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akkoma/lib/pleroma/emoji/pack.ex
Oneric ddd79ff22d Proactively harden emoji pack against path traversal
No new path traversal attacks are known. But given the many entrypoints
and code flow complexity inside pack.ex, it unfortunately seems
possible a future refactor or addition might reintroduce one.
Furthermore, some old packs might still contain traversing path entries
which could trigger undesireable actions on rename or delete.

To ensure this can never happen, assert safety during path construction.

Path.safe_relative was introduced in Elixir 1.14, but
fortunately, we already require at least 1.14 anyway.
2024-03-18 22:33:10 -01:00

706 lines
20 KiB
Elixir

# Pleroma: A lightweight social networking server
# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
defmodule Pleroma.Emoji.Pack do
@derive {Jason.Encoder, only: [:files, :pack, :files_count]}
defstruct files: %{},
files_count: 0,
pack_file: nil,
path: nil,
pack: %{},
name: nil
@type t() :: %__MODULE__{
files: %{String.t() => Path.t()},
files_count: non_neg_integer(),
pack_file: Path.t(),
path: Path.t(),
pack: map(),
name: String.t()
}
@cachex Pleroma.Config.get([:cachex, :provider], Cachex)
alias Pleroma.Emoji
alias Pleroma.Emoji.Pack
alias Pleroma.Utils
# Invalid/Malicious names are supposed to be filtered out before path joining,
# but there are many entrypoints to affected functions so as the code changes
# we might accidentally let an unsanitised name slip through.
# To make sure, use the below which crash the process otherwise.
# ALWAYS use this when constructing paths from external name!
# (name meaning it must be only a single path component)
defp path_join_name_safe(dir, name) do
if to_string(name) != Path.basename(name) or name in ["..", ".", ""] do
raise "Invalid or malicious pack name: #{name}"
else
Path.join(dir, name)
end
end
# ALWAYS use this to join external paths
# (which are allowed to have several components)
defp path_join_safe(dir, path) do
{:ok, safe_path} = Path.safe_relative(path)
Path.join(dir, safe_path)
end
@spec create(String.t()) :: {:ok, t()} | {:error, File.posix()} | {:error, :empty_values}
def create(name) do
with :ok <- validate_not_empty([name]),
dir <- path_join_name_safe(emoji_path(), name),
:ok <- File.mkdir(dir) do
save_pack(%__MODULE__{
path: dir,
pack_file: Path.join(dir, "pack.json")
})
end
end
defp paginate(entities, 1, page_size), do: Enum.take(entities, page_size)
defp paginate(entities, page, page_size) do
entities
|> Enum.chunk_every(page_size)
|> Enum.at(page - 1)
end
@spec show(keyword()) :: {:ok, t()} | {:error, atom()}
def show(opts) do
name = opts[:name]
with :ok <- validate_not_empty([name]),
{:ok, pack} <- load_pack(name) do
shortcodes =
pack.files
|> Map.keys()
|> Enum.sort()
|> paginate(opts[:page], opts[:page_size])
pack = Map.put(pack, :files, Map.take(pack.files, shortcodes))
{:ok, validate_pack(pack)}
end
end
@spec delete(String.t()) ::
{:ok, [binary()]} | {:error, File.posix(), binary()} | {:error, :empty_values}
def delete(name) do
with :ok <- validate_not_empty([name]),
pack_path <- path_join_name_safe(emoji_path(), name) do
File.rm_rf(pack_path)
end
end
@spec unpack_zip_emojies(list(tuple())) :: list(map())
defp unpack_zip_emojies(zip_files) do
Enum.reduce(zip_files, [], fn
