2 files changed, 17 insertions, 3 deletions
diff --git a/lib/pleroma/web/media_proxy/controller.ex b/lib/pleroma/web/media_proxy/controller.ex
index de79cad73..c0552d89f 100644
--- a/lib/pleroma/web/media_proxy/controller.ex
+++ b/lib/pleroma/web/media_proxy/controller.ex
@@ -4,11 +4,12 @@
 
 defmodule Pleroma.Web.MediaProxy.MediaProxyController do
   use Pleroma.Web, :controller
-  alias Pleroma.{Web.MediaProxy, ReverseProxy}
+  alias Pleroma.ReverseProxy
+  alias Pleroma.Web.MediaProxy
 
   @default_proxy_opts [max_body_length: 25 * 1_048_576, http: [follow_redirect: true]]
 
-  def remote(conn, params = %{"sig" => sig64, "url" => url64}) do
+  def remote(conn, %{"sig" => sig64, "url" => url64} = params) do
     with config <- Pleroma.Config.get([:media_proxy], []),
          true <- Keyword.get(config, :enabled, false),
          {:ok, url} <- MediaProxy.decode_url(sig64, url64),
diff --git a/lib/pleroma/web/media_proxy/media_proxy.ex b/lib/pleroma/web/media_proxy/media_proxy.ex
index e1eb1472d..39a725a69 100644
--- a/lib/pleroma/web/media_proxy/media_proxy.ex
+++ b/lib/pleroma/web/media_proxy/media_proxy.ex
@@ -9,7 +9,7 @@ defmodule Pleroma.Web.MediaProxy do
 
   def url(""), do: nil
 
-  def url(url = "/" <> _), do: url
+  def url("/" <> _ = url), do: url
 
   def url(url) do
     config = Application.get_env(:pleroma, :media_proxy, [])
@@ -19,11 +19,16 @@ defmodule Pleroma.Web.MediaProxy do
     else
       secret = Application.get_env(:pleroma, Pleroma.Web.Endpoint)[:secret_key_base]
 
+      # Must preserve `%2F` for compatibility with S3 (https://git.pleroma.social/pleroma/pleroma/issues/580)
+      replacement = get_replacement(url, ":2F:")
+
       # The URL is url-decoded and encoded again to ensure it is correctly encoded and not twice.
       base64 =
         url
+        |> String.replace("%2F", replacement)
         |> URI.decode()
         |> URI.encode()
+        |> String.replace(replacement, "%2F")
         |> Base.url_encode64(@base64_opts)
 
       sig = :crypto.hmac(:sha, secret, base64)
@@ -60,4 +65,12 @@ defmodule Pleroma.Web.MediaProxy do
     |> Enum.filter(fn value -> value end)
     |> Path.join()
   end
+
+  defp get_replacement(url, replacement) do
+    if String.contains?(url, replacement) do
+      get_replacement(url, replacement <> replacement)
+    else
+      replacement
+    end
+  end
 end