pkcspad.cpp

// pkcspad.cpp - written and placed in the public domain by Wei Dai

#include "pch.h"

#ifndef CRYPTOPP_PKCSPAD_CPP    // SunCC workaround: compiler could cause this file to be included twice
#define CRYPTOPP_PKCSPAD_CPP

#include "pkcspad.h"
#include <assert.h>

NAMESPACE_BEGIN(CryptoPP)

// more in dll.cpp
template<> const byte PKCS_DigestDecoration<MD2>::decoration[] = {0x30,0x20,0x30,0x0c,0x06,0x08,0x2a,0x86,0x48,0x86,0xf7,0x0d,0x02,0x02,0x05,0x00,0x04,0x10};
template<> const unsigned int PKCS_DigestDecoration<MD2>::length = sizeof(PKCS_DigestDecoration<MD2>::decoration);

template<> const byte PKCS_DigestDecoration<MD5>::decoration[] = {0x30,0x20,0x30,0x0c,0x06,0x08,0x2a,0x86,0x48,0x86,0xf7,0x0d,0x02,0x05,0x05,0x00,0x04,0x10};
template<> const unsigned int PKCS_DigestDecoration<MD5>::length = sizeof(PKCS_DigestDecoration<MD5>::decoration);

template<> const byte PKCS_DigestDecoration<RIPEMD160>::decoration[] = {0x30,0x21,0x30,0x09,0x06,0x05,0x2b,0x24,0x03,0x02,0x01,0x05,0x00,0x04,0x14};
template<> const unsigned int PKCS_DigestDecoration<RIPEMD160>::length = sizeof(PKCS_DigestDecoration<RIPEMD160>::decoration);

template<> const byte PKCS_DigestDecoration<Tiger>::decoration[] = {0x30,0x29,0x30,0x0D,0x06,0x09,0x2B,0x06,0x01,0x04,0x01,0xDA,0x47,0x0C,0x02,0x05,0x00,0x04,0x18};
template<> const unsigned int PKCS_DigestDecoration<Tiger>::length = sizeof(PKCS_DigestDecoration<Tiger>::decoration);

size_t PKCS_EncryptionPaddingScheme::MaxUnpaddedLength(size_t paddedLength) const
{
        return SaturatingSubtract(paddedLength/8, 10U);
}

void PKCS_EncryptionPaddingScheme::Pad(RandomNumberGenerator &rng, const byte *input, size_t inputLen, byte *pkcsBlock, size_t pkcsBlockLen, const NameValuePairs &parameters) const
{
        assert (inputLen <= MaxUnpaddedLength(pkcsBlockLen));   // this should be checked by caller

        // convert from bit length to byte length
        if (pkcsBlockLen % 8 != 0)
        {
                pkcsBlock[0] = 0;
                pkcsBlock++;
        }
        pkcsBlockLen /= 8;

        pkcsBlock[0] = 2;  // block type 2

        // pad with non-zero random bytes
        for (unsigned i = 1; i < pkcsBlockLen-inputLen-1; i++)
                pkcsBlock[i] = (byte)rng.GenerateWord32(1, 0xff);

        pkcsBlock[pkcsBlockLen-inputLen-1] = 0;     // separator
        memcpy(pkcsBlock+pkcsBlockLen-inputLen, input, inputLen);
}

DecodingResult PKCS_EncryptionPaddingScheme::Unpad(const byte *pkcsBlock, size_t pkcsBlockLen, byte *output, const NameValuePairs &parameters) const
{
        bool invalid = false;
        size_t maxOutputLen = MaxUnpaddedLength(pkcsBlockLen);

        // convert from bit length to byte length
        if (pkcsBlockLen % 8 != 0)
        {
                invalid = (pkcsBlock[0] != 0) || invalid;
                pkcsBlock++;
        }
        pkcsBlockLen /= 8;

        // Require block type 2.
        invalid = (pkcsBlock[0] != 2) || invalid;

        // skip past the padding until we find the separator
        size_t i=1;
        while (i<pkcsBlockLen && pkcsBlock[i++]) { // null body
                }
        assert(i==pkcsBlockLen || pkcsBlock[i-1]==0);

        size_t outputLen = pkcsBlockLen - i;
        invalid = (outputLen > maxOutputLen) || invalid;

        if (invalid)
                return DecodingResult();

        memcpy (output, pkcsBlock+i, outputLen);
        return DecodingResult(outputLen);
}

// ********************************************************

#ifndef CRYPTOPP_IMPORTS

void PKCS1v15_SignatureMessageEncodingMethod::ComputeMessageRepresentative(RandomNumberGenerator &rng, 
        const byte *recoverableMessage, size_t recoverableMessageLength,
        HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
        byte *representative, size_t representativeBitLength) const
{
        assert(representativeBitLength >= MinRepresentativeBitLength(hashIdentifier.second, hash.DigestSize()));

        size_t pkcsBlockLen = representativeBitLength;
        // convert from bit length to byte length
        if (pkcsBlockLen % 8 != 0)
        {
                representative[0] = 0;
                representative++;
        }
        pkcsBlockLen /= 8;

        representative[0] = 1;   // block type 1

        unsigned int digestSize = hash.DigestSize();
        byte *pPadding = representative + 1;
        byte *pDigest = representative + pkcsBlockLen - digestSize;
        byte *pHashId = pDigest - hashIdentifier.second;
        byte *pSeparator = pHashId - 1;

        // pad with 0xff
        memset(pPadding, 0xff, pSeparator-pPadding);
        *pSeparator = 0;
        memcpy(pHashId, hashIdentifier.first, hashIdentifier.second);
        hash.Final(pDigest);
}

#endif

NAMESPACE_END

#endif

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