Hi,
We are developing an EAP module for the Windows Mobile 5.0 as per the documentation provided at the MSDN site for the EAP extension development.
http://msdn2.microsoft.com/en-gb/library/aa363504.aspx

We succeeded in writing the whole EAP module. The whole EAP authentication goes through well with the AAA server(RADIUS) with the extension dll we wrote and we finally receive the outer EAP success, sent as part of the Access-Accept from RADIUS, which indicates the EAP authentication has succeeded. Now as per the documentation in MSDN, we are supposed to pass the MPPE-Send key and MPPE-Recv Key from the RasEapMakeMessage function using the pUserAttributes member of the pEapOutput structure in the final step. These keys are supposed to be used in the EAPOL module in the 4way handshake for the WPA MSK derivation.

But its not much clear on how the pUserAttributes is to be filled with these keys. We filled in the pUserAttributes pointer from what we can make out from the following MSDN link in the Remarks section at
http://msdn2.microsoft.com/en-gb/library/aa363518.aspx .
and another section that appears in the EAP Host documentation for Windows Vista and XP on how MPPE keys are to be handled at http://msdn2.microsoft.com/en-us/library/aa363636.aspx, which we think might also be relevant for the EAP extension development. But they don't seem to work.

We tried a lot of combinations but nothing seems to work. When we sniffed/traced on Access Point's logs the supplicant doesn't seem to respond to the EAPOL key request at all as part of the 4 way handshake for the WPA key(MSK) generation.
There is int much help at the MSDN apart from the above. The following is the code peice on how we filled in the fields, can anyone check if the code and tell what is wrong with this and the correct way of doing it


The excerpts from the code is as follows:

typedef unsigned char u8;
struct vsa
{
u8 attr_type;
u8 length;
u8 salt[2];
u8 lenofkey;
u8 value[32];
u8 padding[15];
};

struct vsa mppe_send_key, mppe_recv_key;
char *pos = NULL;
// 1-MPPE-Send Key, 1-MPPE-Recv Key, 1-raatMinimum(for termination)
lenofuserattr = 3 * sizeof(RAS_AUTH_ATTRIBUTE);
pEapOutput->pUserAttributes = (RAS_AUTH_ATTRIBUTE *) malloc(lenofuserattr);
pos = (u8 *) pEapOutput->pUserAttributes;
memset(pos, 0, lenofuserattr);
/*
As per MSDN
52 for the sub-attribute AVP which would hold the MPPE keys
4 for Vendor-Id(311 for Microsoft)
*/
lenofvalue = 52 + 4;

//MPPE-RECV-KEY
pEapOutput->pUserAttributes[0].raaType = (raatVendorSpecific); //ras auth attribute type (VSA)
pEapOutput->pUserAttributes[0].dwLength = (lenofvalue);
pEapOutput->pUserAttributes[0].Value = (u8 *) malloc( sizeof(u8) * (lenofvalue) );
pos = (u8 *) pEapOutput->pUserAttributes[0].Value;

memset(pos, 0, lenofvalue);
vid= ntohl(311);
memcpy(pos, &vid, 4);
pos += 4;

mppe_recv_key.attr_type = 17;//Type MPPE-Recv-Key
mppe_recv_key.length = 52; //Total AVP length

mppe_recv_key.salt[0] = 0x00;
mppe_recv_key.salt[1] = 0x00;

mppe_recv_key.lenofkey = 32; // Key length only
// The second 32 bits of the buffer 'mppe_keys' is the MPPE-Recv key
memcpy(mppe_recv_key.value, mppe_keys + 32, 32);//MPPE-Recv Key
memset(mppe_recv_key.padding, 0, 15); //padding

memcpy(pos, &mppe_recv_key, sizeof(struct vsa)); //sizeof(struct vsa) is equal to 52


//MPPE-SEND-KEY
pEapOutput->pUserAttributes[1].raaType = (raatVendorSpecific); //ras auth attribute type (VSA)
pEapOutput->pUserAttributes[1].dwLength = (lenofvalue);//4 - Vendor-Id
pEapOutput->pUserAttributes[1].Value = (u8 *) malloc( sizeof(u8) * (lenofvalue));
pos = (u8 *) pEapOutput->pUserAttributes[1].Value;

memset(pos, 0, lenofvalue);
vid= ntohl(311);
memcpy(pos, &vid, 4);

pos += 4;

mppe_send_key.attr_type = 16; //Type MPPE-Send-Key
mppe_send_key.length = 52; //Total AVP length

mppe_send_key.salt[0] = 0x00;
mppe_send_key.salt[1] = 0x00;

mppe_send_key.lenofkey = 32; // Key length only
// The first 32 bits of the buffer 'mppe_keys' is the MPPE-Send key
memcpy(mppe_send_key.value, mppe_keys, 32); //MPPE-Send-Key
memset(mppe_send_key.padding, 0, 15); // Padding

memcpy(pos, &mppe_send_key, 52);

//Terminate with raat Minimum
pEapOutput->pUserAttributes[2].raaType = (raatMinimum);
pEapOutput->pUserAttributes[2].dwLength = (0);
pEapOutput->pUserAttributes[2].Value = NULL;

Thanks,
Vijay