Parsing v3 extensions from a CSR
A parsed CSR struct (`mbedtls_x509_csr`) now includes some of the
X.509v3 extensions included in the CSR -- the key usage, Netscape
cert-type, and Subject Alternative Names.
Author: Jens Alfke <jens@couchbase.com>
Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
diff --git a/library/x509_csr.c b/library/x509_csr.c
index 0c664d9..824d17a 100644
--- a/library/x509_csr.c
+++ b/library/x509_csr.c
@@ -70,6 +70,153 @@
}
/*
+ * Parse CSR extension requests in DER format
+ */
+static int x509_csr_parse_extensions(mbedtls_x509_csr *csr,
+ unsigned char **p, const unsigned char *end)
+{
+ int ret;
+ size_t len;
+ unsigned char *end_ext_data;
+
+ while (*p < end) {
+ mbedtls_x509_buf extn_oid = { 0, 0, NULL };
+ int ext_type = 0;
+
+ /* Read sequence tag */
+ if ((ret = mbedtls_asn1_get_tag(p, end, &len,
+ MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE)) != 0) {
+ return MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret;
+ }
+
+ end_ext_data = *p + len;
+
+ /* Get extension ID */
+ if ((ret = mbedtls_asn1_get_tag(p, end_ext_data, &extn_oid.len,
+ MBEDTLS_ASN1_OID)) != 0) {
+ return MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret;
+ }
+
+ extn_oid.tag = MBEDTLS_ASN1_OID;
+ extn_oid.p = *p;
+ *p += extn_oid.len;
+
+ /* Data should be octet string type */
+ if ((ret = mbedtls_asn1_get_tag(p, end_ext_data, &len,
+ MBEDTLS_ASN1_OCTET_STRING)) != 0) {
+ return MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret;
+ }
+ if (*p + len != end_ext_data) {
+ return MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
+ MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
+ }
+
+ if (mbedtls_oid_get_x509_ext_type(&extn_oid, &ext_type) == 0) {
+ switch (ext_type) {
+ case MBEDTLS_X509_EXT_KEY_USAGE:
+ /* Parse key usage */
+ if ((ret = x509_get_key_usage(p, end_ext_data,
+ &csr->key_usage)) != 0) {
+ return ret;
+ }
+ break;
+
+ case MBEDTLS_X509_EXT_SUBJECT_ALT_NAME:
+ /* Parse subject alt name */
+ if ((ret = x509_get_subject_alt_name(p, end_ext_data,
+ &csr->subject_alt_names)) != 0) {
+ return ret;
+ }
+ break;
+
+ case MBEDTLS_X509_EXT_NS_CERT_TYPE:
+ /* Parse netscape certificate type */
+ if ((ret = x509_get_ns_cert_type(p, end_ext_data,
+ &csr->ns_cert_type)) != 0) {
+ return ret;
+ }
+ break;
+ default:
+ break;
+ }
+ }
+
+ *p = end_ext_data;
+ }
+
+ if (*p != end) {
+ return MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
+ MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
+ }
+
+ return 0;
+}
+
+/*
+ * Parse CSR attributes in DER format
+ */
+static int x509_csr_parse_attributes(mbedtls_x509_csr *csr,
+ const unsigned char *start, const unsigned char *end)
+{
+ int ret;
+ size_t len;
+ unsigned char *end_attr_data;
+ unsigned char **p = (unsigned char **) &start;
+
+ while (*p < end) {
+ mbedtls_x509_buf attr_oid = { 0, 0, NULL };
+
+ if ((ret = mbedtls_asn1_get_tag(p, end, &len,
+ MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE)) != 0) {
+ return MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret;
+ }
+ end_attr_data = *p + len;
+
+ /* Get attribute ID */
+ if ((ret = mbedtls_asn1_get_tag(p, end_attr_data, &attr_oid.len,
+ MBEDTLS_ASN1_OID)) != 0) {
+ return MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret;
+ }
+
+ attr_oid.tag = MBEDTLS_ASN1_OID;
+ attr_oid.p = *p;
+ *p += attr_oid.len;
+
+ /* Check that this is an extension-request attribute */
+ if (MBEDTLS_OID_CMP(MBEDTLS_OID_PKCS9_CSR_EXT_REQ, &attr_oid) == 0) {
+ if ((ret = mbedtls_asn1_get_tag(p, end, &len,
+ MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SET)) != 0) {
+ return MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret;
+ }
+
+ if ((ret = mbedtls_asn1_get_tag(p, end, &len,
+ MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE)) !=
+ 0) {
+ return MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret;
+ }
+
+ if ((ret = x509_csr_parse_extensions(csr, p, *p + len)) != 0) {
+ return MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret;
+ }
+
+ if (*p != end_attr_data) {
+ return MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
+ MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
+ }
+ }
+
+ *p = end_attr_data;
+ }
+
+ if (*p != end) {
+ return MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
+ MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
+ }
+
+ return 0;
+}
+
+/*
* Parse a CSR in DER format
*/
int mbedtls_x509_csr_parse_der(mbedtls_x509_csr *csr,
@@ -197,6 +344,11 @@
return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_FORMAT, ret);
}
+ if ((ret = x509_csr_parse_attributes(csr, p, p + len)) != 0) {
+ mbedtls_x509_csr_free(csr);
+ return ret;
+ }
+
p += len;
end = csr->raw.p + csr->raw.len;