If you are using an infrastructure-as-a-service offering to host your WordPress site, you might find the following suggestions useful. If you have web access to site administration, e.g., via CPanel, there’s not much more you can do beyond:

• Install WordFence.
• Pick a very long password for your admin account. Have a look at secondary authentication options [described below].
• Keep your software up to date.
• Have a long hard look at all of those plugins you’re using, and try to cut them to the bone.

Here are a few Linux specific things to consider:

• Install fail2ban.
• Install the fail2ban WordPress plugin.
• Change the default port you are running sshd on from 22 to something above 1024. You might want to check the IANA port listing to avoid colliding with other daemons you may be running on your box. This is pretty painless to do. You could do the same for all of your other network services [obviously excluding your web site and mail transfer agent, if you’re using one].
• Consider running TCP wrappers on your ssh daemon access. Be careful not to lock yourself out if you don’t have a fixed IP address from your service provider. I use BT: a bit of googling suggested a couple of likely address ranges [81. and 86.], but my get out of jail card is a static IP I can use with a VPN service, which I’ve also configured.
• Consider restricting access to mysqld to localhost. You may have already done this during install. I have to admit I was pretty careless when I was installing the database in terms of notetaking so I just added a TCP wrapper to be on the safe side.
• Have an extremely long password for your admin account. Mine is basically half a mile long in 8 point text.
• Have a look at some secondary authentication [or at least Captcha style robot identification] mechanism on the login form. I’ve experimented with Duo in the past. Make sure you understand the implications of changing your mobile phone if you are using one of the app based mechanisms.
• Consider chrooting your website. I don’t but I may.
• Have a look at some of the security scanners, like ZAP. Again, be careful not to lock yourself out with fail2ban.

The rest of these are host specific. A good starting point is to run

nmap -n localhost

to confirm what network services you are running. For instance, I found that my Linux distro had an FTP server running out of the box which I didn’t know about. In my case it was as simple as

pgrep ftp

to get the process id, then

ps -ef | grep <process_number>

[substituting appropriately] to find what the process was, and then finally

apt-get remove <package_name>

For any other servers you need to run, there’s a pretty good chance that there is fail2ban config that you can use off the shelf.

Why I felt I needed to pay more attention…

A few months ago, based on the daily activity reports I get from WordFence, I started blocking ranges of addresses using iptables. So if I got repeated brute force attempt on my admin password from say 192.187.111.146 [this is a real example], I’d block the the entire range by doing:

iptables -A INPUT -s 192.187.0.0/16 -j DROP

This was pretty tedious, but I only needed to do it around once a week. For some reason [presumably it’s some sort of off the shelf attack script], the attack counts from specific IPs always seemed to top out at exactly 1460 hits. Last week, I got my daily email which showed someone had hit the site 49k times that day. By the time I got home and did some digging in the logs, it was totalling more than 80k for the week. I suddenly realised that my manual blocking was way too blunt a tool, so last weekend I wrote a log scanning  script launched by cron every 30 minutes. It pattern matches on the login form in the Apache log file and sends me an email if an individual IP tops out at over a certain threshold. The longer term plan was that I’d call another script that would automatically insert the block rule in iptables. There would be a bit of messing around with state management [seek to a point in the log file based on the timestamp to not go over the same ground twice or something] and it would have to be run as root, but it would be better than nothing. I happened to mention this to someone at work who told me about fail2ban, which is doing the same thing [but better than I could have implemented it].

I also had a dig around at ssh logs, and discovered that some kind soul was trying to brute force the root password, and was up to 8k attempts for the week. Subsequent digging showed that the same thing was happening with my Imap server, but on a smaller scale.

While what I’ve suggested here isn’t necessarily bullet proof, it’s a reasonable start. Bear in mind that the types of attacks I’m seeing are commensurate with the value of my site, which in commercial terms is zero. And oh, the irony, when my server gets brought to its knees next week by someone with serious intent :).

The short version: there is no short version. Implementing server side functionality inevitably involves a fair amount of legwork. Also, an advance warning: I’m a novice at the programming language I chose to implement my web service in – Java. For this reason, I’m only going to post code snippets for problems you need to solve. There may be better ways of doing this. Finally, I’m leaving my Skill permanently in development mode: I don’t intend to publish. While it’s something I find useful, this was primarily a learning exercise for me. If you’ve ended up here via Google, hopefully you’ll find something you can re-purpose.

