From time to time, Amazon Web Services adds new IP address ranges (it keeps growing!). These new addresses are published in the forums, such as via this post from EricS. I was creating a bucket policy to restrict access only to nonymous users who are within my region – I’m happy for the access requests, but I don’t want to pay the bandwidth charges. So here’s a small Perl script that takes the copy-and-paste text from EricS’s forum post, and creates an S3 buck policy element suitable for this:
#!/usr/bin/perl
open F, 'ips.txt' or die "Cannot read list of IPs: $!";
my @ip_conditions;
while (<F>) {
 push @ip_conditions, $1 if /^(\d+\.\d+\.\d+\.\d+\/\d+)\s/;
}
print "\t\"aws:SourceIp\": [" . join(",", @ip_conditions) . "]\n";