Implement DOH Client

README.md

@@ -99,6 +99,13 @@ Server listening at 8000
 iex(3)> Process.exit(server_pid, :normal)
 ```
 
+### DOH client
+
+```elixir
+iex> DOH.resolve("www.google.com")
+{:ok, [{172, 217, 13, 228}]}
+```
+
 For more information, see [API Reference](https://hexdocs.pm/dns/2.1.2/api-reference.html)
 
 ## License

lib/doh.ex

@@ -0,0 +1,53 @@
+defmodule DOH do
+  def resolve(domain, type \\ :a, doh_server \\ {"https://dns.google/dns-query", []}) do
+    case query(domain, type, doh_server).anlist do
+      answers when is_list(answers) and length(answers) > 0 ->
+        data =
+          answers
+          |> Enum.map(& &1.data)
+          |> Enum.reject(&is_nil/1)
+
+        {:ok, data}
+
+      _ ->
+        {:error, :not_found}
+    end
+  end
+
+  def query(domain, type \\ :a, doh_server \\ {"https://dns.google/dns-query", []}) do
+    record = %DNS.Record{
+      header: %DNS.Header{rd: true},
+      qdlist: [%DNS.Query{domain: to_charlist(domain), type: type, class: :in}]
+    }
+
+    dns_request = DNS.Record.encode(record)
+
+    case request(dns_request, doh_server) do
+      {:ok, response} -> response
+      {:error, _} -> %DNS.Record{}
+    end
+  end
+
+  defp request(query, doh_server) do
+    {http_server, options} = doh_server
+
+    case HTTPoison.post(
+           http_server,
+           query,
+           [{"Content-Type", "application/dns-message"}],
+           options
+         ) do
+      {:ok, %HTTPoison.Response{status_code: 200, body: response}} ->
+        {:ok, DNS.Record.decode(response)}
+
+      {:ok, %HTTPoison.Response{}} ->
+        {:error, "query error"}
+
+      {:error, :fmt} ->
+        {:error, "http error"}
+
+      {:error, %HTTPoison.Error{reason: reason}} ->
+        {:error, reason}
+    end
+  end
+end

mix.exs

@@ -22,7 +22,8 @@ defmodule DNS.Mixfile do
       {:socket, "~> 0.3.13"},
       {:ex_doc, ">= 0.0.0", only: [:dev]},
       {:earmark, ">= 0.0.0", only: [:dev]},
-      {:credo, "~> 0.9.0-rc1", only: [:dev, :test], runtime: false}
+      {:credo, "~> 0.9.0-rc1", only: [:dev, :test], runtime: false},
+      {:httpoison, "~> 1.6"},
     ]
   end
 

mix.lock

@@ -1,8 +1,17 @@
 %{
   "bunt": {:hex, :bunt, "0.2.0", "951c6e801e8b1d2cbe58ebbd3e616a869061ddadcc4863d0a2182541acae9a38", [:mix], [], "hexpm"},
+  "certifi": {:hex, :certifi, "2.5.1", "867ce347f7c7d78563450a18a6a28a8090331e77fa02380b4a21962a65d36ee5", [:rebar3], [{:parse_trans, "~>3.3", [hex: :parse_trans, repo: "hexpm", optional: false]}], "hexpm"},
   "credo": {:hex, :credo, "0.9.1", "f021affa11b32a94dc2e807a6472ce0914289c9132f99644a97fc84432b202a1", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:poison, ">= 0.0.0", [hex: :poison, repo: "hexpm", optional: false]}], "hexpm"},
   "earmark": {:hex, :earmark, "1.2.4", "99b637c62a4d65a20a9fb674b8cffb8baa771c04605a80c911c4418c69b75439", [:mix], [], "hexpm"},
   "ex_doc": {:hex, :ex_doc, "0.18.2", "993e0a95e9fbb790ac54ea58e700b45b299bd48bc44b4ae0404f28161f37a83e", [:mix], [{:earmark, "~> 1.1", [hex: :earmark, repo: "hexpm", optional: false]}], "hexpm"},
+  "hackney": {:hex, :hackney, "1.15.2", "07e33c794f8f8964ee86cebec1a8ed88db5070e52e904b8f12209773c1036085", [:rebar3], [{:certifi, "2.5.1", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "6.0.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "1.0.1", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~>1.1", [hex: :mimerl, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "1.1.5", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}], "hexpm"},
+  "httpoison": {:hex, :httpoison, "1.6.1", "2ce5bf6e535cd0ab02e905ba8c276580bab80052c5c549f53ddea52d72e81f33", [:mix], [{:hackney, "~> 1.15 and >= 1.15.2", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm"},
+  "idna": {:hex, :idna, "6.0.0", "689c46cbcdf3524c44d5f3dde8001f364cd7608a99556d8fbd8239a5798d4c10", [:rebar3], [{:unicode_util_compat, "0.4.1", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm"},
+  "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [:rebar3], [], "hexpm"},
+  "mimerl": {:hex, :mimerl, "1.2.0", "67e2d3f571088d5cfd3e550c383094b47159f3eee8ffa08e64106cdf5e981be3", [:rebar3], [], "hexpm"},
+  "parse_trans": {:hex, :parse_trans, "3.3.0", "09765507a3c7590a784615cfd421d101aec25098d50b89d7aa1d66646bc571c1", [:rebar3], [], "hexpm"},
   "poison": {:hex, :poison, "3.1.0", "d9eb636610e096f86f25d9a46f35a9facac35609a7591b3be3326e99a0484665", [:mix], [], "hexpm"},
   "socket": {:hex, :socket, "0.3.13", "98a2ab20ce17f95fb512c5cadddba32b57273e0d2dba2d2e5f976c5969d0c632", [:mix], [], "hexpm"},
+  "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.5", "6eaf7ad16cb568bb01753dbbd7a95ff8b91c7979482b95f38443fe2c8852a79b", [:make, :mix, :rebar3], [], "hexpm"},
+  "unicode_util_compat": {:hex, :unicode_util_compat, "0.4.1", "d869e4c68901dd9531385bb0c8c40444ebf624e60b6962d95952775cac5e90cd", [:rebar3], [], "hexpm"},
 }

test/dns_test.exs

@@ -19,6 +19,21 @@ defmodule DNSTest do
     test "responds with error if domain not found" do
       assert {:error, :not_found} = DNS.resolve('uifqourefhoqeirhfqeurfhqehfqoerfiuqe.com')
     end
+
+    test "default DNS-over-HTTPS servers" do
+      {:ok, results} = DOH.resolve("www.google.com")
+
+      assert is_list(results)
+      assert length(results) > 0
+    end
+
+    test "can query custom DOH server" do
+      {:ok, results} =
+        DOH.resolve("www.google.com", :a, {"https://cloudflare-dns.com/dns-query", []})
+
+      assert is_list(results)
+      assert length(results) > 0
+    end
   end
 
   describe "query" do