Merge pull request 'Exiftool: Strip all non-essential metadata tags' (#745) from Oneric/akkoma:exiftool-strip-all into develop

Reviewed-on: https://akkoma.dev/AkkomaGang/akkoma/pulls/745

CHANGELOG.md

@@ -10,10 +10,13 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Support for [FEP-fffd](https://codeberg.org/fediverse/fep/src/branch/main/fep/fffd/fep-fffd.md) (proxy objects)
 - Verified support for elixir 1.16
 - Uploadfilter `Pleroma.Upload.Filter.Exiftool.ReadDescription` returns description values to the FE so they can pre fill the image description field
+  NOTE: this filter MUST be placed before `Exiftool.StripMetadata` to work
 
 ## Changed
 - Inbound pipeline error handing was modified somewhat, which should lead to less incomprehensible log spam. Hopefully.
-- Uploadfilter `Pleroma.Upload.Filter.Exiftool` has been renamed to `Pleroma.Upload.Filter.Exiftool.StripMetadata`
+- Uploadfilter `Pleroma.Upload.Filter.Exiftool` was replaced by `Pleroma.Upload.Filter.Exiftool.StripMetadata`;
+  the latter strips all non-essential metadata by default but can be configured.
+  To regain the old behaviour of only stripping GPS data set `purge: ["gps:all"]`.
 
 ## Fixed
 - Issue preventing fetching anything from IPv6-only instances

config/description.exs

@@ -222,6 +222,26 @@ config :pleroma, :config_description, [
       }
     ]
   },
+  %{
+    group: :pleroma,
+    key: Pleroma.Upload.Filter.Exiftool.StripMetadata,
+    type: :group,
+    description: "Strip specified metadata from image uploads",
+    children: [
+      %{
+        key: :purge,
+        description: "Metadata fields or groups to strip",
+        type: {:list, :string},
+        suggestions: ["all", "CommonIFD0"]
+      },
+      %{
+        key: :preserve,
+        description: "Metadata fields or groups to preserve (takes precedence over stripping)",
+        type: {:list, :string},
+        suggestions: ["ColorSpaces", "Orientation"]
+      }
+    ]
+  },
   %{
     group: :pleroma,
     key: Pleroma.Emails.Mailer,

docs/docs/administration/CLI_tasks/instance.md

@@ -37,7 +37,7 @@ If any of the options are left unspecified, you will be prompted interactively.
 - `--static-dir <path>` - the directory custom public files should be read from (custom emojis, frontend bundle overrides, robots.txt, etc.)
 - `--listen-ip <ip>` - the ip the app should listen to, defaults to 127.0.0.1
 - `--listen-port <port>` - the port the app should listen to, defaults to 4000
-- `--strip-uploads-metadata <Y|N>` - use ExifTool to strip uploads of sensitive metadata
+- `--strip-uploads-metadata <Y|N>` - use ExifTool to strip uploads of metadata when possible
 - `--read-uploads-description <Y|N>` - use ExifTool to read image descriptions from uploads
 - `--anonymize-uploads <Y|N>` - randomize uploaded filenames
 - `--dedupe-uploads <Y|N>` - store files based on their hash to reduce data storage requirements if duplicates are uploaded with different filenames

docs/docs/configuration/cheatsheet.md

@@ -656,9 +656,10 @@ This filter replaces the declared filename (not the path) of an upload.
 
 #### Pleroma.Upload.Filter.Exiftool.StripMetadata
 
-This filter only strips the GPS and location metadata with Exiftool leaving color profiles and attributes intact.
+This filter strips metadata with Exiftool leaving color profiles and orientation intact.
 
-No specific configuration.
+* `purge`: List of Exiftool tag names or tag group names to purge
+* `preserve`: List of Exiftool tag names or tag group names to preserve even if they occur in the purge list
 
 
 #### Pleroma.Upload.Filter.Exiftool.ReadDescription

docs/docs/installation/optional/media_graphics_packages.md

@@ -14,7 +14,7 @@ Note: the packages are not required with the current default settings of Akkoma.
 `ImageMagick` is a set of tools to create, edit, compose, or convert bitmap images.
 
 It is required for the following Akkoma features:
-  * `Pleroma.Upload.Filters.Mogrify`, `Pleroma.Upload.Filters.Mogrifun` upload filters (related config: `Plaroma.Upload/filters` in `config/config.exs`)
+  * `Pleroma.Upload.Filters.Mogrify`, `Pleroma.Upload.Filters.Mogrifun` upload filters (related config: `Pleroma.Upload/filters` in `config/config.exs`)
   * Media preview proxy for still images (related config: `media_preview_proxy/enabled` in `config/config.exs`)
   
 ## `ffmpeg`
@@ -29,5 +29,5 @@ It is required for the following Akkoma features:
 `exiftool` is media files metadata reader/writer.
 
