Source/core/loader/TextResourceDecoderBuilder.cpp

/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
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 * in the documentation and/or other materials provided with the
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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#include "config.h"
#include "core/loader/TextResourceDecoderBuilder.h"

#include "core/dom/Document.h"
#include "core/frame/Frame.h"
#include "core/frame/Settings.h"
#include "platform/weborigin/SecurityOrigin.h"

namespace WebCore {

static inline bool canReferToParentFrameEncoding(const Frame* frame, const Frame* parentFrame)
{
    return parentFrame && parentFrame->document()->securityOrigin()->canAccess(frame->document()->securityOrigin());
}


TextResourceDecoderBuilder::TextResourceDecoderBuilder(const AtomicString& mimeType, const AtomicString& encoding, bool encodingUserChoosen)
    : m_mimeType(mimeType)
    , m_encoding(encoding)
    , m_encodingWasChosenByUser(encodingUserChoosen)
{
}

TextResourceDecoderBuilder::~TextResourceDecoderBuilder()
{
}


inline PassOwnPtr<TextResourceDecoder> TextResourceDecoderBuilder::createDecoderInstance(Document* document)
{
    if (Frame* frame = document->frame()) {
        if (Settings* settings = frame->settings())
            return TextResourceDecoder::create(m_mimeType, settings->defaultTextEncodingName(), settings->usesEncodingDetector());
    }

    return TextResourceDecoder::create(m_mimeType, String());
}

inline void TextResourceDecoderBuilder::setupEncoding(TextResourceDecoder* decoder, Document* document)
{
    Frame* frame = document->frame();
    Frame* parentFrame = frame ? frame->tree().parent() : 0;

    if (!m_encoding.isEmpty())
        decoder->setEncoding(m_encoding.string(), m_encodingWasChosenByUser ? TextResourceDecoder::UserChosenEncoding : TextResourceDecoder::EncodingFromHTTPHeader);

    // Set the hint encoding to the parent frame encoding only if
    // the parent and the current frames share the security origin.
    // We impose this condition because somebody can make a child frameg63
    // containing a carefully crafted html/javascript in one encoding
    // that can be mistaken for hintEncoding (or related encoding) by
    // an auto detector. When interpreted in the latter, it could be
    // an attack vector.
    // FIXME: This might be too cautious for non-7bit-encodings and
    // we may consider relaxing this later after testing.
    if (frame && canReferToParentFrameEncoding(frame, parentFrame)) {
        if (parentFrame->document()->encodingWasDetectedHeuristically())
            decoder->setHintEncoding(parentFrame->document()->encoding());

        if (m_encoding.isEmpty())
            decoder->setEncoding(parentFrame->document()->inputEncoding().string(), TextResourceDecoder::EncodingFromParentFrame);
    }
}

PassOwnPtr<TextResourceDecoder> TextResourceDecoderBuilder::buildFor(Document* document)
{
    OwnPtr<TextResourceDecoder> decoder = createDecoderInstance(document);
    setupEncoding(decoder.get(), document);
    return decoder.release();
}

void TextResourceDecoderBuilder::clear()
{
    if (!m_encodingWasChosenByUser)
        m_encoding = nullAtom;
}

}