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SECURITY VULNERABILITIES OF FILEMAKER PLATFORM API’S: AN UPDATE

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Steven H. Blackwell

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Security Vulnerabilities of FileMaker Platform API’s:  An Update

 January 9th 2017

In an April 2016 entry on this BLOG titled The FileMaker Platform API’s Are Your Friends, Right? [http://fmforums.com/blogs/entry/1535-the-filemaker-platform-api’s-are-your-friends-right/] I discussed a number of FileMaker Platform security issues centered on the uncontrolled use of a number of external Application Program Interfaces (API’s). There are at least nine of these API, possibly more, if ExecuteSQL is included. The central thesis of that article was that these API’s provide unexpected attack vectors to compromise FileMaker Platform files.  As noted at the time:

Many FileMaker developers are not aware, however, that these API’s have the capability to access customer or client solutions in unexpected ways and to extract or insert data, to manipulate business processes developers embedded into these solutions, and to compromise the integrity of these solutions. 

Unfortunately, in the intervening nine-month time span, we continue to see cases where several of these API have been used for malicious purposes to compromise FileMaker Platform files’ business process integrity, to manipulate data, and to extract data.  And many in the developer community remain unaware of this problem. In this BLOG entry, I will describe two of these API’s in greater specificity and detail, including describing a variety of attacks they can facilitate.  This article will not discuss the ActiveX API that is available on Windows OS; however, developers should give similar attention to that approach. Developers need to be aware of these items in order to protect their files and those of their clients.

The two API at the center of this focus are Apple Events and the FMPURL process.  In the earlier article, I noted several elements about these that bear repeating here:

[These API] cause particular concern because of their breadth and relative ease of use….

The Apple Events Suite has an extensive set of commands that can read and write data, read metadata, manipulate the UI, and trigger scripts. In addition, they can work outside the normal constraints found on layouts in a file. [http://thefmkb.com/5671]

The FMPURLcan open a file and run a script in it.  If the file is already open, then the script will still run. [http://thefmkb.com/5560]

 

A few general comments about both of these API’s:

·      They are not platform-specific in the sense that just because a client organization is an all Windows OS environment that it is immune from an Apple Event attack.  It’s the OS of the attacker that controls whether the API can be used.

·      There are some ways within Privilege Sets to constrain behavior of these API commands when they are applied on a file. The Export privilege bit can control the ability of Apple Events to extract data from a file. The Layout Access privilege bits can also constrain the ability to see contents of a layout. Likewise, Script Access privilege bits can control the availability of a script to either of these API.

·      These API often perform actions in unexpected fashions that fall outside the normal, traditional, and familiar FileMaker Pro User Interface behavior. This is part of what catches developers by surprise.

 

—Apple Events—

When a file is open, whether standalone or hosted by FileMaker Server, an attacker can send Apple Event commands to it causing it to perform a variety of actions, including:

·      Run any script to which the user has access, irrespective of whether that script is in the list of Scripts or whether it is attached to some UI element, such as a button.

·      Navigate to any Layout irrespective of whether that Layout’s name is in the list of Layouts or not. If the user’s Privilege Set has access to see that Layout, then its contents are visible whether the developer ever intended for the user to view the Layout or not.

·      Return various metadata about the file, including such items as Script Names, Value List Items, Layout Names, Field Names, etc. If a user’s Privilege Set does not allow access to the item, its name does not appear in the list returned.

·      Put data into any field in the database or extract data from any field, irrespective of whether that field is on the active Layout or is on any Layout for that matter.

 

Here are several examples of these scripts, all working on a file named Our_Secret_Information.fmp12.

