Canonical Representation Issues

Book: Writing Secure Code

這章很有意思，特別是 Canonical Web-Based Issues。為什麼會發生呢?

1. Many applications make security decisions based on the name of a URL, or a component of a URL.
2. There are many ways of representing URL.

例子：某 security software 有這個漏洞，大家可以鑽鑽看。怎麼鑽？把 blocked domain name 轉成 IP 就不會被擋，超有趣的。

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Remarks.

1. 把 IP 再轉成 dotless IP 也不會被擋。(參考 Something about Dotless IP's)
2. Exercise: Try URL encoding.