public IReadOnlyList <ISignature> Extract(string filePath)
{
EncodingType encodingType;
CryptQueryContentType contentType;
CryptQueryFormatType formatType;
CryptMsgSafeHandle message = CryptMsgSafeHandle.InvalidHandle;
var result = Crypt32.CryptQueryObject(CryptQueryObjectType.CERT_QUERY_OBJECT_FILE, filePath, CryptQueryContentFlagType.CERT_QUERY_CONTENT_FLAG_PKCS7_SIGNED_EMBED, CryptQueryFormatFlagType.CERT_QUERY_FORMAT_FLAG_BINARY, CryptQueryObjectFlags.NONE, out encodingType, out contentType, out formatType, IntPtr.Zero, out message, IntPtr.Zero);
if (!result)
{
var resultCode = Marshal.GetLastWin32Error();
switch (unchecked ((uint)resultCode))
{
case 0x80092009: //Cannot find request object. There's no signature.
return(Array.Empty <ISignature>());
default:
throw new Win32Exception(resultCode, "Failed to extract signature.");
}
}
using (message)
{
if (message.IsInvalid || message.IsClosed)
{
return(Array.Empty <ISignature>());
}
return(GetSignatures(message));
}
}
private static unsafe IReadOnlyList <ICmsSignature> GetSignatures(CryptMsgSafeHandle messageHandle)
{
var countSize = 0u;
if (!Crypt32.CryptMsgGetParam(messageHandle, CryptMsgParamType.CMSG_SIGNER_COUNT_PARAM, 0, LocalBufferSafeHandle.Zero, ref countSize))
{
return(Array.Empty <ICmsSignature>());
}
uint signerCount;
using (var countHandle = LocalBufferSafeHandle.Alloc(countSize))
{
if (!Crypt32.CryptMsgGetParam(messageHandle, CryptMsgParamType.CMSG_SIGNER_COUNT_PARAM, 0, countHandle, ref countSize))
{
return(Array.Empty <ICmsSignature>());
}
signerCount = (uint)Marshal.ReadInt32(countHandle.DangerousGetHandle());
}
var signatures = new List <ICmsSignature>();
var contentSize = 0u;
byte[] content = null;
if (Crypt32.CryptMsgGetParam(messageHandle, CryptMsgParamType.CMSG_CONTENT_PARAM, 0, LocalBufferSafeHandle.Zero, ref contentSize))
{
using (var contentHandle = LocalBufferSafeHandle.Alloc(contentSize))
{
if (Crypt32.CryptMsgGetParam(messageHandle, CryptMsgParamType.CMSG_CONTENT_PARAM, 0, contentHandle, ref contentSize))
{
content = new byte[contentSize];
Marshal.Copy(contentHandle.DangerousGetHandle(), content, 0, (int)contentSize);
}
}
}
for (var i = 0u; i < signerCount; i++)
{
var signerSize = 0u;
if (!Crypt32.CryptMsgGetParam(messageHandle, CryptMsgParamType.CMSG_SIGNER_INFO_PARAM, i, LocalBufferSafeHandle.Zero, ref signerSize))
{
continue;
}
using (var signerHandle = LocalBufferSafeHandle.Alloc(signerSize))
{
if (!Crypt32.CryptMsgGetParam(messageHandle, CryptMsgParamType.CMSG_SIGNER_INFO_PARAM, i, signerHandle, ref signerSize))
{
continue;
}
var signature = new CmsSignature(SignatureKind.Signature, messageHandle, signerHandle, content);
signatures.Add(signature);
}
}
return(signatures.AsReadOnly());
}
private void InitFromHandles(CryptMsgSafeHandle messageHandle, LocalBufferSafeHandle signerHandle)
{
var signerInfo = Marshal.PtrToStructure <CMSG_SIGNER_INFO>(signerHandle.DangerousGetHandle());
var subjectId = new UniversalSubjectIdentifier(signerInfo.Issuer, signerInfo.SerialNumber);
var certs = GetCertificatesFromMessage(messageHandle);
if (subjectId.Type == SubjectIdentifierType.SubjectKeyIdentifier)
{
Certificate = FindCertificate((string)subjectId.Value, certs);
}
else if (subjectId.Type == SubjectIdentifierType.IssuerAndSerialNumber)
{
Certificate = FindCertificate((X509IssuerSerial)subjectId.Value, certs);
}
AdditionalCertificates = certs;
DigestAlgorithm = new Oid(signerInfo.HashAlgorithm.pszObjId);
HashEncryptionAlgorithm = new Oid(signerInfo.HashEncryptionAlgorithm.pszObjId);
SerialNumber = ReadBlob(signerInfo.SerialNumber);
UnsignedAttributes = ReadAttributes(signerInfo.UnauthAttrs);
SignedAttributes = ReadAttributes(signerInfo.AuthAttrs);
}
internal X509Certificate2Collection GetCertificatesFromMessage(CryptMsgSafeHandle handle)
{
var size = (uint)Marshal.SizeOf <uint>();
var certs = new X509Certificate2Collection();
uint certCount;
using (var certCountLocalBuffer = LocalBufferSafeHandle.Alloc(size))
{
if (!Crypt32.CryptMsgGetParam(handle, CryptMsgParamType.CMSG_CERT_COUNT_PARAM, 0, certCountLocalBuffer, ref size))
{
return(certs);
}
certCount = unchecked ((uint)Marshal.ReadInt32(certCountLocalBuffer.DangerousGetHandle(), 0));
}
if (certCount == 0)
{
return(certs);
}
for (var i = 0u; i < certCount; i++)
{
uint certSize = 0;
if (!Crypt32.CryptMsgGetParam(handle, CryptMsgParamType.CMSG_CERT_PARAM, i, LocalBufferSafeHandle.Zero, ref certSize))
{
continue;
}
using (var certLocalBuffer = LocalBufferSafeHandle.Alloc(certSize))
{
if (!Crypt32.CryptMsgGetParam(handle, CryptMsgParamType.CMSG_CERT_PARAM, i, certLocalBuffer, ref certSize))
{
continue;
}
var data = new byte[certSize];
Marshal.Copy(certLocalBuffer.DangerousGetHandle(), data, 0, data.Length);
var cert = new X509Certificate2(data);
certs.Add(cert);
}
}
return(certs);
}
static CryptMsgSafeHandle()
{
InvalidHandle = new CryptMsgSafeHandle(true);
InvalidHandle.SetHandleAsInvalid();
}
internal Signature(SignatureKind kind, CryptMsgSafeHandle messageHandle, LocalBufferSafeHandle signerHandle)
{
Kind = kind;
InitFromHandles(messageHandle, signerHandle);
}
