Status set##name(T input) {                   \
@@ -81,6 +86,7 @@ public:
 
     GENERATE_GETTER_SETTER(String, String16);
     GENERATE_GETTER_SETTER(SingleDataParcelable, SingleDataParcelable);
+    GENERATE_GETTER_SETTER(Binder, sp<IBinder>);
 
     GENERATE_GETTER_SETTER(BooleanArray, std::vector<bool>);
     GENERATE_GETTER_SETTER(ByteArray, std::vector<uint8_t>);
@@ -91,12 +97,22 @@ public:
     GENERATE_GETTER_SETTER(DoubleArray, std::vector<double>);
     GENERATE_GETTER_SETTER(StringArray, std::vector<::android::String16>);
     GENERATE_GETTER_SETTER(SingleDataParcelableArray, std::vector<SingleDataParcelable>);
+
+    Status setFileDescriptor(unique_fd input) {
+        mFd = std::move(unique_fd(dup(input)));
+        return Status::ok();
+    }
+
+    Status getFileDescriptor(unique_fd* output) {
+        *output = std::move(unique_fd(dup(mFd)));
+        return Status::ok();
+    }
+    unique_fd mFd;
 };
 
 std::vector<uint8_t> retrieveData(borrowed_fd fd) {
     struct stat fdStat;
     EXPECT_TRUE(fstat(fd.get(), &fdStat) != -1);
-    EXPECT_TRUE(fdStat.st_size != 0);
 
     std::vector<uint8_t> buffer(fdStat.st_size);
     auto readResult = android::base::ReadFully(fd, buffer.data(), fdStat.st_size);
@@ -115,6 +131,7 @@ void replayFuzzService(const sp<BpBinder>& binder, const RecordedTransaction& tr
     // Read the data which has been written to seed corpus
     ASSERT_EQ(0, lseek(seedFd.get(), 0, SEEK_SET));
     std::vector<uint8_t> seedData = retrieveData(seedFd);
+    EXPECT_TRUE(seedData.size() != 0);
 
     // use fuzzService to replay the corpus
     FuzzedDataProvider provider(seedData.data(), seedData.size());
@@ -148,7 +165,14 @@ public:
     template <typename T, typename U>
     void recordReplay(Status (IBinderRecordReplayTest::*set)(T), U recordedValue,
                       Status (IBinderRecordReplayTest::*get)(U*), U changedValue) {
-        auto replayFunctions = {&replayBinder, &replayFuzzService};
+        using ReplayFunc = decltype(&replayFuzzService);
+        vector<ReplayFunc> replayFunctions = {&replayFuzzService};
+        if (!std::is_same_v<U, unique_fd> && !std::is_same_v<U, sp<IBinder>>) {
+            // Parcel retrieved from record replay doesn't have object information. use it for
+            // replaying primitive types only.
+            replayFunctions.push_back(&replayBinder);
+        }
+
         for (auto replayFunc : replayFunctions) {
             unique_fd fd(open("/data/local/tmp/binderRecordReplayTest.rec",
                               O_RDWR | O_CREAT | O_CLOEXEC, 0666));
@@ -156,7 +180,7 @@ public:
 
             // record a transaction
             mBpBinder->startRecordingBinder(fd);
-            auto status = (*mInterface.*set)(recordedValue);
+            auto status = (*mInterface.*set)(std::move(recordedValue));
             EXPECT_TRUE(status.isOk());
             mBpBinder->stopRecordingBinder();
 
@@ -164,16 +188,22 @@ public:
             U output;
             status = (*mInterface.*get)(&output);
             EXPECT_TRUE(status.isOk());
-            EXPECT_EQ(output, recordedValue);
+
+            // Expect this equal only if types are primitives
+            if (!std::is_same_v<U, unique_fd> && !std::is_same_v<U, sp<IBinder>>) {
+                EXPECT_EQ(output, recordedValue);
+            }
 
             // write over the existing state
-            status = (*mInterface.*set)(changedValue);
+            status = (*mInterface.*set)(std::move(changedValue));
             EXPECT_TRUE(status.isOk());
 
             status = (*mInterface.*get)(&output);
             EXPECT_TRUE(status.isOk());
 
-            EXPECT_EQ(output, changedValue);
+            if (!std::is_same_v<U, unique_fd> && !std::is_same_v<U, sp<IBinder>>) {
+                EXPECT_EQ(output, changedValue);
+            }
 
