Add x509_crt_check_extended_key_usage()
diff --git a/include/polarssl/x509_crt.h b/include/polarssl/x509_crt.h
index 93340ec..8e63381 100644
--- a/include/polarssl/x509_crt.h
+++ b/include/polarssl/x509_crt.h
@@ -264,6 +264,24 @@
int x509_crt_check_key_usage( const x509_crt *crt, int usage );
#endif /* POLARSSL_X509_CHECK_KEY_USAGE) */
+#if defined(POLARSSL_X509_CHECK_EXTENDED_KEY_USAGE)
+/**
+ * \brief Check usage of certificate against extentedJeyUsage.
+ *
+ * \param crt Leaf certificate used.
+ * \param usage_oid Intended usage (eg OID_SERVER_AUTH or OID_CLIENT_AUTH).
+ * \param usage_len Length of usage_oid (eg given by OID_SIZE()).
+ *
+ * \return 0 is this use of the certificate is allowed,
+ * POLARSSL_ERR_X509_BAD_INPUT_DATA if not.
+ *
+ * \note Usually only makes sense on leaf certificates.
+ */
+int x509_crt_check_extended_key_usage( const x509_crt *crt,
+ const char *usage_oid,
+ size_t usage_len );
+#endif /* POLARSSL_X509_CHECK_EXTENDED_KEY_USAGE) */
+
#if defined(POLARSSL_X509_CRL_PARSE_C)
/**
* \brief Verify the certificate revocation status