That's my understanding too. From a quick glance at the source it falls back onto stuff from /proc /sys. I guess there are weaker links in a system dough, but I'm also no expert.
On a side note there are the matsano crypto challanges that are pretty cool, in case you haven't heard of them, I never got to the implementing/cracking prngs dough, simply not enough time... [0] https://github.com/mkj/dropbear/blob/master/dbrandom.c#L205 http://cryptopals.com/
