linux-kernel - Re: [PATCH 3/5] X.509: Support leap seconds

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Date:	Fri, 18 Dec 2015 10:10:12 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	David Howells <dhowells@...hat.com>
Cc:	keyrings@...r.kernel.org,
	David Woodhouse <David.Woodhouse@...el.com>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	Rudolf Polzer <rpolzer@...gle.com>,
	John Stultz <john.stultz@...aro.org>
Subject: Re: [PATCH 3/5] X.509: Support leap seconds

On Friday 18 December 2015 00:02:09 David Howells wrote:
> The format of ASN.1 GeneralizedTime seems to be specified by ISO 8601
> [X.680 46.3] and this apparently supports leap seconds (ie. the seconds
> field is 60).  It's not entirely clear that ASN.1 expects it, but we can
> relax the seconds check slightly for GeneralizedTime.
> 
> This, however, results in us passing a time with sec as 60 to mktime64()
> which, unpatched, doesn't really handle such things.  What it will do is
> equate the 60th second of a minute to the 0th second of the next minute.
> 
> We can't really do otherwise without giving the kernel much greater
> knowledge of where all the leap seconds are.  Unfortunately, this would
> require change the mapping of the kernel's current-time-in-seconds.
> 
> UTCTime, however, only supports a seconds value in the range 00-59.
> 
> Without this patch, certain X.509 certificates will be rejected,
> potentially making a kernel unbootable.
> 
> Reported-by: Rudolf Polzer <rpolzer@...gle.com>
> Signed-off-by: David Howells <dhowells@...hat.com>
> cc: David Woodhouse <David.Woodhouse@...el.com>
> cc: John Stultz <john.stultz@...aro.org>
> cc: Arnd Bergmann <arnd@...db.de>
> cc: stable@...r.kernel.org

Acked-by: Arnd Bergmann <arnd@...db.de>
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