             // replay transaction
             ASSERT_EQ(0, lseek(fd.get(), 0, SEEK_SET));
@@ -186,7 +216,23 @@ public:
 
             status = (*mInterface.*get)(&output);
             EXPECT_TRUE(status.isOk());
-            EXPECT_EQ(output, recordedValue);
+
+            // FDs and binders will be replaced with random fd and random binders
+            if constexpr (std::is_same_v<U, unique_fd>) {
+                // verify that replayed fd is /dev/null. This is being replayed from random_fd.cpp
+                // and choosing /dav/null while generating seed in binder2corpus
+                std::string fdPath = "/proc/self/fd/" + std::to_string(output.get());
+                char path[PATH_MAX];
+                ASSERT_GT(readlink(fdPath.c_str(), path, sizeof(path)), 0);
+                EXPECT_EQ(strcmp("/dev/null", path), 0);
+            } else if constexpr (std::is_same_v<U, sp<IBinder>>) {
+                // This is binder is replayed from random_binder.cpp using seed data which writes
+                // this interface.
+                EXPECT_EQ(String16(kRandomInterfaceName.c_str(), kRandomInterfaceName.size()),
+                          output->getInterfaceDescriptor());
+            } else {
+                ASSERT_EQ(recordedValue, output);
+            }
         }
     }
 
@@ -319,6 +365,32 @@ TEST_F(BinderRecordReplayTest, ReplaySingleDataParcelableArray) {
                  &IBinderRecordReplayTest::getSingleDataParcelableArray, changed);
 }
 
+TEST_F(BinderRecordReplayTest, ReplayBinder) {
+    vector<uint8_t> data = {0x8A, 0x19, 0x0D, 0x44, 0x37, 0x0D, 0x38, 0x5E, 0x9B, 0xAA, 0xF3, 0xDA};
+    sp<IBinder> saved = new RandomBinder(String16("random_interface"), std::move(data));
+    sp<IBinder> changed = IInterface::asBinder(defaultServiceManager());
+    recordReplay(&IBinderRecordReplayTest::setBinder, saved, &IBinderRecordReplayTest::getBinder,
+                 changed);
+}
+
+TEST_F(BinderRecordReplayTest, ReplayFd) {
+    // Write something to both fds we are setting
+    unique_fd saved(open("/data/local/tmp/test_fd", O_RDWR | O_CREAT | O_CLOEXEC, 0666));
+    std::string contentSaved = "This will be never read again for recorded fd!";
+    CHECK(android::base::WriteFully(saved, contentSaved.data(), contentSaved.size()))
+            << saved.get();
+
+    unique_fd changed(open("/data/local/tmp/test_des", O_RDWR | O_CREAT | O_CLOEXEC, 0666));
+    std::string contentChanged = "This will be never read again from changed fd!";
+    CHECK(android::base::WriteFully(changed, contentChanged.data(), contentChanged.size()))
+            << changed.get();
+
+    // When fds are replayed, it will be replaced by /dev/null..reading from it should yield
+    // null data
+    recordReplay(&IBinderRecordReplayTest::setFileDescriptor, std::move(unique_fd(dup(saved))),
+                 &IBinderRecordReplayTest::getFileDescriptor, std::move(unique_fd(dup(changed))));
+}
+
 int main(int argc, char** argv) {
     ::testing::InitGoogleTest(&argc, argv);
 
