src/core/SkReadBuffer.cpp

/*
 * Copyright 2012 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "include/core/SkBitmap.h"
#include "include/core/SkData.h"
#include "include/core/SkImage.h"
#include "include/core/SkImageGenerator.h"
#include "include/core/SkStream.h"
#include "include/core/SkTypeface.h"
#include "src/core/SkAutoMalloc.h"
#include "src/core/SkMathPriv.h"
#include "src/core/SkMatrixPriv.h"
#include "src/core/SkReadBuffer.h"
#include "src/core/SkSafeMath.h"

namespace {
    // This generator intentionally should always fail on all attempts to get its pixels,
    // simulating a bad or empty codec stream.
    class EmptyImageGenerator final : public SkImageGenerator {
    public:
        EmptyImageGenerator(const SkImageInfo& info) : INHERITED(info) { }

    private:
        typedef SkImageGenerator INHERITED;
    };

    static sk_sp<SkImage> MakeEmptyImage(int width, int height) {
        return SkImage::MakeFromGenerator(
              std::make_unique<EmptyImageGenerator>(SkImageInfo::MakeN32Premul(width, height)));
    }

} // anonymous namespace

void SkReadBuffer::setMemory(const void* data, size_t size) {
    this->validate(IsPtrAlign4(data) && (SkAlign4(size) == size));
    if (!fError) {
        fBase = fCurr = (const char*)data;
        fStop = fBase + size;
    }
}

void SkReadBuffer::setInvalid() {
    if (!fError) {
        // When an error is found, send the read cursor to the end of the stream
        fCurr = fStop;
        fError = true;
    }
}

const void* SkReadBuffer::skip(size_t size) {
    size_t inc = SkAlign4(size);
    this->validate(inc >= size);
    const void* addr = fCurr;
    this->validate(IsPtrAlign4(addr) && this->isAvailable(inc));
    if (fError) {
        return nullptr;
    }

    fCurr += inc;
    return addr;
}

const void* SkReadBuffer::skip(size_t count, size_t size) {
    return this->skip(SkSafeMath::Mul(count, size));
}

void SkReadBuffer::setDeserialProcs(const SkDeserialProcs& procs) {
    fProcs = procs;
}

bool SkReadBuffer::readBool() {
    uint32_t value = this->readUInt();
    // Boolean value should be either 0 or 1
    this->validate(!(value & ~1));
    return value != 0;
}

SkColor SkReadBuffer::readColor() {
    return this->readUInt();
}

int32_t SkReadBuffer::readInt() {
    const size_t inc = sizeof(int32_t);
    if (!this->validate(IsPtrAlign4(fCurr) && this->isAvailable(inc))) {
        return 0;
    }
    int32_t value = *((const int32_t*)fCurr);
    fCurr += inc;
    return value;
}

SkScalar SkReadBuffer::readScalar() {
    const size_t inc = sizeof(SkScalar);
    if (!this->validate(IsPtrAlign4(fCurr) && this->isAvailable(inc))) {
        return 0;
    }
    SkScalar value = *((const SkScalar*)fCurr);
    fCurr += inc;
    return value;
}

uint32_t SkReadBuffer::readUInt() {
    return this->readInt();
}

int32_t SkReadBuffer::read32() {
    return this->readInt();
}

uint8_t SkReadBuffer::peekByte() {
    if (this->available() <= 0) {
        fError = true;
        return 0;
    }
    return *((uint8_t*)fCurr);
}

bool SkReadBuffer::readPad32(void* buffer, size_t bytes) {
    if (const void* src = this->skip(bytes)) {
        // buffer might be null if bytes is zero (see SkAutoMalloc), hence we call
        // the careful version of memcpy.
        sk_careful_memcpy(buffer, src, bytes);
        return true;
    }
    return false;
}

const char* SkReadBuffer::readString(size_t* len) {
    *len = this->readUInt();

    // The string is len characters and a terminating \0.
    const char* c_str = this->skipT<char>(*len+1);

    if (this->validate(c_str && c_str[*len] == '\0')) {
        return c_str;
    }
    return nullptr;
}

void SkReadBuffer::readString(SkString* string) {
    size_t len;
    if (const char* c_str = this->readString(&len)) {
        string->set(c_str, len);
        return;
    }
    string->reset();
}

void SkReadBuffer::readColor4f(SkColor4f* color) {
    if (!this->readPad32(color, sizeof(SkColor4f))) {
        *color = {0, 0, 0, 0};
    }
}

void SkReadBuffer::readPoint(SkPoint* point) {
    point->fX = this->readScalar();
    point->fY = this->readScalar();
}

void SkReadBuffer::readPoint3(SkPoint3* point) {
    this->readPad32(point, sizeof(SkPoint3));
}

