Vid Penetration tester Marcus Murray says attackers can use malicious JPEGs to pop modern Windows servers, to gain expanded privileges over networks.
In a live hack set down for RSA San Francisco this week, the TrueSec boffin shows how he used the hack to access an unnamed US Government agency that ran a buggy photo upload portal.
A key part of the stunt is achieved by inserting active content into the attributes of a jpg image, such that the file name read image.jpg.aspx. “I'm going to try to compromise the web server, then go for back end resources, and ultimately compromise a domain controller,” Murray said, adding the hack is not that difficult.
“Even in mixed environments, when you own the domain controller you usually own the entire infrastructure of that company and that is true because they have Linux server you usually use Windows clients for connect to them.
“From this point (compromising the domain controller) we can do anything; we can upload domain admin tools, and manage it like it was our own.”
Some uploading portals so weak, he says, malicious dynamic content will be accepted merely because it carries a .jpg extension. The service on Murray's government client, however, validated the guts of images (ensuing an image is actually an image), but not the file extension types.
Uploaded into a server and previewed, these files display as the text that has been inserted into image comment fields rather than the expected picture.
Murray used this to upload a remote access trojan created using Metasploit and used various tools and compilers that exist in modern Windows servers to pull off the rest of the attack.
Full step-by-step details of his hack is available in a recorded video. ®