Adding attributes to PKCS#7 envelpe

Hello, currently I'm trying to add attributes to pcks#7 envelope but I cannot find any info how to add attributes.

Here is an example from MS.

http://msdn.microsoft.com/en-us/library/windows/desktop/aa382367(v=vs.85).aspx

I am trying to add 3 attributes into SignPara.rgAuthAttr.

First initialize CRYPT_ATTRIBUTE structure.

SignPara.cAuthAttr = 3;

CRYPT_ATTRIBUTE* pkimsg_attrs = (CRYPT_ATTRIBUTE*)malloc(SignPara.cAuthAttr * sizeof(CRYPT_ATTRIBUTE));

Then add BLOB object and add it into pkimsg_attrs .

Then assign it as

SignPara.rgAuthAttr = pkimsg_attrs;

But when I decrypt the envelope, the attributes are all invalid.

Below is how I add new attribute into pkimsg_attrs;

PCRYPT_INTEGER_BLOB request_type_str = new CRYPT_INTEGER_BLOB();
//request_type_str->cbData = 1;
request_type_str->cbData = 2;
request_type_str->pbData = (BYTE*)"19";
LPSTR nid_messageType = "2.16.840.1.113733.1.9.2";//STR
pkimsg_attrs->pszObjId = new char[strlen(nid_messageType)];
strcpy(pkimsg_attrs->pszObjId,nid_messageType);
pkimsg_attrs->cValue=1;
pkimsg_attrs->rgValue = request_type_str;