1. IPsec Problems and Solutions
This presentation is about the problems and their solutions related to IPsec protocol
Yasir Jan
Future Internet
29th May, 2008

2. Contents Definition Architecture Types Modes of Operation Key Exchange
Multiple Options
IPsec problems and solutions
Summary
References
These are the contents of the presentation

3. IPsec Definition
IP security refers to security mechanisms implemented at the IP (Internet Protocol) Layer to ensure integrity, authentication and confidentiality of data during transmission in the open Internet environment.
IP security is basically a secure method of transmission through internet
Fig: Security

4. IPsec Architecture Types
Authentication Header
Integrity + Authentication
Encapsulating Security Payload
Integrity + Authentication + Confidentiality
The are two types of architectures related to IPsec.
One is Authentication header and other is Encapsulating security payload.
AH provides us the functionality of Integrity and authentication of data. While ESP provides us Confidentiality of the data along with Integrity and Authentication.
Authentication Header
Encapsulating Security Payload
Integrity
Authentication
Integrity
Authentication
Confidentiality
Fig: AH and ESP comparison

5. IPsec Modes of Operation
Transport Mode
Only payload of the IP packet is encrypted and/or authenticated.
Tunnel Mode
Entire IP packet (data plus the message headers) is encrypted and/or authenticated
There are two modes of operation in IPsec.
One is Transport mode, and other is Tunnel mode.
Transport mode does not include the header, while tunnel mode covers the header part as well for authentication and encryption.
AH Transport mode IP
Header AH
Header
Upper Protocol Headers
and Packet Data
AH Tunnel mode
New IP
Header
Old IP AH
Upper Protocol Headers
and Packet Data
ESP Transport mode IP
Header
ESP
Header
Upper Protocol Headers
and Packet Data
ESP Tunnel mode
New IP
Header
ESP
Header
Old IP
Header
Upper Protocol Headers
and Packet Data
Fig: Modes of operation

6. IPsec Key Exchange
IPsec Key Exchange Protocol is a combination of many protocols
ISAKMP is a generic protocol
OAKLEY is a specific mechanism using various modes. Most of IKE is done using OAKLEY
SKEME provides features of public key encryption and fast re-keying feature
IKEv2 also concerns protection against denial-of-service attacks using spoofed packets
The devices are able to use facilities of IPsecurity, because of their shared keys.
The key exchange protocol is a combination of many protocols, which include ISAKMP, OAKLEY and SKEME. The new version IKEv2 provides extra protection.
Fig: Key exchange

7. IPsec Multiple options
Use any Authentication method
Cryptographic hash algorithms such as MD5 or SHA-1, or Hashed Message Authentication Code (HMAC)
Use any Encryption Schemes
Data Encryption Standard (DES), triple-DES, Advanced Encryption Standard (AES), and Blowfish in common use
Use any protocols in IKE
IPsec provides too much flexibility related to selection of authentication methods and encryption schemes.
Different levels of authentication may be used for different types of networks.
Fig: Many options

8. IPsec problems and solutions
1) Key Management in Large Networks
When IPsec is largely developed, key management becomes very difficult
2) Difficult Traffic analysis
Cannot check and process flags at intermediate devices because of encryptions
IP security becomes a big problem when networks become big. The key management becomes difficult as well as setting the policies is also difficult.
Traffic analysis becomes difficult, because cannot check and process flags during the transmission. The packets are encrypted and secured.
Fig: Big Networks

9. IPsec problems and solutions
3) Resource Consumption
Encryption decryption processes are computational intensive
Cisco designed VPN accelerator card to handle computation separately
4) Too much flexibility
Unnecessary multiple options available for choosing algorithms and modes
Solution: Reduced flexibility is sometimes better (Remove AH)
3) IPsec is computational intensive and so consume the processing resources a lot. Cisco has designed a separate card to do the computation separately.
4) IPsec has too much options available. It should combine the activities of two or more modes into one single mode. Like Authentication is also provided by ESP, so AH should be removed completely. And so a common set of algorithms should be used. IT is also helpful for multiple vendors compativbility.
Fig: Consume many resources

10. IPsec problems and solutions
5) Client software
IPsec is not implemented in TCP/IP stack, needs a client installed
Danger of installing malicious unreliable software by a user
Solution: Install clients from reliable sources
6) Relayed ICMP messages
ICMP inner data is revealed to attacker, so it can be intercepted
Using ICMP header information IPsec packets could be redirected, in some cases, or error messages can be generated [1]
Solution: Use ESP along with AH
5) Users may install malicious client software which may monitor all IP secured data.
6) An attacker can modify sections of the IPsec packet, causing either the clear text inner packet to be redirected or a network host to generate an error message
We can also avoid it by removing the error reporting by restricting the generation of ICMP messages or by filtering these messages at a firewall or security gateway
Also a combination of both AH and ESP should be used.
Fig: Malicious Software

