Greg Woods wrote:
>It was one of those things where a shell script did something like
>/usr/ucb/Mail $address_obtained_from_news_article
>Implications of that are obvious (just slip in an address like
>"user @
host .
domain; rm *" and see what happens)
Nothing happens. Shell meta characters are parsed *before* variables
are substituted. In this case mail would have attemted to send mail off
to "*", "rm" and ";". (If you don't believe me, just try it, though
you probably wouldn't dare using "rm *")
Meta characters are expanded after variable situation.
(The order is parsing, command subsitution (``), parameter substitution,
blank interpretation, redirection, wildcard expansion. But note that
meta characaters are only interpreted once in the first step)
As someone else noted, it was UCB mail's broken notice of allowing ~
escapes in non-interactive use that caused the problem.
E.g.,
~! <any-shell-command>
in a control message.
I first noticed this problem in '93 when I got "Unknown tilde escape"
messages in the INN logs from someone posting newgroup messages
with a signature boxed in ~.
Casper
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