Authentication and authentication protocols

Authentication is the one of the fundamental requirements for ensuring security of important assets. Authentication is the process of validating the identity of an object trying to access an asset. Authentication can be done based on the implementation of one or more the following:

  1. Authentication by what you know.
  2. Authentication by what you have.
  3. Authentication by what you are.

When attempting to authenticate a user/application several industry standard types of authentication may be used depending on various conditions that exists on a subjective basis.

Various types of authentication protocols that is supported by Microsoft Windows Server 2003 family includes:

  1. Kerberos v5 authentication.
  2. SSL/TLS authentication.
  3. NTLM authentication.
  4. Digest authentication.
  5. Passport authentication.

Kerberos v5 authentication protocols: This protocol is either used with password or a smart card for interactive logon. It is also the default method for network authentication of services. The process works like this:

  1. The user on a client system using a password or a smart card authenticates to the KDC.
  2. The KDC issues a TGT to the client. The client system uses the TGT to access the Ticket Granting Service (TGS) which is the part of the Kerberos V5 authentication mechanism on the domain controller.
  3. The TGS issues a service ticket to the client.
  4. The client supplies the required network service with the service ticket. The service ticket provides both the user identity to the service and also the service identity to the user.

So the Kerberos v5 authentication protocol has the following main parts:

  1. Key Distribution Center (KDC)
  2. Ticket Granting Ticket (TGT)
  3. Ticket Granting Service (TGS)

The Kerberos v5 services are installed on each domain controller and a Kerberos client is installed on each workstation and server.

Each domain controller acts as a KDC. The client service uses the DNS to look up for the nearest nearest domain controller and in turn the nearest KDC.

Beginning Windows Server 2003, Kerberos is implemented as a SSP (Security Service Provider) that can be accessed using the SSPI (Security Support Provider Interface)

SSL/TLS authentication Protocols: TLS/SSL authenticates and secures data transfer by using certificate based authentication and symmetric encryption keys. Windows Server 2003 onwards, SSL/TLS protocols are implemented as a Security Service Providers (SSP) using dynamic link libraries that are called SChalnnels that is supplied with the OS implementation. Which one gets used is decided based on the capability of the computer on the other side of the connection. The default SSPs for Windows Server 2003 include the following: Kerberos, Digest, NTLM, SChannel and Negotiate authentication protocols as DLLs in the SSPI.

SChannel SSP is used to access web enabled services such as emails and personal information served over the internet on web pages. The SChannel SSP uses the public key encryption to authenticate parties. It included four authentication protocols that it supports:

  1. TLS v1.0
  2. SSL v3.0
  3. SSL v2.0
  4. Also supports PCT (Private Communications Transport) for backward compatibility.

Schannel then selects the most preferred authentication protocol that both parties can support.

TLS/SSL Architecture: TLS/SSL protocols are layered between the Application layer and the TCP/IP layer, where it can secure and send the application data to the transport layer for farther transport. Just because TLS/SSL works between the application layer and the transport layer it can support multiple application layer protocols.

TLS/SSL assumes that TCP/IP is in use. The main advantage of using TLS/SSL is that it provide the following:

  1. Message Integrity
  2. Message confidentiality
  3. Message authentication

The step by step of how SSL/TLS works:

  1. Client tries to connect to a SSL/TLS enabled service on port 443. The browser will send out the information that will include its supported methods of encrypting data. This includes an encryption type, some random data that encryption program on both side can use in the scrambling routine, and other ssl related data.
  2. Server responds by sending its own random data to be used for the encryption as well as other ssl information that will include its SSL certificate with the public key that the browser will use in the subsequent steps.
  3. The client browser checks the information it has received and compares it to the domain it to the domain it was trying to connect securely with.If the secure certificate information on the web site doesn’t match the domain name the browser will notify the customer that there is a problem. The certificate expiration date and valid certificate authority are also checked at this point.
  4. After validating the server certificate, the browser uses a random data that it encrypts using the agreed upon encryption method. For encryption it uses the public key sent by the server and send this encrypted secret to the server.
  5. With the string that the server received from the browser, both the browser and the web server create a new string and use it to create session keys that their encryption programs use for the rest of the session to scramble and descramble (or encrypt/decrypt) all transmissions for the rest of the session. With the Master Secret key in place, both sides are also able to verify that the data didn’t change in route.

NTLM Authentication: NTLM is the abbreviation for Windows NT LAN Manager This is a Windows network authentication protocol that uses challenge/response system to allow a client to prove its identity without sending the password over the network.  NTLM is the authentication protocol for computers that are not participating in a domain, such as stand-alone servers and workgroups. NTLM is a challenge-response authentication protocol which uses three messages to authenticate a client in a connection oriented environment (connectionless is similar), and a fourth additional message if integrity is desired.

Kerberos has mostly replaced NTLM in domain controller environment within AD implementation, but NTLM still find wide spread usage in environments where the domain controller is unavailable or reachable.