I’ll come to the Amazon side of things in a bit. First up, you will need a server to host your web service. You have a couple of options here [as an alternative to Lambda]: first, you can host on your home network. If you have DHCP, the typical process is to configure your broadband router for DDNS, and have a port forwarding rule on to your server. I decided to take another approach, simply because I wanted to try it out. I’ve paid for a vm with a hosting outfit called OVH. They have a really nice setup, so I’ve spent less than £10 for a server for 3 months. I’ll probably keep it on permanently as I like the flexibility.

I decided to implement my web service as a servlet. There are plenty of tutorials on how to set up the stub methods [and all the various libraries and files structures you will need when you come to export a War file]. I used Eclipse as my IDE. My testing cycle – which I imagine is pretty common – was to run tomcat on my laptop where I was doing the development. I could then build and deploy to that locally, and then test the interface by POSTing data to it with the Chrome plugin Postman. When I had something I wanted to deploy to my vm, I exported the WAR file, scp’ed it to the OVH server’s web apps directory, removed the old War [and expanded directory] and restarted.

A couple of foundational steps on the remote server. The OVH setup is a vanilla install of your operating system of choice – I went with Debian. As well as installing your server software [tomcat] and its requirements [Java], you’ll need to create a user for it. As Amazon requires the server to run on a privileged port, you’ll need to take this into account. As you really won’t want to run the server as root, I googled around for a snippet of C code which I could adapt and compile, which could use setuid to start my server as another user. This is something to take care over if you intend to run your service in anger, and you have no choice: you have got to run your service on port 443.

The next step on the server side, related to that privileged port, is TLS. Because I tried a ‘real’ CA, which I thought was on Amazon’s supported list [Let’s Encrypt], I also went to the trouble of registering a name for my vm’s IP. If you’re going to stay in developer mode, you may not need to do this. When I realised I was getting TLS handshake errors, I changed the config and went with an openssl self-signed certificate.

Turning to the configuration set up on the Amazon side, it’s generally pretty well documented, but there are a couple of exceptions to this. First, in the Skill Information, you have to provide an Invocation Name. I know of one other developer who made the same mistake as me because of the way the debugging pop-up information is worded: I assumed that the invocation string needed to start with ‘ask’, or equivalent. It doesn’t. If you just want your skill to be invoked with ‘widget counter’, you just have those two words, and then kick it off on your Echo with ‘Alexa, ask widget counter’, followed by one of your sample utterances.

This seems incredibly obvious, but there is a warning on the testing page which states, ‘Please complete the Interaction Model tab to start testing this skill’, I went off on a wild goose chase thinking I’d done something else wrong. That warning is arguably one of the misleading features of the whole orchestration interface that Amazon provides. It stays there permanently, no matter what you do.

There are some good examples of the Intent Schema, and other parts of the interaction model already out there but one more can’t hurt. Before I get into it, a quick explanation of what my skill does. My server side code ‘screen scrapes’ a train operator’s web site every 10 minutes. I then parse the rendered HTML looking for specific information about service conditions. That information forms the basis of the response.

Intent Schema:

{
   "intents":[
      {
         "intent":"TrainTimes",
         "slots":[
            {
               "name":"TrainServices",
               "type":"LIST_OF_SERVICES"
            }
         ]
      }
    ]
}

The custom slot looks like:

LIST_OF_SERVICES Peterborough | Luton | Cambridge | Brighton

and then some sample utterances:

TrainTimes how is {TrainServices}
TrainTimes how is the {TrainServices} service
TrainTimes how is the {TrainServices} line

[Brief aside: why ‘train times’, when it’s not timing related? This is a vestige of trying to navigate the mistake I made with the invocation name. I have a strong accent and so was trying all sorts, so at one point it was called ‘big dog’ :)].

