feat(upload): add Exif.StripLocation and Exif.ReadDescription filters

Pure-Elixir filters based on exif_stripper. StripLocation also handles
WebP and HEIC/AVIF, which the exiftool filter skipped.

lib/pleroma/upload/filter/exif/read_description.ex

@@ -0,0 +1,32 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2026 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Upload.Filter.Exif.ReadDescription do
+  @moduledoc """
+  Reads a description from image metadata when the upload has none yet.
+
+  Checks EXIF ImageDescription, then IPTC Caption-Abstract, then XMP. Blank
+  values and values longer than `[:instance, :description_limit]` are ignored.
+  """
+
+  @behaviour Pleroma.Upload.Filter
+
+  @impl true
+  def filter(%Pleroma.Upload{description: description}) when is_binary(description),
+    do: {:ok, :noop}
+
+  def filter(%Pleroma.Upload{tempfile: file, content_type: "image" <> _} = upload) do
+    max_length = Pleroma.Config.get([:instance, :description_limit])
+
+    case ExifStripper.Description.read_file(file, max_length: max_length) do
+      description when is_binary(description) ->
+        {:ok, :filtered, %{upload | description: description}}
+
+      nil ->
+        {:ok, :noop}
+    end
+  end
+
+  def filter(_), do: {:ok, :noop}
+end

lib/pleroma/upload/filter/exif/strip_location.ex

@@ -0,0 +1,25 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2026 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Upload.Filter.Exif.StripLocation do
+  @moduledoc """
+  Strips GPS metadata from uploaded images and overwrites the file in place.
+
+  Supports JPEG, PNG, WebP and ISO-BMFF images (HEIC, AVIF). This is lossless:
+  the image data is not re-encoded. Other image types are left untouched.
+  """
+
+  @behaviour Pleroma.Upload.Filter
+
+  @impl true
+  def filter(%Pleroma.Upload{tempfile: file, content_type: "image" <> _}) do
+    case ExifStripper.GpsStripper.strip_gps_data(file, file) do
+      :ok -> {:ok, :filtered}
+      :noop -> {:ok, :noop}
+      {:error, _} = error -> error
+    end
+  end
+
+  def filter(_), do: {:ok, :noop}
+end

test/pleroma/upload/filter/exif/read_description_test.exs

@@ -0,0 +1,85 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Upload.Filter.Exif.ReadDescriptionTest do
+  use Pleroma.DataCase, async: true
+
+  alias Pleroma.Upload.Filter.Exif.ReadDescription
+
+  defp upload(fixture, attrs \\ []) do
+    path = Path.absname(Path.join("test/fixtures", fixture))
+
+    struct!(
+      %Pleroma.Upload{
+        name: fixture,
+        content_type: "image/" <> String.trim_leading(Path.extname(fixture), "."),
+        path: path,
+        tempfile: path,
+        description: nil
+      },
+      attrs
+    )
+  end
+
+  test "keeps description when not empty" do
+    upload =
+      upload("image_with_imagedescription_and_caption-abstract.jpg",
+        description: "Some description"
+      )
+
+    assert ReadDescription.filter(upload) == {:ok, :noop}
+  end
+
+  test "otherwise returns ImageDescription when present" do
+    upload = upload("image_with_imagedescription_and_caption-abstract.jpg")
+
+    assert ReadDescription.filter(upload) ==
+             {:ok, :filtered, %{upload | description: "a descriptive white pixel"}}
+  end
+
+  test "ignores stray data after the image" do
+    upload = upload("image_with_imagedescription_and_caption-abstract_and_stray_data_after.png")
+
+    assert {:ok, :filtered, %{description: "a descriptive white pixel"}} =
+             ReadDescription.filter(upload)
+
+    assert ReadDescription.filter(upload("image_with_stray_data_after.png")) == {:ok, :noop}
+  end
+
+  test "otherwise returns iptc:Caption-Abstract when present" do
+    upload = upload("image_with_caption-abstract.jpg")
+
+    assert ReadDescription.filter(upload) ==
+             {:ok, :filtered, %{upload | description: "an abstract white pixel"}}
+  end
+
+  test "reads ImageDescription from WebP and HEIC" do
+    assert {:ok, :filtered, %{description: "a webp with a location"}} =
+             ReadDescription.filter(upload("strip_location_gps.webp"))
+
+    assert {:ok, :filtered, %{description: "a heic with a location"}} =
+             ReadDescription.filter(upload("strip_location_gps.heic"))
+  end
+
+  test "does nothing when there is no description" do
+    assert ReadDescription.filter(upload("image_with_no_description.jpg")) == {:ok, :noop}
+  end
+
+  test "ignores descriptions that exceed the maximum length" do
+    clear_config([:instance, :description_limit], 5)
+
+    upload = upload("image_with_imagedescription_and_caption-abstract.jpg")
+    assert ReadDescription.filter(upload) == {:ok, :noop}
+  end
+
+  test "ignores content with only whitespace" do
+    upload = upload("image_with_imagedescription_and_caption-abstract_whitespaces.jpg")
+    assert ReadDescription.filter(upload) == {:ok, :noop}
+  end
+
+  test "does nothing when the file can't be read" do
+    upload = %{upload("image.jpg") | tempfile: Path.absname("test/fixtures/non-existant_tmp.jpg")}
+    assert ReadDescription.filter(upload) == {:ok, :noop}
+  end
+end

