linux-kernel - Re: [PATCH] X.509: if signature is unsupported skip validation

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Message-Id: <CUZ1JSW865LV.2LMR3F0UJSRWZ@suppilovahvero>
Date:   Tue, 22 Aug 2023 14:36:10 +0300
From:   "Jarkko Sakkinen" <jarkko@...nel.org>
To:     "Thore Sommer" <public@...on.de>, <dhowells@...hat.com>,
        <herbert@...dor.apana.org.au>, <davem@...emloft.net>
Cc:     <keyrings@...r.kernel.org>, <linux-crypto@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] X.509: if signature is unsupported skip validation

On Mon Aug 21, 2023 at 1:30 PM EEST, Thore Sommer wrote:
> On 16.08.23 23:54, Jarkko Sakkinen wrote:
> > On Tue Aug 15, 2023 at 2:29 PM EEST, Thore Sommer wrote:
> >> When the hash algorithm for the signature is not available the digest size
> >> is 0 and the signature in the certificate is marked as unsupported.
> >>
> >> When validating a self-signed certificate, this needs to be checked,
> >> because otherwise trying to validate the signature will fail with an
> >> warning:
> >>
> >> Loading compiled-in X.509 certificates
> >> WARNING: CPU: 0 PID: 1 at crypto/rsa-pkcs1pad.c:537 \
> >> pkcs1pad_verify+0x46/0x12c
> >> ...
> >> Problem loading in-kernel X.509 certificate (-22)
> >>
> >> Signed-off-by: Thore Sommer <public@...on.de>
> >> ---
> >>   crypto/asymmetric_keys/x509_public_key.c | 5 +++++
> >>   1 file changed, 5 insertions(+)
> >>
> >> diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
> >> index 6fdfc82e23a8..7c71db3ac23d 100644
> >> --- a/crypto/asymmetric_keys/x509_public_key.c
> >> +++ b/crypto/asymmetric_keys/x509_public_key.c
> >> @@ -130,6 +130,11 @@ int x509_check_for_self_signed(struct x509_certificate *cert)
> >>   			goto out;
> >>   	}
> >>   
> >> +	if (cert->unsupported_sig) {
> >> +		ret = 0;
> >> +		goto out;
> >> +	}
> >> +
> >>   	ret = public_key_verify_signature(cert->pub, cert->sig);
> >>   	if (ret < 0) {
> >>   		if (ret == -ENOPKG) {
> >> -- 
> >> 2.41.0
> > 
> > Should have:
> > 
> > Cc: stable@...r.kernel.org # v4.7+
> > Fixes: 6c2dc5ae4ab7 ("X.509: Extract signature digest and make self-signed cert checks earlier")
> > 
> > BR, Jarkko
>
> Hi Jarkko,
>
> should I resend it with the stable mailing list in CC or will it be 
> added when a maintainer includes the change?

AFAIK the correct tags, and automation takes care of the rest.

If there is a merge conflict to some stable branch, the bots will call
back to you :-)

BR, Jarkko