Security Protocols: IPSec and SSL

Security Protocols

• The purpose is, to present the different protocols that make secure information exchange possible over the Internet
• All protocols share a strong cryptographic base

Security Services

• Security protocols provide confidentiality by making information unintelligible to attackers
• Authentication of the message sender/receiver is for identity verification
• Endpoint authentication become especially important with the rise of e-commerce
• It is important to ensure the message sender/receiver is who they claim to be to prevent phishing or bank fraud

Secure Communication

• Multiple protocols utilize cryptographic algorithms
• Protocols in use: IPSec and SSL

Introduction to IPSec

• IPSec [RFC4301] incorporates appropriate security services at the network level
• Objective: to provide confidentiality, integrity, and authentication to communications
• IPSec use is optional in IPv4
• IPsec was mandatory in early IPv6 versions
• IPsec is now optional for specific cases

Security Association

• A Security Association (SA) describes how two or more entities use security services for secure communication
• In this agreement, aspects such as encryption algorithms, association duration, and authentication methods are established
• Security protocols require parameter negotiation for proper implementation
• Security association is the fundamental negotiation unit for specifying security service details

IP Security Architecture

• The IP security architecture considers two protocols

Authentication Header Protocol AH

• The authentication header [RFC4302] provides integrity and authentication to IP datagrams
• The receiver of the message can detect if it was tampered with
• The receiver can detect if the author is who they claim to be

Encapsulating Security Payload ESP

• Encapsulating Security Payload [RFC 4303] adds confidentiality to IP datagrams
• Guarantees that encrypted information is only accessible to authorized entities

Authentication Header

• It provides authentication and integrity mechanisms to IP datagrams
• Authentication data is placed after the original IP datagram header
• Systems not participating in authentication can ignore the data and route packets accordingly
• Communication performance decreases on sender and receiver sides
• Each IP datagram containing an AH header requires verification
• Authentication data is calculated over the entire packet
• The exception is : IP Header fields modified during transit, such as TTL
• Communication endpoints have to agree on secure communication characteristics
• Security associations are unidirectional i.e. for each communication direction between endpoints

Authentication Header Format

• Next Header specifies the type of header that follows
• Payload Length indicates the header size in 32-bit words
• Reserved is space reserved for future use
• Security Parameter Index (SPI) is a 32-bit pseudo-random number
• SPI identifies a specific Security Association (SA)
• SPI, combined with the destination IP address and security protocol (AH), uniquely identifies the security association for the datagram
• Sequence Number prevents replay attacks
• Authentication Data carries the authentication code of the following content
• A keyed hash function algorithm is used for authentication

Sender obligations

• The sender must identify the appropriate security association
• The security association indicates the algorithm, key, and other necessary security parameters
• The sender calculates the authentication information and places it in header AH, then sends the packet to its destination

Encapsulation Security Payload

• Facilitates a mechanism to provide end-to-end service confidentiality in the network layer (IP level)
• ESP contributes to integrity and authentication that was provided by the AH header
• Encryption of data enables this
• In case only a specific security service is wanted the protocol supports encryption-only and authentication-only
• Both communication endpoints have to agree on communication security characteristics

ESP header format

• Includes a security parameter index (SPI)
• A sequence number that prevents against replay attacks
• Encrypted Data and Parameters contain an initialization vector field

Authentication Data

• A value that allows for authentication and ESP integrity verification
• This control includes the ESP trailer, ESP payload, and ESP header
• Authentication Data does not consider the IP header or its Authentication Data field

ISAKMP and IKE Protocols

• The Internet Security Association and Key Management Protocol (ISAKMP) was the initial protocol
• The ISAKMP protocol describes a secure negotiation framework for developing security protocols
• Intention: strengthen security associations in the IPSec architecture
• ISAKMP defines procedures and packet formats for establishing, negotiating, modifying, and deleting security associations
• Internet Key Exchange (IKE) is now the primary standard. The IETF has released an improved version, IKEv2, outlined in RFC4306 and RFC4307 standards

Secure Channel Creation

• The IKE protocol serves as a preliminary agreement and negotiation element between IPSec endpoints
• Both ends have security components for setting up a secure channel
• Once set up, the flow of data across the internet is protected
• IKE is a two-phase protocol

IKE Phase 1.

• Both endpoints establish a session key called: IKE session key, SA ISAKMP
• Endpoints authenticate each other
• Details of communication can be seen in:
  • Negotiation of IKE parameters
  • Exchange of cryptographic material using Diffie-Hellman key agreement algorithms
  • Derivation of IKE session keys from an established master secret of cryptographic material
  • Mutual authentication of endpoints

IKE Phase 1 Modes of Operation

• Main mode:
  • Requires protected identification of both parties
  • Is a safer method
• Aggressive :
  • Bypasses the identification step
  • Is unadvised for critical events

IKE Phase 2

• Establishes a new security association negotiation
• Done with full guarantees after Phase 1 is complete
• Security key secures the communication

Phase 2 processes

• Suggestion-selection of security attributes
• Exchange of cryptographic data to derive a new key
• Continual renegotiation of IPSec security association

