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[PATCH v4 3/6] KEYS: X.509: Parse Basic Constraints for CA

Eric Snowberg posted 6 patches 2 years, 7 months ago
There is a newer version of this series
[PATCH v4 3/6] KEYS: X.509: Parse Basic Constraints for CA
Posted by Eric Snowberg 2 years, 7 months ago 
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 the public_key.  This will be used
in a follow on patch that requires knowing if the public key is a CA.

Link: https://www.rfc-editor.org/rfc/rfc5280#section-4.2.1.9
Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
---
 crypto/asymmetric_keys/x509_cert_parser.c | 22 ++++++++++++++++++++++
 include/crypto/public_key.h               |  2 ++
 2 files changed, 24 insertions(+)

diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
index 7a9b084e2043..77547d4bd94d 100644
--- a/crypto/asymmetric_keys/x509_cert_parser.c
+++ b/crypto/asymmetric_keys/x509_cert_parser.c
@@ -586,6 +586,28 @@ int x509_process_extension(void *context, size_t hdrlen,
 		return 0;
 	}
 
+	if (ctx->last_oid == OID_basicConstraints) {
+		/*
+		 * Get hold of the basicConstraints
+		 * v[1] is the encoding size
+		 *	(Expect 0x2 or greater, making it 1 or more bytes)
+		 * v[2] is the encoding type
+		 *	(Expect an ASN1_BOOL for the CA)
+		 * v[3] is the contents of the ASN1_BOOL
+		 *      (Expect 1 if the CA is TRUE)
+		 * vlen should match the entire extension size
+		 */
+		if (v[0] != (ASN1_CONS_BIT | ASN1_SEQ))
+			return -EBADMSG;
+		if (vlen < 2)
+			return -EBADMSG;
+		if (v[1] != vlen - 2)
+			return -EBADMSG;
+		if (vlen >= 4 && v[1] != 0 && v[2] == ASN1_BOOL && v[3] == 1)
+			ctx->cert->pub->key_eflags |= 1 << KEY_EFLAG_CA;
+		return 0;
+	}
+
 	return 0;
 }
 
diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
index 6d61695e1cde..c401762850f2 100644
--- a/include/crypto/public_key.h
+++ b/include/crypto/public_key.h
@@ -28,6 +28,8 @@ struct public_key {
 	bool key_is_private;
 	const char *id_type;
 	const char *pkey_algo;
+	unsigned long key_eflags;	/* key extension flags */
+#define KEY_EFLAG_CA		0	/* set if the CA basic constraints is set */
 };
 
 extern void public_key_free(struct public_key *key);
-- 
2.27.0
Re: [PATCH v4 3/6] KEYS: X.509: Parse Basic Constraints for CA
Posted by Jarkko Sakkinen 2 years, 7 months ago 
On Mon, Feb 06, 2023 at 09:59:55PM -0500, 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 the public_key.  This will be used
> in a follow on patch that requires knowing if the public key is a CA.
> 
> Link: https://www.rfc-editor.org/rfc/rfc5280#section-4.2.1.9
> Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
> ---
>  crypto/asymmetric_keys/x509_cert_parser.c | 22 ++++++++++++++++++++++
>  include/crypto/public_key.h               |  2 ++
>  2 files changed, 24 insertions(+)
> 
> diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
> index 7a9b084e2043..77547d4bd94d 100644
> --- a/crypto/asymmetric_keys/x509_cert_parser.c
> +++ b/crypto/asymmetric_keys/x509_cert_parser.c
> @@ -586,6 +586,28 @@ int x509_process_extension(void *context, size_t hdrlen,
>  		return 0;
>  	}
>  
> +	if (ctx->last_oid == OID_basicConstraints) {
> +		/*
> +		 * Get hold of the basicConstraints
> +		 * v[1] is the encoding size
> +		 *	(Expect 0x2 or greater, making it 1 or more bytes)
> +		 * v[2] is the encoding type
> +		 *	(Expect an ASN1_BOOL for the CA)
> +		 * v[3] is the contents of the ASN1_BOOL
> +		 *      (Expect 1 if the CA is TRUE)
> +		 * vlen should match the entire extension size
> +		 */
> +		if (v[0] != (ASN1_CONS_BIT | ASN1_SEQ))
> +			return -EBADMSG;
> +		if (vlen < 2)
> +			return -EBADMSG;
> +		if (v[1] != vlen - 2)
> +			return -EBADMSG;
> +		if (vlen >= 4 && v[1] != 0 && v[2] == ASN1_BOOL && v[3] == 1)
> +			ctx->cert->pub->key_eflags |= 1 << KEY_EFLAG_CA;
> +		return 0;
> +	}
> +
>  	return 0;
>  }
>  
> diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
> index 6d61695e1cde..c401762850f2 100644
> --- a/include/crypto/public_key.h
> +++ b/include/crypto/public_key.h
> @@ -28,6 +28,8 @@ struct public_key {
>  	bool key_is_private;
>  	const char *id_type;
>  	const char *pkey_algo;
> +	unsigned long key_eflags;	/* key extension flags */
> +#define KEY_EFLAG_CA		0	/* set if the CA basic constraints is set */
>  };
>  
>  extern void public_key_free(struct public_key *key);
> -- 
> 2.27.0
> 

Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

BR, Jarkko
Re: [PATCH v4 3/6] KEYS: X.509: Parse Basic Constraints for CA
Posted by Mimi Zohar 2 years, 7 months ago 
On Mon, 2023-02-06 at 21:59 -0500, 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 the public_key.  This will be used
> in a follow on patch that requires knowing if the public key is a CA.
> 
> Link: https://www.rfc-editor.org/rfc/rfc5280#section-4.2.1.9
> Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>

Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>

Patchew 2.1-devel-b67e4c2

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