undefined | Better HN

0 pointsthaumaturgy11y ago0 comments

That was my initial reaction too, but I'm not so sure now that the bash maintainer has responded. I'm trying to get a better PoC working.

edit: OK, I give. I don't understand how this is different from,

    env z='' echo oops

So, assuming you have Stupid Server 2.0, and SS 2.0 allows you to send an Accept: header with,

    '' evil command here

...you still need to find a way to execute that command, which is different from CVE-2014-6271, which caused function embedded in environment variables to be executed when they were read.

Am I missing something?

0 comments

timv11y ago

Am I missing something?

I think so, but the sample exploit isn't really designed to give a clear understanding if you don't already know what's going on.

Try this:

  $ export X="() { (a)=>\\"
  $ bash -c 'echo date'
  bash: X: line 1: syntax error near unexpected token `='
  bash: X: line 1: `'
  bash: error importing function definition for `X'
  $ cat echo
  Thu Sep 25 02:27:07 UTC 2014

Setting "X" in that way confuses the bash env variable parser. It barfs at the "=" and leaves the ">\" unparsed

AFAICT (without digging deep into the code) that leave in the execution buffer as ">\[NEWLINE]echo date" which gets treated the same as

  date > echo

thaumaturgyOP11y ago

Oh that's neat.

j / k navigate · click thread line to collapse