Month: February 2018

Java problem with mutual TLS authentication when using incoming and outgoing connections simultaneously

In most enterprise environments some form of secure communication (e.g. TLS or SSL) is used in connections between applications. In some environments mutual (two-way) authentication is also a non-functional requirement. This is sometimes referred to as two-way SSL or mutual TLS authentication. So as well as the server presenting it's certificate, it requests that the client send it's certificate so that it can then be used to authenticate the caller. A partner of my current client has been developing a server which receives data over MQTT and because the data is quite sensitive the customer decided that the data should be secured using mutual TLS authentication. Additionally, the customer requires that when the aggregated data which this server collects is posted to further downstream services, it is also done using mutual TLS authentication. This server needs to present a server certificate to its callers so that they can verify the hostname and identity, but additionally it must present a client certificate with a valid user ID to the downstream server when requested to do so during the SSL handshake. The initial idea was to implement this using the standard JVM system properties for configuring a keystore: "", i.e. putting both client and server certificates into the single keystore. We soon realised however that this doesn't work, and tracing the SSL debug logs showed that the server was presenting the wrong certificate, either during the incoming SSL handshake or the outgoing SSL handshake. During the incoming handshake it should present its…

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Revisiting Global Data Consistency in Distributed (Microservice) Architectures

Back in 2015 I wrote a couple of articles about how you can piggyback a standard Java EE Transaction Manager to get data consistency across distributed services (here is the original article and here is an article about doing it with Spring Boot, Tomcat or Jetty). Last year I was fortunate enough to work on a small project where we questioned data consistency from the ground up. Our conclusion was that there is another way of getting data consistency guarantees, one that I had not considered in another article that I wrote about patterns for binding resources into transactions. This other solution is to change the architecture from a synchronous one to an asynchronous one. The basic idea is to save business data together with "commands" within a single database transaction. Commands are simply facts that other systems still need to be called.By reducing the number of concurrent transactions to just one, it is possible to guarantee that data will never be lost. Commands which have been committed are then executed as soon as possible and it is the command execution (in a new transaction) which then makes calls to remote systems. Effectively it is an implementation of the BASE consistency model, because from a global point of view, data is only eventually consistent. Imagine the situation where updating an insurance case should result in creating a task in a workflow system so that a person gets a reminder to do something, for example write to the customer. The code…

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