 It is required for the following Akkoma features:
-  * `Pleroma.Upload.Filters.Exiftool.StripMetadata` upload filter (related config: `Plaroma.Upload/filters` in `config/config.exs`)
+  * `Pleroma.Upload.Filters.Exiftool.StripMetadata` upload filter (related config: `Pleroma.Upload/filters` in `config/config.exs`)
-  * `Pleroma.Upload.Filters.Exiftool.ReadDescription` upload filter (related config: `Plaroma.Upload/filters` in `config/config.exs`)
+  * `Pleroma.Upload.Filters.Exiftool.ReadDescription` upload filter (related config: `Pleroma.Upload/filters` in `config/config.exs`)

lib/mix/tasks/pleroma/instance.ex

@@ -172,10 +172,10 @@ defmodule Mix.Tasks.Pleroma.Instance do
 
       {strip_uploads_metadata_message, strip_uploads_metadata_default} =
         if Pleroma.Utils.command_available?("exiftool") do
-          {"Do you want to strip location (GPS) data from uploaded images? This requires exiftool, it was detected as installed. (y/n)",
+          {"Do you want to strip metadata from uploaded images? This requires exiftool, it was detected as installed. (y/n)",
            "y"}
         else
-          {"Do you want to strip location (GPS) data from uploaded images? This requires exiftool, it was detected as not installed, please install it if you answer yes. (y/n)",
+          {"Do you want to strip metadata from uploaded images? This requires exiftool, it was detected as not installed, please install it if you answer yes. (y/n)",
            "n"}
         end
 

lib/pleroma/upload/filter/exiftool/strip_metadata.ex

@@ -4,22 +4,40 @@
 
 defmodule Pleroma.Upload.Filter.Exiftool.StripMetadata do
   @moduledoc """
-  Strips GPS related EXIF tags and overwrites the file in place.
+  Tries to strip all image metadata but colorspace and orientation overwriting the file in place.
   Also strips or replaces filesystem metadata e.g., timestamps.
   """
   @behaviour Pleroma.Upload.Filter
 
+  alias Pleroma.Config
+
+  @purge_default ["all", "CommonIFD0"]
+  @preserve_default ["ColorSpaceTags", "Orientation"]
+
   @spec filter(Pleroma.Upload.t()) :: {:ok, :noop} | {:ok, :filtered} | {:error, String.t()}
 
   # Formats not compatible with exiftool at this time
-  def filter(%Pleroma.Upload{content_type: "image/heic"}), do: {:ok, :noop}
   def filter(%Pleroma.Upload{content_type: "image/webp"}), do: {:ok, :noop}
   def filter(%Pleroma.Upload{content_type: "image/svg+xml"}), do: {:ok, :noop}
-  def filter(%Pleroma.Upload{content_type: "image/jxl"}), do: {:ok, :noop}
 
   def filter(%Pleroma.Upload{tempfile: file, content_type: "image" <> _}) do
+    purge_args =
+      Config.get([__MODULE__, :purge], @purge_default)
+      |> Enum.map(fn mgroup -> "-" <> mgroup <> "=" end)
+
+    preserve_args =
+      Config.get([__MODULE__, :preserve], @preserve_default)
+      |> Enum.map(fn mgroup -> "-" <> mgroup end)
+      |> then(fn
+        # If -TagsFromFile is not followed by tag selectors, it will copy most available tags
+        [] -> []
+        args -> ["-TagsFromFile", "@" | args]
+      end)
+
+    args = ["-ignoreMinorErrors", "-overwrite_original" | purge_args] ++ preserve_args ++ [file]
+
     try do
-      case System.cmd("exiftool", ["-overwrite_original", "-gps:all=", file], parallelism: true) do
+      case System.cmd("exiftool", args, parallelism: true) do
         {_response, 0} -> {:ok, :filtered}
         {error, 1} -> {:error, error}
       end

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

@@ -6,29 +6,104 @@ defmodule Pleroma.Upload.Filter.Exiftool.StripMetadataTest do
   use Pleroma.DataCase
   alias Pleroma.Upload.Filter
 
-  test "apply exiftool filter" do
+  @tag :tmp_dir
+  test "exiftool strip metadata strips GPS etc but preserves Orientation and ColorSpace by default",
+       %{tmp_dir: tmp_dir} do
     assert Pleroma.Utils.command_available?("exiftool")
 
