linux-kernel - Re: [PATCH RESEND/V2] crypto: Ignore validity dates of X.509 certificates at loading/parsing time

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Message-ID: <87d2ryr7l6.fsf@rustcorp.com.au>
Date:	Fri, 07 Jun 2013 11:43:41 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Alexander Holler <holler@...oftware.de>,
	Alexander Holler <holler@...oftware.de>
Cc:	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>,
	David Howells <dhowells@...hat.com>,
	Josh Boyer <jwboyer@...hat.com>,
	David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH  RESEND/V2] crypto: Ignore validity dates of X.509 certificates at loading/parsing time

Alexander Holler <holler@...oftware.de> writes:
> Am 02.05.2013 16:09, schrieb Alexander Holler:
>> I don't see any real use case where checking the validity dates of X.509
>> certificates at parsing time adds any security gain. In contrast, doing so
>> makes MODSIGN unusable on systems without a RTC (or systems with a possible
>> wrong date in a existing RTC, or systems where the RTC is read after the keys
>> got loaded).
>> 
>> If something really cares about the dates, it should check them at the time
>> when the certificates are used, not when they are loaded and parsed.
>> 
>> So just remove the validity check of the dates in the parser.
>> 
>> Signed-off-by: Alexander Holler <holler@...oftware.de>
>> Cc: stable@...r.kernel.org
>
> As it just happened to me again and I've recently posted some patches
> which do make it possible to experience the problem on x86 systems too,
> here is a reminder.
>
> To replay the problem (on x86 or any other arch), apply the 3 patches in
> this series:
>
> https://lkml.org/lkml/2013/6/5/430
>
> build a kernel with CONFIG_MODULE_SIG_FORCE=y and start that kernel with
> hctosys=none as kernel command line parameter.
>
> This will disable the "persistent" clock (and any RTC), thus the kernel
> will refuse to load modules because it doesn't has a valid time when
> loading the certificate.
>
> Regards,
>
> Alexander Holler

David?

Thanks,
Rusty.
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