lib-smtp: client: Make the initialization of the connection after SSL…

… handshake reliable.

Before, the connection was not guaranteed to be fully initialized after the SSL
handshake. The problem would occur when the handshake finished while writing the
SSL output stream. In a similar HTTP client issue, this caused a segfault.

src/lib-smtp/smtp-client-connection.c

@@ -1003,8 +1003,10 @@ static void smtp_client_connection_input(struct connection *_conn)
 			i_assert(ret == 0);
 			return;
 		}
+	}
 
-		/* ready for SMTP handshake */
+	if (!conn->connect_succeeded) {
+		/* just got ready for SMTP handshake */
 		smtp_client_connection_established(conn);
 	}
 
@@ -1137,6 +1139,9 @@ static void smtp_client_connection_destroy(struct connection *_conn)
 static void
 smtp_client_connection_established(struct smtp_client_connection *conn)
 {
+	i_assert(!conn->connect_succeeded);
+	conn->connect_succeeded = TRUE;
+
 	if (conn->to_connect != NULL)
 		timeout_reset(conn->to_connect);
 

src/lib-smtp/smtp-client-private.h

@@ -163,6 +163,7 @@ struct smtp_client_connection {
 	bool authenticated:1;
 	bool initial_xclient_sent:1;
 	bool connect_failed:1;
+	bool connect_succeeded:1;
 	bool handshake_failed:1;
 	bool corked:1;
 	bool sent_quit:1;