fuzz/fuzz.cpp

/*
 * Copyright 2016 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "Fuzz.h"
#include "SkCanvas.h"
#include "SkCodec.h"
#include "SkCommandLineFlags.h"
#include "SkData.h"
#include "SkForceLinking.h"
#include "SkImage.h"
#include "SkImageEncoder.h"
#include "SkMallocPixelRef.h"
#include "SkPicture.h"
#include "SkStream.h"

#include <cmath>
#include <signal.h>
#include <stdlib.h>

// TODO(kjlubick): Remove once http://crrev.com/1671193002 lands
__SK_FORCE_IMAGE_DECODER_LINKING;

DEFINE_string2(bytes, b, "", "A path to a file.  This can be the fuzz bytes or a binary to parse.");
DEFINE_string2(name, n, "", "If --type is 'api', fuzz the API with this name.");

DEFINE_string2(type, t, "api", "How to interpret --bytes, either 'image_scale', 'image_mode', 'skp', or 'api'.");
DEFINE_string2(dump, d, "", "If not empty, dump 'image*' or 'skp' types as a PNG with this name.");

static int printUsage(const char* name) {
    SkDebugf("Usage: %s -t <type> -b <path/to/file> [-n api-to-fuzz]\n", name);
    return 1;
}
static uint8_t calculate_option(SkData*);

static int fuzz_api(SkData*);
static int fuzz_img(SkData*, uint8_t, uint8_t);
static int fuzz_skp(SkData*);

int main(int argc, char** argv) {
    SkCommandLineFlags::Parse(argc, argv);

    const char* path = FLAGS_bytes.isEmpty() ? argv[0] : FLAGS_bytes[0];
    SkAutoTUnref<SkData> bytes(SkData::NewFromFileName(path));
    if (!bytes) {
        SkDebugf("Could not read %s\n", path);
        return 2;
    }

    uint8_t option = calculate_option(bytes);

    if (!FLAGS_type.isEmpty()) {
        switch (FLAGS_type[0][0]) {
            case 'a': return fuzz_api(bytes);

            case 'i':
                // We only allow one degree of freedom to avoid a search space explosion for afl-fuzz.
                if (FLAGS_type[0][6] == 's') { // image_scale
                    return fuzz_img(bytes, option, 0);
                }
                // image_mode
                return fuzz_img(bytes, 0, option);
            case 's': return fuzz_skp(bytes);
        }
    }
    return printUsage(argv[0]);
}

// This adds up the first 1024 bytes and returns it as an 8 bit integer.  This allows afl-fuzz to
// deterministically excercise different paths, or *options* (such as different scaling sizes or
// different image modes) without needing to introduce a parameter.  This way we don't need a
// image_scale1, image_scale2, image_scale4, etc fuzzer, we can just have a image_scale fuzzer.
// Clients are expected to transform this number into a different range, e.g. with modulo (%).
static uint8_t calculate_option(SkData* bytes) {
    uint8_t total = 0;
    const uint8_t* data = bytes->bytes();
    for (size_t i = 0; i < 1024 && i < bytes->size(); i++) {
        total += data[i];
    }
    return total;
}

int fuzz_api(SkData* bytes) {
    const char* name = FLAGS_name.isEmpty() ? "" : FLAGS_name[0];

    for (auto r = SkTRegistry<Fuzzable>::Head(); r; r = r->next()) {
        auto fuzzable = r->factory();
        if (0 == strcmp(name, fuzzable.name)) {
            SkDebugf("Fuzzing %s...\n", fuzzable.name);
            Fuzz fuzz(bytes);
            fuzzable.fn(&fuzz);
            SkDebugf("[terminated] Success!\n");
            return 0;
        }
    }

    SkDebugf("When using --type api, please choose an API to fuzz with --name/-n:\n");
    for (auto r = SkTRegistry<Fuzzable>::Head(); r; r = r->next()) {
        auto fuzzable = r->factory();
        SkDebugf("\t%s\n", fuzzable.name);
    }
    return 1;
}

static void dump_png(SkBitmap bitmap) {
    if (!FLAGS_dump.isEmpty()) {
        SkImageEncoder::EncodeFile(FLAGS_dump[0], bitmap, SkImageEncoder::kPNG_Type, 100);
        SkDebugf("Dumped to %s\n", FLAGS_dump[0]);
    }
}

int fuzz_img(SkData* bytes, uint8_t scale, uint8_t mode) {
    // We can scale 1x, 2x, 4x, 8x, 16x
    scale = scale % 5;
    float fscale = (float)pow(2.0f, scale);
    SkDebugf("Scaling factor: %f\n", fscale);

