Problem - Kevin Tafuro

The worker function GetDistributionPoint( ) will look for a cRLDistributionPoints
extension in a certificate that has a URL. If the extension is present, CryptoAPI will
return the data in Unicode, so we need to convert it back down to the single-byte
OEM codepage.
static LPSTR make_thin(LPWSTR wstr) {
int len;
DWORD dwFlags;
LPSTR str;
dwFlags = WC_COMPOSITECHECK | WC_DISCARDNS;
if (!(len = WideCharToMultiByte(CP_OEMCP, dwFlags, wstr, -1, 0, 0, 0, 0)))
return 0;
if (!(str = (LPSTR)LocalAlloc(LMEM_FIXED, len))) return 0;
WideCharToMultiByte(CP_OEMCP, dwFlags, wstr, -1, str, len, 0, 0);
return str;
}
static LPSTR GetDistributionPoint(PCCERT_CONTEXT pCertContext) {
DWORD cbStructInfo, i, j;
LPSTR lpszURL;
LPVOID pvStructInfo;
CERT_EXTENSION *pExtension;
CERT_ALT_NAME_INFO *pNameInfo;
CRL_DIST_POINTS_INFO *pInfo;
pExtension = CertFindExtension(szOID_CRL_DIST_POINTS,
pCertContext->pCertInfo->cExtension,
pCertContext->pCertInfo->rgExtension);
if (!pExtension) return 0;
if (!CryptDecodeObject(X509_ASN_ENCODING, szOID_CRL_DIST_POINTS,
pExtension->Value.pbData, pExtension->Value.cbData, 0, 0, &cbStructInfo))
return 0;
if (!(pvStructInfo = LocalAlloc(LMEM_FIXED, cbStructInfo))) return 0;
CryptDecodeObject(X509_ASN_ENCODING, szOID_CRL_DIST_POINTS,
pExtension->Value.pbData, pExtension->Value.cbData, 0,
pvStructInfo, &cbStructInfo);
pInfo = (CRL_DIST_POINTS_INFO *)pvStructInfo;
for (i = 0; i < pInfo->cDistPoint; i++) {
if (pInfo->rgDistPoint[i].DistPointName.dwDistPointNameChoice = =
CRL_DIST_POINT_FULL_NAME) {
pNameInfo = &pInfo->rgDistPoint[i].DistPointName.FullName;
for (j = 0; j < pNameInfo->cAltEntry; i++) {
if (pNameInfo->rgAltEntry[j].dwAltNameChoice = = CERT_ALT_NAME_URL) {
if (!(lpszURL = make_thin(pNameInfo->rgAltEntry[i].pwszURL))) break;
LocalFree(pvStructInfo);
return lpszURL;
}
}
}
}
558 | Chapter 10: Public Key Infrastructure
This is the Title of the Book, eMatter Edition
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