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KEYS: X.509: Parse Basic Constraints for CA

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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>
This commit is contained in:
Eric Snowberg 2023-03-02 11:46:49 -05:00 committed by Jarkko Sakkinen
parent ef97e77471
commit 30eae2b037
2 changed files with 24 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

22
crypto/asymmetric_keys/x509_cert_parser.c
View file

@ -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;
}

2
include/crypto/public_key.h
View file

@ -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);