What is exactly Heartbleed? Heartbleed vulnerability, whose official reference is CVE-2014-0160 [6], is the implementation of the Transport Layer Security heartbeat extension which possess a buffer over-read issue, in another word, a circumstance that more data can be read than permitted [7]. Attacking Mechanism In details, Heartbleed is the defect of the Heartbeat extension implemented to TLS in the year 2011. Heartbleed, with its name derived from Heartbeat, breaks the conservation of information transmitted over the networks by reducing the need for session renegotiation, which was the initiative of the implementation of that extension to TLS [5]. In a typical heart-beat protocol (without Heartbleed vulnerability), …show more content…
Normal Usage of Heartbeat) However, a Heartbleed affected Heartbeat protocol would lead to the following scenario:

(Fig 3. Heartbleed causing Malicious Usage to Heartbeat) This is because Heartbleed allows an unauthorized third party (usually an attacker) to read 64KB of memory from the server at a time, without its action being logged by the server [5]. Don’t take this 64KB data as a little piece of cake. This small chunk of memory can be, for instance, username, passwords (in most cases they are in cleartext) and even private keys. Worse more, an attacker is able to request this chunk of data again and again to get as much information as possible, until he obtains what he ultimately wants [5]. In all, Heartbleed makes the Man-In-The-Middle attack more efficient than usual. Remediation A quick and intuitive patch is to denying heartbeat request messages that ask for more data than the payload needs [7]; in version 1.0.1g of OpenSLL, some bounds checks to prevent the buffer over-read is added such as the follows: if(1+2+ payload +16> s->s3->rrec.length)return0;/* silently discard per RFC 6520 sec. 4