Where am I (csh)

[Michael O'Donnell]

Some followup examples, with the last one showing how it can fail:


 ######## shrapnel:/tmp 165---> cat /tmp/nastyHack ; chmod a+x /tmp/nastyHack
 cd $*                   # Stand in specified directory ($HOME if none),
 echo PWD is $PWD        # confirm our location,
 ls -CFl /proc/$$/fd     # demo the concept.

 ######## shrapnel:/tmp 166---> cd / ; /tmp/nastyHack
 PWD is /home/mod
 total 0
 lrwx------    1 mod      mod            64 Jan 15 17:39 0 -> /dev/pts/3
 lrwx------    1 mod      mod            64 Jan 15 17:39 1 -> /dev/pts/3
 lrwx------    1 mod      mod            64 Jan 15 17:39 2 -> /dev/pts/3
 lr-x------    1 mod      mod            64 Jan 15 17:39 255 -> /tmp/nastyHack*

 ######## shrapnel:/ 167---> cd / ; /tmp/nastyHack /etc
 PWD is /etc
 total 0
 lrwx------    1 mod      mod            64 Jan 15 17:39 0 -> /dev/pts/3
 lrwx------    1 mod      mod            64 Jan 15 17:39 1 -> /dev/pts/3
 lrwx------    1 mod      mod            64 Jan 15 17:39 2 -> /dev/pts/3
 lr-x------    1 mod      mod            64 Jan 15 17:39 255 -> /tmp/nastyHack*

 ######## shrapnel:/ 168---> cd /tmp ; ./nastyHack /usr/local
 PWD is /usr/local
 total 0
 lrwx------    1 mod      mod            64 Jan 15 17:40 0 -> /dev/pts/3
 lrwx------    1 mod      mod            64 Jan 15 17:40 1 -> /dev/pts/3
 lrwx------    1 mod      mod            64 Jan 15 17:40 2 -> /dev/pts/3
 lr-x------    1 mod      mod            64 Jan 15 17:40 255 -> /tmp/nastyHack*

 ######## shrapnel:/tmp 169---> cd /var/log ; bash </tmp/nastyHack
 PWD is /home/mod
 total 0
 lr-x------    1 mod      mod            64 Jan 15 17:40 0 -> /tmp/nastyHack*
 lrwx------    1 mod      mod            64 Jan 15 17:40 1 -> /dev/pts/3
 lrwx------    1 mod      mod            64 Jan 15 17:40 2 -> /dev/pts/3

 ######## shrapnel:/var/log 170---> cd /var/log ; cat /tmp/nastyHack | bash
 PWD is /home/mod
 total 3
 lr-x------    1 mod      mod            64 Jan 15 17:45 0 -> pipe:[364424]
 lrwx------    1 mod      mod            64 Jan 15 17:45 1 -> /dev/pts/3
 lrwx------    1 mod      mod            64 Jan 15 17:45 2 -> /dev/pts/3