Web Open Font Format and Embedded OpenType fonts

In the upcoming 0.7.6 release of the Profiler a great effort has been invested into supporting font formats. After SFonts (TrueType and collections) released with 0.7.5, the first font formats I’m going to present are WOFFs and EOTs. Both this font formats are actually containers for SFonts and they are used to deploy fonts on the web and are therefore usually compressed.

The Web Open Font Format (WOFF) is quite easy as format and certainly the more secure and logical of the two.


Being containers for SFonts, the Profiler contains a converter to SFont, which gives the ability to analyze the compressed font.

Same applies to Embedded OpenType fonts which is a format created by Microsoft.


These fonts are not only deployed on the web but can be found in Office documents as well. Unfortunately the Profiler doesn’t yet support compressed Embedded OpenType fonts. The compression happens in stages and uses a custom compression algorithm created by Microsoft and based on lz77 called lzcomp. This algorithm has been used as an exploit vector for remote code execution.

TrueType & TrueType Collection Fonts

We’re happy to announce that the new 0.7.5 version of the Profiler offers support for TrueType (SFNT) fonts. This is the first step in the direction of giving our users a complete solution for font formats and analyze them inside documents. The recent threat landscape has seen the rise of fonts as an infection vector. Two notable examples are Duqu and the iOS 4.3 jailbreak.


In the screenshot above we see several TrueType fonts being analyzed inside of a PDF document.

One of the offered features is the capability to output the code contained in a TrueType font. While this feature can’t be used to establish the risk factor of a font at glance, it is useful to security analysts.

TrueType code

Functions are associated with their glyph name, in order to more easily establish which instructions are associated to a particular character.

The report also shows the metadata, which doesn’t offer any kind of security assurance, but might be of interest to the user.

TrueType metadata

As with every file type supported by the Profiler it is possible to inspect the format of TrueType and TrueType Collections fonts as well.

TTC format

The screenshot above shows the format of a TrueType collection. Collections host more than one font and every one of them can be analyzed.

It should be noted that TrueType fonts are hosted in a format called SFont. SFonts can also host other font types. An example of this scenario are OpenType fonts by Microsoft, which can be TrueType compatible but go beyond the TrueType format. While the current support for TrueType also allows to inspect OpenType fonts, it is our intent in the near future to cover OpenType fonts in detail.

More updates related to fonts should soon be available. So, as usual, stay tuned. 🙂

Pastebin plugin

Coming with the new 0.7.4 release, the Pastebin action is a handy tool for easy sharing of text-based content with colleagues and friends.

Pastebin plugin (result)

Thanks to the new property editor, the full feature set has been implemented; amongst the usual options like syntax highlight, title and content, the user will also be able to change the visibility preference and decide for how long the content should be available online.

Pastebin plugin (settings)

A security confirmation check has also been added to avoid unintentional disclosure of information. 🙂

PDF object search

The soon to be released version 0.7.4 of the Profiler features a useful PDF object search functionality. The introduction of this feature was possible thanks to the newly introduced parameters API and format specific actions.

PDF search action

Through this action it’s possible to perform predefined searches as for object with streams, JavaScript or embedded files.

PDF JavaScript search

But it’s also possible to perform custom dictionary searches.

PDF dictionary search

Matches can be tagged and highlighted. Also new searches can be performed without resetting previous matches. In fact, in the screenshot below we can observe two different type of matches.

PDF search matches

This was a requested feature and it certainly is very useful when analyzing PDFs. Stay tuned as more important news will be soon announced. 🙂

Parameters & Settings

In the upcoming release of the Profiler (0.7.4) actions and scripts have a way to ask the user for parameters and settings: a new set of APIs featuring a property editor dialog.


Here’s the complete code of the sample followed by explanations.

Let’s start with the action code.

This code shows a property editor dialog specifying an XML string to create the dialog, a settings key (optional) and a callback (optional). The return value is a dictionary with the values of the properties with their id as key or None when the dialog is rejected.

I’ll talk later about what the settings key means. Let’s first understand the XML syntax.

