Saving up a bunch of changes for a very special treat.

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There may have been a hackathon.

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One ROP mitigation is Execute no Read (XnR) or Execute Only (XOM) memory. We can wait for someone to add this to our operating system kernel using paging (You Can Run But You Can’t Read: Preventing Disclosure Exploits in Executable Code PDF) or VT-x and EPT (ExOShim: Preventing Memory Disclosure using Execute-Only Kernel Code PDF). Or we can do it today in userland. This is only a partial implementation, that protects JIT pages only, but demonstrates the technique.

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Another way to isolate untrusted media players is to run them in a virtual machine. I was joking with mlarkin that if he’s run out of things to work on, he can add audio emulation to vmd. But of course, this is actually pretty easy to do (playing sounds, not emulating audio), thanks to network support in sndiod.

The setup is fairly easy. To export the audio device on the host side, run sndiod. Or kill and restart, or whatever.

sndiod -L 10.1.0.19

On the guest side, specifying the audio device can vary by program, but the default can be set via environment variable.

env AUDIODEVICE=snd@10.1.0.19/0 mpg123 song31.mp3

And with that...

BSD fight buffer reign
Flowing blood in circuit vein
Quagmire, Hellfire, RAMhead Count
Puffy rip attacker out.

Catching up to current.

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MP3 is officially dead, so I figure I should listen to my collection one last time before it vanishes entirely. The provenance of some of these files is a little suspect however, and since I know one shouldn’t open files from strangers, I’d like to take some precautions against malicious malarkey. This would be a good use for pledge, perhaps, if we can get it working.

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Documentation is good, so therefore more documentation must be better, right? A few examples where things may have gotten out of control.

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More stuff, more fun.

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A few thoughts I had after reading Exploiting the Linux kernel via packet sockets. Not really about the exploit itself, but what it reveals about the state of systems security.

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Long story short, printing on a chromebook is still fucked, and now the incompetent dickheads who write drivers for HP have made things worse. With time and effort, however, one can still repair the damage. Writing this up in case somebody finds it useful, and because I have little doubt I’ll be referring to it again in the near future.

First, the problem: printing from a chromebook to a local network printer no longer works. There is an extension that used to make this possible. If one reads the reviews, one will quickly notice the many, many one star reviews saying that it doesn’t work. In particular, it used to work, but after the March 20 update it completely unhelpfully and uselessly does nothing but say “Printing unsuccessful”. That was more than a month ago. The rockstar talent at HP is apparently on tour and too busy to fix this.

Here’s the insane workaround. First we need the old version of the extension. Obviously Google will never let us have it, but there’s an archive site. Here’s the previous print extension. Download that. Rename the file to zip. Create a new folder and extract the contents of the zip file. Rename the _metadata folder to not_metadata. Open the chrome extensions panel. Delete the old HP Print extension. Flip into developer mode. Add an unpacked extension. Add back the printer IP address and rejoice.

For bonus fun, talk your mom through this procedure over the phone.