diff --git a/libs/binder/tests/parcel_fuzzer/Android.bp b/libs/binder/tests/parcel_fuzzer/Android.bp
index 83db6c9b6d..fbab8f08a9 100644
--- a/libs/binder/tests/parcel_fuzzer/Android.bp
+++ b/libs/binder/tests/parcel_fuzzer/Android.bp
@@ -131,6 +131,13 @@ cc_library {
         "libcutils",
         "libutils",
     ],
+    static_libs: [
+        "libbinder_random_parcel",
+    ],
+    include_dirs: [
+        "bionic/libc/kernel/android/uapi/",
+        "bionic/libc/kernel/uapi/",
+    ],
     local_include_dirs: [
         "include_random_parcel_seeds",
     ],
@@ -140,8 +147,12 @@ cc_library {
 cc_binary_host {
     name: "binder2corpus",
     static_libs: [
+        "libbinder_random_parcel",
         "libbinder_random_parcel_seeds",
     ],
+    cflags: [
+        "-DBINDER_WITH_KERNEL_IPC",
+    ],
     srcs: [
         "binder2corpus/binder2corpus.cpp",
     ],
@@ -149,5 +160,6 @@ cc_binary_host {
         "libbase",
         "libbinder",
         "libutils",
+        "libcutils",
     ],
 }
diff --git a/libs/binder/tests/parcel_fuzzer/include_random_parcel/fuzzbinder/random_binder.h b/libs/binder/tests/parcel_fuzzer/include_random_parcel/fuzzbinder/random_binder.h
index 8fc9263b98..7a1688b7b7 100644
--- a/libs/binder/tests/parcel_fuzzer/include_random_parcel/fuzzbinder/random_binder.h
+++ b/libs/binder/tests/parcel_fuzzer/include_random_parcel/fuzzbinder/random_binder.h
@@ -16,11 +16,25 @@
 
 #pragma once
 
+#include <binder/Binder.h>
 #include <binder/IBinder.h>
 #include <fuzzer/FuzzedDataProvider.h>
 
 namespace android {
 
+class RandomBinder : public BBinder {
+public:
+    RandomBinder(const String16& descriptor, std::vector<uint8_t>&& bytes);
+    const String16& getInterfaceDescriptor() const override;
+    status_t onTransact(uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags) override;
+
+private:
+    String16 mDescriptor;
+    // note may not all be used
+    std::vector<uint8_t> mBytes;
+    FuzzedDataProvider mProvider;
+};
+
 // Get a random binder object for use in fuzzing.
 //
 // May return nullptr.
diff --git a/libs/binder/tests/parcel_fuzzer/random_binder.cpp b/libs/binder/tests/parcel_fuzzer/random_binder.cpp
index 8a1fecb212..f41c35bfbe 100644
--- a/libs/binder/tests/parcel_fuzzer/random_binder.cpp
+++ b/libs/binder/tests/parcel_fuzzer/random_binder.cpp
@@ -21,56 +21,52 @@
 #include <binder/IInterface.h>
 #include <binder/IServiceManager.h>
 
+size_t kRandomInterfaceLength = 50;
 namespace android {
 
-class RandomBinder : public BBinder {
-public:
-    RandomBinder(const String16& descriptor, std::vector<uint8_t>&& bytes)
-          : mDescriptor(descriptor),
-            mBytes(std::move(bytes)),
-            mProvider(mBytes.data(), mBytes.size()) {}
-    const String16& getInterfaceDescriptor() const override { return mDescriptor; }
+RandomBinder::RandomBinder(const String16& descriptor, std::vector<uint8_t>&& bytes)
+      : mDescriptor(descriptor),
+        mBytes(std::move(bytes)),
+        mProvider(mBytes.data(), mBytes.size()) {}
 
-    status_t onTransact(uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags) override {
-        (void)code;
-        (void)data;
-        (void)reply;
-        (void)flags; // note - for maximum coverage even ignore if oneway
+const String16& RandomBinder::getInterfaceDescriptor() const {
+    return mDescriptor;
+}
 
-        if (mProvider.ConsumeBool()) {
-            return mProvider.ConsumeIntegral<status_t>();
-        }
+status_t RandomBinder::onTransact(uint32_t code, const Parcel& data, Parcel* reply,
+                                  uint32_t flags) {
+    (void)code;
+    (void)data;
+    (void)reply;
+    (void)flags; // note - for maximum coverage even ignore if oneway
 
-        if (reply == nullptr) return OK;
+    if (mProvider.ConsumeBool()) {
+        return mProvider.ConsumeIntegral<status_t>();
+    }
 
-        // TODO: things we could do to increase state space
-        // - also pull FDs and binders from 'data'
-        //     (optionally combine these into random parcel 'options')
-        // - also pull FDs and binders from random parcel 'options'
-        RandomParcelOptions options;
+    if (reply == nullptr) return OK;
 