+    tmpfile = Path.join(tmp_dir, "tmp.jpg")
+
     File.cp!(
       "test/fixtures/DSCN0010.jpg",
-      "test/fixtures/DSCN0010_tmp.jpg"
+      tmpfile
     )
 
     upload = %Pleroma.Upload{
       name: "image_with_GPS_data.jpg",
       content_type: "image/jpeg",
       path: Path.absname("test/fixtures/DSCN0010.jpg"),
-      tempfile: Path.absname("test/fixtures/DSCN0010_tmp.jpg")
+      tempfile: Path.absname(tmpfile)
     }
 
     assert Filter.Exiftool.StripMetadata.filter(upload) == {:ok, :filtered}
 
-    {exif_original, 0} = System.cmd("exiftool", ["test/fixtures/DSCN0010.jpg"])
+    exif_original = read_exif("test/fixtures/DSCN0010.jpg")
-    {exif_filtered, 0} = System.cmd("exiftool", ["test/fixtures/DSCN0010_tmp.jpg"])
+    exif_filtered = read_exif(tmpfile)
 
     refute exif_original == exif_filtered
     assert String.match?(exif_original, ~r/GPS/)
     refute String.match?(exif_filtered, ~r/GPS/)
+    assert String.match?(exif_original, ~r/Camera Model Name/)
+    refute String.match?(exif_filtered, ~r/Camera Model Name/)
+    assert String.match?(exif_original, ~r/Orientation/)
+    assert String.match?(exif_filtered, ~r/Orientation/)
+    assert String.match?(exif_original, ~r/Color Space/)
+    assert String.match?(exif_filtered, ~r/Color Space/)
+  end
+
+  # this is a nonsensical configuration, but it shouldn't explode
+  @tag :tmp_dir
+  test "exiftool strip metadata is a noop with empty purge list", %{tmp_dir: tmp_dir} do
+    assert Pleroma.Utils.command_available?("exiftool")
+    clear_config([Pleroma.Upload.Filter.Exiftool.StripMetadata, :purge], [])
+
+    tmpfile = Path.join(tmp_dir, "tmp.jpg")
+
+    File.cp!(
+      "test/fixtures/DSCN0010.jpg",
+      tmpfile
+    )
+
+    upload = %Pleroma.Upload{
+      name: "image_with_GPS_data.jpg",
+      content_type: "image/jpeg",
+      path: Path.absname("test/fixtures/DSCN0010.jpg"),
+      tempfile: Path.absname(tmpfile)
+    }
+
+    assert Filter.Exiftool.StripMetadata.filter(upload) == {:ok, :filtered}
+
+    exif_original = read_exif("test/fixtures/DSCN0010.jpg")
+    exif_filtered = read_exif(tmpfile)
+
+    assert exif_original == exif_filtered
+  end
+
+  @tag :tmp_dir
+  test "exiftool strip metadata works with empty preserve list", %{tmp_dir: tmp_dir} do
+    assert Pleroma.Utils.command_available?("exiftool")
+    clear_config([Pleroma.Upload.Filter.Exiftool.StripMetadata, :preserve], [])
+
+    tmpfile = Path.join(tmp_dir, "tmp.jpg")
+
+    File.cp!(
+      "test/fixtures/DSCN0010.jpg",
+      tmpfile
+    )
+
+    upload = %Pleroma.Upload{
+      name: "image_with_GPS_data.jpg",
+      content_type: "image/jpeg",
+      path: Path.absname("test/fixtures/DSCN0010.jpg"),
+      tempfile: Path.absname(tmpfile)
+    }
+
+    write_exif(["-ImageDescription=Trees and Houses", "-Orientation=1", tmpfile])
+    exif_extended = read_exif(tmpfile)
+    assert String.match?(exif_extended, ~r/Image Description[ \t]*:[ \t]*Trees and Houses/)
+    assert String.match?(exif_extended, ~r/Orientation/)
+
+    assert Filter.Exiftool.StripMetadata.filter(upload) == {:ok, :filtered}
+
+    exif_original = read_exif("test/fixtures/DSCN0010.jpg")
+    exif_filtered = read_exif(tmpfile)
+
+    refute exif_original == exif_filtered
+    refute exif_extended == exif_filtered
+    assert String.match?(exif_original, ~r/GPS/)
+    refute String.match?(exif_filtered, ~r/GPS/)
+    refute String.match?(exif_filtered, ~r/Image Description/)
+    refute String.match?(exif_filtered, ~r/Orientation/)
   end
 
   test "verify webp files are skipped" do
@@ -39,4 +114,35 @@ defmodule Pleroma.Upload.Filter.Exiftool.StripMetadataTest do
 
     assert Filter.Exiftool.StripMetadata.filter(upload) == {:ok, :noop}
   end
+
+  test "verify svg files are skipped" do
+    upload = %Pleroma.Upload{
+      name: "sample.svg",
+      content_type: "image/svg+xml"
+    }
+
+    assert Filter.Exiftool.StripMetadata.filter(upload) == {:ok, :noop}
+  end
+
+  defp read_exif(file) do
+    # time and file path tags cause mismatches even for byte-identical files
+    {exif_data, 0} =
+      System.cmd("exiftool", [
+        "-x",
+        "Time:All",
+        "-x",
+        "Directory",
+        "-x",
+        "FileName",
+        "-x",
+        "FileSize",
+        file
+      ])
+
+    exif_data
+  end
+
+  defp write_exif(args) do
+    {_response, 0} = System.cmd("exiftool", ["-ignoreMinorErrors", "-overwrite_original" | args])
+  end
 end