Attack surface


This chapter defines Zato’s attack surface, these parts of a cluster’s resources that can be used by an adversary to attack Zato.

The attack surface is discussed in terms of entry and exit points in order to give you an understanding of how an attacker could gain access to a cluster. Some notes apply to more than one Zato component whereas certain aspects are specific to a particular component.

When entry points are concerned, it should be noted that all Zato components are installed as a set of files and directories in a file system. Anyone with direct access to the file system will be able to update any configuration files, including ports they’re running on, if any, and any crypto resources that are in use, such as keys and certificates.

Crypto material used by Zato components is not protected by passwords.

Web admin, load-balancer and servers, all of them Python’s own logging package. Depending on their configuration, the logs will written out either to local files or to remote systems, for instance, when using syslogd. Note that when running in DEBUG or TRACE1 level, raw messages passed between Zato components will be logged, including any secrets they may contain.

Zato’s CLI can be used to start, stop and manage other aspects of web admin, load-balancer and servers.

Exactly one of servers in a cluster is considered a connector server. This is the server that will start AMQP, IBM MQ and ZeroMQ connectors in order to accept or send messages coming through these protocols. Note that when a connector server goes down, another server will assume its role.

Certificate Authority (CA)

Entry points

A CA is driven entirely by its CLI. It doesn’t open any ports and can be accessed solely through the command line.


Entry points

A load-balancer uses an agent, a daemon exposing a set of XML-RPC functions through SSL. The agent is used by web admin to administer various aspects of a running load-balancer. Connection between web admin and the agent can optionally use client certificates.

The agent writes to and reads from a load-balancer’s UNIX socket.

A load-balancer is the entry point to Zato servers. Clients never invoke servers directly, all communication is always performed through the load-balancer, which is an HAProxy instance.

Exit points

The main purpose of running a load-balancer is to guarantee access to Zato servers hence it’s the latter that form a load-balancer’s exit points.

Redis KVDB

Entry points

Redis is accessed by Zato servers and it’s always the latter that initiate the connection. Note that depending on how Redis has been configured, the connection from a server to the KVDB may not use any credentials.

Visit Redis documentation for more information regarding its security.


Entry points

Servers accept traffic flowing in from a load-balancer over HTTP through a TCP socket. Depending on the interface a server will bind to, it will also be possible to invoke a server directly using the said socket.

Access to services exposed by Zato servers can be guarded by a security definition, either HTTP Basic Auth, WS-Security or technical accounts.

Servers accept traffic from a cluster’s key/value database (Redis). Each connection to KVDB requires a set of credentials although these can also be empty, depending on how Redis has been configured.

Exit points

Servers access other services, either Zato’s own or belonging to external systems, through AMQP, FTP, IBM MQ, Plain HTTP, SOAP, SQL or ZeroMQ.

Servers need to access Redis and SQL ODB, both read and write, for a proper functioning. It’s not required for servers to have any sort of a DDL authority in the SQL ODB.


Entry points

SQL ODB is accessed by the web admin and servers, for both read and writes. Once the SQL ODB has been created, no Zato component will attempt to issue any DDL statements against it.

Visit your SQL database’s home page for more information regarding its security.

Web admin

Entry points

Web admin is primarily a web console implemented in Django, accessed through a browser.

The web console is listening on a TCP socket. Depending on how it’s been configured, traffic to the console will be either plain HTTP or HTTPS.

Access to the console is controlled by a username and password. All users are considered equal, there are no roles nor ACLs for each action that can be performed using the console.

Exit points

Web admin manages the load-balancer using the latter’s XML-RPC API over SSL, optionally using client certificates.

The load-balancer is also used as an entry point for web admin to invoke a cluster’s services, that is, the console never invokes any server directly, the access is always mediated through the load-balancer. Note, however, that when invoking services (as opposed to managing a load-balancer itself) the communication between web admin a load-balancer isn’t encrypted.

Web admin also allows one to update the load-balancer’s config file, including the password needed to browse the latter’s statistics, addresses of servers running in a cluster and every other bit of configuration.

A few features of web admin require direct access, for both read and write, to the SQL ODB using either Django’s SQL API or SQLAlchemy. Web admin won’t issue DDL queries in the SQL ODB.