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S1L2 - Software Security (AAA) (AAA - Access Control, Authentication &…

- - - - MAC (Mandatory Access Control)
        
        Protection decisions are not decided by owner of objects.
        
        Level of Access defined and is hard-coded in OS and cannot be easily changed
        For example: Delete root files in Windows
      - DAC (Discretionary Access Control)
        
        Defined by the owner of an object.
        
        DISCRETIONARY because protection of data object is set at the discretion of the owner.
        
        A DAC mechanism allows users to grant or revoke access of an object under their control WITHOUT interaction of a system admin.
      - RBAC (Role-Based Access Control)
        
        Defined by job function and much more control in defining.
        
        Allows admin to create "roles" users where each role has specific privileges.
        
        Can be costly and prone to error (because admin has to configure ACL)
  - - - Kerberos
        
        Terminologies
        
        KDC (Key Distribution Center)
        server issuing keys during initial client setup
        .
        
        AS
        In order to authenticate, KDC runs an AS (Authentication Service). AS issues TGT (Ticket Granting Ticket)
        .
        
        TGT
        temporary set of credentials that client uses as proof of identity validation
        .
        
        Kerberos client/user is known as PRINCIPAL
        
        Purpose
        connect a valid user with the service user wishes to access. In order to accomplish this, BOTH server and user must have KEYS REGISTERED with AS
        
        Authentication Process
        
        Principal wants to access service logs onto KDC through network
        
        KDC confirms Principal in DB and AS issues TGT (contains TG key)
        
        Principal issues TGT to TGS
        
        TGS issues TICKET FOR SERVICE and SESSION KEY
        
        An TIMESTAMP associated to request is created and encrypted onto the SESSION KEY. This is known as the AUTHENTICATOR
        
        The Authenticator is then used to eastablish a session key for secure communication
        
        Characteristics
        
        Secure - Prevent eavesdropping, impersonation, replay
        
        Reliable - AS built on robust hw/sw so AS does not fail
        
        Being Centralised
        
        Transparent - User not aware of process taking place
        .
        Advantages
        
        KDC allows use of temporary short lived keys.
        
        KDC does not automaticlly trust. Should prove id through third party
        .
        Disadvantages
        
        KDC becomes performance bottleneck
        
        Need for Protocol
      - CHAP (Challenge Hansdshake Authentication Protocol)
        
        An AUTHENTICATION AGENT sends client program a RANDOM VALUE that is used ONCE and ID value.
        
        Both share a PREDEFINED SECRET.
        
        Peer CONCATENATES random value, ID and secret and calculates one way HASH using MD5.
        
        HASH value sent to AUTHENTICATOR, which builds same string and performs hashing.
        
        Values are compared. If match peer is authenticated.
        .
        By transmitting only Hash, the secret cannot be reverse-engineered. The ID value is increased with each CHAP dialogue to protect against replay attacks
      - Username/Password
        Client sends his username and password which are then compared through all record lists of username/password pairs in database.
      - Certificates
        require CA which are used to create DIGITAL CERTIFICATES used for digital SIGNATURES, MUTUAL IDENTIFICATION, and VERIFICATION
        .
        It is a Password protected and encrypted file that HOLDS an individual's IDENTIFICATION INFO, including a PUBLIC AND PRIVATE KEY.
        Public key used to verify sender's digital signature
        Private key allows individual to log onto third party authority who administers digital certificates
      - Tokens
        Hardware Software components used to GENERATE RANDOM PASSCODES to further secure authentication process
        .
        User enters password then gets random ID that can be used to log into network. Change every 5 minutes
      - Multi- Factor Authentication
        Use of one or more type of authentication to strengthen process such as requiring card and PIN together
        .
        Pros
        Additional check-points to service leads to greater security
        .
        Cons
        Complexity of system increases which may cause inconvenience to users.
      - Mutual Authentication
        using various methods to verify both parties to transaction
        .
        Example:
        Use of Digital Certificates
        Use of Diffie-HellMan key