The XML root tells the function to create a property editor with the (optional) title “Settings”.

A section is created. Properties do not need a section as parent, but it might be visually more appealing to specify one. Child nodes of sections are properties. Properties can have other properties as child nodes, but not sections.

The first property being created is a single line edit field with the id of 0 and a value of “object”. id and type attributes are mandatory for properties. Sections may optionally specify an id as we’ll see later.

Here we have one static property with two integer child properties. A static property is a non-editable text which can only be set programmatically.

An integer property can specify various things, although the only mandatory attributes remain id and type. Most of the attributes are self-explanatory. align specifies the 0s which may prefix the number to obtain the desired alignment. For example, the number 1 with an alignment of 4 will be displayed as 0001. maxbits specifies the maximum number of bits the integer can measure (at the time it defaults to 10000).

Inside a new section a check property is specified.

Following there’s a combo property. The list of the combo is specified as the child node list and the default index is specified as the value attribute.

These three properties are related to file operations. When the user activates one, he will be able to open a file dialog to perform the requested operation.

The text property specifies a multi-line text field. When the user activates this property, a multi-line text input dialog is displayed in order to change the value.

The properties in this section are not any different than those seen before, but it should be noted that in this case the section has an id attribute. Giving an id to a section makes it possible to set the visibility or the enabled/disabled state of the section and its children.

Let’s analyze the callback.

ParamsCallback has three arguments. pe is the ProPropertyEditor class instance. id is the property being modified or the notification code (Init, Accept). userdata is the custom data specified in the askParams method, which in this case is None.

The UpdateSize function updates the value of the static property when one of its children has been changed. Other fields are changed for the purpose of demonstration.

This line sets the visibility of the last section.

The setErrors method allows to highlight properties in red. The idea is that a callback might perform some checks when being notified with the ProPropertyEditor.Accept code, highlight properties which are not accepted and return False to ask the user to enter correct values. Calling clearErrors or setErrors with an empty list will achieve the same result.

Here’s a screenshot with two highlighted properties and the last section hidden.

Properties 2

Let’s go back to askParams method. I haven’t yet explained the settings key (“Test”). This is an optional argument: it specifies if and where the values of the properties should be stored in case the dialog is accepted. The specified key name should be similar or equal to the name of the action to avoid conflicts. If the property dialog changes and the old settings must be discarded, it can be achieved by specifying a version at the end of the key name: “Test#1”. When the version number is omitted, it defaults to 0.

It should be noted that static and multi-line text properties are not saved automatically. The latter to avoid too large values being stored. However, it is still possible to save and restore these values through the Init and Accept notification codes by using the settings API.

Key names starting with “_” are reserved and shouldn’t be used.

Finally, let’s see how actions can now optionally specify a configuration function.

Configure action

config specifies the name of a function to be called inside of file.

This new set of APIs opens the door to many interesting customizations for actions, scripts and other components, and we will soon show you some of them. 🙂

Python 3 SDK: actions & custom scripts

The new version 0.7.3 of the Cerbero Profiler features a powerful Python 3 SDK, which enables to run custom scripts and actions. Let’s first take a look at a simple script. Just press Ctrl+R (or “Execute action…” in the context menu of a view) and go to “Custom”:

Simple script

As it is easy to guess, this basic script shows a message box. Message boxes can be used to notify things to the user or to ask him a question. Most of the time they won’t be necessary and the standard output can be used instead. All the output produced by Python will be visible in the output console. In fact, the console will become visible when something is printed to it (this behavior can be changed from the options).

Output console

The SDK can be used to retrieve data from views, set their data, create new views and so on. But before looking at a more advanced script, let’s talk about a new feature of the Profiler: actions. For the purpose of demonstration let’s take a malware with obfuscated JavaScript.

Obfuscated JS

And now let’s again press Ctrl+R in the context of the obfuscated JavaScript.


By activating the “Beautify JavaScript” action we will get a beautified version (jsbeautifier.org) of the previously obfuscated JavaScript.

