[ruby-core:72446] [Ruby trunk - Bug #11864] [Open] Resolv incorrectly accepts invalid hostnames and caches records between sessions

[osman@surkatty.org]

Issue #11864 has been reported by Osman Surkatty.

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Bug #11864: Resolv incorrectly accepts invalid hostnames and caches records between sessions
https://bugs.ruby-lang.org/issues/11864

* Author: Osman Surkatty
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: ruby 2.2.3p173 (2015-08-18 revision 51636) [x86_64-darwin14]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
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Hello,

While working on a DNS related project I noticed that Resolv's getaddresses() and getaddress() functions will incorrectly accepts an empty String and additionally returns a cached record if a new IRB session is invoked. Resolv correctly rejects nil or empty arguments, but I believe the issue here is that the validation of String should require at a minimum a single valid String character.

Here is an example of what I mean:
$ irb
irb(main):001:0> RUBY_VERSION
=> "2.2.3"
irb(main):002:0> require 'resolv'
=> true
irb(main):003:0> Resolv.getaddresses("surkatty.org")
=> ["54.244.9.126"]
irb(main):004:0> Resolv.getaddresses("example.com")
=> ["93.184.216.34"]
irb(main):005:0> Resolv.getaddresses("NX")
=> []
irb(main):006:0> Resolv.getaddresses("")
=> ["54.244.9.126"]
irb(main):007:0> Resolv.getaddresses()
ArgumentError: wrong number of arguments (0 for 1)
	from /usr/local/Cellar/ruby/2.2.3/lib/ruby/2.2.0/resolv.rb:48:in `getaddresses'
	from (irb):7
	from /usr/local/bin/irb:11:in `<main>'
irb(main):008:0>

On line 006:0, I would have expected Resolv.getaddresses("") to return either:
1. Raise an ArgumentError or some other indicating an invalid String was passed 
2. Return an empty Array

I've also attached a screenshot from my commandline showing the output between IRB sessions as well.

---Files--------------------------------
dns.png (71.5 KB)


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