| Message ID | 20230302164652.83571-5-eric.snowberg@oracle.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Herbert Xu |
| Headers | show |
| Series | Add CA enforcement keyring restrictions | expand |
On Thu, Mar 02, 2023 at 11:46:50AM -0500, Eric Snowberg wrote: > 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 <eric.snowberg@oracle.com> > Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> > --- > crypto/asymmetric_keys/x509_cert_parser.c | 28 +++++++++++++++++++++++ > include/crypto/public_key.h | 2 ++ > 2 files changed, 30 insertions(+) > > diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c > index 77547d4bd94d..0a7049b470c1 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; > diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h > index c401762850f2..03c3fb990d59 100644 > --- a/include/crypto/public_key.h > +++ b/include/crypto/public_key.h > @@ -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); > -- > 2.27.0 > Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> BR, Jarkko
diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c index 77547d4bd94d..0a7049b470c1 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; diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h index c401762850f2..03c3fb990d59 100644 --- a/include/crypto/public_key.h +++ b/include/crypto/public_key.h @@ -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);
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 <eric.snowberg@oracle.com> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> --- crypto/asymmetric_keys/x509_cert_parser.c | 28 +++++++++++++++++++++++ include/crypto/public_key.h | 2 ++ 2 files changed, 30 insertions(+)