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• How to make your plugin configurable – Introducing the Piwik Platform

  18 septembre 2014, par Thomas Steur — Development

  This is the next post of our blog series where we introduce the capabilities of the Piwik platform (our previous post was How to add new pages and menu items to Piwik). This time you will learn how to define settings for your plugin. For this tutorial you will need to have basic knowledge of PHP.

  What can I do with settings ?

  The Settings API offers you a simple way to make your plugin configurable within the Admin interface of Piwik without having to deal with HTML, JavaScript, CSS or CSRF tokens. There are many things you can do with settings, for instance let users configure :

  • connection infos to a third party system such as a WordPress installation.
  • select a metric to be displayed in your widget
  • select a refresh interval for your widget
  • which menu items, reports or widgets should be displayed
  • and much more

  Getting started

  In this series of posts, we assume that you have already set up your development environment. If not, visit the Piwik Developer Zone where you’ll find the tutorial Setting up Piwik.

  To summarize the things you have to do to get setup :

  • Install Piwik (for instance via git).
  • Activate the developer mode : ./console development:enable --full.
  • Generate a plugin : ./console generate:plugin --name="MySettingsPlugin". There should now be a folder plugins/MySettingsPlugin.
  • And activate the created plugin under Settings => Plugins.

  Let’s start creating settings

  We start by using the Piwik Console to create a settings template :

  ./console generate:settings

  The command will ask you to enter the name of the plugin the settings should belong to. I will simply use the above chosen plugin name “MySettingsPlugin”. There should now be a file plugins/MySettingsPlugin/Settings.php which contains already some examples to get you started easily. To see the settings in action go to Settings => Plugin settings in your Piwik installation.

  

  Adding one or more settings

  Settings are added in the init() method of the settings class by calling the method addSetting() and passing an instance of a UserSetting or SystemSetting object. How to create a setting is explained in the next chapter.

  Customising a setting

  To create a setting you have to define a name along some options. For instance which input field should be displayed, what type of value you expect, a validator and more. Depending on the input field we might automatically validate the values for you. For example if you define available values for a select field then we make sure to validate and store only a valid value which provides good security out of the box.

  For a list of possible properties have a look at the SystemSetting and UserSetting API reference.

  class Settings extends \Piwik\Plugin\Settings
  
  {
  
      public $refreshInterval;
  
  
  
      protected function init()
  
      {
  
          $this->setIntroduction('Here you can specify the settings for this plugin.');
  
  
  
          $this->createRefreshIntervalSetting();
  
      }
  
  
  
      private function createRefreshIntervalSetting()
  
      {
  
          $this->refreshInterval = new UserSetting('refreshInterval', 'Refresh Interval');
  
          $this->refreshInterval->type = static::TYPE_INT;
  
          $this->refreshInterval->uiControlType = static::CONTROL_TEXT;
  
          $this->refreshInterval->uiControlAttributes = array('size' => 3);
  
          $this->refreshInterval->description = 'How often the value should be updated';
  
          $this->refreshInterval->inlineHelp = 'Enter a number which is >= 15';
  
          $this->refreshInterval->defaultValue = '30';
  
          $this->refreshInterval->validate = function ($value, $setting) {
  
              if ($value < 15) {
  
                  throw new \Exception('Value is invalid');
  
              }
  
          };
  
  
  
          $this->addSetting($this->refreshInterval);
  
      }
  
  }

  In this example you can see some of those properties. Here we create a setting named “refreshInterval” with the display name “Refresh Interval”. We want the setting value to be an integer and the user should enter this value in a text input field having the size 3. There is a description, an inline help and a default value of 30. The validate function makes sure to accept only integers that are at least 15, otherwise an error in the UI will be shown.

  

  You do not always have to specify a PHP type and a uiControlType. For instance if you specify a PHP type boolean we automatically display a checkbox by default. Similarly if you specify to display a checkbox we assume that you want a boolean value.

  Accessing settings values

  You can access the value of a setting in a widget, in a controller, in a report or anywhere you want. To access the value create an instance of your settings class and get the value like this :

  $settings = new Settings();
  
  $interval = $settings->refreshInterval->getValue()

  Type of settings

  The Piwik platform differentiates between UserSetting and SystemSetting. User settings can be configured by any logged in user and each user can configure the setting independently. The Piwik platform makes sure that settings are stored per user and that a user cannot see another users configuration.

  A system setting applies to all of your users. It can be configured only by a user who has super user access. By default, the value can be read only by a super user as well but often you want to have it readable by anyone or at least by logged in users. If you set a setting readable the value will still be only displayed to super users but you will always be able to access the value in the background.

