Интернет протоколы: IKE және IPsec қауіпсіздігі

Internet protocol
In computing, Internet Key Exchange (IKE, versioned as IKEv1 and IKEv2) is the protocol used to set up a security association (SA) in the IPsec protocol suite. IKE builds upon the Oakley protocol and ISAKMP. IKE uses X.509 certificates for authentication ‒ either pre shared or distributed using DNS (preferably with DNSSEC) ‒ and a Diffie–Hellman key exchange to set up a shared session secret from which cryptographic keys are derived. In addition, a security policy for every peer which will connect must be manually maintained. defined the Internet Security Association and Key Management Protocol (ISAKMP). defined the Internet Key Exchange (IKE). updated IKE to version two (IKEv2) in December 2005. clarified some open details in October 2006. combined these two documents plus additional clarifications into the updated IKEv2, published in September 2010. A later update upgraded the document from Proposed Standard to Internet Standard, published as in October 2014. The parent organization of the IETF, the Internet Society (ISOC), has maintained the copyrights of these standards as freely available to the Internet community.

Most IPsec implementations consist of an IKE daemon that runs in user space and an IPsec stack in the kernel that processes the actual IP packets. User space daemons have easy access to mass storage containing configuration information, such as the IPsec endpoint addresses, keys and certificates, as required. Kernel modules, on the other hand, can process packets efficiently and with minimum overhead—which is important for performance reasons. The IKE protocol uses UDP packets, usually on port 500, and generally requires 4–6 packets with 2–3 round trips to create an ISAKMP security association (SA) on both sides. The negotiated key material is then given to the IPsec stack. For instance, this could be an AES key, information identifying the IP endpoints and ports that are to be protected, as well as what type of IPsec tunnel has been created. The IPsec stack, in turn, intercepts the relevant IP packets if and where appropriate and performs encryption/decryption as required. Implementations vary on how the interception of the packets is done—for example, some use virtual devices, others take a slice out of the firewall, etc. IKEv1 consists of two phases: phase 1 and phase 2.

Leaked NSA presentations released in 2014 by Der Spiegel indicate that IKE is being exploited in an unknown manner to decrypt IPsec traffic, as is ISAKMP. The researchers who discovered the Logjam attack state that breaking a 1024 bit Diffie–Hellman group would break 66% of VPN servers, 18% of the top million HTTPS domains, and 26% of SSH servers, which the researchers claim is consistent with the leaks. This claim was refuted in 2015 by both Eyal Ronen and Adi Shamir in their paper "Critical Review of Imperfect Forward Secrecy" and by Paul Wouters of Libreswan in a 2015 article "66% of VPN’s are not in fact broken"

IPsec VPN configurations which allow for negotiation of multiple configurations are subject to MITM based downgrade attacks between the offered configurations, with both IKEv1 and IKEv2. This can be avoided by careful segregation of client systems onto multiple service access points with stricter configurations. Both versions of the IKE standard are susceptible to an offline dictionary attack when a low entropy password is used. For the IKEv1 this is true for main mode and aggressive mode.