Weak Keys Remain Widespread in Network Devices

In 2012, two academic groups reported having computed the RSA private keys for 0.5% of HTTPS hosts on the internet, and traced the underlying issue to widespread random number generation failures on networked devices. The vulnerability was reported to dozens of vendors, several of whom responded with security advisories, and the Linux kernel was patched to fix a boottime entropy hole that contributed to the failures.

In this paper, we measure the actions taken by vendors and end users over time in response to the original disclosure. We analyzed public internet-wide TLS scans performed between July 2010 and May 2016 and extracted 81 million distinct RSA keys. We then computed the pairwise common divisors for the entire set in order to factor over 313,000 keys vulnerable to the aw, and fingerprinted implementations to study patching behavior over time across vendors. We find that many vendors appear to have never produced a patch, and observed little to no patching behavior by end users of affected devices. The number of vulnerable hosts increased in the years after notification and public disclosure, and several newly vulnerable implementations have appeared since 2012. Vendor notification, positive vendor responses, and even vendor-produced public security advisories appear to have little correlation with end-user security.