[SNMP4J] SecureRandom freezes JVM

[Philip Yarra]

I think this will be because by default, Java will get entropy data from 
/dev/random, which blocks until data is available. We had a similar issue on 
an extremely busy system, where the pool would be emptied faster than it 
could be filled... after a while, Java simply stopped. In your case, maybe 
there is some problem with /dev/random?

In any case, the simple workaround is to use /dev/urandom, which is 
non-blocking. Hopefully /dev/urandom is okay too. See 
http://forum.java.sun.com/thread.jspa?threadID=230198&messageID=820456 for 
more detail. Note that other utilities (ssl, ssh, etc) will also rely on 
/dev/random, so the best course might be to make sure that /dev/random works 
properly.

I'd be interested to hear the resolution of this.

Regards, Philip.

On Tue, 25 Jan 2005 01:05 am, Sasa Markovic wrote:
> Hi.
>
> Did anyone get into problems with the org.snmp4j.security.Salt class?
>
> Basically, I had no problems with SNMP4J on any platform until I tried
> to port my application to a Gentoo Linux box (Linux collector
> 2.6.9-gentoo-r13 #1 SMP Sat Jan 8 21:54:05 CET 2005 i686 Intel(R)
> Xeon(TM) CPU 2.40GHz GenuineIntel GNU/Linux). Apparently, my JVM freezes
> somewhere in the Snmp() constructor. All JVM versions are affected (1.4,
> 1.5).
>
> I had a hard time trying to locate the "freezing point" in the SNMP4J
> source code. Well, I am quite sure that it happens on the next two lines
> of the Salt class:
>
> ...
> SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
> sr.nextBytes(rnd);   <------- THIS LINE FREEZES JVM
> ...
>
> Ok, it's easy to skip these two lines and force code to work. I am just
> curious why this happens. Any ideas?
>
> Greetings,
> Sasa Markovic.
>
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