void SkReadBuffer::readMatrix(SkMatrix* matrix) {
    size_t size = 0;
    if (this->isValid()) {
        size = SkMatrixPriv::ReadFromMemory(matrix, fCurr, this->available());
        (void)this->validate((SkAlign4(size) == size) && (0 != size));
    }
    if (!this->isValid()) {
        matrix->reset();
    }
    (void)this->skip(size);
}

void SkReadBuffer::readIRect(SkIRect* rect) {
    if (!this->readPad32(rect, sizeof(SkIRect))) {
        rect->setEmpty();
    }
}

void SkReadBuffer::readRect(SkRect* rect) {
    if (!this->readPad32(rect, sizeof(SkRect))) {
        rect->setEmpty();
    }
}

void SkReadBuffer::readRRect(SkRRect* rrect) {
    size_t size = 0;
    if (!fError) {
        size = rrect->readFromMemory(fCurr, this->available());
        if (!this->validate((SkAlign4(size) == size) && (0 != size))) {
            rrect->setEmpty();
        }
    }
    (void)this->skip(size);
}

void SkReadBuffer::readRegion(SkRegion* region) {
    size_t size = 0;
    if (!fError) {
        size = region->readFromMemory(fCurr, this->available());
        if (!this->validate((SkAlign4(size) == size) && (0 != size))) {
            region->setEmpty();
        }
    }
    (void)this->skip(size);
}

void SkReadBuffer::readPath(SkPath* path) {
    size_t size = 0;
    if (!fError) {
        size = path->readFromMemory(fCurr, this->available());
        if (!this->validate((SkAlign4(size) == size) && (0 != size))) {
            path->reset();
        }
    }
    (void)this->skip(size);
}

bool SkReadBuffer::readArray(void* value, size_t size, size_t elementSize) {
    const uint32_t count = this->readUInt();
    return this->validate(size == count) &&
           this->readPad32(value, SkSafeMath::Mul(size, elementSize));
}

bool SkReadBuffer::readByteArray(void* value, size_t size) {
    return this->readArray(value, size, sizeof(uint8_t));
}

bool SkReadBuffer::readColorArray(SkColor* colors, size_t size) {
    return this->readArray(colors, size, sizeof(SkColor));
}

bool SkReadBuffer::readColor4fArray(SkColor4f* colors, size_t size) {
    return this->readArray(colors, size, sizeof(SkColor4f));
}

bool SkReadBuffer::readIntArray(int32_t* values, size_t size) {
    return this->readArray(values, size, sizeof(int32_t));
}

bool SkReadBuffer::readPointArray(SkPoint* points, size_t size) {
    return this->readArray(points, size, sizeof(SkPoint));
}

bool SkReadBuffer::readScalarArray(SkScalar* values, size_t size) {
    return this->readArray(values, size, sizeof(SkScalar));
}

const void* SkReadBuffer::skipByteArray(size_t* size) {
    const uint32_t count = this->readUInt();
    const void* buf = this->skip(count);
    if (size) {
        *size = this->isValid() ? count : 0;
    }
    return buf;
}

sk_sp<SkData> SkReadBuffer::readByteArrayAsData() {
    size_t numBytes = this->getArrayCount();
    if (!this->validate(this->isAvailable(numBytes))) {
        return nullptr;
    }

    SkAutoMalloc buffer(numBytes);
    if (!this->readByteArray(buffer.get(), numBytes)) {
        return nullptr;
    }
    return SkData::MakeFromMalloc(buffer.release(), numBytes);
}

uint32_t SkReadBuffer::getArrayCount() {
    const size_t inc = sizeof(uint32_t);
    if (!this->validate(IsPtrAlign4(fCurr) && this->isAvailable(inc))) {
        return 0;
    }
    return *((uint32_t*)fCurr);
}

/*  Format:
 *  (subset) width, height
 *  (subset) origin x, y
 *  size (31bits)
 *  data [ encoded, with raw width/height ]
 */
sk_sp<SkImage> SkReadBuffer::readImage() {
    SkIRect bounds;
    if (this->isVersionLT(SkPicturePriv::kStoreImageBounds_Version)) {
        bounds.fLeft = bounds.fTop = 0;
        bounds.fRight = this->read32();
        bounds.fBottom = this->read32();
    } else {
        this->readIRect(&bounds);
    }
    const int width = bounds.width();
    const int height = bounds.height();
    if (width <= 0 || height <= 0) {    // SkImage never has a zero dimension
        this->validate(false);
        return nullptr;
    }

    int32_t size = this->read32();
    if (size == SK_NaN32) {
        // 0x80000000 is never valid, since it cannot be passed to abs().
        this->validate(false);
        return nullptr;
    }
    if (size == 0) {
        // The image could not be encoded at serialization time - return an empty placeholder.
        return MakeEmptyImage(width, height);
    }

