From 1cb5cbdc6c1cd065e90961a9d538cb72610ae481 Mon Sep 17 00:00:00 2001
From: href <href@random.sh>
Date: Tue, 28 Nov 2017 21:44:25 +0100
Subject: [PATCH] Improve error handling, add configuration

---
 config/config.exs                          |  5 ++
 lib/pleroma/web/media_proxy/controller.ex  | 55 +++++++++++++---------
 lib/pleroma/web/media_proxy/media_proxy.ex | 17 +++----
 3 files changed, 45 insertions(+), 32 deletions(-)

diff --git a/config/config.exs b/config/config.exs
index c4f89c40c..503ce8d64 100644
--- a/config/config.exs
+++ b/config/config.exs
@@ -47,6 +47,11 @@
   limit: 5000,
   registrations_open: true
 
+config :pleroma, :media_proxy,
+  enabled: false,
+  redirect_on_failure: true
+  #base_url: "https://cache.pleroma.social"
+
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.
 import_config "#{Mix.env}.exs"
diff --git a/lib/pleroma/web/media_proxy/controller.ex b/lib/pleroma/web/media_proxy/controller.ex
index fece7cf45..dc122fc3a 100644
--- a/lib/pleroma/web/media_proxy/controller.ex
+++ b/lib/pleroma/web/media_proxy/controller.ex
@@ -2,19 +2,27 @@ defmodule Pleroma.Web.MediaProxy.MediaProxyController do
   use Pleroma.Web, :controller
   require Logger
 
+  @cache_control %{
+    default: "public, max-age=1209600",
+    error:   "public, must-revalidate, max-age=160",
+  }
+
   def remote(conn, %{"sig" => sig, "url" => url}) do
-    {:ok, url} = Pleroma.Web.MediaProxy.decode_url(sig, url)
-    url = url |> URI.encode()
-    case proxy_request(url) do
-      {:ok, content_type, body} ->
-        conn
-        |> put_resp_content_type(content_type)
-        |> set_cache_header(:default)
-        |> send_resp(200, body)
-      other ->
-        conn
-        |> set_cache_header(:error)
-        |> redirect(external: url)
+    config = Application.get_env(:pleroma, :media_proxy, [])
+    with \
+      true <- Keyword.get(config, :enabled, false),
+      {:ok, url} <- Pleroma.Web.MediaProxy.decode_url(sig, url),
+      url = URI.encode(url),
+      {:ok, content_type, body} <- proxy_request(url)
+    do
+      conn
+      |> put_resp_content_type(content_type)
+      |> set_cache_header(:default)
+      |> send_resp(200, body)
+    else
+      false -> send_error(conn, 404)
+      {:error, :invalid_signature} -> send_error(conn, 403)
+      {:error, {:http, _, url}} -> redirect_or_error(conn, url, Keyword.get(config, :redirect_on_failure, true))
     end
   end
 
@@ -28,21 +36,24 @@ defp proxy_request(link) do
         {:ok, headers["Content-Type"], body}
       {:ok, status, _, _} ->
         Logger.warn "MediaProxy: request failed, status #{status}, link: #{link}"
-        {:error, :bad_status}
+        {:error, {:http, :bad_status, link}}
       {:error, error} ->
         Logger.warn "MediaProxy: request failed, error #{inspect error}, link: #{link}"
-        {:error, error}
+        {:error, {:http, error, link}}
     end
   end
 
-  @cache_control %{
-    default: "public, max-age=1209600",
-    error:   "public, must-revalidate, max-age=160",
-  }
+  defp set_cache_header(conn, key) do
+    Plug.Conn.put_resp_header(conn, "cache-control", @cache_control[key])
+  end
 
-  defp set_cache_header(conn, true), do: set_cache_header(conn, :default)
-  defp set_cache_header(conn, false), do: set_cache_header(conn, :error)
-  defp set_cache_header(conn, key) when is_atom(key), do: set_cache_header(conn, @cache_control[key])
-  defp set_cache_header(conn, value) when is_binary(value), do: Plug.Conn.put_resp_header(conn, "cache-control", value)
+  defp redirect_or_error(conn, url, true), do: redirect(conn, external: url)
+  defp redirect_or_error(conn, url, _), do: send_error(conn, 502, "Media proxy error: " <> url)
+
+  defp send_error(conn, code, body \\ "") do
+    conn
+    |> set_cache_header(:error)
+    |> send_resp(code, body)
+  end
 
 end
diff --git a/lib/pleroma/web/media_proxy/media_proxy.ex b/lib/pleroma/web/media_proxy/media_proxy.ex
index 9c1d71748..21ebdfbbc 100644
--- a/lib/pleroma/web/media_proxy/media_proxy.ex
+++ b/lib/pleroma/web/media_proxy/media_proxy.ex
@@ -1,23 +1,25 @@
 defmodule Pleroma.Web.MediaProxy do
   @base64_opts [padding: false]
-  @base64_key Application.get_env(:pleroma, Pleroma.Web.Endpoint)[:secret_key_base]
 
   def url(nil), do: nil
 
   def url(url) do
-    if String.starts_with?(url, Pleroma.Web.base_url) do
+    config = Application.get_env(:pleroma, :media_proxy, [])
+    if !Keyword.get(config, :enabled, false) or String.starts_with?(url, Pleroma.Web.base_url) do
       url
     else
+      secret = Application.get_env(:pleroma, Pleroma.Web.Endpoint)[:secret_key_base]
       base64 = Base.url_encode64(url, @base64_opts)
-      sig = :crypto.hmac(:sha, @base64_key, base64)
+      sig = :crypto.hmac(:sha, secret, base64)
       sig64 = sig |> Base.url_encode64(@base64_opts)
-      cache_url("#{sig64}/#{base64}")
+      Keyword.get(config, :base_url, Pleroma.Web.base_url) <> "/proxy/#{sig64}/#{base64}"
     end
   end
 
   def decode_url(sig, url) do
+    secret = Application.get_env(:pleroma, Pleroma.Web.Endpoint)[:secret_key_base]
     sig = Base.url_decode64!(sig, @base64_opts)
-    local_sig = :crypto.hmac(:sha, @base64_key, url)
+    local_sig = :crypto.hmac(:sha, secret, url)
     if local_sig == sig do
       {:ok, Base.url_decode64!(url, @base64_opts)}
     else
@@ -25,9 +27,4 @@ def decode_url(sig, url) do
     end
   end
 
-  defp cache_url(path) do
-    "/proxy/" <> path
-  end
-
-
 end