{_, path, s, _, _, _}, acc when elem(s, 2) == :regular ->
with(
filename <- Path.basename(path),
shortcode <- Path.basename(filename, Path.extname(filename)),
false <- Emoji.exist?(shortcode)
) do
[%{path: path, filename: path, shortcode: shortcode} | acc]
else
_ -> acc
end
_, acc ->
acc
end)
end
@spec add_file(t(), String.t(), Path.t(), Plug.Upload.t() | binary()) ::
{:ok, t()}
| {:error, File.posix() | atom()}
def add_file(%Pack{} = pack, _, _, %Plug.Upload{content_type: "application/zip"} = file) do
with {:ok, zip_files} <- :zip.table(to_charlist(file.path)),
[_ | _] = emojies <- unpack_zip_emojies(zip_files),
{:ok, tmp_dir} <- Utils.tmp_dir("emoji") do
try do
{:ok, _emoji_files} =
:zip.unzip(
to_charlist(file.path),
[{:file_list, Enum.map(emojies, & &1[:path])}, {:cwd, tmp_dir}]
)
{_, updated_pack} =
Enum.map_reduce(emojies, pack, fn item, emoji_pack ->
emoji_file = %Plug.Upload{
filename: item[:filename],
path: path_join_safe(tmp_dir, item[:path])
}
{:ok, updated_pack} =
do_add_file(
emoji_pack,
item[:shortcode],
to_string(item[:filename]),
emoji_file
)
{item, updated_pack}
end)
Emoji.reload()
{:ok, updated_pack}
after
File.rm_rf(tmp_dir)
end
else
{:error, _} = error ->
error
_ ->
{:ok, pack}
end
end
def add_file(%Pack{} = pack, shortcode, filename, %Plug.Upload{} = file) do
try_add_file(pack, shortcode, filename, file)
end
def add_file(%Pack{} = pack, shortcode, filename, filedata) when is_binary(filedata) do
try_add_file(pack, shortcode, filename, filedata)
end
defp try_add_file(%Pack{} = pack, shortcode, filename, file) do
with :ok <- validate_not_empty([shortcode, filename]),
:ok <- validate_emoji_not_exists(shortcode),
{:ok, updated_pack} <- do_add_file(pack, shortcode, filename, file) do
Emoji.reload()
{:ok, updated_pack}
end
end
defp do_add_file(pack, shortcode, filename, file) do
with :ok <- save_file(file, pack, filename) do
pack
|> put_emoji(shortcode, filename)
|> save_pack()
end
end
@spec delete_file(t(), String.t()) ::
{:ok, t()} | {:error, File.posix() | atom()}
def delete_file(%Pack{} = pack, shortcode) do
with :ok <- validate_not_empty([shortcode]),
:ok <- remove_file(pack, shortcode),
{:ok, updated_pack} <- pack |> delete_emoji(shortcode) |> save_pack() do
Emoji.reload()
{:ok, updated_pack}
end
end
@spec update_file(t(), String.t(), String.t(), String.t(), boolean()) ::
{:ok, t()} | {:error, File.posix() | atom()}
def update_file(%Pack{} = pack, shortcode, new_shortcode, new_filename, force) do
with :ok <- validate_not_empty([shortcode, new_shortcode, new_filename]),
{:ok, filename} <- get_filename(pack, shortcode),
:ok <- validate_emoji_not_exists(new_shortcode, force),
:ok <- rename_file(pack, filename, new_filename),
{:ok, updated_pack} <-
pack
|> delete_emoji(shortcode)
|> put_emoji(new_shortcode, new_filename)
|> save_pack() do
Emoji.reload()
{:ok, updated_pack}
end
end
@spec import_from_filesystem() :: {:ok, [String.t()]} | {:error, File.posix() | atom()}
def import_from_filesystem do
emoji_path = emoji_path()
with {:ok, %{access: :read_write}} <- File.stat(emoji_path),
{:ok, results} <- File.ls(emoji_path) do
names =
results
# items come from File.ls, thus safe
|> Enum.map(&Path.join(emoji_path, &1))
|> Enum.reject(fn path ->
File.dir?(path) and File.exists?(Path.join(path, "pack.json"))
end)
|> Enum.map(&write_pack_contents/1)
|> Enum.reject(&is_nil/1)
{:ok, names}
