//Decrypt Buffer in Place
void cpl::crypt::blowfish::decrypt(buffer &buf, int iMode)
{
int n = buf.size();
// n MUST be a power of 8. If not, then we are going to get very strange results.
int rem = 8-(n%8);
if (rem != 8)
{
buf.insert(buf.end(), rem, '\0');
n += rem;
}
assert( n % 8 == 0 ) ;
if (n == 0)
return; // Nothing to do...
block work;
buffer bytes(8);
block crypt, chain(m_oChain);
switch (iMode)
{
case CBC: //CBC mode, using the Chain
for(; n >= 8; n -= 8)
{
copy(buf.begin()+n-8, buf.begin()+n, bytes.begin());
work = bytesToBlock(bytes);
crypt = work;
decrypt(work);
work ^= chain;
chain = crypt;
bytes = blockToBytes(work);
copy(bytes.begin(), bytes.end(), buf.begin()+n-8);
}
break;
case CFB: //CFB mode, using the Chain, not using Decrypt()
for(; n >= 8; n -= 8)
{
copy(buf.begin()+n-8, buf.begin()+n, bytes.begin());
work = bytesToBlock(bytes);
encrypt(chain);
crypt = work;
work ^= chain;
chain = crypt;
bytes = blockToBytes(work);
copy(bytes.begin(), bytes.end(), buf.begin()+n-8);
}
break;
case ECB: //ECB mode, not using the Chain
default:
for(; n >= 8; n -= 8)
{
copy(buf.begin()+n-8, buf.begin()+n, bytes.begin());
work = bytesToBlock(bytes);
decrypt(work);
bytes = blockToBytes(work);
copy(bytes.begin(), bytes.end(), buf.begin()+n-8);
}
break;
}
// get the size out of the first 8 chars in the buffer, and then resize it.
buffer sizeBuf(8);
copy(buf.begin(), buf.begin()+8, sizeBuf.begin());
buf.erase(buf.begin(), buf.begin()+8);
int size = decodeInt(sizeBuf);
// remove the padding from the end of the file
buf.erase(buf.end() - (buf.size() - size), buf.end());
}
