From e47c50666d2dd66eb3751daca5efd069adac67f7 Mon Sep 17 00:00:00 2001
From: Oneric <oneric@oneric.stub>
Date: Sun, 28 Jan 2024 22:15:54 +0100
Subject: [PATCH 1/2] Fix obfuscation of short domains

Fixes https://akkoma.dev/AkkomaGang/akkoma/issues/645
---
 CHANGELOG.md                                     |  1 +
 .../web/activity_pub/mrf/simple_policy.ex        | 16 +++++++++++++++-
 .../web/activity_pub/mrf/simple_policy_test.exs  |  2 +-
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e2a3635f6..8a38e80ba 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -19,6 +19,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Documentation issue in which a non-existing nginx file was referenced
 - Issue where a bad inbox URL could break federation
 - Issue where hashtag rel values would be scrubbed
+- Issue where short domains listed in `transparency_obfuscate_domains` were not actually obfuscated
 
 ## 2023.08
 
diff --git a/lib/pleroma/web/activity_pub/mrf/simple_policy.ex b/lib/pleroma/web/activity_pub/mrf/simple_policy.ex
index ba54eb674..c2e17ca9e 100644
--- a/lib/pleroma/web/activity_pub/mrf/simple_policy.ex
+++ b/lib/pleroma/web/activity_pub/mrf/simple_policy.ex
@@ -314,6 +314,20 @@ defmodule Pleroma.Web.ActivityPub.MRF.SimplePolicy do
   def filter(object), do: {:ok, object}
 
   defp obfuscate(string) when is_binary(string) do
+    # Want to strip at least two neighbouring chars
+    # to ensure at least one non-dot char is in the obfuscation area
+    stripped = String.length(string) - 6
+
+    {keepstart, keepend} =
+      if stripped > 1 do
+        {3, 3}
+      else
+        {
+          2 - div(1 - stripped, 2),
+          2 + div(stripped, 2)
+        }
+      end
+
     string
     |> to_charlist()
     |> Enum.with_index()
@@ -322,7 +336,7 @@ defmodule Pleroma.Web.ActivityPub.MRF.SimplePolicy do
         ?.
 
       {char, index} ->
-        if 3 <= index && index < String.length(string) - 3, do: ?*, else: char
+        if keepstart <= index && index < String.length(string) - keepend, do: ?*, else: char
     end)
     |> to_string()
   end
diff --git a/test/pleroma/web/activity_pub/mrf/simple_policy_test.exs b/test/pleroma/web/activity_pub/mrf/simple_policy_test.exs
index 875cf8f43..c6600f001 100644
--- a/test/pleroma/web/activity_pub/mrf/simple_policy_test.exs
+++ b/test/pleroma/web/activity_pub/mrf/simple_policy_test.exs
@@ -283,7 +283,7 @@ defmodule Pleroma.Web.ActivityPub.MRF.SimplePolicyTest do
 
       assert {:ok,
               %{
-                mrf_simple: %{reject: ["rem***.*****nce", "a.b"]},
+                mrf_simple: %{reject: ["rem***.*****nce", "*.b"]},
                 mrf_simple_info: %{reject: %{"rem***.*****nce" => %{}}}
               }} = SimplePolicy.describe()
     end

From 3cd882528eb816d18c7d79ea5d797dfb3599c757 Mon Sep 17 00:00:00 2001
From: Oneric <oneric@oneric.stub>
Date: Sun, 28 Jan 2024 23:12:59 +0100
Subject: [PATCH 2/2] More prominently document MRF transparency and
 obfuscation

And point to the cheat sheet for all other MRF policies
and their configuration details.
---
 docs/docs/configuration/mrf.md | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/docs/docs/configuration/mrf.md b/docs/docs/configuration/mrf.md
index a74cfa90d..170b26792 100644
--- a/docs/docs/configuration/mrf.md
+++ b/docs/docs/configuration/mrf.md
@@ -61,6 +61,32 @@ config :pleroma, :mrf_simple,
 
 The effects of MRF policies can be very drastic. It is important to use this functionality carefully. Always try to talk to an admin before writing an MRF policy concerning their instance.
 
+## Hiding or Obfuscating Policies
+
+You can opt out of publicly displaying all MRF policies or only hide or obfuscate selected domains.
+
+To just hide everything set:
+
+```elixir
+config :pleroma, :mrf,
+  ...
+  transparency: false,
+```
+
+To hide or obfuscate only select entries, use:
+
+```elixir
+config :pleroma, :mrf,
+  ...
+  transparency_obfuscate_domains: ["handholdi.ng", "badword.com"],
+  transparency_exclusions: [{"ghost.club", "even a fragment is too spoopy for humans"}]
+```
+
+## More MRF Policies
+
+See the [documentation cheatsheet](cheatsheet.md)
+for all available MRF policies and their options.
+
 ## Writing your own MRF Policy
 
 As discussed above, the MRF system is a modular system that supports pluggable policies. This means that an admin may write a custom MRF policy in Elixir or any other language that runs on the Erlang VM, by specifying the module name in the `policies` config setting.