test/pleroma/upload/filter/exif/strip_location_test.exs

@@ -0,0 +1,49 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2026 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Upload.Filter.Exif.StripLocationTest do
+  use Pleroma.DataCase, async: true
+
+  import Pleroma.Tests.ExifHelpers
+
+  alias Pleroma.Upload.Filter.Exif.StripLocation
+
+  for {fixture, content_type} <- [
+        {"DSCN0010.jpg", "image/jpeg"},
+        {"DSCN0010.png", "image/png"},
+        {"strip_location_gps.webp", "image/webp"},
+        {"strip_location_gps.heic", "image/heic"}
+      ] do
+    test "strips GPS data from #{content_type}" do
+      upload = upload_copy(unquote(fixture), unquote(content_type))
+      assert gps_tags(upload.tempfile) =~ "GPS Latitude"
+
+      assert StripLocation.filter(upload) == {:ok, :filtered}
+      assert gps_tags(upload.tempfile) == ""
+    end
+  end
+
+  test "keeps other EXIF data in HEIC" do
+    upload = upload_copy("strip_location_gps.heic", "image/heic")
+
+    assert StripLocation.filter(upload) == {:ok, :filtered}
+    assert tag(upload.tempfile, "ImageDescription") == "a heic with a location"
+    assert tag(upload.tempfile, "ImageSize") == "64x48"
+  end
+
+  test "does nothing when there is no GPS data" do
+    upload = upload_copy("image.jpg", "image/jpeg")
+    original = File.read!(upload.tempfile)
+
+    assert StripLocation.filter(upload) == {:ok, :noop}
+    assert File.read!(upload.tempfile) == original
+  end
+
+  test "ignores non-image uploads" do
+    upload = upload_copy("DSCN0010.jpg", "application/octet-stream")
+
+    assert StripLocation.filter(upload) == {:ok, :noop}
+    assert gps_tags(upload.tempfile) =~ "GPS Latitude"
+  end
+end

