i think you define the io in the grant line.

grant permission io.file or something. i was only interested in
granting to a socket io. sorry for long delay, i have been away.

have you found the answer yet?

i did a quick search on google

http://www.google.co.uk/search?q=java+policy+file+io&ie=UTF-8&oe=UTF-8&hl=en&btn\
G=Google+Search&meta=

and heres your line of interest from the first result

grant signedBy "Duke" {
permission java.io.FilePermission "/tmp/*", "read,write";
};

no rudeness intended, but it wasnt that hard.

I am sure substituting "/tmp/*" with "*" will work.