    // we used to negate the size for "custom" encoded images -- ignore that signal (Dec-2017)
    size = SkAbs32(size);
    if (size == 1) {
        // legacy check (we stopped writing this for "raw" images Nov-2017)
        this->validate(false);
        return nullptr;
    }

    // Preflight check to make sure there's enough stuff in the buffer before
    // we allocate the memory. This helps the fuzzer avoid OOM when it creates
    // bad/corrupt input.
    if (!this->validateCanReadN<uint8_t>(size)) {
        return nullptr;
    }

    sk_sp<SkData> data = SkData::MakeUninitialized(size);
    if (!this->readPad32(data->writable_data(), size)) {
        this->validate(false);
        return nullptr;
    }
    if (this->isVersionLT(SkPicturePriv::kDontNegateImageSize_Version)) {
        (void)this->read32();   // originX
        (void)this->read32();   // originY
    }

    sk_sp<SkImage> image;
    if (fProcs.fImageProc) {
        image = fProcs.fImageProc(data->data(), data->size(), fProcs.fImageCtx);
    }
    if (!image) {
        image = SkImage::MakeFromEncoded(std::move(data));
    }
    if (image) {
        if (bounds.x() || bounds.y() || width < image->width() || height < image->height()) {
            image = image->makeSubset(bounds);
        }
    }
    // Question: are we correct to return an "empty" image instead of nullptr, if the decoder
    //           failed for some reason?
    return image ? image : MakeEmptyImage(width, height);
}

sk_sp<SkTypeface> SkReadBuffer::readTypeface() {
    // Read 32 bits (signed)
    //   0 -- return null (default font)
    //  >0 -- index
    //  <0 -- custom (serial procs) : negative size in bytes

    int32_t index = this->read32();
    if (index == 0) {
        return nullptr;
    } else if (index > 0) {
        if (!this->validate(index <= fTFCount)) {
            return nullptr;
        }
        return fTFArray[index - 1];
    } else {    // custom
        size_t size = sk_negate_to_size_t(index);
        const void* data = this->skip(size);
        if (!this->validate(data != nullptr && fProcs.fTypefaceProc)) {
            return nullptr;
        }
        return fProcs.fTypefaceProc(data, size, fProcs.fTypefaceCtx);
    }
}

SkFlattenable* SkReadBuffer::readFlattenable(SkFlattenable::Type ft) {
    SkFlattenable::Factory factory = nullptr;

    if (fFactoryCount > 0) {
        int32_t index = this->read32();
        if (0 == index || !this->isValid()) {
            return nullptr; // writer failed to give us the flattenable
        }
        index -= 1;     // we stored the index-base-1
        if ((unsigned)index >= (unsigned)fFactoryCount) {
            this->validate(false);
            return nullptr;
        }
        factory = fFactoryArray[index];
    } else {
        if (this->peekByte() != 0) {
            // If the first byte is non-zero, the flattenable is specified by a string.
            size_t ignored_length;
            if (const char* name = this->readString(&ignored_length)) {
                factory = SkFlattenable::NameToFactory(name);
                fFlattenableDict.set(fFlattenableDict.count() + 1, factory);
            }
        } else {
            // Read the index.  We are guaranteed that the first byte
            // is zeroed, so we must shift down a byte.
            uint32_t index = this->readUInt() >> 8;
            if (index == 0) {
                return nullptr; // writer failed to give us the flattenable
            }

            if (SkFlattenable::Factory* found = fFlattenableDict.find(index)) {
                factory = *found;
            }
        }

        if (!this->validate(factory != nullptr)) {
            return nullptr;
        }
    }

    // if we get here, factory may still be null, but if that is the case, the
    // failure was ours, not the writer.
    sk_sp<SkFlattenable> obj;
    uint32_t sizeRecorded = this->read32();
    if (factory) {
        size_t offset = this->offset();
        obj = (*factory)(*this);
        // check that we read the amount we expected
        size_t sizeRead = this->offset() - offset;
        if (sizeRecorded != sizeRead) {
            this->validate(false);
            return nullptr;
        }
        if (obj && obj->getFlattenableType() != ft) {
            this->validate(false);
            return nullptr;
        }
    } else {
        // we must skip the remaining data
        this->skip(sizeRecorded);
    }
    if (!this->isValid()) {
        return nullptr;
    }
    return obj.release();
}

///////////////////////////////////////////////////////////////////////////////////////////////////

int32_t SkReadBuffer::checkInt(int32_t min, int32_t max) {
    SkASSERT(min <= max);
    int32_t value = this->read32();
    if (value < min || value > max) {
        this->validate(false);
        value = min;
    }
    return value;
}

SkFilterQuality SkReadBuffer::checkFilterQuality() {
    return this->checkRange<SkFilterQuality>(kNone_SkFilterQuality, kLast_SkFilterQuality);
}