IFS

• One last example

• Consider the command:

        cp foo.pl /tmp/perl

• The command here is cp, the arguments foo and /tmp/bar

• Why?

• Because IFS contains white space

• If IFS = "p" the command is c

  • And the arguments are:

        " foo."
        "l /tm"
        "/"
        "erl"

• To sabotage a shell script, change IFS

• The shell is incredibly complicated

  • Way too many weird features

  • Behavior is too hard to predict

• Solution: forbid setuid shell scripts

Next

Copyright © 2005 M. J. Dominus