/// <summary>
/// Handle asynchronous packet reception.
/// </summary>
/// <param name="ar">The operation's <see cref="IAsyncResult" /> instance.</param>
private void OnReceive(IAsyncResult ar)
{
RadiusPacket request = null;
ServerState state = null;
int cbRecv;
using (TimedLock.Lock(this))
{
// Finish receiving the next request packet
try
{
cbRecv = sock.EndReceiveFrom(ar, ref remoteEP);
}
catch (SocketClosedException)
{
// We'll see this when the RADIUS server instance is closed.
// I'm not going to report this to the event log.
return;
}
catch (Exception e)
{
// I'm going to assume that something really bad has
// happened to the socket, log the exception and then
// return without initiating another receive. This
// effectively stops the server.
SysLog.LogException(e);
return;
}
// Parse the request. We're going to initiate the
// authentication below, outside of the lock.
try
{
request = new RadiusPacket((IPEndPoint)remoteEP, recvBuf, cbRecv);
// Unit tests can use this hook to monitor incoming packets
// as well cause them to be ignored.
if (DiagnosticHook != null && !DiagnosticHook(this, request))
{
request = null;
}
if (request != null && request.Code == RadiusCode.AccessRequest)
{
state = new ServerState(this);
}
else
{
// Ignore all RADIUS requests except for Access-Request
request = null;
}
}
catch (Exception e)
{
SysLog.LogException(e);
}
// Initiate reception of the next request
try
{
sock.BeginReceiveFrom(recvBuf, 0, recvBuf.Length, SocketFlags.None, ref remoteEP, onReceive, null);
}
catch (Exception e)
{
SysLog.LogException(e);
}
}
if (request == null)
{
return; // We're ignoring the packet
}
// Validate the packet and the NAS
RadiusNasInfo nasInfo;
IPAddress nasIPAddress;
byte[] nasIdentifier;
string userName;
string realm;
string account;
byte[] encryptedPassword;
string password;
if (!request.GetAttributeAsAddress(RadiusAttributeType.NasIpAddress, out nasIPAddress) &&
!request.GetAttributeAsBinary(RadiusAttributeType.NasIdentifier, out nasIdentifier))
{
// Access-Request packets are required by RFC 2865 to have either a NAS-IP-Address
// or a NAS-IP-Identifier attribute. Discard any packets that don't have one
// of these.
return;
}
if (!request.GetAttributeAsText(RadiusAttributeType.UserName, out userName) ||
!request.GetAttributeAsBinary(RadiusAttributeType.UserPassword, out encryptedPassword))
{
// The User-Name attribute is required by RFC 2865 and this implementation
// requires a User-Password attribute. Ignore packets without these.
return;
}
// Parse the realm and account from the user name
Helper.ParseUserName(realmFormat, userName, out realm, out account);
// Lookup the NAS shared secret and decrypt the password.
nasInfo = GetNasInfo(state, request.SourceEP.Address);
if (nasInfo == null)
{
if (defSecret == null)
{
// Not being able to find information about a NAS device could
// represent a serious security problem or attack so I'm going
// to log this.
Log(state, false, RadiusLogEntryType.UnknownNas, realm, account, "RADIUS: Unknown NAS device NAS=[{0}].", request.SourceEP);
return;
}
nasInfo = new RadiusNasInfo(request.SourceEP.Address, defSecret);
}
password = request.DecryptUserPassword(encryptedPassword, nasInfo.Secret);
// Perform the authentication, compute the response
// authenticator and then send a response packet.
RadiusPacket response;
if (Authenticate(state, realm, account, password))
{
Log(state, true, RadiusLogEntryType.Authentication, realm, account,
"Authenticated: realm=[{0}] account=[{1}] NAS=[{2}]", realm, account, request.SourceEP);
response = new RadiusPacket(RadiusCode.AccessAccept, request.Identifier, null,
new RadiusAttribute(RadiusAttributeType.ServiceType, (int)RadiusServiceType.Login));
}
else
{
Log(state, false, RadiusLogEntryType.Authentication, realm, account,
"Authentication Fail: realm=[{0}] account=[{1}] NAS=[{2}]", realm, account, request.SourceEP);
response = new RadiusPacket(RadiusCode.AccessReject, request.Identifier, null);
}
response.ComputeResponseAuthenticator(request, nasInfo.Secret);
try
{
sock.SendTo(response.ToArray(), request.SourceEP);
}
catch (SocketClosedException)
{
// We'll see this when the RADIUS server instance is closed.
// I'm not going to report this to the event log.
}
catch (Exception e)
{
SysLog.LogException(e);
}
}