    // We have 4 different modes of decoding, just like DM.
    mode = mode % 4;
    SkDebugf("Mode: %d\n", mode);

    // This is mostly copied from DMSrcSink's CodecSrc::draw method.
    SkDebugf("Decoding\n");
    SkAutoTDelete<SkCodec> codec(SkCodec::NewFromData(bytes));
    if (nullptr == codec.get()) {
        SkDebugf("[terminated] Couldn't create codec.\n");
        return 3;
    }

    SkImageInfo decodeInfo = codec->getInfo();

    SkISize size = codec->getScaledDimensions(fscale);
    decodeInfo = decodeInfo.makeWH(size.width(), size.height());

    // Construct a color table for the decode if necessary
    SkAutoTUnref<SkColorTable> colorTable(nullptr);
    SkPMColor* colorPtr = nullptr;
    int* colorCountPtr = nullptr;
    int maxColors = 256;
    if (kIndex_8_SkColorType == decodeInfo.colorType()) {
        SkPMColor colors[256];
        colorTable.reset(new SkColorTable(colors, maxColors));
        colorPtr = const_cast<SkPMColor*>(colorTable->readColors());
        colorCountPtr = &maxColors;
    }

    SkBitmap bitmap;
    SkMallocPixelRef::ZeroedPRFactory zeroFactory;
    SkCodec::Options options;
    options.fZeroInitialized = SkCodec::kYes_ZeroInitialized;

    if (!bitmap.tryAllocPixels(decodeInfo, &zeroFactory, colorTable.get())) {
        SkDebugf("[terminated] Could not allocate memory.  Image might be too large (%d x %d)",
                 decodeInfo.width(), decodeInfo.height());
        return 4;
    }

    switch (mode) {
        case 0: {//kCodecZeroInit_Mode, kCodec_Mode
            switch (codec->getPixels(decodeInfo, bitmap.getPixels(), bitmap.rowBytes(), &options,
                                     colorPtr, colorCountPtr)) {
                case SkCodec::kSuccess:
                    SkDebugf("[terminated] Success!\n");
                    break;
                case SkCodec::kIncompleteInput:
                    SkDebugf("[terminated] Partial Success\n");
                    break;
                case SkCodec::kInvalidConversion:
                    SkDebugf("Incompatible colortype conversion\n");
                    // Crash to allow afl-fuzz to know this was a bug.
                    raise(SIGSEGV);
                default:
                    SkDebugf("[terminated] Couldn't getPixels.\n");
                    return 6;
            }
            break;
        }
        case 1: {//kScanline_Mode
            if (SkCodec::kSuccess != codec->startScanlineDecode(decodeInfo, NULL, colorPtr,
                                                                colorCountPtr)) {
                    SkDebugf("[terminated] Could not start scanline decoder\n");
                    return 7;
                }

            void* dst = bitmap.getAddr(0, 0);
            size_t rowBytes = bitmap.rowBytes();
            uint32_t height = decodeInfo.height();
            switch (codec->getScanlineOrder()) {
                case SkCodec::kTopDown_SkScanlineOrder:
                case SkCodec::kBottomUp_SkScanlineOrder:
                case SkCodec::kNone_SkScanlineOrder:
                    // We do not need to check the return value.  On an incomplete
                    // image, memory will be filled with a default value.
                    codec->getScanlines(dst, height, rowBytes);
                    break;
                case SkCodec::kOutOfOrder_SkScanlineOrder: {
                    for (int y = 0; y < decodeInfo.height(); y++) {
                        int dstY = codec->outputScanline(y);
                        void* dstPtr = bitmap.getAddr(0, dstY);
                        // We complete the loop, even if this call begins to fail
                        // due to an incomplete image.  This ensures any uninitialized
                        // memory will be filled with the proper value.
                        codec->getScanlines(dstPtr, 1, bitmap.rowBytes());
                    }
                    break;
                }
            }
            SkDebugf("[terminated] Success!\n");
            break;
        }
        case 2: { //kStripe_Mode
            const int height = decodeInfo.height();
            // This value is chosen arbitrarily.  We exercise more cases by choosing a value that
            // does not align with image blocks.
            const int stripeHeight = 37;
            const int numStripes = (height + stripeHeight - 1) / stripeHeight;