-        // random output
-        std::vector<uint8_t> subData = mProvider.ConsumeBytes<uint8_t>(
-                mProvider.ConsumeIntegralInRange<size_t>(0, mProvider.remaining_bytes()));
-        fillRandomParcel(reply, FuzzedDataProvider(subData.data(), subData.size()), &options);
+    // TODO: things we could do to increase state space
+    // - also pull FDs and binders from 'data'
+    //     (optionally combine these into random parcel 'options')
+    // - also pull FDs and binders from random parcel 'options'
+    RandomParcelOptions options;
 
-        return OK;
-    }
+    // random output
+    std::vector<uint8_t> subData = mProvider.ConsumeBytes<uint8_t>(
+            mProvider.ConsumeIntegralInRange<size_t>(0, mProvider.remaining_bytes()));
+    fillRandomParcel(reply, FuzzedDataProvider(subData.data(), subData.size()), &options);
 
-private:
-    String16 mDescriptor;
-
-    // note may not all be used
-    std::vector<uint8_t> mBytes;
-    FuzzedDataProvider mProvider;
-};
+    return OK;
+}
 
 sp<IBinder> getRandomBinder(FuzzedDataProvider* provider) {
     auto makeFunc = provider->PickValueInArray<const std::function<sp<IBinder>()>>({
             [&]() {
                 // descriptor is the length of a class name, e.g.
                 // "some.package.Foo"
-                std::string str = provider->ConsumeRandomLengthString(100 /*max length*/);
+                std::string str =
+                        provider->ConsumeRandomLengthString(kRandomInterfaceLength /*max length*/);
 
                 // arbitrarily consume remaining data to create a binder that can return
                 // random results - coverage guided fuzzer should ensure all of the remaining
diff --git a/libs/binder/tests/parcel_fuzzer/random_parcel.cpp b/libs/binder/tests/parcel_fuzzer/random_parcel.cpp
index 4e58dc4899..62b84330cd 100644
--- a/libs/binder/tests/parcel_fuzzer/random_parcel.cpp
+++ b/libs/binder/tests/parcel_fuzzer/random_parcel.cpp
@@ -73,7 +73,7 @@ void fillRandomParcel(Parcel* p, FuzzedDataProvider&& provider, RandomParcelOpti
                         return;
                     }
 
-                    if (options->extraFds.size() > 0 && provider.ConsumeBool()) {
+                    if (provider.ConsumeBool() && options->extraFds.size() > 0) {
                         const unique_fd& fd = options->extraFds.at(
                                 provider.ConsumeIntegralInRange<size_t>(0,
                                                                         options->extraFds.size() -
@@ -102,7 +102,7 @@ void fillRandomParcel(Parcel* p, FuzzedDataProvider&& provider, RandomParcelOpti
                     }
 
                     sp<IBinder> binder;
-                    if (options->extraBinders.size() > 0 && provider.ConsumeBool()) {
+                    if (provider.ConsumeBool() && options->extraBinders.size() > 0) {
                         binder = options->extraBinders.at(
                                 provider.ConsumeIntegralInRange<size_t>(0,
                                                                         options->extraBinders
diff --git a/libs/binder/tests/parcel_fuzzer/random_parcel_seeds.cpp b/libs/binder/tests/parcel_fuzzer/random_parcel_seeds.cpp
index 7b3c80642b..fd9777a916 100644
--- a/libs/binder/tests/parcel_fuzzer/random_parcel_seeds.cpp
+++ b/libs/binder/tests/parcel_fuzzer/random_parcel_seeds.cpp
@@ -14,16 +14,26 @@
  * limitations under the License.
  */
 
+#include <linux/android/binder.h>
+
 #include <android-base/logging.h>
 
+#include <binder/Parcel.h>
 #include <binder/RecordedTransaction.h>
 
 #include <fuzzseeds/random_parcel_seeds.h>
 
+#include <stack>
+#include <string>
 #include "../../file.h"
 
 using android::binder::borrowed_fd;
 using android::binder::WriteFully;
+using std::stack;
+
+extern size_t kRandomInterfaceLength;
+// Keep this in sync with max_length in random_binder.cpp while creating a RandomBinder
+std::string kRandomInterfaceName(kRandomInterfaceLength, 'i');
 
 namespace android {
 namespace impl {
@@ -66,6 +76,162 @@ void writeReversedBuffer(std::vector<uint8_t>& integralBuffer, T val) {
 