  Imagine you are building a widget that fetches data from a third party system where you need to configure an API URL and token. While no regular user should see the value of both settings, the value should still be readable by any logged in user. Otherwise when logged in users cannot read the setting value then the data cannot be fetched in the background when this user wants to see the content of the widget. Solve this by making the setting readable by the current user :

  $setting->readableByCurrentUser = !Piwik::isUserIsAnonymous();

  Publishing your Plugin on the Marketplace

  In case you want to share your settings or your plugin with other Piwik users you can do this by pushing your plugin to a public GitHub repository and creating a tag. Easy as that. Read more about how to distribute a plugin.

  Advanced features

  Isn’t it easy to create settings for plugins ? We never even created a file ! The Settings API already offers many possibilities but it might not yet be as flexible as your use case requires. So let us know in case you are missing something and we hope to add this feature at some point in the future.
  
  If you have any feedback regarding our APIs or our guides in the Developer Zone feel free to send it to us.

• How to make your plugin configurable – Introducing the Piwik Platform

  18 septembre 2014, par Thomas Steur — Development

  This is the next post of our blog series where we introduce the capabilities of the Piwik platform (our previous post was How to add new pages and menu items to Piwik). This time you will learn how to define settings for your plugin. For this tutorial you will need to have basic knowledge of PHP.

  What can I do with settings ?

  The Settings API offers you a simple way to make your plugin configurable within the Admin interface of Piwik without having to deal with HTML, JavaScript, CSS or CSRF tokens. There are many things you can do with settings, for instance let users configure :

  • connection infos to a third party system such as a WordPress installation.
  • select a metric to be displayed in your widget
  • select a refresh interval for your widget
  • which menu items, reports or widgets should be displayed
  • and much more

  Getting started

  In this series of posts, we assume that you have already set up your development environment. If not, visit the Piwik Developer Zone where you’ll find the tutorial Setting up Piwik.

  To summarize the things you have to do to get setup :

  • Install Piwik (for instance via git).
  • Activate the developer mode : ./console development:enable --full.
  • Generate a plugin : ./console generate:plugin --name="MySettingsPlugin". There should now be a folder plugins/MySettingsPlugin.
  • And activate the created plugin under Settings => Plugins.

  Let’s start creating settings

  We start by using the Piwik Console to create a settings template :

  ./console generate:settings

  The command will ask you to enter the name of the plugin the settings should belong to. I will simply use the above chosen plugin name “MySettingsPlugin”. There should now be a file plugins/MySettingsPlugin/Settings.php which contains already some examples to get you started easily. To see the settings in action go to Settings => Plugin settings in your Piwik installation.

  

  Adding one or more settings

  Settings are added in the init() method of the settings class by calling the method addSetting() and passing an instance of a UserSetting or SystemSetting object. How to create a setting is explained in the next chapter.

  Customising a setting

  To create a setting you have to define a name along some options. For instance which input field should be displayed, what type of value you expect, a validator and more. Depending on the input field we might automatically validate the values for you. For example if you define available values for a select field then we make sure to validate and store only a valid value which provides good security out of the box.

  For a list of possible properties have a look at the SystemSetting and UserSetting API reference.

  class Settings extends \Piwik\Plugin\Settings
  
  {
  
      public $refreshInterval;
  
  
  
      protected function init()
  
      {
  
          $this->setIntroduction('Here you can specify the settings for this plugin.');
  
  
  
          $this->createRefreshIntervalSetting();
  
      }
  
  
  
      private function createRefreshIntervalSetting()
  
      {
  
          $this->refreshInterval = new UserSetting('refreshInterval', 'Refresh Interval');
  
          $this->refreshInterval->type = static::TYPE_INT;
  
          $this->refreshInterval->uiControlType = static::CONTROL_TEXT;
  
          $this->refreshInterval->uiControlAttributes = array('size' => 3);
  
          $this->refreshInterval->description = 'How often the value should be updated';
  
          $this->refreshInterval->inlineHelp = 'Enter a number which is >= 15';
  
          $this->refreshInterval->defaultValue = '30';
  
          $this->refreshInterval->validate = function ($value, $setting) {
  
              if ($value < 15) {
  
                  throw new \Exception('Value is invalid');
  
              }
  
          };
  
  
  
          $this->addSetting($this->refreshInterval);
  
      }
  
  }

  In this example you can see some of those properties. Here we create a setting named “refreshInterval” with the display name “Refresh Interval”. We want the setting value to be an integer and the user should enter this value in a text input field having the size 3. There is a description, an inline help and a default value of 30. The validate function makes sure to accept only integers that are at least 15, otherwise an error in the UI will be shown.