            // Decode odd stripes
            if (SkCodec::kSuccess != codec->startScanlineDecode(decodeInfo, NULL, colorPtr,
                                                                colorCountPtr)
                    || SkCodec::kTopDown_SkScanlineOrder != codec->getScanlineOrder()) {
                // This mode was designed to test the new skip scanlines API in libjpeg-turbo.
                // Jpegs have kTopDown_SkScanlineOrder, and at this time, it is not interesting
                // to run this test for image types that do not have this scanline ordering.
                SkDebugf("[terminated] Could not start top-down scanline decoder\n");
                return 8;
            }

            for (int i = 0; i < numStripes; i += 2) {
                // Skip a stripe
                const int linesToSkip = SkTMin(stripeHeight, height - i * stripeHeight);
                codec->skipScanlines(linesToSkip);

                // Read a stripe
                const int startY = (i + 1) * stripeHeight;
                const int linesToRead = SkTMin(stripeHeight, height - startY);
                if (linesToRead > 0) {
                    codec->getScanlines(bitmap.getAddr(0, startY), linesToRead, bitmap.rowBytes());
                }
            }

            // Decode even stripes
            const SkCodec::Result startResult = codec->startScanlineDecode(decodeInfo, nullptr,
                    colorPtr, colorCountPtr);
            if (SkCodec::kSuccess != startResult) {
                SkDebugf("[terminated] Failed to restart scanline decoder with same parameters.\n");
                return 9;
            }
            for (int i = 0; i < numStripes; i += 2) {
                // Read a stripe
                const int startY = i * stripeHeight;
                const int linesToRead = SkTMin(stripeHeight, height - startY);
                codec->getScanlines(bitmap.getAddr(0, startY), linesToRead, bitmap.rowBytes());

                // Skip a stripe
                const int linesToSkip = SkTMin(stripeHeight, height - (i + 1) * stripeHeight);
                if (linesToSkip > 0) {
                    codec->skipScanlines(linesToSkip);
                }
            }
            SkDebugf("[terminated] Success!\n");
            break;
        }
        case 3: { //kSubset_Mode
            // Arbitrarily choose a divisor.
            int divisor = 2;
            // Total width/height of the image.
            const int W = codec->getInfo().width();
            const int H = codec->getInfo().height();
            if (divisor > W || divisor > H) {
                SkDebugf("[terminated] Cannot codec subset: divisor %d is too big "
                         "with dimensions (%d x %d)\n", divisor, W, H);
                return 10;
            }
            // subset dimensions
            // SkWebpCodec, the only one that supports subsets, requires even top/left boundaries.
            const int w = SkAlign2(W / divisor);
            const int h = SkAlign2(H / divisor);
            SkIRect subset;
            SkCodec::Options opts;
            opts.fSubset = &subset;
            SkBitmap subsetBm;
            // We will reuse pixel memory from bitmap.
            void* pixels = bitmap.getPixels();
            // Keep track of left and top (for drawing subsetBm into canvas). We could use
            // fscale * x and fscale * y, but we want integers such that the next subset will start
            // where the last one ended. So we'll add decodeInfo.width() and height().
            int left = 0;
            for (int x = 0; x < W; x += w) {
                int top = 0;
                for (int y = 0; y < H; y+= h) {
                    // Do not make the subset go off the edge of the image.
                    const int preScaleW = SkTMin(w, W - x);
                    const int preScaleH = SkTMin(h, H - y);
                    subset.setXYWH(x, y, preScaleW, preScaleH);
                    // And fscale
                    // FIXME: Should we have a version of getScaledDimensions that takes a subset
                    // into account?
                    decodeInfo = decodeInfo.makeWH(
                            SkTMax(1, SkScalarRoundToInt(preScaleW * fscale)),
                            SkTMax(1, SkScalarRoundToInt(preScaleH * fscale)));
                    size_t rowBytes = decodeInfo.minRowBytes();
                    if (!subsetBm.installPixels(decodeInfo, pixels, rowBytes, colorTable.get(),
                                                nullptr, nullptr)) {
                        SkDebugf("[terminated] Could not install pixels.\n");
                        return 11;
                    }
                    const SkCodec::Result result = codec->getPixels(decodeInfo, pixels, rowBytes,
                            &opts, colorPtr, colorCountPtr);
                    switch (result) {
                        case SkCodec::kSuccess:
                        case SkCodec::kIncompleteInput:
                            SkDebugf("okay\n");
                            break;
                        case SkCodec::kInvalidConversion:
                            if (0 == (x|y)) {
                                // First subset is okay to return unimplemented.
                                SkDebugf("[terminated] Incompatible colortype conversion\n");
                                return 12;
                            }
                            // If the first subset succeeded, a later one should not fail.
                            // fall through to failure
                        case SkCodec::kUnimplemented:
                            if (0 == (x|y)) {
                                // First subset is okay to return unimplemented.
                                SkDebugf("[terminated] subset codec not supported\n");
                                return 13;
                            }
                            // If the first subset succeeded, why would a later one fail?
                            // fall through to failure
                        default:
                            SkDebugf("[terminated] subset codec failed to decode (%d, %d, %d, %d) "
                                                  "with dimensions (%d x %d)\t error %d\n",
                                                  x, y, decodeInfo.width(), decodeInfo.height(),
                                                  W, H, result);
                            return 14;
                    }
                    // translate by the scaled height.
                    top += decodeInfo.height();
                }
                // translate by the scaled width.
                left += decodeInfo.width();
            }
            SkDebugf("[terminated] Success!\n");
            break;
        }
        default:
            SkDebugf("[terminated] Mode not implemented yet\n");
    }

