by Dan Goodin
For a more detailed analysis of this catastrophic bug, see this update, which went live about 18 hours after Ars published this initial post.
Researchers have discovered an extremely critical defect in the cryptographic software library an estimated two-thirds of Web servers use to identify themselves to end users and prevent the eavesdropping of passwords, banking credentials, and other sensitive data.
The warning about the bug in OpenSSL coincided with the release of version 1.0.1g of the open-source program, which is the default cryptographic library used in the Apache and nginx Web server applications, as well as a wide variety of operating systems and e-mail and instant-messaging clients. The bug, which has resided in production versions of OpenSSL for more than two years, could make it possible for people to recover the private encryption key at the heart of the digital certificates used to authenticate Internet servers and to encrypt data traveling between them and end users. Attacks leave no traces in server logs, so there’s no way of knowing if the bug has been actively exploited. Still, the risk is extraordinary, given the ability to disclose keys, passwords, and other credentials that could be used in future compromises.
“Bugs in single software or library come and go and are fixed by new versions,” the researchers who discovered the vulnerability wrote in a blog post published Monday. “However this bug has left a large amount of private keys and other secrets exposed to the Internet. Considering the long exposure, ease of exploitations and attacks leaving no trace this exposure should be taken seriously.”
The researchers, who work at Google and software security firm Codenomicon, said even after vulnerable websites install the OpenSSL patch, they may still remain vulnerable to attacks. The risk stems from the possibility that attackers already exploited the vulnerability to recover the private key of the digital certificate, passwords used to administer the sites, or authentication cookies and similar credentials used to validate users to restricted parts of a website. Fully recovering from the two-year-long vulnerability may also require revoking any exposed keys, reissuing new keys, and invalidating all session keys and session cookies. Members of the Tor anonymity project have a brief write-up of the bug here, and a this analysis provides useful technical details.
OpenSSL is by far the Internet’s most popular open-source cryptographic library and TLS implementation. It is the default encryption engine for Apache, nginx, which according to Netcraft runs 66 percent of websites. OpenSSL also ships in a wide variety of operating systems and applications, including the Debian Wheezy, Ubuntu, CENTOS, Fedora, OpenBSD, FreeBSD, and OpenSUSE distributions of Linux. The missing bounds check in the handling of the Transport Layer Security (TLS) heartbeat extension affects OpenSSL 1.0.1 through 1.0.1f.