On May 13th, 2008 the Debian project announced that Luciano Bello found an interesting vulnerability in the OpenSSL package they were distributing. The bug in question was caused by the removal of the following line of code from md_rand.c
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These lines were removed because they caused the Valgrind and Purify tools to produce warnings about the use of uninitialized data in any code that was linked to OpenSSL. You can see one such report to the OpenSSL team here. Removing this code has the side effect of crippling the seeding process for the OpenSSL PRNG. Instead of mixing in random data for the initial seed, the only “random” value that was used was the current process ID. On the Linux platform, the default maximum process ID is 32,768, resulting in a very small number of seed values being used for all PRNG operations.
Debian OpenSSL Predictable PRNG Toys. Wow, this is huge, both in terms of level of embarrassment for affected Linux vendors and (more importantly) potential impact to their customers. Even I’m a little embarrassed about only having learned of this so long after the announcement, but that’s (partly) because I don’t personally run any Linux boxes these days.