    dump_png(bitmap);
    return 0;
}

int fuzz_skp(SkData* bytes) {
    SkMemoryStream stream(bytes);
    SkDebugf("Decoding\n");
    SkAutoTUnref<SkPicture> pic(SkPicture::CreateFromStream(&stream));
    if (!pic) {
        SkDebugf("[terminated] Couldn't decode as a picture.\n");
        return 3;
    }
    SkDebugf("Rendering\n");
    SkBitmap bitmap;
    if (!FLAGS_dump.isEmpty()) {
        SkIRect size = pic->cullRect().roundOut();
        bitmap.allocN32Pixels(size.width(), size.height());
    }
    SkCanvas canvas(bitmap);
    canvas.drawPicture(pic);
    SkDebugf("[terminated] Success! Decoded and rendered an SkPicture!\n");
    dump_png(bitmap);
    return 0;
}

Fuzz::Fuzz(SkData* bytes) : fBytes(SkSafeRef(bytes)), fNextByte(0) {}

void Fuzz::signalBug   () { raise(SIGSEGV); }
void Fuzz::signalBoring() { exit(0); }

template <typename T>
T Fuzz::nextT() {
    if (fNextByte + sizeof(T) > fBytes->size()) {
        this->signalBoring();
    }

    T val;
    memcpy(&val, fBytes->bytes() + fNextByte, sizeof(T));
    fNextByte += sizeof(T);
    return val;
}

uint8_t  Fuzz::nextB() { return this->nextT<uint8_t >(); }
bool  Fuzz::nextBool() { return nextB()&1; }
uint32_t Fuzz::nextU() { return this->nextT<uint32_t>(); }
float    Fuzz::nextF() { return this->nextT<float   >(); }


uint32_t Fuzz::nextRangeU(uint32_t min, uint32_t max) {
    if (min > max) {
        SkDebugf("Check mins and maxes (%d, %d)\n", min, max);
        this->signalBoring();
    }
    uint32_t range = max - min + 1;
    if (0 == range) {
        return this->nextU();
    } else {
        return min + this->nextU() % range;
    }
}
float Fuzz::nextRangeF(float min, float max) {
    if (min > max) {
        SkDebugf("Check mins and maxes (%f, %f)\n", min, max);
        this->signalBoring();
    }
    float f = std::abs(this->nextF());
    if (!std::isnormal(f) && f != 0.0) {
        this->signalBoring();
    }
    return min + fmod(f, (max - min + 1));
}