[ruby/resolv] Implement dohpath SvcParam

(https://github.com/ruby/resolv/pull/33)

* Implement dohpath SvcParam [RFC 9461]

This patch implements "dohpath" SvcParam proposed in
[draft-ietf-add-svcb-dns-08]. This parameter specifies a URI template
for the :path used in DNS-over-HTTPS requests.

"dohpath" is employed by [DDR], also a to-be-published Proposed Standard
that specifies how to upgrade DNS transport to a more secure one, i.d.,
DNS-over-TLS or DNS-over-HTTPS. DDR is deployed in the public DNS
resolvers including Cloudflare DNS, Google Public DNS, and Quad9.

[RFC 9461]: https://datatracker.ietf.org/doc/rfc9461/
[DDR]: https://datatracker.ietf.org/doc/draft-ietf-add-ddr/

https://github.com/ruby/resolv/commit/da9c023539

Co-authored-by: Sorah Fukumori <her@sorah.jp>

lib/resolv.rb

@@ -2027,6 +2027,35 @@ class Resolv
         end
       end
 
+      ##
+      # "dohpath" SvcParam -- DNS over HTTPS path template [RFC9461]
+
+      class DoHPath < SvcParam
+        KeyName = :dohpath
+        KeyNumber = 7
+        ClassHash[KeyName] = ClassHash[KeyNumber] = self # :nodoc:
+
+        ##
+        # URI template for DoH queries.
+
+        attr_reader :template
+
+        ##
+        # Initialize "dohpath" ScvParam.
+
+        def initialize(template)
+          @template = template.encode('utf-8')
+        end
+
+        def encode(msg) # :nodoc:
+          msg.put_bytes(@template)
+        end
+
+        def self.decode(msg) # :nodoc:
+          template = msg.get_bytes.force_encoding('utf-8')
+          return self.new(template)
+        end
+      end
     end
 
     ##

test/resolv/test_svcb_https.rb

@@ -83,7 +83,6 @@ class TestResolvSvcbHttps < Test::Unit::TestCase
     assert_equal expected, msg.encode
   end
 
-
   ## Test vectors from [RFC9460]
 
   def test_alias_mode
@@ -201,4 +200,32 @@ class TestResolvSvcbHttps < Test::Unit::TestCase
 
     assert_equal wire, msg.encode
   end
+
+  ## For [RFC9461]
+
+  def test_dohpath
+    wire = wrap_rdata 64, 1, "\x00\x01\x03one\x03one\x03one\x03one\x00" +
+      "\x00\x01\x00\x03\x02h2" +
+      "\x00\x03\x00\x02\x01\xbb" +
+      "\x00\x04\x00\x08\x01\x01\x01\x01\x01\x00\x00\x01" +
+      "\x00\x06\x00\x20" +
+      ("\x26\x06\x47\x00\x47\x00\x00\x00\x00\x00\x00\x00\x00\x00\x11\x11" +
+       "\x26\x06\x47\x00\x47\x00\x00\x00\x00\x00\x00\x00\x00\x00\x10\x01") +
+      "\x00\x07\x00\x10/dns-query{?dns}"
+    msg = Resolv::DNS::Message.decode(wire)
+    _, _, rr = msg.answer.first
+
+    assert_equal 1, rr.priority
+    assert_equal Resolv::DNS::Name.create('one.one.one.one.'), rr.target
+    assert_equal 5, rr.params.count
+    assert_equal ['h2'], rr.params[:alpn].protocol_ids
+    assert_equal 443, rr.params[:port].port
+    assert_equal [Resolv::IPv4.create('1.1.1.1'), Resolv::IPv4.create('1.0.0.1')],
+      rr.params[:ipv4hint].addresses
+    assert_equal [Resolv::IPv6.create('2606:4700:4700::1111'), Resolv::IPv6.create('2606:4700:4700::1001')],
+      rr.params[:ipv6hint].addresses
+    assert_equal '/dns-query{?dns}', rr.params[:dohpath].template
+
+    assert_equal wire, msg.encode
+  end
 end