The rest of the Amazon interface is pretty straightforward, such as the uploading of self signed certificate [if that’s the approach you choose to take]. One final step before moving away from the interface is the testing. The example question, ‘how is the peterborough service’ gets transformed into the following blob of JSON:

{
  "session": {
    "sessionId": "SessionId.[GUID here]",
    "application": {
      "applicationId": "amzn1.ask.skill.[another GUID here]"
    },
    "attributes": {},
    "user": {
      "userId": "amzn1.ask.account.[long account string here]"
    },
    "new": true
  },
  "request": {
    "type": "IntentRequest",
    "requestId": "EdwRequestId.[one more GUID here]",
    "locale": "en-GB",
    "timestamp": "2017-02-06T13:43:37Z",
    "intent": {
      "name": "TrainTimes",
      "slots": {
        "TrainServices": {
          "name": "TrainServices",
          "value": "Peterborough"
        }
      }
    }
  },
  "version": "1.0"
}

You will obviously need to check that your web service is able to parse this. As per my comments on  my testing cycle, I copied this into Postman as the raw content of a POST.

I’ll briefly go into some more detail about how my implementation works, because when you get into the business end of parsing the input JSON, you need to map it back to some data to respond with.

The parsing of the train company website as a skill isn’t my first bite at the implementation. I started by trying to write a widget for Android. It’s not as simple as just grabbing the HTML, though: the site uses Ajax to render the results. I ended up using HtmlUnit. Because it’s pretty slow, I implemented a class outside the servlet which uses a combination of a ServletContextListener, and then a ScheduledExectuorService. I got the example code from here to work from. The one gotcha is that your web.xml needs to refer to the class.

Next we get on to the hacky part of passing the information on to the servlet. What I did – having the listener write to a flat file which the servlet reads – is a reflection of my novice levels with Java.

So, returning to the list of general problems to solve: having received the POST data, your service then needs to get hold of the data, and then parse the JSON. For the first part, I tried  a few different options and then settled on the getBody implementation I found here.

The parsing of the JSON itself: it’s the first time I’ve ever done this and it feels way more complicated than it should be. I tried a couple of different parsing libraries, but ended up using JSON.simple.

Going back to the JSON data from the Amazon test interface, you have two consecutive objects, the session and the request. For an industrial strength implementation, there are things you need to do with the session data [I’ve also skipped over the TLS client certificate validation, which Amazon stipulates. While perfectly sensible for security purposes, it’s not necessary to get your development implementation up and running.

So the request itself contains a series of embedded objects that you need to unpack, in turn, until I finally get to the slots data. Your implementation will vary, but mine looks like this:

        JSONParser parser = new JSONParser();
        try {
            JSONObject obj = (JSONObject) parser.parse(postData);
            JSONObject jrequest = (JSONObject) obj.get("request");
            log.warning("request: " + jrequest.toString());
            JSONObject intent = (JSONObject) jrequest.get("intent");
            log.warning("intent: " + intent.toString());
            JSONObject slots = (JSONObject) intent.get("slots");
            log.warning("slots: " + slots.toString());
            JSONObject trainSvces = (JSONObject) slots.get("TrainServices");
            log.warning("trainSvces: " + trainSvces.toString());
            String trainSvceVal = (String) trainSvces.get("value");
            log.warning("trainSvceVal: " + trainSvceVal);
            resultString = trainSvceVal;
        } catch (ParseException e) {
            log.warning("ParseException error: ");
            ...
        } 

Again, for a ‘proper’ implementation, you are going to have to test each of the sub-objects. My code is taking a leap of faith :).

Having lost the will to live with the parsing, I have to admit that, having figured out which piece of the train-related data the web service needs to respond with, I then print the JSON straight out in the required format.

        response.setContentType("application/json;charset=UTF-8");
        PrintWriter out = response.getWriter();
        out.println("{");
        out.println("  \"response\": {");
        out.println("      \"outputSpeech\": {");
        out.println("         \"type\": \"PlainText\",");
        out.println("         \"text\": \"" + resultsString + "\"");
        out.println("    },");
        out.println("    \"shouldEndSession\": true");
        out.println("    }");
        out.println("}"); 

So, not exactly a thing of beauty, but it works.

If I have any better ideas for future skills to implement, I’ll start with the certificate that Amazon needs. There’s an outfit called StartSSL which it looks like they accept, but which requires email based validation on an address corresponding to the domain. I started looking at setting up PostFix for this – one for another day.