Allow admin to configure bucket ACL settings

To upload to Backblaze B2, the ACL needs to match bucket settings, and
if you have a CDN in front of your media server you may want to restrict
public access to the bucket to avoid expensive non-cdn transfers and
bucket enumeration.

config/config.exs

@@ -70,6 +70,7 @@
 config :pleroma, Pleroma.Uploaders.Local, uploads: "uploads"
 
 config :pleroma, Pleroma.Uploaders.S3,
+  acl: :public_read,
   bucket: nil,
   bucket_namespace: nil,
   truncated_namespace: nil,

docs/docs/configuration/cheatsheet.md

@@ -33,7 +33,7 @@ To add configuration to your config file, you can copy it from the base config.
 * `federation_incoming_replies_max_depth`: Max. depth of reply-to activities fetching on incoming federation, to prevent out-of-memory situations while fetching very long threads. If set to `nil`, threads of any depth will be fetched. Lower this value if you experience out-of-memory crashes.
 * `federation_reachability_timeout_days`: Timeout (in days) of each external federation target being unreachable prior to pausing federating to it.
 * `allow_relay`: Permits remote instances to subscribe to all public posts of your instance. This may increase the visibility of your instance.
-* `public`: Allows unauthenticated access to public resources on your instance. This is essentially used as the default value for `:restrict_unauthenticated`. 
+* `public`: Allows unauthenticated access to public resources on your instance. This is essentially used as the default value for `:restrict_unauthenticated`.
    See `restrict_unauthenticated` for more details.
 * `quarantined_instances`: *DEPRECATED* ActivityPub instances where activities will not be sent. They can still reach there via other means, we just won't send them.
 * `allowed_post_formats`: MIME-type list of formats allowed to be posted (transformed into HTML).
@@ -576,6 +576,7 @@ the source code is here: [kocaptcha](https://github.com/koto-bank/kocaptcha). Th
 
 Don't forget to configure [Ex AWS S3](#ex-aws-s3-settings)
 
+* `acl`: The ACL the uploaded media will have. By default media will be `:public_read`, and thus directly accessible from the bucket. Set this to `:private` if you have a CDN in front of your media proxy which sends authenticated requests to your S3 provider. On some providers, like Backblaze B2, this needs to match bucket settings!
 * `bucket`: S3 bucket name.
 * `bucket_namespace`: S3 bucket namespace.
 * `truncated_namespace`: If you use S3 compatible service such as Digital Ocean Spaces or CDN, set folder name or "" etc.

lib/pleroma/uploaders/s3.ex

@@ -25,6 +25,7 @@ def put_file(%Pleroma.Upload{} = upload) do
     config = Config.get([__MODULE__])
     bucket = Keyword.get(config, :bucket)
     streaming = Keyword.get(config, :streaming_enabled)
+    acl = Keyword.get(config, :acl)
 
     s3_name = strict_encode(upload.path)
 
@@ -33,14 +34,14 @@ def put_file(%Pleroma.Upload{} = upload) do
         upload.tempfile
         |> ExAws.S3.Upload.stream_file()
         |> ExAws.S3.upload(bucket, s3_name, [
-          {:acl, :public_read},
+          {:acl, acl},
           {:content_type, upload.content_type}
         ])
       else
         {:ok, file_data} = File.read(upload.tempfile)
 
         ExAws.S3.put_object(bucket, s3_name, file_data, [
-          {:acl, :public_read},
+          {:acl, acl},
           {:content_type, upload.content_type}
         ])
       end

test/pleroma/uploaders/s3_test.exs

@@ -66,7 +66,11 @@ test "it returns path with bucket namespace when namespace is set" do
     end
 
     test "save file", %{file_upload: file_upload} do
-      with_mock ExAws, request: fn _ -> {:ok, :ok} end do
+      with_mock ExAws, request: (fn _ ->
+        assert op.opts[:acl] == :public_read
+        {:ok, :ok}
+      end)
+      do
         assert S3.put_file(file_upload) == {:ok, {:file, "test_folder/image-tet.jpg"}}
       end
     end
@@ -78,6 +82,16 @@ test "returns error", %{file_upload: file_upload} do
                end) =~ "Elixir.Pleroma.Uploaders.S3: {:error, \"S3 Upload failed\"}"
       end
     end
+
+    test "respects acl setting", %{file_upload: file_upload} do
+      clear_config([Pleroma.Uploaders.S3, :acl], :private)
+      with_mock ExAws, request: (fn(op) ->
+        assert op.opts[:acl] == :private
+        {:ok, :ok}
+      end) do
+        assert S3.put_file(file_upload) == {:ok, {:file, "test_folder/image-tet.jpg"}}
+      end
+    end
   end
 
   describe "delete_file/1" do