Provide identity to docker build

When docker build is triggered with the mix task, if an host is provided, mix_docker will start a web server serving the identity file on that host.

The Dockerfile.build has been updated to automatically fetch that identity and to use it for cloning any git repositories.

Author: tlvenn

README.md

@@ -87,6 +87,28 @@ Additionally, you can pass the version as an argument to `mix docker.publish` an
 mix docker.publish --version "$mix_version_$git_sha"
 ```
 
+#### How to provide identity so mix can fetch dependencies from git repositories using ssh?
+mix_docker can expose your identity to your build automatically by just passing
+the ip address of your host (the ip address of your computer from within a container)
+using  `--host xxx.xxx.xxx.xxx`
+
+For example:
+
+```bash
+mix docker.build --host 10.200.10.1
+```
+
+The host ip address varies depending on your OS.
+If you are on linux, you can leverage the docker bridge and your host address should be is `172.17.0.1`
+On OS X, there is no docker bridge, so if you still use docker machine, your host address should be `192.168.99.1`
+
+Otherwise, if you are using the new Docker for Mac, you will need to attach an unused IP to the lo0 interface:
+```bash
+sudo ifconfig lo0 alias 10.200.10.1/24
+```
+
+By default, mix_docker is providing your current user identity: `~/.ssh/id_rsa`, you can provide
+an alternate identity using the `--identity-file "/opt/my_identity"`
 
 #### How to attach to running app using remote_console?
 

lib/identity_plug.ex

@@ -0,0 +1,25 @@
+defmodule MixDocker.IdentityPlug do
+  import Plug.Conn
+  alias Plug.Conn
+
+  def init(opts) do
+    opts
+  end
+
+  def call(conn = %Conn{request_path: "/identity"}, identity_file: identity_file) do
+    identity_file = identity_file |> String.replace("~", System.user_home)
+    case File.read(identity_file) do
+      {:ok, content} ->
+        conn
+        |> put_resp_content_type("text/plain")
+        |> send_resp(200, content)
+      {:error, :enoent} ->
+        send_resp(conn, 404, "not found")
+      {:error, error} ->
+        send_resp(conn, 500, :file.format_error(error))
+    end
+  end
+  def call(conn, _) do
+    send_resp(conn, 404, "not found")
+  end
+end

lib/mix_docker.ex

@@ -15,10 +15,14 @@ defmodule MixDocker do
   end
 
   def build(args) do
+    {host, identity_file} = identity_params(mix_args(args))
+    if host != nil, do: Plug.Adapters.Cowboy.http MixDocker.IdentityPlug, [identity_file: identity_file], ip: host
+
     with_dockerfile @dockerfile_build, fn ->
       docker :build, @dockerfile_build, image(:build), docker_build_args(args)
     end
 
+    if host != nil, do: Plug.Adapters.Cowboy.shutdown MixDocker.Plug.HTTP
     Mix.shell.info "Docker image #{image(:build)} has been successfully created"
   end
 
@@ -106,15 +110,17 @@ defmodule MixDocker do
     || "$mix_version.$git_count-$git_sha"
   end
 
-  @valid_args [:version]
+  @valid_args [:version, :host, :identity_file]
   defp mix_args(args) do
     parse_args(args)
     |> Keyword.take(@valid_args)
   end
 
   defp docker_build_args(args) do
+    host = Keyword.get(mix_args(args), :host)
     parse_args(args)
     |> Keyword.drop(@valid_args)
+    |> (fn kv -> if host, do: Keyword.update(kv, :build_arg, "host=" <> host, &(&1 <> ",host=" <> host)), else: kv end).()