  

  You do not always have to specify a PHP type and a uiControlType. For instance if you specify a PHP type boolean we automatically display a checkbox by default. Similarly if you specify to display a checkbox we assume that you want a boolean value.

  Accessing settings values

  You can access the value of a setting in a widget, in a controller, in a report or anywhere you want. To access the value create an instance of your settings class and get the value like this :

  $settings = new Settings();
  
  $interval = $settings->refreshInterval->getValue()

  Type of settings

  The Piwik platform differentiates between UserSetting and SystemSetting. User settings can be configured by any logged in user and each user can configure the setting independently. The Piwik platform makes sure that settings are stored per user and that a user cannot see another users configuration.

  A system setting applies to all of your users. It can be configured only by a user who has super user access. By default, the value can be read only by a super user as well but often you want to have it readable by anyone or at least by logged in users. If you set a setting readable the value will still be only displayed to super users but you will always be able to access the value in the background.

  Imagine you are building a widget that fetches data from a third party system where you need to configure an API URL and token. While no regular user should see the value of both settings, the value should still be readable by any logged in user. Otherwise when logged in users cannot read the setting value then the data cannot be fetched in the background when this user wants to see the content of the widget. Solve this by making the setting readable by the current user :

  $setting->readableByCurrentUser = !Piwik::isUserIsAnonymous();

  Publishing your Plugin on the Marketplace

  In case you want to share your settings or your plugin with other Piwik users you can do this by pushing your plugin to a public GitHub repository and creating a tag. Easy as that. Read more about how to distribute a plugin.

  Advanced features

  Isn’t it easy to create settings for plugins ? We never even created a file ! The Settings API already offers many possibilities but it might not yet be as flexible as your use case requires. So let us know in case you are missing something and we hope to add this feature at some point in the future.
  
  If you have any feedback regarding our APIs or our guides in the Developer Zone feel free to send it to us.

• An introduction to reverse engineering

  22 janvier 2011

  (This blog is still in hibernation, but I needed somewhere to post this)

  Reverse engineering is one of those wonderful topics, covering everything from simple "guess how this program works" problem solving, to poking at silicon with scanning electron microscopes. I’m always hugely fascinated by articles that walk through the steps involved in these types of activities, so I thought I’d contribute one back to the world.

  In this case, I’m going to be looking at the export bundle format created by the Tandberg Content Server, a device for recording video conferences. The bundle is intended for moving recordings between Tandberg devices, but it’s also the easiest way to get all of the related assets for a recorded conference. Unfortunately, there’s no parser available to take the bundle files (.tcb) and output the component pieces. Well, that just won’t do.

  For this type of reverse engineering, I basically want to learn enough about the TCB format to be able to parse out the individual files within it. The only tools I’ll need in this process are a hex editor, a notepad, and a way to convert between hex and decimal (the OS X calculator will do fine if you’re not the type to do it in your head).

  Step 1 : Basic Research
  After Googling around to see if this was a solved issue, I decided to dive into the format. I brought a sample bundle into my trusty hex editor (in this case Hex Fiend).

  

  A few things are immediately obvious. First, we see the first four bytes are the letters TCSB. Another quick visit to Google confirms this header type isn’t found elsewhere, and there’s essentially no discussion of it. Going a few bytes further, we see "contents.xml." And a few bytes after that, we see what looks like plaintext XML. This is a pretty good clue that the TCB file consists of a . Let’s scan a bit further and see if we can confirm that.
  
  In this segment, we see the end of the XML, and something that could be another filename - "dbtransfer" - followed by what looks like gibberish. That doesn’t help too much. Let’s keep looking.
  
  Great - a .jpg ! Looking a bit further, we see the letters "JFIF," which is recognizable as part of a JPEG header. If you weren’t already familiar with that, a quick google for "jpg hex header" would clear up any confusion. So, we’ve got the basics of the file format down, but we’ll need a little bit more information if we’re going to write a parser.

  Step 2 : Finding the pattern
  We can make an educated guess that a file like this has to provide a few hints to a decoder. We would either expect a table of contents, describing where in the bundle each individual file was located, some sort of stop bit marking the boundary between files, byte offsets describing the locations of files, or a listing of file lengths.

