internal static extern unsafe SafeCryptMsgHandle CryptMsgOpenToEncode(
MsgEncodingType dwMsgEncodingType,
int dwFlags,
CryptMsgType dwMsgType,
CMSG_ENVELOPED_ENCODE_INFO *pvMsgEncodeInfo,
[MarshalAs(UnmanagedType.LPStr)] string pszInnerContentObjID,
IntPtr pStreamInfo);
public static SafeCryptMsgHandle CreateCryptMsgHandleToEncode(CmsRecipientCollection recipients, Oid innerContentType, AlgorithmIdentifier contentEncryptionAlgorithm, X509Certificate2Collection originatorCerts, CryptographicAttributeObjectCollection unprotectedAttributes)
{
using (HeapBlockRetainer hb = new HeapBlockRetainer())
{
// Deep copy the CmsRecipients (and especially their underlying X509Certificate2 objects). This will prevent malicious callers from altering them or disposing them while we're performing
// unsafe memory crawling inside them.
recipients = recipients.DeepCopy();
// We must keep all the certificates inside recipients alive until the call to CryptMsgOpenToEncode() finishes. The CMSG_ENVELOPED_ENCODE_INFO* structure we passed to it
// contains direct pointers to memory owned by the CERT_INFO memory block whose lifetime is that of the certificate.
hb.KeepAlive(recipients);
unsafe
{
CMSG_ENVELOPED_ENCODE_INFO *pEnvelopedEncodeInfo = CreateCmsEnvelopedEncodeInfo(recipients, contentEncryptionAlgorithm, originatorCerts, unprotectedAttributes, hb);
SafeCryptMsgHandle hCryptMsg = Interop.Crypt32.CryptMsgOpenToEncode(MsgEncodingType.All, 0, CryptMsgType.CMSG_ENVELOPED, pEnvelopedEncodeInfo, innerContentType.Value, IntPtr.Zero);
if (hCryptMsg == null || hCryptMsg.IsInvalid)
{
throw Marshal.GetLastWin32Error().ToCryptographicException();
}
return(hCryptMsg);
}
}
}
//
// This returns an allocated native memory block. Its lifetime (and that of any allocated subblocks it may point to) is that of "hb".
//
private static unsafe CMSG_ENVELOPED_ENCODE_INFO *CreateCmsEnvelopedEncodeInfo(CmsRecipientCollection recipients, AlgorithmIdentifier contentEncryptionAlgorithm, X509Certificate2Collection originatorCerts, CryptographicAttributeObjectCollection unprotectedAttributes, HeapBlockRetainer hb)
{
CMSG_ENVELOPED_ENCODE_INFO *pEnvelopedEncodeInfo = (CMSG_ENVELOPED_ENCODE_INFO *)(hb.Alloc(sizeof(CMSG_ENVELOPED_ENCODE_INFO)));
pEnvelopedEncodeInfo->cbSize = sizeof(CMSG_ENVELOPED_ENCODE_INFO);
pEnvelopedEncodeInfo->hCryptProv = IntPtr.Zero;
string algorithmOidValue = contentEncryptionAlgorithm.Oid.Value;
pEnvelopedEncodeInfo->ContentEncryptionAlgorithm.pszObjId = hb.AllocAsciiString(algorithmOidValue);
// Desktop compat: Though it seems like we could copy over the contents of contentEncryptionAlgorithm.Parameters, that property is for retrieving information from decoded Cms's only, and it
// massages the raw data so it wouldn't be usable here anyway. To hammer home that fact, the EncryptedCms constructer rather rudely forces contentEncryptionAlgorithm.Parameters to be the empty array.
pEnvelopedEncodeInfo->ContentEncryptionAlgorithm.Parameters.cbData = 0;
pEnvelopedEncodeInfo->ContentEncryptionAlgorithm.Parameters.pbData = IntPtr.Zero;
pEnvelopedEncodeInfo->pvEncryptionAuxInfo = GenerateEncryptionAuxInfoIfNeeded(contentEncryptionAlgorithm, hb);
int numRecipients = recipients.Count;
pEnvelopedEncodeInfo->cRecipients = numRecipients;
pEnvelopedEncodeInfo->rgpRecipients = IntPtr.Zero;
CMSG_RECIPIENT_ENCODE_INFO *rgCmsRecipients = (CMSG_RECIPIENT_ENCODE_INFO *)(hb.Alloc(numRecipients, sizeof(CMSG_RECIPIENT_ENCODE_INFO)));
for (int index = 0; index < numRecipients; index++)
{
rgCmsRecipients[index] = EncodeRecipientInfo(recipients[index], contentEncryptionAlgorithm, hb);
}
pEnvelopedEncodeInfo->rgCmsRecipients = rgCmsRecipients;
int numCertificates = originatorCerts.Count;
pEnvelopedEncodeInfo->cCertEncoded = numCertificates;
pEnvelopedEncodeInfo->rgCertEncoded = null;
if (numCertificates != 0)
{
DATA_BLOB *pCertEncoded = (DATA_BLOB *)(hb.Alloc(numCertificates, sizeof(DATA_BLOB)));
for (int i = 0; i < numCertificates; i++)
{
byte[] certEncoded = originatorCerts[i].Export(X509ContentType.Cert);
pCertEncoded[i].cbData = (uint)(certEncoded.Length);
pCertEncoded[i].pbData = hb.AllocBytes(certEncoded);
}
pEnvelopedEncodeInfo->rgCertEncoded = pCertEncoded;
}
pEnvelopedEncodeInfo->cCrlEncoded = 0;
pEnvelopedEncodeInfo->rgCrlEncoded = null;
pEnvelopedEncodeInfo->cAttrCertEncoded = 0;
pEnvelopedEncodeInfo->rgAttrCertEncoded = null;
int numUnprotectedAttributes = unprotectedAttributes.Count;
pEnvelopedEncodeInfo->cUnprotectedAttr = numUnprotectedAttributes;
pEnvelopedEncodeInfo->rgUnprotectedAttr = null;
if (numUnprotectedAttributes != 0)
{
CRYPT_ATTRIBUTE *pCryptAttribute = (CRYPT_ATTRIBUTE *)(hb.Alloc(numUnprotectedAttributes, sizeof(CRYPT_ATTRIBUTE)));
for (int i = 0; i < numUnprotectedAttributes; i++)
{
CryptographicAttributeObject attribute = unprotectedAttributes[i];
pCryptAttribute[i].pszObjId = hb.AllocAsciiString(attribute.Oid.Value);
AsnEncodedDataCollection values = attribute.Values;
int numValues = values.Count;
pCryptAttribute[i].cValue = numValues;
DATA_BLOB *pValues = (DATA_BLOB *)(hb.Alloc(numValues, sizeof(DATA_BLOB)));
for (int j = 0; j < numValues; j++)
{
byte[] rawData = values[j].RawData;
pValues[j].cbData = (uint)(rawData.Length);
pValues[j].pbData = hb.AllocBytes(rawData);
}
pCryptAttribute[i].rgValue = pValues;
}
pEnvelopedEncodeInfo->rgUnprotectedAttr = pCryptAttribute;
}
return(pEnvelopedEncodeInfo);
}