test/pleroma/upload/filter/exiftool/read_description_test.exs

@@ -1,144 +0,0 @@
-# Pleroma: A lightweight social networking server
-# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
-# SPDX-License-Identifier: AGPL-3.0-only
-
-defmodule Pleroma.Upload.Filter.Exiftool.ReadDescriptionTest do
-  use Pleroma.DataCase
-  alias Pleroma.Upload.Filter
-
-  @uploads %Pleroma.Upload{
-    name: "image_with_imagedescription_and_caption-abstract.jpg",
-    content_type: "image/jpeg",
-    path: Path.absname("test/fixtures/image_with_imagedescription_and_caption-abstract.jpg"),
-    tempfile: Path.absname("test/fixtures/image_with_imagedescription_and_caption-abstract.jpg"),
-    description: nil
-  }
-
-  test "keeps description when not empty" do
-    uploads = %Pleroma.Upload{
-      name: "image_with_imagedescription_and_caption-abstract.jpg",
-      content_type: "image/jpeg",
-      path: Path.absname("test/fixtures/image_with_imagedescription_and_caption-abstract.jpg"),
-      tempfile:
-        Path.absname("test/fixtures/image_with_imagedescription_and_caption-abstract.jpg"),
-      description: "Some description"
-    }
-
-    assert Filter.Exiftool.ReadDescription.filter(uploads) ==
-             {:ok, :noop}
-  end
-
-  test "otherwise returns ImageDescription when present" do
-    uploads_after = %Pleroma.Upload{
-      name: "image_with_imagedescription_and_caption-abstract.jpg",
-      content_type: "image/jpeg",
-      path: Path.absname("test/fixtures/image_with_imagedescription_and_caption-abstract.jpg"),
-      tempfile:
-        Path.absname("test/fixtures/image_with_imagedescription_and_caption-abstract.jpg"),
-      description: "a descriptive white pixel"
-    }
-
-    assert Filter.Exiftool.ReadDescription.filter(@uploads) ==
-             {:ok, :filtered, uploads_after}
-  end
-
-  test "Ignores warnings" do
-    uploads = %Pleroma.Upload{
-      name: "image_with_imagedescription_and_caption-abstract_and_stray_data_after.png",
-      content_type: "image/png",
-      path:
-        Path.absname(
-          "test/fixtures/image_with_imagedescription_and_caption-abstract_and_stray_data_after.png"
-        ),
-      tempfile:
-        Path.absname(
-          "test/fixtures/image_with_imagedescription_and_caption-abstract_and_stray_data_after.png"
-        )
-    }
-
-    assert {:ok, :filtered, %{description: "a descriptive white pixel"}} =
-             Filter.Exiftool.ReadDescription.filter(uploads)
-
-    uploads = %Pleroma.Upload{
-      name: "image_with_stray_data_after.png",
-      content_type: "image/png",
-      path: Path.absname("test/fixtures/image_with_stray_data_after.png"),
-      tempfile: Path.absname("test/fixtures/image_with_stray_data_after.png")
-    }
-
-    assert {:ok, :filtered, %{description: nil}} = Filter.Exiftool.ReadDescription.filter(uploads)
-  end
-
-  test "otherwise returns iptc:Caption-Abstract when present" do
-    upload = %Pleroma.Upload{
-      name: "image_with_caption-abstract.jpg",
-      content_type: "image/jpeg",
-      path: Path.absname("test/fixtures/image_with_caption-abstract.jpg"),
-      tempfile: Path.absname("test/fixtures/image_with_caption-abstract.jpg"),
-      description: nil
-    }
-
-    upload_after = %Pleroma.Upload{
-      name: "image_with_caption-abstract.jpg",
-      content_type: "image/jpeg",
-      path: Path.absname("test/fixtures/image_with_caption-abstract.jpg"),
-      tempfile: Path.absname("test/fixtures/image_with_caption-abstract.jpg"),
-      description: "an abstract white pixel"
-    }
-
-    assert Filter.Exiftool.ReadDescription.filter(upload) ==
-             {:ok, :filtered, upload_after}
-  end
-
-  test "otherwise returns nil" do
-    uploads = %Pleroma.Upload{
-      name: "image_with_no_description.jpg",
-      content_type: "image/jpeg",
-      path: Path.absname("test/fixtures/image_with_no_description.jpg"),
-      tempfile: Path.absname("test/fixtures/image_with_no_description.jpg"),
-      description: nil
-    }
-
-    assert Filter.Exiftool.ReadDescription.filter(uploads) ==
-             {:ok, :filtered, uploads}
-  end
-
-  test "Return nil when image description from EXIF data exceeds the maximum length" do
-    clear_config([:instance, :description_limit], 5)
-
-    assert Filter.Exiftool.ReadDescription.filter(@uploads) ==
-             {:ok, :filtered, @uploads}
-  end
-
-  test "Ignores content with only whitespace" do
-    uploads = %Pleroma.Upload{
-      name: "non-existant.jpg",
-      content_type: "image/jpeg",
-      path:
-        Path.absname(
-          "test/fixtures/image_with_imagedescription_and_caption-abstract_whitespaces.jpg"
-        ),
-      tempfile:
-        Path.absname(
-          "test/fixtures/image_with_imagedescription_and_caption-abstract_whitespaces.jpg"
-        ),
-      description: nil
-    }
-
-    assert Filter.Exiftool.ReadDescription.filter(uploads) ==
-             {:ok, :filtered, uploads}
-  end
-
-  test "Return nil when image description from EXIF data can't be read" do
-    uploads = %Pleroma.Upload{
-      name: "non-existant.jpg",
-      content_type: "image/jpeg",
-      path: Path.absname("test/fixtures/non-existant.jpg"),
-      tempfile: Path.absname("test/fixtures/non-existant_tmp.jpg"),
-      description: nil
-    }
-
-    assert Filter.Exiftool.ReadDescription.filter(uploads) ==
-             {:ok, :filtered, uploads}
-  end
-end

test/support/exif_helpers.ex

@@ -0,0 +1,44 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2026 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Tests.ExifHelpers do
+  @moduledoc """
+  Helpers for upload filter tests that use exiftool as an independent oracle.
+  """
+
+  @doc "Copies a fixture to a unique temporary file and returns an upload for it."
+  def upload_copy(fixture, content_type, attrs \\ []) do
+    source = Path.absname(Path.join("test/fixtures", fixture))
+
+    tempfile =
+      Path.join(
+        System.tmp_dir!(),
+        "pleroma_exif_#{System.unique_integer([:positive])}#{Path.extname(fixture)}"
+      )
+
+    File.cp!(source, tempfile)
+    ExUnit.Callbacks.on_exit(fn -> File.rm(tempfile) end)
+
+    struct!(
+      %Pleroma.Upload{
+        name: fixture,
+        content_type: content_type,
+        path: source,
+        tempfile: tempfile
+      },
+      attrs
+    )
+  end
+
+  @doc "Returns the GPS tags exiftool finds in a file, as text."
+  def gps_tags(path), do: exiftool!(["-gps:all", path])
+
+  @doc "Returns the value of one tag as exiftool reads it."
+  def tag(path, tag), do: exiftool!(["-s3", "-#{tag}", path])
+
+  defp exiftool!(args) do
+    {output, 0} = System.cmd("exiftool", ["-m" | args])
+    String.trim(output)
+  end
+end