Secure Web-Based Licensing
By Mike Scanlon, November 01, 2000
If you want to protect your software from misuse, you have to outsmart potential thieves and still not annoy your legitimate customers. This is not as easy as you might at first think.
November 2000/Secure Web-Based Licensing/Listing 4
STDMETHODIMP
CCryptoLicense::GrantLicense(BSTR cookie, BSTR *license)
{
long lCookie = 0;
char szLicense[64];
ZeroMemory(szLicense,64);
char szTmp[13];
ZeroMemory(szTmp,13);
unsigned short crc = 0;
USES_CONVERSION;
//Decrypt the cookie
Decrypt(W2A(cookie),"UnbreakableKey",szLicense, 64);
//Validate the cookie's crc
sscanf(szLicense,"%08X%04X",&lCookie,&crc);
if (!crc || ComputeCRC(lCookie) != crc)
{
char err[]="Error: Cookie invalid\n";
Error(err);
*license = T2BSTR("0");
return E_FAIL;
}
//Compute the new license
lCookie = lCookie + 30*86400;
//Append a crc
sprintf(szTmp,"%08X%04X",lCookie,ComputeCRC(lCookie));
//Encrypt the new license
ZeroMemory(szLicense,64);
Encrypt(szTmp,"UnbreakableKey",szLicense, 64);
*license = T2BSTR(szLicense);
return S_OK;
}
