From 567671281a751b80918a4531c4ba84b90a2a42c0 Mon Sep 17 00:00:00 2001 From: Eric Snowberg Date: Thu, 2 Mar 2023 11:46:50 -0500 Subject: 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: Eric Snowberg Reviewed-by: Mimi Zohar Reviewed-by: Jarkko Sakkinen Tested-by: Mimi Zohar Signed-off-by: Jarkko Sakkinen --- crypto/asymmetric_keys/x509_cert_parser.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) (limited to 'crypto') diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c index 77547d4bd94dd4..0a7049b470c181 100644 --- a/crypto/asymmetric_keys/x509_cert_parser.c +++ b/crypto/asymmetric_keys/x509_cert_parser.c @@ -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; -- cgit 1.2.3-korg