Heartburn over Heartbleed: OpenSSL memory leak burns slowly

CHELMSFORD, USA: A very serious vulnerability present in OpenSSL 1.0.1 for two years has been disclosed (CVE-2014-0160). This "Heartbleed" vulnerability allows an attacker to reveal up to 64kb of memory to a connected client or server.

This buffer-over-read vulnerability can be used in rapid succession to exfiltration larger sections of memory, potentially exposing private keys, usernames and passwords, cookies, session tokens, email, or any other data that resides in the affected memory region. This flaw does not affect versions of OpenSSL prior to 1.0.1.

This is an extremely serious situation, which highlights the manual nature of the tasks required to secure critical Internet services such as basic encryption and privacy protection.

As the vulnerability has been present for over two years, many modern operating systems and applications have deployed vulnerable versions of OpenSSL. OpenSSL is the default cryptographic library for Apache and nginx Web server applications, which together account for an estimated two-thirds of all Web servers.

OpenSSL is also used in a variety of operating systems, including BSD variants such as FreeBSD, and Linux distributions such as Ubuntu, CENTOS, Fedora and more. Other networking gear such as load-balancers, reverse proxies, VPN concentrators, and various types of embedded devices are also potentially vulnerable if they rely on OpenSSL, which many do.

Additionally, since the vulnerability's disclosure, several high-profile sites such as Yahoo Mail, Lastpass, and the main FBI site have reportedly leaked information. Others have discussed the impact on underground economy crime forums, which were reportedly vulnerable to the matter and were attacked.

A key lesson is that OpenSSL, which is a vital component of the confidentiality and integrity of uncounted systems, applications and sites across the Internet, is an underfunded, volunteer-run project, which is desperately in need of major sponsorship and attendant allocation of resources.

Mitigation

Anyone running OpenSSL on a server should upgrade to version 1.0.1g. For earlier versions, re-compiling with the OPENSSL_NO_HEARTBEATS flag enabled will mitigate this vulnerability. For OpenSSL 1.0.2, the vulnerability will be fixed in 1.0.2-beta2. In terms of remediation, there's a huge amount of work that must be done, not only for servers, but also for load-balancers, reverse proxies, VPN concentrators, various types of embedded devices, etc.

Applications which were statically compiled against vulnerable versions of the underlying OpenSSL libraries must be re-complied; private keys must be invalidated, re-generated, and re-issued; certificates must be invalidated, re-generated, and re-issued - and there are a whole host of problems and operational challenges associated with these vital procedures.

Some systems may be difficult to patch, so network access control restrictions or the deployment of non-vulnerable proxies may be considered where possible to reduce the attack surface.

Exploitation

In most cases, exploitation of this vulnerability leaves no sign in server logs, making it difficult for organizations to know if they have been compromised. In addition, even after applying the OpenSSL patch, private keys, passwords, authentication credentials or any other data that was stored in heap memory used by OpenSSL may have already been compromised by attackers, potentially going as far back as two years.

Of significant concern is the compromise of private key material, and one security organization reported that they were able to obtain this material during testing. Others reported difficulty in obtaining certificate material but were able to discover significant amounts of other sensitive data.

Considering how easy it is for attackers to hammer this vulnerability over and over again in a very quick sequence, the amount of memory being disclosed can be quite substantial. Memory contents will vary depending on program state and controlling what is returned and what position in memory the contents are read from is much like a game of roulette.

Risk to private key material

Security researchers in a Twitter exchange starting on April 8 2014 indicate that private keys have been extracted in testing scenarios, and other researchers suggest that attacking the servers during or just after log rotation and restart scripts run could expose private key material. This allegation has not been tested by ASERT.

The authors are with Arbor Networks, USA.