tls: Introduce a generic TLS purpose that accepts NULL encryption ciphers

src/libtls/tls.c

@@ -447,6 +447,7 @@ tls_t *tls_create(bool is_server, identification_t *server,
 		case TLS_PURPOSE_EAP_TTLS:
 		case TLS_PURPOSE_EAP_PEAP:
 		case TLS_PURPOSE_GENERIC:
+		case TLS_PURPOSE_GENERIC_NULLOK:
 			break;
 		default:
 			return NULL;

src/libtls/tls.h

@@ -107,6 +107,8 @@ enum tls_purpose_t {
 	TLS_PURPOSE_EAP_PEAP,
 	/** non-EAP TLS */
 	TLS_PURPOSE_GENERIC,
+	/** non-EAP TLS accepting NULL encryption */
+	TLS_PURPOSE_GENERIC_NULLOK,
 	/** EAP binding for TNC */
 	TLS_PURPOSE_EAP_TNC
 };

src/libtls/tls_crypto.c

@@ -1846,6 +1846,9 @@ tls_crypto_t *tls_crypto_create(tls_t *tls, tls_cache_t *cache)
 		case TLS_PURPOSE_GENERIC:
 			build_cipher_suite_list(this, TRUE);
 			break;
+		case TLS_PURPOSE_GENERIC_NULLOK:
+			build_cipher_suite_list(this, FALSE);
+			break;
 		default:
 			break;
 	}