Add content type and charset to the default error page

src/civetweb.c

@@ -2830,7 +2830,7 @@ send_http_error(struct mg_connection *conn, int status, const char *fmt, ...)
 {
 	char buf[MG_BUF_LEN];
 	va_list ap;
-	int len, i, page_handler_found, scope, truncated;
+	int len, i, page_handler_found, scope, truncated, has_body;
 	char date[64];
 	time_t curtime = time(NULL);
 	const char *error_handler = NULL;
@@ -2917,17 +2917,24 @@ send_http_error(struct mg_connection *conn, int status, const char *fmt, ...)
 		/* No custom error page. Send default error page. */
 		gmt_time_string(date, sizeof(date), &curtime);
 
+		/* Errors 1xx, 204 and 304 MUST NOT send a body */
+		has_body = (status > 199 && status != 204 && status != 304);
+
 		conn->must_close = 1;
 		mg_printf(conn, "HTTP/1.1 %d %s\r\n", status, status_text);
 		send_no_cache_header(conn);
+		if (has_body) {
+			mg_printf(conn,
+			          "%s",
+			          "Content-Type: text/plain; charset=utf-8\r\n");
+		}
 		mg_printf(conn,
 		          "Date: %s\r\n"
 		          "Connection: close\r\n\r\n",
 		          date);
 
 		/* Errors 1xx, 204 and 304 MUST NOT send a body */
-		if (status > 199 && status != 204 && status != 304) {
-
+		if (has_body) {
 			mg_printf(conn, "Error %d: %s\n", status, status_text);
 
 			if (fmt != NULL) {
@@ -11389,7 +11396,8 @@ ssl_get_client_cert_info(struct mg_connection *conn)
 		/* Calculate SHA1 fingerprint and store as a hex string */
 		ulen = 0;
 		ASN1_digest((int (*)())i2d_X509, digest, (char *)cert, buf, &ulen);
-		if (!hexdump2string(buf, (int)ulen, str_finger, (int)sizeof(str_finger))) {
+		if (!hexdump2string(
+		        buf, (int)ulen, str_finger, (int)sizeof(str_finger))) {
 			*str_finger = 0;
 		}