else
{:ok, %{access: _}} -> {:error, :no_read_write}
e -> e
end
end
@spec list_remote(keyword()) :: {:ok, map()} | {:error, atom()}
def list_remote(opts) do
uri = opts[:url] |> String.trim() |> URI.parse()
with :ok <- validate_shareable_packs_available(uri) do
uri
|> URI.merge(
"/api/v1/pleroma/emoji/packs?page=#{opts[:page]}&page_size=#{opts[:page_size]}"
)
|> http_get()
end
end
@spec list_local(keyword()) :: {:ok, map(), non_neg_integer()}
def list_local(opts) do
with {:ok, results} <- list_packs_dir() do
all_packs =
results
|> Enum.map(fn name ->
case load_pack(name) do
{:ok, pack} -> pack
_ -> nil
end
end)
|> Enum.reject(&is_nil/1)
packs =
all_packs
|> paginate(opts[:page], opts[:page_size])
|> Map.new(fn pack -> {pack.name, validate_pack(pack)} end)
{:ok, packs, length(all_packs)}
end
end
@spec get_archive(String.t()) :: {:ok, binary()} | {:error, atom()}
def get_archive(name) do
with {:ok, pack} <- load_pack(name),
:ok <- validate_downloadable(pack) do
{:ok, fetch_archive(pack)}
end
end
@spec download(String.t(), String.t(), String.t()) :: {:ok, t()} | {:error, atom()}
def download(name, url, as) do
uri = url |> String.trim() |> URI.parse()
with :ok <- validate_shareable_packs_available(uri),
{:ok, remote_pack} <-
uri |> URI.merge("/api/v1/pleroma/emoji/pack?name=#{URI.encode(name)}") |> http_get(),
{:ok, %{sha: sha, url: url} = pack_info} <- fetch_pack_info(remote_pack, uri, name),
{:ok, archive} <- download_archive(url, sha),
pack <- copy_as(remote_pack, as || name),
{:ok, _} = unzip(archive, pack_info, remote_pack, pack) do
# Fallback can't contain a pack.json file, since that would cause the fallback-src-sha256
# in it to depend on itself
if pack_info[:fallback] do
save_pack(pack)
else
{:ok, pack}
end
end
end
@spec save_metadata(map(), t()) :: {:ok, t()} | {:error, File.posix()}
def save_metadata(metadata, %__MODULE__{} = pack) do
pack
|> Map.put(:pack, metadata)
|> save_pack()
end
@spec update_metadata(String.t(), map()) :: {:ok, t()} | {:error, File.posix()}
def update_metadata(name, data) do
with {:ok, pack} <- load_pack(name) do
if fallback_sha_changed?(pack, data) do
update_sha_and_save_metadata(pack, data)
else
save_metadata(data, pack)
end
end
end
@spec load_pack(String.t()) :: {:ok, t()} | {:error, :file.posix()}
def load_pack(name) do
pack_dir = path_join_name_safe(emoji_path(), name)
pack_file = Path.join(pack_dir, "pack.json")
with {:ok, _} <- File.stat(pack_file),
{:ok, pack_data} <- File.read(pack_file) do
pack =
from_json(
pack_data,
%{
pack_file: pack_file,
path: Path.dirname(pack_file),
name: name
}
)
files_count =
pack.files
|> Map.keys()
|> length()
{:ok, Map.put(pack, :files_count, files_count)}
end
end
@spec emoji_path() :: Path.t()
defp emoji_path do
[:instance, :static_dir]
|> Pleroma.Config.get!()
|> Path.join("emoji")
end
defp validate_emoji_not_exists(shortcode, force \\ false)
defp validate_emoji_not_exists(_shortcode, true), do: :ok
defp validate_emoji_not_exists(shortcode, _) do
if Emoji.exist?(shortcode) do
{:error, :already_exists}
else
:ok
end
end
defp write_pack_contents(path) do
pack = %__MODULE__{
files: files_from_path(path),
path: path,
pack_file: Path.join(path, "pack.json")
}
case save_pack(pack) do
{:ok, _pack} -> Path.basename(path)
_ -> nil
end
end
defp files_from_path(path) do
txt_path = Path.join(path, "emoji.txt")
