linux-kernel - Re: [PATCH] Fix x509_key_preparse() not to reject keys outside their validity time range

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Date:	Tue, 19 Mar 2013 22:06:39 +0100
From:	Alexander Holler <holler@...oftware.de>
To:	David Woodhouse <dwmw2@...radead.org>
CC:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	David Howells <dhowells@...hat.com>, rusty@...tcorp.com.au,
	herbert@...dor.hengli.com.au, pjones@...hat.com,
	jwboyer@...hat.com, linux-crypto@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, keyrings@...ux-nfs.org
Subject: Re: [PATCH] Fix x509_key_preparse() not to reject keys outside their
 validity time range

Am 14.03.2013 13:24, schrieb David Woodhouse:
> The x509_key_preparse() function will refuse to even *parse* a
> certificate when the system clock happens to be set to a time before the
> ValidFrom or after the ValidTo date.
>
> This is wrong. If date checks are to be done, they need to be done at
> the time the cert is *used*. It should be perfectly possible to load a
> cert which is post-dated, and can only be used for validation at some
> point in the future. The key in question should immediately start
> working at its ValidFrom date, and stop again at its ValidTo date. It
> should be allowed to *exist* in the kernel both before and after those
> times.
>
> On systems where the hardware clock is inaccurate (a common occurrence
> and one which doesn't even get noticed when you use NTP or something
> else to fix it during the boot sequence), this was preventing the module
> signing cert from being loaded during boot. When the clock got fixed
> later on in he boot sequence, things *should* have started working. But
> they didn't...
>
> Signed-off-by: David Woodhouse <David.Woodhouse@...el.com>
> ---
>
> Arguably, for the specific case of module signing we shouldn't bother
> checking for a current time before the ValidFrom date *at all*. It's
> *always* going to be a screwed up system clock, because we don't have a
> usage model of post-dating module signatures. We should simply document
> that the date is *not* checked for module signing, and have done with
> it. But that's a separate issue.
>
> diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
> index 06007f0..326dc80 100644
> --- a/crypto/asymmetric_keys/x509_public_key.c
> +++ b/crypto/asymmetric_keys/x509_public_key.c
> @@ -154,8 +154,6 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
>   		     (now.tm_sec < cert->valid_from.tm_sec
>   		      ))))))))))) {
>   		pr_warn("Cert %s is not yet valid\n", cert->fingerprint);
> -		ret = -EKEYREJECTED;
> -		goto error_free_cert;
>   	}
>   	if (now.tm_year > cert->valid_to.tm_year ||
>   	    (now.tm_year == cert->valid_to.tm_year &&
> @@ -170,8 +168,6 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
>   		     (now.tm_sec > cert->valid_to.tm_sec
>   		      ))))))))))) {
>   		pr_warn("Cert %s has expired\n", cert->fingerprint);
> -		ret = -EKEYEXPIRED;
> -		goto error_free_cert;
>   	}
>
>   	cert->pub->algo = x509_public_key_algorithms[cert->pkey_algo];

Why not remove the check and warning there too?

Regards,

Alexander

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