The Heartbleed bug
On New Year’s Eve 2011, German researcher and OpenSSL contributor Robin Seggelmann added code implementing a new feature called “heartbeats”.
The idea was straightforward: if a connection between two computers stays silent for too long, it is disconnected, so periodic “heartbeat” messages can keep the connection going.
As well as a simple “I’m here”, messages contain a arbitrary “payload” which is sent back and forth, a little like this:
Computer 1: “Hi, I’m still here, the payload is 5 characters long and is ‘12345’.”
Computer 2: “Hi, great, you’re still there, and your payload was 5 characters long and was ‘12345’.”
Unfortunately, Seggelmann’s code didn’t check that the payload was of the indicated length, so a malicious request could request more data than was in the payload:
Computer 1: “Hi, I’m still here, the payload is 50,000 characters long and is ‘12345’.”
Computer 2 would then send back a message with a payload of the requested length, the first characters of which would be the 12345 sent. The rest would be whatever happened to be in the computer’s memory next to the payload.
The exact contents sent back varied between systems and over time. But as well as information such as user passwords or private data, it could contain something called the private master key.
With access to this key, an “attacker” can electronically impersonate the organisation who rightfully owns the key, and unscramble all the private messages sent to that organisation â€" including old ones, if they’ve kept the previously unreadable scrambled versions.
Criminals could, for instance, steal the key of a major bank and then electronically impersonate it. It’s a potential field day for spies, too.
Ref:
http://phys.org/news/2014-04-heartbleed-bug-reveals-flaw-online.html
