KEYS: X.509: Parse Basic Constraints for CA

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>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Tested-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
index 7a9b084e2043d72fa8859f6220316ab44ac79f92..77547d4bd94dd44b520cc6214907e2ac2d836f8c 100644 (file)
--- 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 6d61695e1cdeb10ec7af0bc22a3d39efc40dd546..c401762850f20a1e9c6d0c4c0ebcb292ba74e4f4 100644 (file)
--- 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);