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/* rsa.cpp
*
* Copyright (C) 2003 Sawtooth Consulting Ltd.
*
* This file is part of yaSSL.
*
* yaSSL is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* There are special exceptions to the terms and conditions of the GPL as it
* is applied to yaSSL. View the full text of the exception in the file
* FLOSS-EXCEPTIONS in the directory of this software distribution.
*
* yaSSL is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
/* based on Wei Dai's rsa.cpp from CryptoPP */
#include "runtime.hpp"
#include "rsa.hpp"
#include "asn.hpp"
#include "modarith.hpp"
namespace TaoCrypt {
Integer RSA_PublicKey::ApplyFunction(const Integer& x) const
{
return a_exp_b_mod_c(x, e_, n_);
}
RSA_PublicKey::RSA_PublicKey(Source& source)
{
Initialize(source);
}
void RSA_PublicKey::Initialize(Source& source)
{
RSA_Public_Decoder decoder(source);
decoder.Decode(*this);
}
Integer RSA_PrivateKey::CalculateInverse(RandomNumberGenerator& rng,
const Integer& x) const
{
ModularArithmetic modn(n_);
Integer r(rng, Integer::One(), n_ - Integer::One());
Integer re = modn.Exponentiate(r, e_);
re = modn.Multiply(re, x); // blind
// here we follow the notation of PKCS #1 and let u=q inverse mod p
// but in ModRoot, u=p inverse mod q, so we reverse the order of p and q
Integer y = ModularRoot(re, dq_, dp_, q_, p_, u_);
y = modn.Divide(y, r); // unblind
assert(modn.Exponentiate(y, e_) == x); // check
return y;
}
RSA_PrivateKey::RSA_PrivateKey(Source& source)
{
Initialize(source);
}
void RSA_PrivateKey::Initialize(Source& source)
{
RSA_Private_Decoder decoder(source);
decoder.Decode(*this);
}
void RSA_BlockType2::Pad(const byte *input, word32 inputLen, byte *pkcsBlock,
word32 pkcsBlockLen, RandomNumberGenerator& rng) const
{
// 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
word32 padLen = pkcsBlockLen - inputLen - 1;
rng.GenerateBlock(&pkcsBlock[1], padLen);
for (word32 i = 1; i < padLen; i++)
if (pkcsBlock[i] == 0) pkcsBlock[i] = 0x01;
pkcsBlock[pkcsBlockLen-inputLen-1] = 0; // separator
memcpy(pkcsBlock+pkcsBlockLen-inputLen, input, inputLen);
}
word32 RSA_BlockType2::UnPad(const byte *pkcsBlock, unsigned int pkcsBlockLen,
byte *output) const
{
bool invalid = false;
unsigned int maxOutputLen = SaturatingSubtract(pkcsBlockLen / 8, 10U);
// 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
unsigned i=1;
while (i<pkcsBlockLen && pkcsBlock[i++]) { // null body
}
assert(i==pkcsBlockLen || pkcsBlock[i-1]==0);
unsigned int outputLen = pkcsBlockLen - i;
invalid = (outputLen > maxOutputLen) || invalid;
if (invalid)
return 0;
memcpy (output, pkcsBlock+i, outputLen);
return outputLen;
}
void RSA_BlockType1::Pad(const byte* input, word32 inputLen, byte* pkcsBlock,
word32 pkcsBlockLen, RandomNumberGenerator&) const
{
// convert from bit length to byte length
if (pkcsBlockLen % 8 != 0)
{
pkcsBlock[0] = 0;
pkcsBlock++;
}
pkcsBlockLen /= 8;
pkcsBlock[0] = 1; // block type 1 for SSL
// pad with 0xff bytes
memset(&pkcsBlock[1], 0xFF, pkcsBlockLen - inputLen - 2);
pkcsBlock[pkcsBlockLen-inputLen-1] = 0; // separator
memcpy(pkcsBlock+pkcsBlockLen-inputLen, input, inputLen);
}
word32 RSA_BlockType1::UnPad(const byte* pkcsBlock, word32 pkcsBlockLen,
byte* output) const
{
bool invalid = false;
unsigned int maxOutputLen = SaturatingSubtract(pkcsBlockLen / 8, 10U);
// convert from bit length to byte length
if (pkcsBlockLen % 8 != 0)
{
invalid = (pkcsBlock[0] != 0) || invalid;
pkcsBlock++;
}
pkcsBlockLen /= 8;
// Require block type 1 for SSL.
invalid = (pkcsBlock[0] != 1) || invalid;
// skip past the padding until we find the separator
unsigned i=1;
while (i<pkcsBlockLen && pkcsBlock[i++]) { // null body
}
assert(i==pkcsBlockLen || pkcsBlock[i-1]==0);
unsigned int outputLen = pkcsBlockLen - i;
invalid = (outputLen > maxOutputLen) || invalid;
if (invalid)
return 0;
memcpy(output, pkcsBlock+i, outputLen);
return outputLen;
}
word32 SSL_Decrypt(const RSA_PublicKey& key, const byte* sig, byte* plain)
{
PK_Lengths lengths(key.GetModulus());
ByteBlock paddedBlock(BitsToBytes(lengths.PaddedBlockBitLength()));
Integer x = key.ApplyFunction(Integer(sig,
lengths.FixedCiphertextLength()));
if (x.ByteCount() > paddedBlock.size())
x = Integer::Zero();
x.Encode(paddedBlock.get_buffer(), paddedBlock.size());
return RSA_BlockType1().UnPad(paddedBlock.get_buffer(),
lengths.PaddedBlockBitLength(), plain);
}
} // namespace
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