From 542f8b2aef34a1a3cade2d7e3e52ef0c80e3889c Mon Sep 17 00:00:00 2001
From: Lain Soykaf <lain@lain.com>
Date: Sat, 31 Oct 2026 15:37:42 +0400
Subject: [PATCH] fix(media_proxy): do not proxy data: URLs

Ported from Akkoma 7632765b4.

Co-authored-by: nopjmp <nop@unearthly.dev>
---
 changelog.d/media-proxy-data-urls.fix |  1 +
 lib/pleroma/web/media_proxy.ex        |  6 ++++--
 test/pleroma/web/media_proxy_test.exs | 12 ++++++++++++
 3 files changed, 17 insertions(+), 2 deletions(-)
 create mode 100644 changelog.d/media-proxy-data-urls.fix

diff --git a/changelog.d/media-proxy-data-urls.fix b/changelog.d/media-proxy-data-urls.fix
new file mode 100644
index 000000000..a83b8ef29
--- /dev/null
+++ b/changelog.d/media-proxy-data-urls.fix
@@ -0,0 +1 @@
+MediaProxy: Do not proxy data: URLs
diff --git a/lib/pleroma/web/media_proxy.ex b/lib/pleroma/web/media_proxy.ex
index 82a070767..a318ab10f 100644
--- a/lib/pleroma/web/media_proxy.ex
+++ b/lib/pleroma/web/media_proxy.ex
@@ -45,7 +45,7 @@ defmodule Pleroma.Web.MediaProxy do
   def url("/" <> _ = url), do: url
 
   def url(url) do
-    if enabled?() and url_proxiable?(url) do
+    if enabled?() and not data_url?(url) and url_proxiable?(url) do
       encode_url(url)
     else
       url
@@ -61,7 +61,7 @@ defmodule Pleroma.Web.MediaProxy do
   def preview_url("//" <> _ = url, pparams), do: preview_url("https:" <> url, pparams)
 
   def preview_url(url, preview_params) do
-    if preview_enabled?() do
+    if preview_enabled?() and not data_url?(url) do
       encode_preview_url(url, preview_params)
     else
       url(url)
@@ -74,6 +74,8 @@ defmodule Pleroma.Web.MediaProxy do
   #   non-local non-whitelisted URLs through it and be sure that body size constraint is preserved.
   def preview_enabled?, do: enabled?() and !!Config.get([:media_preview_proxy, :enabled])
 
+  defp data_url?(url), do: url |> String.slice(0, 5) |> String.downcase() == "data:"
+
   def local?(url), do: String.starts_with?(url, Endpoint.url())
 
   def whitelisted?(url) do
diff --git a/test/pleroma/web/media_proxy_test.exs b/test/pleroma/web/media_proxy_test.exs
index ab707a061..433a0fe95 100644
--- a/test/pleroma/web/media_proxy_test.exs
+++ b/test/pleroma/web/media_proxy_test.exs
@@ -45,6 +45,18 @@ defmodule Pleroma.Web.MediaProxyTest do
       assert MediaProxy.url(local_root) == local_root
     end
 
+    test "ignores data url" do
+      assert MediaProxy.url("data:image/png;base64,AAAA") == "data:image/png;base64,AAAA"
+      assert MediaProxy.url("DATA:image/png;base64,AAAA") == "DATA:image/png;base64,AAAA"
+    end
+
+    test "preview_url ignores data url" do
+      clear_config([:media_preview_proxy, :enabled], true)
+
+      assert MediaProxy.preview_url("data:image/png;base64,AAAA") ==
+               "data:image/png;base64,AAAA"
+    end
+
     test "encodes and decodes URL" do
       url = "https://pleroma.soykaf.com/static/logo.png"
       encoded = MediaProxy.url(url)