  There isn’t any sign of a table of contents. Let’s start looking for a stop bit, as that would make writing our parser really easy. Want I’m going to do is pull out all of the data between two prospective files, and I want two sets to compare.
  I’ve placed asterisks to flag the bytes corresponding to the filenames, since those are known.

  1E D1 70 4C 25 06 36 4D 42 E9 65 6A 9F 5D 88 38 0A 00 *64 62 74 72 61 6E 73 66 65 72* 42 06 ED 48 0B 50 0A C4 14 D6 63 42 F2 BF E3 9D 20 29 00 00 00 00 00 00 DE E5 FD

  01 0C 00 *63 6F 6E 74 65 6E 74 73 2E 78 6D 6C* 9E 0E FE D3 C9 3A 3A 85 F4 E4 22 FE D0 21 DC D7 53 03 00 00 00 00 00 00

  The first line corresponds to the "dbtransfer" entry, the second to the "contents.xml" entry. Let’s trim the first entry to match the second.

  38 0A 00 *64 62 74 72 61 6E 73 66 65 72* 42 06 ED 48 0B 50 0A C4 14 D6 63 42 F2 BF E3 9D 20 29 00 00 00 00 00 00

  01 0C 00 *63 6F 6E 74 65 6E 74 73 2E 78 6D 6C* 9E 0E FE D3 C9 3A 3A 85 F4 E4 22 FE D0 21 DC D7 53 03 00 00 00 00 00 00

  It looks like we’ve got three bytes before the filename, followed by 18 bytes, followed by six bytes of zero. Unfortunately, there’s no obvious pattern of bits which would correspond to a "break" between segments. However, looking at those first three bytes, we see a 0x0A, and a 0x0C, two small values in the same place. 10 and 12. Interesting - the 12 entry corresponds with "contents.xml" and the 10 entry corresponds with "dbtransfer". Could that byte describe the length of the filename ? Let’s look at our much longer JPG entry to be sure.

  70 4A 00 *77 77 77 5C 73 6C 69 64 65 73 5C 64 37 30 64 35 34 63 66 2D 32 39 35 62 2D 34 31 34 63 2D 61 38 64 66 2D 32 66 37 32 64 66 33 30 31 31 35 65 5C 74 68 75 6D 62 6E 61 69 6C 73 5C 74 68 75 6D 62 6E 61 69 6C 30 30 2E 6A 70 67*

  0x4A - 74, corresponding to a 74 character filename. Looks like we’re in business.

  At this point, it’s worth an aside to talk about endianness. I happen to know that the Tandberg Content Server runs Windows on Intel, so I went into this with the assumption that the format was little-endian. However, if you’re not sure, it’s always worth looking at words backwards and forwards, just in case.

  So we know how to find our filename. Now how do we find our file data ? Let’s go back to our JPEG. We know that JPEGs start with 0xFFD8FFE0, and a quick trip to Google also tells us that they end with 0xFFD9. We can use that to pull a sample jpeg out of our TCB, save it to disk, and confirm that we’re on the right track.
  

  This is one of those great steps in reverse engineering - concrete proof that you’re on the right track. Everything seems to go quicker from this point on.

  So, we know we’ve got a JPEG file in a continuous 2177 byte segment. We know that the format used byte lengths to describe filenames - maybe it also uses byte lengths to describe file lengths. Let’s look for 2177, or 0x8108, near our JPEG.

  

  Well, that’s a good sign. But, it could be coincidental, so at this point we’d want to check a few other files to be sure. In fact, looking further in some file, we find some larger .mp4 files which don’t quite match our guess. It turns out that file length is a 32bit value, not a 16bit value - with our two jpegs, the larger bytes just happened to be zeros.

  Step 3 : Writing a parser

  "Bbbbbut...", I hear you say ! "You have all these chunks of data you don’t understand !"

  True enough, but all I care about is getting the files out, with the proper names. I don’t care about creation dates, file permissions, or any of the other crud that this file format likely contains.

  

  Let’s look at the first two files in this bundle. A little bit of byte counting shows us the pattern that we can follow. We’ll treat the first file as a special case. After that, we seek 16 bytes from the end of file data to find the filename length (2 bytes), then we’re at the filename, then we seek 16 bytes to find the file length (4 bytes) and seek another 4 bytes to find the start of the file data. Rinse, repeat.

  I wrote a quick parser in PHP, since the eventual use for this information is part of a larger PHP-based application, but any language with basic raw file handling would work just as well.

  tcsParser.txt
  This was about the simplest possible type of reverse engineering - we had known data in an unknown format, without any compression or encryption. It only gets harder from here...