Beautified JS

Python actions are defined in the config/actions.cfg file.

The section name (JSBeautify) specifies the id of the action and is also the name of the function to be called in file. The file field supports absolute paths as well, otherwise the script will be loaded from plugins/python. The category and label specify in which category inside the execute action dialog the action should be grouped and its description. When the category field is omitted, it will default to “Other”.

The context field is very important as it specifies when the action should be available for use. In this specific case, the action can be used in any text view. An action can also be available in more than one context.

Now let’s see how to create an action which decodes some selected text from base64 and shows the decoded bytes in a new hex view. First it is necessary to define the action.

And here’s the Python code.

Let’s see it in action with a PGP public key.

PGP Public Key

And the decoded data.

PGP decoded key

Although the SDK is brand new, you will see very soon some new useful actions implemented. 🙂

MSI support

Even though CAB file support is still under development, the CFBF parser already lets us inspect Windows Installer packages and patches.

MSI streams

Having such feature comes in handy when you want to analyse their contents, and eliminates the need for external tools.

In the screenshot above, I’ve selected one of the DLLs that link to MSI custom actions, i.e. code that is potentially executed as soon as Windows Installer opens the package.

Data type quotas

While it is already possible to inspect data ranges through the hex view and its bar on the left, now there’s a new view to express the type data quotas. This is useful in order to understand at first sight how much of a file is actually part of the format, how much is custom data and how much is foreign or unreferenced data.

Data quotas pie

Also, from the options it is possible to fine tune at which point foreign data should be reported as a security problem. The amount can be expressed either in percentage and/or size.

Foreign quota limit

The security of non-exec files

This article is based on a speech I gave couple of months ago at DeepSec. I wrote it during the summer, which means I would now expand on some of the paragraphs. Nonetheless, I hope you’ll enjoy the read.


As we know there’s has been a huge increase of malware attacks carried out with files other than executable ones. I’m aware that this is a very generic definition. If we consider a PDF with JavaScript stored inside, would you call it an executable? Probably you wouldn’t, although the script might be executed. Even saying that an executable can only be a file which contains native machine code isn’t accurate. A .NET assembly which contains only managed code would still be considered an executable. But a Shockwave Flash file (with its SWF extension) may not be regarded as standing in the same category. Of course, a Shockwave Flash file is not the same thing as a .NET assembly, but they both contain byte code which at some point is converted into machine code and is executed.

This means that the barriers between executable and non-executable files are thin and in many cases there’s a problem of perception, hence the difficulty of giving this article a completely accurate title. A more appropriate one would have been: the security of all those files generally perceived as harmless or, at least, less dangerous than applications. You may guess why I opted for the other title.

Does this look infected? (no, I’m talking about the file)

This is the most feared issue. How can a non-exec file infect a system? Basically through:

  • Scripting or byte code
  • Shellcode (buffer overflows)
  • Dangerous format features

These vectors are the most common for infection.

Scripting and byte code (security α 1/functionality)

Many file types offer the capability to execute code. However, a distinction has to be drawn between those file formats which offer it just as an additional feature and those formats which completely rely on it.

Shockwave Flash has been a very popular infection vector thanks to its powerful byte code. While it may be apparent even to an unskilled user that a Flash game on the internet is a sort of application, it’s not as apparent under other circumstances.

Very often playing a video in a web browser involves Flash. And I’ve heard many users referring to this as “Flash videos”. They don’t know that what actually happens is that a Flash file is downloaded and its ActionScript code executed.

Download the PDF to continue the reading.

Automatic hierarchical profiling

One of the technical priorities of the Cerbero Profiler is to automatically analyze files embedded in the main file being profiled. Not only that, it automatically analyzes files embedded into embedded files as well, and so on, going completely through the embedding hierarchy.

This is necessary, because otherwise it is not possible to fully evaluate the threats and privacy issues which a file contains. To demonstrate this feature, I’ve built a silly Shockwave Flash file with a multiple level embedding hierarchy.

Stay tuned, there’s more to come.