I recently implemented a system which stores DNS names, and writes out
DNS zone files. I found these to be rather useful tests:
def test_name_with_newline_fails
z = Zone.new(:name => “test\nzone”)
assert !z.valid?
assert z.errors.on(:name)
end
def test_name_with_space_fails
z = Zone.new(:name => “test zone”)
assert !z.valid?
assert z.errors.on(:name)
end
When I use these zone names, I always append a specific string, e.g.
‘.example.com.’
If someone creates a zone called “foo” I will call it
“foo.example.com.” So, when I write out an A record, it would be
something like:
puts “#{zone}.example.com. A #{address}”
If the user happened to submit: “hacker\n@ NS
hacker-nameserver.example.com.” – we would have problems.
I thought this regular expression would catch it:
/^[a-zA-Z0-9\-\_\.]$/
and indeed it does catch spaces, random control characters… but not
newlines! Much to my surprise, I needed to use \A instead of ^ and \Z
instead of $. ^ matches the beginning of a line and $ the end. \A
and \Z match the beginning and ends of STRINGS.
Just a FYI, perhaps I am the only one out there who did not know this.
–Michael