Received-SPF: softfail (google.com: domain of transitioning linux-crypto-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Message-ID: <b6e9eb1e-846c-c98e-ad16-c651b5e1dad7@linux.ibm.com>
Date:   Fri, 4 Mar 2022 10:10:17 -0500
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.5.0
Subject: Re: [PATCH 2/4] X.509: Parse Basic Constraints for CA
Content-Language: en-US
To:     Eric Snowberg <eric.snowberg@oracle.com>, zohar@linux.ibm.com,
        jarkko@kernel.org, dhowells@redhat.com, dwmw2@infradead.org
Cc:     herbert@gondor.apana.org.au, davem@davemloft.net,
        jmorris@namei.org, serge@hallyn.com, nayna@linux.ibm.com,
        mic@linux.microsoft.com, konrad.wilk@oracle.com,
        keyrings@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-crypto@vger.kernel.org, linux-security-module@vger.kernel.org
References: <20220301173651.3435350-1-eric.snowberg@oracle.com>
 <20220301173651.3435350-3-eric.snowberg@oracle.com>
From:   Stefan Berger <stefanb@linux.ibm.com>
In-Reply-To: <20220301173651.3435350-3-eric.snowberg@oracle.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk


On 3/1/22 12:36, Eric Snowberg wrote:
> Parse the X.509 Basic Constraints.  The basic constraints extension
> identifies whether the subject of the certificate is a CA.
>
> BasicConstraints ::= SEQUENCE {
>          cA                      BOOLEAN DEFAULT FALSE,
>          pathLenConstraint       INTEGER (0..MAX) OPTIONAL }
>
> If the CA is true, store it in a new public_key field call key_is_ca.
> This will be used in a follow on patch that requires knowing if the
> public key is a CA.
>
> Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
> ---
>   crypto/asymmetric_keys/x509_cert_parser.c | 9 +++++++++
>   include/crypto/public_key.h               | 1 +
>   2 files changed, 10 insertions(+)
>
> diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
> index 2899ed80bb18..38c907f4ce27 100644
> --- a/crypto/asymmetric_keys/x509_cert_parser.c
> +++ b/crypto/asymmetric_keys/x509_cert_parser.c
> @@ -583,6 +583,15 @@ int x509_process_extension(void *context, size_t hdrlen,
>   		return 0;
>   	}
>   
> +	if (ctx->last_oid == OID_basicConstraints) {

Don't you have to check whether you can access v[0] and v[1]?

if (vlen < 3)

     return -EBADMSG;

or should it even be

if (vlen != 3)

      return -EBADMSG;


> +		if (v[0] != (ASN1_CONS_BIT | ASN1_SEQ))
> +			return -EBADMSG;
> +		if (v[1] != vlen - 2)
> +			return -EBADMSG;
> +		if (v[1] != 0 && v[2] == ASN1_BOOL && v[3] == 1)
> +			ctx->cert->pub->key_is_ca = true;
> +	}
> +
>   	return 0;
>   }
>   
> diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
> index 6d61695e1cde..0521241764b7 100644
> --- a/include/crypto/public_key.h
> +++ b/include/crypto/public_key.h
> @@ -26,6 +26,7 @@ struct public_key {
>   	void *params;
>   	u32 paramlen;
>   	bool key_is_private;
> +	bool key_is_ca;
>   	const char *id_type;
>   	const char *pkey_algo;
>   };