 } // namespace impl
 
+struct ProviderMetadata {
+    size_t position;
+    size_t value;
+
+    ProviderMetadata() {
+        value = 0;
+        position = 0;
+    }
+};
+
+// Assuming current seed path is inside the fillRandomParcel function, start of the loop.
+void writeRandomBinder(borrowed_fd fd, vector<uint8_t>& fillParcelBuffer,
+                       stack<ProviderMetadata>& remainingPositions) {
+    // Choose 2 index in array
+    size_t fillFuncIndex = 2;
+    impl::writeReversedBuffer(fillParcelBuffer, static_cast<size_t>(0), static_cast<size_t>(2),
+                              fillFuncIndex);
+
+    // navigate to getRandomBinder. provide consume bool false
+    bool flag = false;
+    impl::writeReversedBuffer(fillParcelBuffer, flag);
+
+    // selecting RandomBinder, other binders in the list are not recorded as KernelObjects
+    size_t randomBinderIndex = 0;
+    impl::writeReversedBuffer(fillParcelBuffer, static_cast<size_t>(0), static_cast<size_t>(2),
+                              randomBinderIndex);
+
+    // write random string of length 100 in actual buffer array.
+    CHECK(WriteFully(fd, kRandomInterfaceName.c_str(), kRandomInterfaceName.size())) << fd.get();
+
+    // These will be bytes which are used inside of RandomBinder
+    // simplest path for these bytes is going to be consume bool -> return random status
+    vector<uint8_t> randomBinderBuffer;
+
+    bool returnRandomInt = true;
+    impl::writeReversedBuffer(randomBinderBuffer, returnRandomInt);
+
+    status_t randomStatus = 0;
+    impl::writeReversedBuffer(randomBinderBuffer, randomStatus);
+
+    // write integral in range to consume bytes for random binder
+    ProviderMetadata providerData;
+    providerData.position = fillParcelBuffer.size();
+    providerData.value = randomBinderBuffer.size();
+    remainingPositions.push(providerData);
+
+    // Write to fd
+    CHECK(WriteFully(fd, randomBinderBuffer.data(), randomBinderBuffer.size())) << fd.get();
+}
+
+// Assuming current seed path is inside the fillRandomParcelFunction, start of the loop.
+void writeRandomFd(vector<uint8_t>& fillParcelBuffer) {
+    // path to random fd
+    size_t fillFuncIndex = 1;
+    impl::writeReversedBuffer(fillParcelBuffer, static_cast<size_t>(0), static_cast<size_t>(2),
+                              fillFuncIndex);
+
+    bool flag = false;
+    impl::writeReversedBuffer(fillParcelBuffer, flag);
+
+    // go for /dev/null index 1
+    size_t fdIndex = 1;
+    impl::writeReversedBuffer(fillParcelBuffer, static_cast<size_t>(0), static_cast<size_t>(3),
+                              fdIndex);
+}
+
+void writeParcelData(borrowed_fd fd, vector<uint8_t>& fillParcelBuffer,
+                     stack<ProviderMetadata>& remainingPositions, const uint8_t* data, size_t start,
+                     size_t length) {
+    // need to write parcel data till next offset with instructions to pick random bytes till offset
+    size_t fillFuncIndex = 0;
+    impl::writeReversedBuffer(fillParcelBuffer, static_cast<size_t>(0), static_cast<size_t>(2),
+                              fillFuncIndex);
+
+    // provide how much bytes to read in control buffer
+    ProviderMetadata providerData;
+    providerData.position = fillParcelBuffer.size();
+    providerData.value = length;
+    remainingPositions.push(providerData);
+
+    // provide actual bytes
+    CHECK(WriteFully(fd, data + start, length)) << fd.get();
+}
+
+/**
+ *   Generate sequence of copy data, write fd and write binder instructions and required data.
+ *   Data which will be read using consumeBytes is written to fd directly. Data which is read in
+ *   form integer is consumed from rear end FuzzedDataProvider. So insert it in fillParcelBuffer and
+ *   then write to fd
+ */
+size_t regenerateParcel(borrowed_fd fd, vector<uint8_t>& fillParcelBuffer, const Parcel& p,
+                        size_t dataSize, const vector<uint64_t>& objectOffsets) {
+    stack<ProviderMetadata> remainingPositions;
+    size_t copiedDataPosition = 0;
+    const uint8_t* parcelData = p.data();
+    size_t numBinders = 0;
+    size_t numFds = 0;
+
+    for (auto offset : objectOffsets) {