if File.exists?(txt_path) do
# There's an emoji.txt file, it's likely from a pack installed by the pack manager.
# Make a pack.json file from the contents of that emoji.txt file
# FIXME: Copy-pasted from Pleroma.Emoji/load_from_file_stream/2
# Create a map of shortcodes to filenames from emoji.txt
txt_path
|> File.read!()
|> String.split("\n")
|> Enum.map(&String.trim/1)
|> Enum.map(fn line ->
case String.split(line, ~r/,\s*/) do
# This matches both strings with and without tags
# and we don't care about tags here
[name, file | _] ->
file_dir_name = Path.dirname(file)
if String.ends_with?(path, file_dir_name) do
{name, Path.basename(file)}
else
{name, file}
end
_ ->
nil
end
end)
|> Enum.reject(&is_nil/1)
|> Map.new()
else
# If there's no emoji.txt, assume all files
# that are of certain extensions from the config are emojis and import them all
pack_extensions = Pleroma.Config.get!([:emoji, :pack_extensions])
Emoji.Loader.make_shortcode_to_file_map(path, pack_extensions)
end
end
defp validate_pack(pack) do
info =
if downloadable?(pack) do
archive = fetch_archive(pack)
archive_sha = :crypto.hash(:sha256, archive) |> Base.encode16()
pack.pack
|> Map.put("can-download", true)
|> Map.put("download-sha256", archive_sha)
else
Map.put(pack.pack, "can-download", false)
end
Map.put(pack, :pack, info)
end
defp downloadable?(pack) do
# If the pack is set as shared, check if it can be downloaded
# That means that when asked, the pack can be packed and sent to the remote
# Otherwise, they'd have to download it from external-src
pack.pack["share-files"] &&
Enum.all?(pack.files, fn {_, file} ->
pack.path
|> Path.join(file)
|> File.exists?()
end)
end
defp create_archive_and_cache(pack, hash) do
files = [
~c"pack.json"
| Enum.map(pack.files, fn {_, file} ->
{:ok, file} = Path.safe_relative(file)
to_charlist(file)
end)
]
{:ok, {_, result}} =
:zip.zip(~c"#{pack.name}.zip", files, [:memory, cwd: to_charlist(pack.path)])
ttl_per_file = Pleroma.Config.get!([:emoji, :shared_pack_cache_seconds_per_file])
overall_ttl = :timer.seconds(ttl_per_file * Enum.count(files))
@cachex.put(
:emoji_packs_cache,
pack.name,
# if pack.json MD5 changes, the cache is not valid anymore
%{hash: hash, pack_data: result},
# Add a minute to cache time for every file in the pack
ttl: overall_ttl
)
result
end
defp save_pack(pack) do
with {:ok, json} <- Jason.encode(pack, pretty: true),
:ok <- File.write(pack.pack_file, json) do
{:ok, pack}
end
end
defp from_json(json, attrs) do
map = Jason.decode!(json)
pack_attrs =
attrs
|> Map.merge(%{
files: map["files"],
pack: map["pack"]
})
struct(__MODULE__, pack_attrs)
end
defp validate_shareable_packs_available(uri) do
with {:ok, %{"links" => links}} <- uri |> URI.merge("/.well-known/nodeinfo") |> http_get(),
# Get the actual nodeinfo address and fetch it
{:ok, %{"metadata" => %{"features" => features}}} <-
links |> List.last() |> Map.get("href") |> http_get() do
if Enum.member?(features, "shareable_emoji_packs") do
:ok
else
{:error, :not_shareable}
end
end
end
defp validate_not_empty(list) do
if Enum.all?(list, fn i -> is_binary(i) and i != "" end) do
:ok
else
{:error, :empty_values}
end
end
defp save_file(%Plug.Upload{path: upload_path}, pack, filename) do
file_path = path_join_safe(pack.path, filename)
create_subdirs(file_path)
with {:ok, _} <- File.copy(upload_path, file_path) do
:ok
end
end
defp save_file(file_data, pack, filename) when is_binary(file_data) do
file_path = path_join_safe(pack.path, filename)
create_subdirs(file_path)
File.write(file_path, file_data, [:binary])
end
defp put_emoji(pack, shortcode, filename) do
files = Map.put(pack.files, shortcode, filename)
%{pack | files: files, files_count: length(Map.keys(files))}
end
defp delete_emoji(pack, shortcode) do
files = Map.delete(pack.files, shortcode)
%{pack | files: files}
end
defp rename_file(pack, filename, new_filename) do
old_path = path_join_safe(pack.path, filename)
new_path = path_join_safe(pack.path, new_filename)