Quick Mode Phase 2

• Authentication does not take place as entities were already authenticated in the prior phase
• Once the secure IPSec channel is established, data traffic is safely transmitted over the Internet

IPSec Modes

• IPsec is for establishing a secure channel between two gateways or two hosts
• There are 2 modes

Tunnel Mode in IPSec

• Tunneling is not only exclusive to IPSec, various stack levels, and multiple different mechanisms can implement it
• Tunnel mode provides a method for securing an entire network area
• It makes sure that devices securing the communication are not the final sending/receiving devices
• Primarily used in a VPN implementation
• IP packet is encapsulated with headers

Transport Mode in IPSec

• Preserves the transport layer header
• IPSec AH and ESP protocols intercept packets flowing from the transport layer to the network layer
• The addition of AH and/or ESP headers happens after the TCP or UDP packet passes from the transport to the network layer
• Used when point-to-point communication needs to be ensured

SSL/TLS

• Secure Socket Layer (SSL) created by Netscape
• Version 1.0 was not published
• Version 2.0 was published in 1995
• Version 2.0 contained several security holes, and was replaced by version 3.0 in 1996
• Later, the Internet Engineering Task Force (IETF) formed a working group to standardize the protocol

IETF Improvements

• In 1999 the IETF working group introduced some improvements to SSLv3
• These changes led to the first version of the Transport Layer Security (TLS) protocol, labeled as SSL version 3.1
• TLS has versions 1.0, 1.1, 1.2, and 1.3
• Current recommended versions are 1.2 and 1.3

SSL Architeture

• SSL provides authentication, integrity, and message confidentiality via cryptographic mechanisms
• Typically, the server is authenticated, and this authentication establishes a confidential channel while the client remains unauthenticated
• SSL provides for mutual authentications to provide authentication options
• Authentication options appear in smaller apps or environments with few users
• A public key infrastructure is required for internet-scale operation
• Anonymous cryptographic algorithms can be used, allowing the server to remain unauthenticated

SSL Key Phases

• Includes server authentication, client authentication and data integrity and confidentiality

Server Authentication

• The server's public key is sent in the X.509 certificate when the connection is established
• Digital signature
• Users should validate the server certificate
• SSL-enabled websites generally have their certificates signed by valid certificate authorities

Data Integrity and Confidentiality

• Once the user receives the server's public key
• The user employs this to securely send cryptographic data for the session key

User Authentication

• Digital signature is generated by the user using the private key
• The digital signature sends the public key through a X.509 certificate
• The option necessitates that the web server has to validate the certificate
• It is helpful in systems where only a few users are being authenticated for their site

SSL Protocols

• Session protocols and connection protocols are outlined in the official SSL formatting protocol

Secure Sessions

• Created by the handshake protocol by way of client/server communication
• Establishing cryptographic security parameters for multiple connections
• Every session includes: a session identifier, a peer entity certificate such as X.509, an optional compression method, and 48 bit master keys
• The cipher specification includes symmetric cipher, MAC algorithm for authentication code calculations, and key size and session resumption

Connections

• A transport providing a service associated with a session
• A connection is associated with random values shared between client and server, and secret keys

SSL Protocols Two Layers

• SSL is a two-layer protocol supported in TCP
• SSL is between Application and transport layers
• Transport layers like HTTP, FTP, and POP3 employ SSL methods for transaction security
• SSL Record Protocol is in the first layer and applies SSL to encode higher-level processes
• A second layer includes SSL protocols, primarily the Handshake protocol. Then followed by client-server authentication and cryptography tools

Change Cipher Spec Protocol

• Informs an external connection that it can begin using material created during protocol execution

SSL Record Protocol

• Ensures confidentiality, integrity, and encryption of the connection using a generated shared key
• A message from an application is taken to transmit along is ciphered and assigned a MAC and undergoes encryption
• Finalized TCP segments are transmitted back

SSL Handshake Protocol

• Authenticates server and client
• Negotiates encryption algorithms
• Computes MAC keys and symmetrical keys to protect the data that is then being sent through the SSL Record

Composed of a string of client-server messages including three parameters

• Type is for one of the 10 potential forms that a message can take
• Length delineates the length of the number of bytes contained in the message
• Content contains linked parameters within the message

Series of Messages Between Server and Client

• The handshake is separate and can be put into either 4 phases as such
• The first phase deals with capabilities of each end
• Second is authentication
• Third is the exchange of the established keys

Handshake Protocol

• Clients and servers utilize Hello messages to exchange transport methods
• Then a random number code is assigned, session ID, and the coding algorithms
• This will dictate how a SSL will interact with various tasks

Change Cipher Specifications

• Is the last function
• Data transfer and negotiation

Datagram TLS (DTLS) Protocols

• DTLS a TLS protocol extension and gives the exact same safety
• DTLS offers these functions over UDP
• Characteristics
  • A connectionless key exchange done with a single UDP

TCP

• A need to implement controls using TCP connections
• Trust and control over retransmission

Security

• Confidentiality
• Message and integrity control
• Limitations for oversite

Keys

• Logs will not fragment
• Encryption mode

Cookies

• Prevents denial of service attacks from taking effect.