 

tell application "FileMaker Pro Advanced"

       activate

       go to first layout

end tell

 

tell application "FileMaker Pro Advanced"

       activate

       do script FileMaker script "Relog_as_Admin"

end tell

 

tell application "FileMaker Pro Advanced"

       activate

       set somevar to name of every layout

end tell

 

tell application "FileMaker Pro Advanced"

       activate

       set somevar to name of every field

end tell

 

tell application "FileMaker Pro Advanced"

       activate

       set somevar to get data field "CreditCardNumber"

end tell

 

 

 

 

—FMPURL—

 

The FMPURL command’s principal attack vector is that it can be used to run any Script in a file to which a user’s privileges has access. Similar to Apple Events, this occurs irrespective of whether that script is in the list of Scripts or whether it is attached to some UI element, such as a button.

If the file is closed, the command first opens the file with supplied credentials, then runs any OnFirstWindowOpen script, and then runs the designated script from the FMPURL command.  As a result of this behavior, a Halt Script step at the end of the opening script has the effect of blocking the running of the FMPURL designated script. Some developers have utilized this technique to block FMPURL calls to scripts in a file.

However, if the file is already opened or if there is no opening script, then the designated script does run.

Here is an example of calling a script, again in our file Our_Secret_Information.fmp12 being hosted at a server at IP address 0.0.0.0.

 

fmp://0.0.0.0/Our_Secret_Information.fmp12?script= Relog_as_Admin

 

 

—What Is the Significance Of This and

How Do We Address This?—

 

One of the many reasons we caution developers against embedding security elements such as Identity and Access Management controls into the data layer of FileMaker Pro databases is precisely because such elements are vulnerable to these API attacks. Think for a minute about that Relog_as_Admin script that presumably relogs into the file with a [Full Access] Account.  If an Attacker can trigger that script and cause it to run, irrespective of what the developer might have intended, then the Attacker has full access to the file. This has actually happened.

Or, suppose that a developer has made a “Developer_Only” layout in the file, removed it from the list of layouts, and left sensitive information on it. If the Attacker can navigate to that layout, and if it is not protected by settings in the Privilege Set, then the Attacker can learn the contents of the information on it.  This has actually happened in numerous instances, including unbelievably, the appearance of [Full Access] level credentials left exposed on the layout!

Likewise, suppose that a developer has made a so-called “Privileges Table” with various fields that purport to control whether a user can do such things as create records. Using the Apple Event Set Data command, an Attacker could likely change the values in these fields if they do not enjoy additional protection.  More likely even, the Attacker could simply issue a Make New Record command and create the record.  That is a process frequently used to thwart developer-imposed limitations on the number of records in a demonstration version of a vertical market solution.

So, what can be done to manage this situation and to prevent these type attacks?  In FileMaker® Pro 15, FileMaker, Inc. added a new Extended Privilege option in the Privilege Set called fmscriptdisabled.  Developers must explicitly invoke this option; it is not a default option.  What it does is to prevent Apple Events (Macintosh OS) and ActiveX commands (Windows OS) from activating scripts, just as the name implies.  It has no impact on FMPURL or on other Apple Event commands that do not involve triggering of scripts.

Some of the other items in a Privilege Set, notably Export and data layer modification elements, can control Get Data and Set Data Apple Events.  If Export is disabled, then Get Data will not return data from the selected field. In tables where the editing privileges are restricted, likewise, Set Data will not add data to a field.  Creation and deletion privileges behave in similar fashion. Remember, we are talking here only about Apple Events.  Other processes may behave differently. Controlling API behavior is important; however, it is not the only security feature that developers must invoke to assure Confidentiality, Availability, and Integrity of their database systems.

So, clearly what we need here is a way to block these API from interacting with FileMaker Pro files. FileMaker, Inc. is aware of these issues and has been working on new ways to address them. In the Product Road Map Webinar presented on November 30th 2016, FileMaker, Inc. noted that the next version of the FileMaker Platform will contain a number of additional security enhancements. I am authorized to say that one of those enhancements will be a new process for more closely and granularly controlling several of these API’s.

At such time as there is any new version of the FileMaker Platform, I will have additional comments and analyses of the issues related to these API’s.


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