create_subdirs(new_path)
with :ok <- File.rename(old_path, new_path) do
remove_dir_if_empty(old_path, filename)
end
end
defp create_subdirs(file_path) do
with true <- String.contains?(file_path, "/"),
path <- Path.dirname(file_path),
false <- File.exists?(path) do
File.mkdir_p!(path)
end
end
defp remove_file(pack, shortcode) do
with {:ok, filename} <- get_filename(pack, shortcode),
emoji <- path_join_safe(pack.path, filename),
:ok <- File.rm(emoji) do
remove_dir_if_empty(emoji, filename)
end
end
defp remove_dir_if_empty(emoji, filename) do
dir = Path.dirname(emoji)
if String.contains?(filename, "/") and File.ls!(dir) == [] do
File.rmdir!(dir)
else
:ok
end
end
defp get_filename(pack, shortcode) do
with %{^shortcode => filename} when is_binary(filename) <- pack.files,
file_path <- path_join_safe(pack.path, filename),
{:ok, _} <- File.stat(file_path) do
{:ok, filename}
else
{:error, _} = error ->
error
_ ->
{:error, :doesnt_exist}
end
end
defp http_get(%URI{} = url), do: url |> to_string() |> http_get()
defp http_get(url) do
with {:ok, %{body: body}} <- Pleroma.HTTP.get(url, [], []) do
Jason.decode(body)
end
end
defp list_packs_dir do
emoji_path = emoji_path()
# Create the directory first if it does not exist. This is probably the first request made
# with the API so it should be sufficient
with {:create_dir, :ok} <- {:create_dir, File.mkdir_p(emoji_path)},
{:ls, {:ok, results}} <- {:ls, File.ls(emoji_path)} do
{:ok, Enum.sort(results)}
else
{:create_dir, {:error, e}} -> {:error, :create_dir, e}
{:ls, {:error, e}} -> {:error, :ls, e}
end
end
defp validate_downloadable(pack) do
if downloadable?(pack), do: :ok, else: {:error, :cant_download}
end
defp copy_as(remote_pack, local_name) do
path = path_join_name_safe(emoji_path(), local_name)
%__MODULE__{
name: local_name,
path: path,
files: remote_pack["files"],
pack_file: Path.join(path, "pack.json")
}
end
defp unzip(archive, pack_info, remote_pack, local_pack) do
with :ok <- File.mkdir_p!(local_pack.path) do
files = Enum.map(remote_pack["files"], fn {_, path} -> to_charlist(path) end)
# Fallback cannot contain a pack.json file
files = if pack_info[:fallback], do: files, else: [~c"pack.json" | files]
:zip.unzip(archive, cwd: to_charlist(local_pack.path), file_list: files)
end
end
defp fetch_pack_info(remote_pack, uri, name) do
case remote_pack["pack"] do
%{"share-files" => true, "can-download" => true, "download-sha256" => sha} ->
{:ok,
%{
sha: sha,
url:
URI.merge(uri, "/api/v1/pleroma/emoji/packs/archive?name=#{URI.encode(name)}")
|> to_string()
}}
%{"fallback-src" => src, "fallback-src-sha256" => sha} when is_binary(src) ->
{:ok,
%{
sha: sha,
url: src,
fallback: true
}}
_ ->
{:error, "The pack was not set as shared and there is no fallback src to download from"}
end
end
defp download_archive(url, sha) do
with {:ok, %{body: archive}} <- Pleroma.HTTP.get(url) do
if Base.decode16!(sha) == :crypto.hash(:sha256, archive) do
{:ok, archive}
else
{:error, :invalid_checksum}
end
end
end
defp fetch_archive(pack) do
hash = :crypto.hash(:md5, File.read!(pack.pack_file))
case @cachex.get!(:emoji_packs_cache, pack.name) do
%{hash: ^hash, pack_data: archive} -> archive
_ -> create_archive_and_cache(pack, hash)
end
end
defp fallback_sha_changed?(pack, data) do
is_binary(data[:"fallback-src"]) and data[:"fallback-src"] != pack.pack["fallback-src"]
end
defp update_sha_and_save_metadata(pack, data) do
with {:ok, %{body: zip}} <- Pleroma.HTTP.get(data[:"fallback-src"]),
:ok <- validate_has_all_files(pack, zip) do
fallback_sha = :sha256 |> :crypto.hash(zip) |> Base.encode16()
data
|> Map.put("fallback-src-sha256", fallback_sha)
|> save_metadata(pack)
end
end
defp validate_has_all_files(pack, zip) do
with {:ok, f_list} <- :zip.unzip(zip, [:memory]) do
# Check if all files from the pack.json are in the archive
pack.files
|> Enum.all?(fn {_, from_manifest} ->
List.keyfind(f_list, to_charlist(from_manifest), 0)
end)
|> if(do: :ok, else: {:error, :incomplete})
end
end
end