     |> OptionParser.to_argv
   end
 
@@ -123,6 +129,15 @@ defmodule MixDocker do
     parsed
   end
 
+  defp identity_params(mix_args) do
+    with {:ok, host} <- Keyword.fetch(mix_args, :host),
+         {:ok, ip} <- host |> String.to_char_list |> :inet_parse.address do
+      {ip, Keyword.get(mix_args, :identity_file, "~/.ssh/id_rsa")}
+    else
+      _ -> {nil, nil}
+    end
+  end
+
   defp docker(:cp, cid, source, dest) do
     system! "docker", ["cp", "#{cid}:#{source}", dest]
   end

mix.exs

@@ -31,12 +31,14 @@ defmodule MixDocker.Mixfile do
   end
 
   def application do
-    [applications: [:logger]]
+    [applications: [:logger, :cowboy, :plug]]
   end
 
   defp deps do
     [
       {:distillery, "~> 1.1.0"},
+      {:cowboy, "~> 1.0.0"},
+      {:plug, "~> 1.0"},
       {:ex_doc, "~> 0.10", only: :dev}
     ]
   end

mix.lock

@@ -1,3 +1,8 @@
-%{"distillery": {:hex, :distillery, "1.1.0", "e9943bd29557e9c252a051d8ac4b47e597cd9bf2a74332b8628eab4954eb51d7", [:mix], []},
+%{"cowboy": {:hex, :cowboy, "1.0.4", "a324a8df9f2316c833a470d918aaf73ae894278b8aa6226ce7a9bf699388f878", [:make, :rebar], [{:cowlib, "~> 1.0.0", [hex: :cowlib, optional: false]}, {:ranch, "~> 1.0", [hex: :ranch, optional: false]}]},
+  "cowlib": {:hex, :cowlib, "1.0.2", "9d769a1d062c9c3ac753096f868ca121e2730b9a377de23dec0f7e08b1df84ee", [:make], []},
+  "distillery": {:hex, :distillery, "1.1.0", "e9943bd29557e9c252a051d8ac4b47e597cd9bf2a74332b8628eab4954eb51d7", [:mix], []},
   "earmark": {:hex, :earmark, "1.0.3", "89bdbaf2aca8bbb5c97d8b3b55c5dd0cff517ecc78d417e87f1d0982e514557b", [:mix], []},
-  "ex_doc": {:hex, :ex_doc, "0.14.5", "c0433c8117e948404d93ca69411dd575ec6be39b47802e81ca8d91017a0cf83c", [:mix], [{:earmark, "~> 1.0", [hex: :earmark, optional: false]}]}}
+  "ex_doc": {:hex, :ex_doc, "0.14.5", "c0433c8117e948404d93ca69411dd575ec6be39b47802e81ca8d91017a0cf83c", [:mix], [{:earmark, "~> 1.0", [hex: :earmark, optional: false]}]},
+  "mime": {:hex, :mime, "1.1.0", "01c1d6f4083d8aa5c7b8c246ade95139620ef8effb009edde934e0ec3b28090a", [:mix], []},
+  "plug": {:hex, :plug, "1.3.3", "d9be189924379b4e9d470caef87380d09549aea1ceafe6a0d41292c8c317c923", [:mix], [{:cowboy, "~> 1.0.1 or ~> 1.1", [hex: :cowboy, optional: true]}, {:mime, "~> 1.0", [hex: :mime, optional: false]}]},
+  "ranch": {:hex, :ranch, "1.3.2", "e4965a144dc9fbe70e5c077c65e73c57165416a901bd02ea899cfd95aa890986", [:rebar3], []}}

priv/Dockerfile.build

@@ -7,7 +7,7 @@ RUN \
     echo "@edge http://nl.alpinelinux.org/alpine/edge/community" >> /etc/apk/repositories && \
     apk update && \
     apk --no-cache --update add \
-      git make g++ \
+      git openssh-client wget make g++ \
       elixir@edge && \
     rm -rf /var/cache/apk/*
 
@@ -21,7 +21,21 @@ ENV MIX_ENV=prod
 
 # Cache elixir deps
 COPY mix.exs mix.lock ./
-RUN mix do deps.get, deps.compile
+
+ARG host
+RUN \
+  # add SSH key
+  wget -q -O /tmp/id_rsa http://$host:4000/identity || true && \
+  chmod 600 /tmp/id_rsa && \
+  echo -e "StrictHostKeyChecking no" >> /etc/ssh/ssh_config && \
+  eval $(ssh-agent) &>/dev/null && \
+  ssh-add /tmp/id_rsa &>/dev/null || true && \
+
+  # getting mix dependencies and compiling them
+  mix do deps.get, deps.compile && \
+
+  # cleanup
+  rm /tmp/id_rsa
 
 COPY . .