11. IPsec problems and solutions
7) Scrambled Group passwords recovery
IPsec passwords were first sniffed from memories, when used, so Cisco VPN clients were designed to scramble the passwords in memory, but they were hacked again
Once getting group password, an attacker can hijack a connection from a user and get other usernames and passwords
8) No End-End Protection
Applications use their own SSL or other techniques
IETF working on API integrated with IPsec to achieve maximum use
7) IPsec passwords when used for decryption purposes was present in memory, from where an attacker could read it. So design was changed to scramble the password in the memory, while keeping the original in hard drive. But now the scrambled passwords have also become vulnerable, and are descrambled.
8) Application layer securities are useful in some cases, when end to end security is required. IPsec does not provide security at all levels. A combination of both SSL and IPsec should be used for more better performance
Fig: Scrambled passwords

12. IPsec problems and solutions
9) Firewalls
firewalls monitor the ports and protocols that the traffic originates from and is designated for, to determine the traffic’s “acceptability” before allowing the traffic through
Firewall is easy to setup with the standard exceptions and any customizations you need
With IPsec you have to create rules with filter lists and actions and then add these to a policy, and then distribute them and ….
But IPsec has many good things as compared to firewalls like encryption, no bottle necks etc
9) Firewalls also provide certain level of security which IPsec doesn’t do. Both should be used in parallel for better performance.
Fig: IPsec vs firewalls

13. IPsec problems and solutions
10) VoIP Quality loss
Scheduling causes packet loss in real time applications
Latency in VoIPs
11) Denial of Service
Send too many acknowledge messages to the victim during wait period of TCP connection timeout
Solution: IKEv2 has the solution
10) Scheduling causes delay in performance. IPsec pockets are numbered and scheduled at the receiver end, which may cause latency, so sometimes the packets are dropped to achieve real time application quality.
11) Attacker may send too many messages to a victim causing its buffer to overflow and hence making it to deny all further activities. IKEv2 provides the facility of preventing denial of service.
Fig: Voice quality
and
Denial of service

14. IPsec problems and solutions
12) Multicast Traffic
Packets have single destination addresses, so difficult to mange SPI
Some applications using streaming multimedia assign port numbers dynamically, so IPsec policy becomes difficult to assign
IPsec has multicast option but is not enough for all occasions
13) Security within algorithms
IPsec works with other protocols for security. They should be secure enough to stop attacker otherwise only secure IPsec is useless
12) It is difficult to assign multicast addresses. We can do group assignments, i.e. message from certain sender is send to a group of receivers. So a group policy is assigned to specific sender address. Also a specific destination address may be assigned to multiple receivers. But in both cases the manual grouping is difficult.
13) The encryption and authentication algorithms should have enough security otherwise IPsec becomes useless
Fig: Multicast traffic

15. IPsec problems and solutions
14) Brute Force Attack
ESP initiation scheme is fixed 3 steps of Aggressive mode, so intruder may try to delay the initiation during which it will find the key by brute force attack
Crack Tool was used with Pre-Shared-Key IKE authentication [2] for guessing with brute force
14) A brute force attack will try to delay the devices temporarily and make a brute force attack to know the password. There are Crack tools available which can do so.
Fig: Trying out ALL options by brute force

16. IPsec problems and solutions
15) Incompatibility with NAT (RFC 3715)
Network Address Translation (NAT) was developed to answer the impending problems of the limit of IPv4 addresses
When NAT changes the IP addresses or ports in the IP header, IPSec cannot re-calculate the hash because it is not knowledgeable about the key and so IPsec drops the packets. In ESP the NAT device cannot access and change the port information inside the encrypted TCP headers of the packets
Solution: NAT-T (encapsulation of the IPsec part of the IP packet in yet another UDP header between the ESP portion of the packet and the original IP header. )
15) NAT and IPsec cannot go together because Nat tries to modify the address while IP tries to secure the address.
NAT-T is used which can provide compatibility by putting extra UDP header between ESP portion and original IP header
Fig: IPsec and NAT are incompatible

17. Summary IPsec has multiple components
Security and authentication is provided by additional components so they should be also secure
IPsec have some incompatibility issues
IPsec is overall complex, needs simplification
This slide shows the summary of whole presentation
Fig: Summary

18. References
Images taken from various sources on internet
These are the references
Fig: References

19. Thankyou
Thankyou for listening
Any questions, do ask.
Fig: Questions