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https://issues.apache.org/jira/browse/KAFKA-4050?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15423354#comment-15423354
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Ismael Juma commented on KAFKA-4050:
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Nice find. :)
> Allow configuration of the PRNG used for SSL
> --------------------------------------------
>
> Key: KAFKA-4050
> URL: https://issues.apache.org/jira/browse/KAFKA-4050
> Project: Kafka
> Issue Type: Improvement
> Components: security
> Affects Versions: 0.10.0.1
> Reporter: Todd Palino
> Assignee: Todd Palino
> Labels: security, ssl
>
> This change will make the pseudo-random number generator (PRNG)
> implementation used by the SSLContext configurable. The configuration is not
> required, and the default is to use whatever the default PRNG for the JDK/JRE
> is. Providing a string, such as "SHA1PRNG", will cause that specific
> SecureRandom implementation to get passed to the SSLContext.
> When enabling inter-broker SSL in our certification cluster, we observed
> severe performance issues. For reference, this cluster can take up to 600
> MB/sec of inbound produce traffic over SSL, with RF=2, before it gets close
> to saturation, and the mirror maker normally produces about 400 MB/sec
> (unless it is lagging). When we enabled inter-broker SSL, we saw persistent
> replication problems in the cluster at any inbound rate of more than about 6
> or 7 MB/sec per-broker. This was narrowed down to all the network threads
> blocking on a single lock in the SecureRandom code.
> It turns out that the default PRNG implementation on Linux is NativePRNG.
> This uses randomness from /dev/urandom (which, by itself, is a non-blocking
> read) and mixes it with randomness from SHA1. The problem is that the entire
> application shares a single SecureRandom instance, and NativePRNG has a
> global lock within the implNextBytes method. Switching to another
> implementation (SHA1PRNG, which has better performance characteristics and is
> still considered secure) completely eliminated the bottleneck and allowed the
> cluster to work properly at saturation.
> The SSLContext initialization has an optional argument to provide a
> SecureRandom instance, which the code currently sets to null. This change
> creates a new config to specify an implementation, and instantiates that and
> passes it to SSLContext if provided. This will also let someone select a
> stronger source of randomness (obviously at a performance cost) if desired.
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