Commit 56767128 authored by Eric Snowberg's avatar Eric Snowberg Committed by Jarkko Sakkinen
Browse files

KEYS: X.509: Parse Key Usage 

Parse the X.509 Key Usage.  The key usage extension defines the purpose of
the key contained in the certificate.

   id-ce-keyUsage OBJECT IDENTIFIER ::=  { id-ce 15 }

      KeyUsage ::= BIT STRING {
           digitalSignature        (0),
           contentCommitment       (1),
           keyEncipherment         (2),
           dataEncipherment        (3),
           keyAgreement            (4),
           keyCertSign             (5),
           cRLSign                 (6),
           encipherOnly            (7),
           decipherOnly            (8) }

If the keyCertSign or digitalSignature is set, store it in the
public_key structure. Having the purpose of the key being stored
during parsing, allows enforcement on the usage field in the future.
This will be used in a follow on patch that requires knowing the
certificate key usage type.

Link: https://www.rfc-editor.org/rfc/rfc5280#section-4.2.1.3


Signed-off-by: default avatarEric Snowberg <eric.snowberg@oracle.com>
Reviewed-by: default avatarMimi Zohar <zohar@linux.ibm.com>
Reviewed-by: default avatarJarkko Sakkinen <jarkko@kernel.org>
Tested-by: default avatarMimi Zohar <zohar@linux.ibm.com>
Signed-off-by: default avatarJarkko Sakkinen <jarkko@kernel.org>
parent 30eae2b0

crypto/asymmetric_keys/x509_cert_parser.c

+28 −0
Original line number Diff line number Diff line
@@ -579,6 +579,34 @@ int x509_process_extension(void *context, size_t hdrlen, 
		return 0;

	}



	if (ctx->last_oid == OID_keyUsage) {

		/*

		 * Get hold of the keyUsage bit string

		 * v[1] is the encoding size

		 *       (Expect either 0x02 or 0x03, making it 1 or 2 bytes)

		 * v[2] is the number of unused bits in the bit string

		 *       (If >= 3 keyCertSign is missing when v[1] = 0x02)

		 * v[3] and possibly v[4] contain the bit string

		 *

		 * From RFC 5280 4.2.1.3:

		 *   0x04 is where keyCertSign lands in this bit string

		 *   0x80 is where digitalSignature lands in this bit string

		 */

		if (v[0] != ASN1_BTS)

			return -EBADMSG;

		if (vlen < 4)

			return -EBADMSG;

		if (v[2] >= 8)

			return -EBADMSG;

		if (v[3] & 0x80)

			ctx->cert->pub->key_eflags |= 1 << KEY_EFLAG_DIGITALSIG;

		if (v[1] == 0x02 && v[2] <= 2 && (v[3] & 0x04))

			ctx->cert->pub->key_eflags |= 1 << KEY_EFLAG_KEYCERTSIGN;

		else if (vlen > 4 && v[1] == 0x03 && (v[3] & 0x04))

			ctx->cert->pub->key_eflags |= 1 << KEY_EFLAG_KEYCERTSIGN;

		return 0;

	}



	if (ctx->last_oid == OID_authorityKeyIdentifier) {

		/* Get hold of the CA key fingerprint */

		ctx->raw_akid = v;

include/crypto/public_key.h

+2 −0
Original line number Diff line number Diff line
@@ -30,6 +30,8 @@ struct public_key { 
	const char *pkey_algo;

	unsigned long key_eflags;	/* key extension flags */

#define KEY_EFLAG_CA		0	/* set if the CA basic constraints is set */

#define KEY_EFLAG_DIGITALSIG	1	/* set if the digitalSignature usage is set */

#define KEY_EFLAG_KEYCERTSIGN	2	/* set if the keyCertSign usage is set */

};



extern void public_key_free(struct public_key *key);