CSEC 701 VPN

VPN

an encrypted connection between private networks over a public network such as the internet (tunnel )

IPSec

a protocol suite developed by the IETF for securing IP communications by authenticating and encrypting each IP packet (used to deploy VPN)

IPSec benefits

network level peer authentication, data origin authenticity, data integrity, data confidentiality, replay protection

Where is IPSec in the stack

in network layer, is transparent to applications, header increases IP packet size beyond original MTU

IPSec headers

contains information on the VPN link and the packet, network layer protocol on top of another network layer protocol(IP), includes AH & ESP

IPSec modes

methods of transportation of user data, transport vs tunnel mode

IPSec IKE

mutual authentication, establish shared symmetric key, two phases

authentication header AH

data integrity, origin authentication, anti-replay (with sequence number), NO encryption

data integrity

no modification of data in transit, integrity check value (ICV) via HMAC, protects everything beyond IP header and some fields of IP header

origin authentication 

ensures packets definitely came from the peer

encapsulated security payload ESP

Encryption, confidentiality, integrity, with optional authentication (it does AH’s job)

confidentiality

all of the data and info above the network layer is encrypted

integrity

protects everything beyond IP header

authentication

make sure packet came from peer and not attacker by using a shared secret key (keyed hash)

keyed hash

uses MD5 and SHA-1

anti-replay protection

sequence number and sliding window

sequence number (32-bit)

if sequence number hits 2³², the system must rekey (no reuse)

sliding window 

packets are accepted when its sequence number falls within a window of sequence numbers, and MAC is ok

transport mode

encapsulates only the payload of the IP packets, leaving the header untouched; authenticates two connected computers, has an option to encrypt data transfer , between TWO hosts (1 IP header, then TCP/UDP header), end-to-end security between hosts, MORE efficient 

tunnel mode

encapsulates both the payload and the header, between VPN gateways, has an option to encrypt data transfer, applied to an IP tunnel (outer and inner), site-to-site, IPsec server at each site, no security within local networks

outer IP header

IPSec processing destination

inner IP header

ultimate packet destination

IKE

Ipsec protocol that produces security keys and other protocols, mutual authentication + session key establishment; hybrid protocol, works on UDP port 500

ISAKMP

established cryptographic keys and security associates 

oakley

a key agreement protocol, which uses DH algorithm to create master key, and a key that is specific to each session, uses nonces to protect against replay attacks

DH vulnerable to DoS attack

attacker, spoofing multiple source addresses, gets victims to do numerous Dh exponentiations, clogging the victim

cookie

first perform cookie exchange before exponentiating, A sends B some random data and B retruns it, similarly B sends A random data and A retruns it, if ACK comes back then perform exponentiation 

IKE phase 1

secure, mututally authenticated connection is established, creates session keys for encrypting IKE phase 2 messages, establishes IKE SA (expensive)

IKE phase 2

the security services and details for an SA are negotiated, can occur multiple times, establishes IPsec SA (simple)

SA lifetime

for good security, SA and keys should be changed periodically 

lifetime type

measures in number of bytes transmitted or amount of time

SA unit of measure

kilobytes or seconds

what happens when SA time expires 

Ipsec recognizes the upcoming expiration and reestablish new SA in advance to avoid disruption 

openVPN

creates secure point-to-point or site-to-site connections, authentication with pre-shared secret keys, certifications or passwords; encryption using OpenSSL and TLS protocol

wireguard

free and open source software applications and communication protocol to create secure tunnel

SSL

uses X.509 digital certificates for authentication, there is no trust hierarchy so browers are preloaded with certificates of trusted CAs, pop-up window of unauthorized sugnature 

SSL architecture

SSL handshake protocol, SSL change cipher spec protocol, SSL alert protocol, applications; then SSL record protocl; TCP; IP

SSL handshake protocol

initializes communication between client and server, needs symmetric keys (MAC, encryption, and IV at record layer), negotiates the protocols to be used for authentication and encryption (28 byte pre- and master secret)

SSL change cipher spec protocol

initializes secure communication  

SSL alert protocol

error notifications

SSL record protocol

fragmentation, compression, MAC, encryption

SSL client hello message

client_version, client_random, session_id, cipher_suites

SSL server hello message

server_version, server_random, session_id, cipher_suite

cipher suite

= key exchange algorithm + cipherSpec

key exchange method

RSA, fixed DH, ephemeral DH, anonymous DH, fortezza

cipher suite names

2 bytes, human readable names by concatenation of choices