> On 12 Dec 2014, at 5:02, Theo de Raadt wrote:
>
> > In all of these code blocks are a well-known piece of information
> > (same time on your machine as everywhere else) is being used to seed a
> > deterministic number generator.
> >
> > At some later point, deterministic numbers are taken out using rand(),
> > random(), drand48(), lrand48(), mrand48(), or srand48(), or some
> > derivative function inside the program itself, and used for WHO KNOWS
> > WHAT PURPOSE.
> >
> > I did not audit what the numbers are being used for.
> >
> > Quite likely some numbers are just used to help hashing. Some could
> > be used to print pretty pictures. But in xulrunner? In the zip
> > password
> > creator? In postgresql, or say in openldap (a network related thing)?
> >
> > It is doubtful they are all fine.
> >
> > For the benefit of other projects who haven't taken the same steps as
> > OpenBSD, it would be nice if some people helped out these pieces of
> > software.
> >
> > EMBOSS-6.0.1 srand((unsigned) time(&tm));
> [...]
>
> What you say makes sense. Is there a best practice alternative you
> suggest or did I miss that? Perhaps just some better initiation value,
> preferably not all from the same place?
These code sequences do not need deterministic values. They actually
want non-deterministic values. Steps are like this:
1. Remove the srand(), srandom(), srand48(), seed48(),
lcong48() calls.
2. Replace all rand(), random(), lrand48(), mrand48() calls with
arc4random()
3. If the calls use %, consider using arcrandom_uniform() instead.
4. If it loops to fill a buffer, use arc4random_buf()
5. Replace drand48() with arc4random and some floating point, but
be careful. drand48() is very rare.
Now, talk to the upstream projects. They will reject your changes
because Linux lacks arc4random().
Basically, only Linux and Solaris lack arc4random(). All the other
platforms have it.
There are libraries available which provide arc4random() on Linux, so
maybe you find an upstream software provider who is willing to create
a dependency on such a library on Linux.
Lots of software is doing precisely that, so don't be afraid.