Information Security: Phishing and Microsoft Phishing filters

Phishing is one of the fastest growing threats of identity theft and abuse on the internet. It is so prevalent that almost any site of importance will have a warning mentioned somewhere to be careful about phishing attacks.

The very basis of Phishing attacks are phony websites that will give a perfect actual site like feeling to the user. This way the attackers manage to fool the user and get the important personal and financial information ranging from SSNs to credit card details.

Often phishing requests are sent over innocent looking emails that reflect the actual emails sent out by the legitimate organizations, requesting users for information. A not so tech savvy user may not be careful enough and hence loss of important information happens.

To fight against phishing scams, Microsoft has taken a number of steps that include:

1. Including SenderID to all of its email  email products and services

2. The Phishing filter (SmartScreen filter)


The Sender ID Framework is an e-mail authentication technology protocol that helps address the problem of spoofing and phishing by verifying the domain name from which e-mail messages are sent. Sender ID validates the origin of e-mail messages by verifying the IP address of the sender against the alleged owner of the sending domain.

The SmartScreen filter is a feature of Windows Internet Explorer 8. It is designed to help protect the user from fraudulent websites trying to steal personal information. SmartScreen filter also helps protect from installing malicious software or malware.

SmartScreen filter helps to protect you in three key ways:

  • It operates in the background as you browse the web, analyzing webpages and determining if they have any characteristics that might be suspicious. If it finds suspicious webpages, SmartScreen filter will display the “Are you trying to visit this website?” fly-out, giving you an opportunity to provide feedback and advising you to proceed with caution.
  • SmartScreen filter checks the sites you visit against an up-to-the-hour, dynamic list of reported phishing sites and malicious software sites. If it finds a match, SmartScreen filter will show you a red warning notifying you that the site has been blocked for your safety.
  • SmartScreen filter also checks files downloaded from the web against the same dynamic list of reported malicious software sites. If it finds a match, SmartScreen filter will show a red warning notifying you that the download has been blocked for your safety.

Application Security: Internet Explorer and Cross Site Scripting

Cross site scripting (aka XSS) is one of the most prevalent web application security issue. In OWASP top 10 for 2010, cross site featured prominently in number 2.

Considering the damage that a successful cross site scripting attack is capable of doing, almost all the successful commercial browsers have tried to provide security features that makes it difficult to execute a successful cross site scripting attack. One of the main ways this attack is carried out is by exploiting the browser’s capability for executing scripts.

Starting Internet Explorer 6 SP1, a new attribute is introduced to the cookies to counter the menace of XSS.

This attribute makes the cookie inaccessible to the scripts, thus stopping malicious script code from executing. The cookies with this attribute set are called HTTP only cookie.

A cookie is set on the client with an HTTP response header.

Set-Cookie: =[; =]
[; expires=][; domain=]
[; path=][; secure][; HttpOnly]

The HttpOnly attribute is not case sensitive and it is important to be noted that this feature must be used in coordination with other XSS mitigation to effectively counter XSS, like:

1. Proper input validation.

2. Adequate output encoding whenever any possible user controlled values are rendered back to the browser.

Application Security: Internet Explorer 8 vulnerabilities

The main class of vulnerability that is detected and patched on Internet Explorer 8 for Windows server include is  Remote Code Execution

As of this writing the latest patch came out on Feb 8, 2011 that contained fixes for the a number of  issues. Some of these include:

CSS Memory Corruption Vulnerability.

Per CVE-2010-3971 this issue came up because of a vulnerability in the CSharedStyleSheet::Notify function in the Cascading Style Sheets (CSS) parser in mshtml.dll, that is used in Microsoft Internet Explorer 6 through 8 and other products.  This vulnerability allows remote attackers to execute arbitrary code or cause a denial of service (application crash) via a self-referential @import rule in a style sheet.

Uninitialized Memory Corruption Vulnerability.

Per CVE-2011-0035 Microsoft Internet Explorer 8 does not properly handle objects in memory, which allows remote attackers to execute arbitrary code by accessing an object that (1) was not properly initialized or (2) is deleted, leading to memory corruption.

Almost all the issues reported lead to remote code execution that if successfully exploited could gain the same user rights as the logged-on user. If a user is logged on with administrative user rights, an attacker who successfully exploited this vulnerability could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

Application Security: What is CIA?

Been a long time I wrote anything in this blog. I am preparing for my CISSP examination and thought that I will share some notes here.

CIA forms the fundamental triad of information security and stands for CONFIDENTIALITY, INTEGRITY and AVAILABILITY.

What is Confidentiality? Any item of importance for an individual/organization (also called an asset) should not be disclosed to anyone who has not be granted explicit rights to it.

What is Integrity? Assurance that the data is free of unauthorized manipulation.

What is Availability? All data and services should be available to the legitimate users each time they need.

Anything and everything we do in information security are always directed towards ensuring that the triad is maintained.

Loss of any one of the three may have extreme legal/reputational impact on the organization/individual.