+        // Check what type of object is present here
+        const flat_binder_object* flatObject =
+                reinterpret_cast<const flat_binder_object*>(parcelData + offset);
+        // Copy till the object offset
+        writeParcelData(fd, fillParcelBuffer, remainingPositions, parcelData, copiedDataPosition,
+                        offset - copiedDataPosition);
+        copiedDataPosition = offset;
+        if (flatObject->hdr.type == BINDER_TYPE_BINDER ||
+            flatObject->hdr.type == BINDER_TYPE_HANDLE) {
+            writeRandomBinder(fd, fillParcelBuffer, remainingPositions);
+            numBinders++;
+            // In case of binder, stability is written after the binder object.
+            // We want to move the copiedDataPosition further to account for this stability field
+            copiedDataPosition += sizeof(int32_t) + sizeof(flat_binder_object);
+        } else if (flatObject->hdr.type == BINDER_TYPE_FD) {
+            writeRandomFd(fillParcelBuffer);
+            numFds++;
+            copiedDataPosition += sizeof(flat_binder_object);
+        }
+    }
+
+    if (copiedDataPosition < dataSize) {
+        // copy remaining data from recorded parcel -> last Object to end of the data
+        writeParcelData(fd, fillParcelBuffer, remainingPositions, parcelData, copiedDataPosition,
+                        dataSize - copiedDataPosition);
+    }
+
+    // We need to write bytes for selecting integer within range of  0 to provide.remaining_bytes()
+    // is called.
+    size_t totalWrittenBytes = dataSize - (sizeof(flat_binder_object) * objectOffsets.size()) -
+            (sizeof(int32_t) * numBinders) +
+            (kRandomInterfaceName.size() /*Interface String*/ + sizeof(bool) + sizeof(status_t)) *
+                    numBinders;
+
+    // Code in fuzzService relies on provider.remaining_bytes() to select random bytes using
+    // consume integer. use the calculated remaining_bytes to generate byte buffer which can
+    // generate required fds and binders in fillRandomParcel function.
+    while (!remainingPositions.empty()) {
+        auto meta = remainingPositions.top();
+        remainingPositions.pop();
+        size_t remainingBytes = totalWrittenBytes + fillParcelBuffer.size() - meta.position;
+
+        vector<uint8_t> remReversedBytes;
+        impl::writeReversedBuffer(remReversedBytes, static_cast<size_t>(0), remainingBytes,
+                                  meta.value);
+        // Check the order of buffer which is being written
+        fillParcelBuffer.insert(fillParcelBuffer.end() - meta.position, remReversedBytes.begin(),
+                                remReversedBytes.end());
+    }
+
+    return totalWrittenBytes;
+}
+
+/**
+ * Current corpus format
+ * |Reserved bytes(8)|parcel data|fillParcelBuffer|integralBuffer|
+ */
 void generateSeedsFromRecording(borrowed_fd fd,
                                 const binder::debug::RecordedTransaction& transaction) {
     // Write Reserved bytes for future use
@@ -123,17 +289,9 @@ void generateSeedsFromRecording(borrowed_fd fd,
     uint8_t writeHeaderInternal = 0;
     impl::writeReversedBuffer(fillParcelBuffer, writeHeaderInternal);
 
-    // Choose to write data in parcel
-    size_t fillFuncIndex = 0;
-    impl::writeReversedBuffer(fillParcelBuffer, static_cast<size_t>(0), static_cast<size_t>(2),
-                              fillFuncIndex);
-
-    // Write parcel data size from recorded transaction
-    size_t toWrite = transaction.getDataParcel().dataBufferSize();
-    impl::writeReversedBuffer(fillParcelBuffer, static_cast<size_t>(0), toWrite, toWrite);
-
-    // Write parcel data with size towrite from recorded transaction
-    CHECK(WriteFully(fd, dataParcel.data(), toWrite)) << fd.get();
+    auto objectMetadata = transaction.getObjectOffsets();
+    size_t toWrite = regenerateParcel(fd, fillParcelBuffer, dataParcel, dataParcel.dataBufferSize(),
+                                      objectMetadata);
 
     // Write Fill Parcel buffer size in integralBuffer so that fuzzService knows size of data
     size_t subDataSize = toWrite + fillParcelBuffer.size();