Bug 1025554

Summary:	generating keys using dnssec-keygen is very slow
Product:	[Fedora] Fedora	Reporter:	Jan Včelák <jv+fedora>
Component:	openssl	Assignee:	Tomas Mraz <tmraz>
Status:	CLOSED NOTABUG	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	19	CC:	tmraz
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Fixed In Version:		Doc Type:	Bug Fix
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Last Closed:	2013-11-01 09:35:39 UTC	Type:	Bug
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
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Description Jan Včelák 2013-10-31 21:24:22 UTC

Description of problem:

Generating of RSASHA1 keys is very slow since openssl upgrade.

It seems that last working version is openssl-1.0.1e-4.fc19.1.x86_64


Version-Release number of selected component (if applicable):
openssl-1.0.1e-30.fc19


How reproducible:
always


Steps to Reproduce:
1. dnssec-keygen example.com
2.
3.

Actual results:
It takes minutes to generate the key.


Expected results:
It takes less than a second to generate the key.


Additional info:

Comment 1 Tomas Mraz 2013-11-01 09:35:39 UTC

This is actually a fixed bug. dnssec-keygen changes RNG in OpenSSL so it reads random numbers directly from /dev/random. There was a bug in the old openssl builds that made OpenSSL to ignore the RNG engine modification.

You can use -r /dev/urandom to speed the key generation up.

Comment 2 Jan Včelák 2013-11-01 09:53:00 UTC

I see. Does it mean that /dev/urandom was used before the fix? Are the keys generated before less secure?

Comment 3 Tomas Mraz 2013-11-01 10:09:11 UTC

Yes, to the first question. To the second question - theoretically they are less secure, but in practice this is not a real problem unless you generate the keys on a machine that has almost no entropy source and do it immediately after installation. As there always is at least some entropy source and the previous RNG state is saved and reloaded on reboot the keys generated after some time of the machine running after installation should be secure enough.

Note that for example ssh-keygen uses the /dev/urandom as well.

Using /dev/random is in general not recommended unless you have a fast entropy source - possibly hardware one. And even more the dnssec-keygen does it in a wrong way because it reads much more random bytes than necessary from the /dev/random.

Comment 4 Jan Včelák 2013-11-01 12:57:32 UTC

Great explanation. Thank you! I'm fine with that.