Problem - Kevin Tafuro

lpFullBuffer = lpNewBuffer;
lpBuffer = (LPVOID)((LPBYTE)lpFullBuffer + dwContentLength);
}
if ((lpNewBuffer = LocalReAlloc(lpFullBuffer, dwContentLength, 0)) != 0)
lpFullBuffer = lpNewBuffer;
InternetCloseHandle(hRequest);
InternetCloseHandle(hSession);
*lpdwDataLength = dwContentLength;
return (BYTE *)lpFullBuffer;
}
The primary function used in this recipe is SpcRetrieveCRL( ). It ties all of the other
functions together in a neat little package, returning a CRL_CONTEXT object to the caller
if a CRLcan be successfully obtained using the information from the subject and
issuer certificates that are required as arguments. SpcRetrieveCRL( ) uses the URL
information from cRLDistributionPoints extensions in either certificate before consulting
the internal table of CA fingerprints and CRLURLs. Unfortunately, the
cRLDistributionPoints extension often contains a URLthat is invalid, so this case is
handled by falling back on the table lookup if the data cannot be retrieved from the
cRLDistributionPoints information.
If the function is successful, it returns a CRL_CONTEXT object created using CryptoAPI.
When the object is no longer needed, it should be destroyed using
CertFreeCRLContext( ). If a CRLcannot be created for some reason, NULL is returned,
and the Win32 function GetLastError( ) can be used to determine what went wrong.
PCCRL_CONTEXT SpcRetrieveCRL(PCCERT_CONTEXT pSubject, PCCERT_CONTEXT pIssuer) {
BYTE *pbData;
DWORD cbData;
LPSTR lpszURL, lpszSecondURL;
PCCRL_CONTEXT pCRL;
if (!(lpszURL = SpcGetCertCRLURL(pSubject, pIssuer, FALSE))) return 0;
if (!(pbData = RetrieveWebData(lpszURL, &cbData))) {
lpszSecondURL = SpcGetCertCRLURL(pSubject, pIssuer, TRUE);
if (!lpszSecondURL || !lstrcmpA(lpszURL, lpszSecondURL)) {
if (lpszSecondURL) LocalFree(lpszSecondURL);
LocalFree(lpszURL);
return 0;
}
pbData = RetrieveWebData(lpszSecondURL, &cbData);
LocalFree(lpszSecondURL);
}
if (pbData) {
pCRL = CertCreateCRLContext(X509_ASN_ENCODING, pbData, cbData);
LocalFree(pbData);
}
LocalFree(lpszURL);
return pCRL;
}
Obtaining CRLs with CryptoAPI | 561
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