Source/WebCore/crypto/mac/CommonCryptoDERUtilities.cpp

/*
 * Copyright (C) 2017 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"
#include "CommonCryptoDERUtilities.h"

#if ENABLE(SUBTLE_CRYPTO)

namespace WebCore {

size_t bytesUsedToEncodedLength(uint8_t octet)
{
    if (octet < MaxLengthInOneByte)
        return 1;
    return octet - MaxLengthInOneByte + 1;
}

size_t extraBytesNeededForEncodedLength(size_t length)
{
    if (!length)
        return 0;
    size_t result = 1;
    while (result < sizeof(length) && length >= (1 << (result * 8)))
        result += 1;
    return result;
}

void addEncodedASN1Length(Vector<uint8_t>& in, size_t length)
{
    if (length < MaxLengthInOneByte) {
        in.append(length);
        return;
    }

    size_t extraBytes = extraBytesNeededForEncodedLength(length);
    in.append(128 + extraBytes); // 128 is used to set the first bit of this byte.

    size_t lastPosition = in.size() + extraBytes - 1;
    in.grow(in.size() + extraBytes);
    for (size_t i = 0; i < extraBytes; i++) {
        in[lastPosition - i] = length & 0xff;
        length = length >> 8;
    }
}

size_t bytesNeededForEncodedLength(size_t length)
{
    if (length < MaxLengthInOneByte)
        return 1;
    return 1 + extraBytesNeededForEncodedLength(length);
}

} // namespace WebCore

#endif // ENABLE(SUBTLE_CRYPTO)