How Poor Punctuation Can Break Windows

An anonymous reader writes with a report at Ars Technica about how a small bug can lead to a security problem. In this case, the problem is that quotation marks — or the lack of them — can be significant. From the Ars article: "The scenario... requires a 'standard' user with access rights to create a directory to a fileserver and an administrator executing a vulnerable script," Frank Lycops and Raf Cox, security researchers with The Security Factory, said in an e-mail interview. "This allows the attacker to gain the privileges of the user running the script, thus becoming an administrator." While the attack falls short of the severity of the Shellshock family of Linux shell vulnerabilities, the two researchers stressed that it's a good example of how untrusted input can be used to execute commands on a system. The researchers identified at least one popular script with the vulnerability. When the script attempts to set the starting directory for system administration work, it inadvertently runs the command appended to the malicious directory's name as well. ... The solution is to use proper coding practices—in this case, the judicious use of quotation marks. Quotation marks are used in the shell environment to make sure that the data inside the quotes is not interpreted by the program as a command.

Comments

Re:oblg xkcd

[michelcolman]

Actually, it's Bobby Tables

Re:Shellshock is way worse

[BronsCon]

The patch didn't need patching, there were two separate exploits, one discovered during a decode review prompted by the other. There were actually 6 CVEs published about this, all of which can be found here. Might want to get your facts straight before you spout off.

If your applications are passing executable code as user-specifiable data that then gets passed as environment variables to a forked process that then spawns a system call eventually involving Bash, then you should be glad the patch broke it, as it just revealed a massive security vulnerability within your application. If you need that application to remain functional while you patch the issue, roll back to the previous version of Bash and work under the assumption that the gaping security hole that you're calling an application has already been compromised, because what it's doing is so much worse than Shellshock. More to the point, if your application were passing executable code or commands in this manner, the likely scenario is that you have some sort of command processor on the other end parsing and executing them; if you're exploiting Shellshock to accomplish this, you deserve prison time for gross negligence for A) incorporating the vulnerability into your application and B) not disclosing it so it could be patched.

At any rate, it's not a Linux issue, it's a Bash issue. Again, since Bash can run on *anything*, that makes it and "anything running Bash" issue, including your precious Windows in the majority of server environments, where a POSIX layer like Cygwin or MinGW (both of which include Bash) is likely to be in use.

Furthermore, simply having Bash installed does not make a system vulnerable; there has to be some service listening that passes unsanitized user-specified data as environment variables to a system call eventually handled by Bash. So surprisingly few competently written applications do this; GNU dhcpd was one, I'll give you that if you can give me another.

Re:Shellshock is way worse

[El_Oscuro]

Windows has its own version of shellshock in CMD.EXE C:\Usersl>set foo=bar^&ping -n 1 google.com
C:\Usersl>echo %foo%
bar

Pinging google.com [74.125.228.105] with 32 bytes of data:
Reply from 74.125.228.105: bytes=32 time=8ms TTL=250

Ping statistics for 74.125.228.105:
Packets: Sent = 1, Received = 1, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 8ms, Maximum = 8ms, Average = 8ms
C:\Users>
Unlike Linux, I don't think this has been patched.