distraction.party/lib/pleroma/web/plugs/rate_limiter.ex

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# Pleroma: A lightweight social networking server
# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
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# SPDX-License-Identifier: AGPL-3.0-only
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defmodule Pleroma.Web.Plugs.RateLimiter do
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@moduledoc """
## Configuration
A keyword list of rate limiters where a key is a limiter name and value is the limiter configuration.
The basic configuration is a tuple where:
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* The first element: `scale` (Integer). The time scale in milliseconds.
* The second element: `limit` (Integer). How many requests to limit in the time scale provided.
It is also possible to have different limits for unauthenticated and authenticated users: the keyword value must be a
list of two tuples where the first one is a config for unauthenticated users and the second one is for authenticated.
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To disable a limiter set its value to `nil`.
### Example
config :pleroma, :rate_limit,
one: {1000, 10},
two: [{10_000, 10}, {10_000, 50}],
foobar: nil
Here we have three limiters:
* `one` which is not over 10req/1s
* `two` which has two limits: 10req/10s for unauthenticated users and 50req/10s for authenticated users
* `foobar` which is disabled
## Usage
AllowedSyntax:
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plug(Pleroma.Web.Plugs.RateLimiter, name: :limiter_name)
plug(Pleroma.Web.Plugs.RateLimiter, options) # :name is a required option
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Allowed options:
* `name` required, always used to fetch the limit values from the config
* `bucket_name` overrides name for counting purposes (e.g. to have a separate limit for a set of actions)
* `params` appends values of specified request params (e.g. ["id"]) to bucket name
Inside a controller:
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plug(Pleroma.Web.Plugs.RateLimiter, [name: :one] when action == :one)
plug(Pleroma.Web.Plugs.RateLimiter, [name: :two] when action in [:two, :three])
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plug(
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Pleroma.Web.Plugs.RateLimiter,
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[name: :status_id_action, bucket_name: "status_id_action:fav_unfav", params: ["id"]]
when action in ~w(fav_status unfav_status)a
)
or inside a router pipeline:
pipeline :api do
...
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plug(Pleroma.Web.Plugs.RateLimiter, name: :one)
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...
end
"""
import Pleroma.Web.TranslationHelpers
import Plug.Conn
alias Pleroma.Config
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alias Pleroma.User
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alias Pleroma.Web.Plugs.RateLimiter.LimiterSupervisor
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require Logger
@doc false
def init(plug_opts) do
plug_opts
end
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def call(conn, plug_opts) do
if disabled?(conn) do
handle_disabled(conn)
else
action_settings = action_settings(plug_opts)
handle(conn, action_settings)
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end
end
defp handle_disabled(conn) do
Logger.warn(
"Rate limiter disabled due to forwarded IP not being found. Please ensure your reverse proxy is providing the X-Forwarded-For header or disable the RemoteIP plug/rate limiter."
)
conn
end
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defp handle(conn, nil), do: conn
defp handle(conn, action_settings) do
action_settings
|> incorporate_conn_info(conn)
|> check_rate()
|> case do
{:ok, _count} ->
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conn
{:error, _count} ->
render_throttled_error(conn)
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end
end
def disabled?(conn) do
if Map.has_key?(conn.assigns, :remote_ip_found),
do: !conn.assigns.remote_ip_found,
else: false
end
@inspect_bucket_not_found {:error, :not_found}
def inspect_bucket(conn, bucket_name_root, plug_opts) do
with %{name: _} = action_settings <- action_settings(plug_opts) do
action_settings = incorporate_conn_info(action_settings, conn)
bucket_name = make_bucket_name(%{action_settings | name: bucket_name_root})
key_name = make_key_name(action_settings)
limit = get_limits(action_settings)
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case Cachex.get(bucket_name, key_name) do
{:error, :no_cache} ->
@inspect_bucket_not_found
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{:ok, nil} ->
{0, limit}
{:ok, value} ->
{value, limit - value}
end
else
_ -> @inspect_bucket_not_found
end
end
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def action_settings(plug_opts) do
with limiter_name when is_atom(limiter_name) <- plug_opts[:name],
limits when not is_nil(limits) <- Config.get([:rate_limit, limiter_name]) do
bucket_name_root = Keyword.get(plug_opts, :bucket_name, limiter_name)
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%{
name: bucket_name_root,
limits: limits,
opts: plug_opts
}
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end
end
defp check_rate(action_settings) do
bucket_name = make_bucket_name(action_settings)
key_name = make_key_name(action_settings)
limit = get_limits(action_settings)
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case Cachex.get_and_update(bucket_name, key_name, &increment_value(&1, limit)) do
{:commit, value} ->
{:ok, value}
{:ignore, value} ->
{:error, value}
{:error, :no_cache} ->
initialize_buckets!(action_settings)
check_rate(action_settings)
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end
end
defp increment_value(nil, _limit), do: {:commit, 1}
defp increment_value(val, limit) when val >= limit, do: {:ignore, val}
defp increment_value(val, _limit), do: {:commit, val + 1}
defp incorporate_conn_info(action_settings, %{
assigns: %{user: %User{id: user_id}},
params: params
}) do
Map.merge(action_settings, %{
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mode: :user,
conn_params: params,
conn_info: "#{user_id}"
})
end
defp incorporate_conn_info(action_settings, %{params: params} = conn) do
Map.merge(action_settings, %{
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mode: :anon,
conn_params: params,
conn_info: "#{ip(conn)}"
})
end
defp ip(%{remote_ip: remote_ip}) do
remote_ip
|> Tuple.to_list()
|> Enum.join(".")
end
defp render_throttled_error(conn) do
conn
|> render_error(:too_many_requests, "Throttled")
|> halt()
end
defp make_key_name(action_settings) do
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""
|> attach_selected_params(action_settings)
|> attach_identity(action_settings)
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end
defp get_scale(_, {scale, _}), do: scale
defp get_scale(:anon, [{scale, _}, {_, _}]), do: scale
defp get_scale(:user, [{_, _}, {scale, _}]), do: scale
defp get_limits(%{limits: {_scale, limit}}), do: limit
defp get_limits(%{mode: :user, limits: [_, {_, limit}]}), do: limit
defp get_limits(%{limits: [{_, limit}, _]}), do: limit
defp make_bucket_name(%{mode: :user, name: bucket_name_root}),
do: user_bucket_name(bucket_name_root)
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defp make_bucket_name(%{mode: :anon, name: bucket_name_root}),
do: anon_bucket_name(bucket_name_root)
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defp attach_selected_params(input, %{conn_params: conn_params, opts: plug_opts}) do
params_string =
plug_opts
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|> Keyword.get(:params, [])
|> Enum.sort()
|> Enum.map(&Map.get(conn_params, &1, ""))
|> Enum.join(":")
[input, params_string]
|> Enum.join(":")
|> String.replace_leading(":", "")
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end
defp initialize_buckets!(%{name: _name, limits: nil}), do: :ok
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defp initialize_buckets!(%{name: name, limits: limits}) do
{:ok, _pid} =
LimiterSupervisor.add_or_return_limiter(anon_bucket_name(name), get_scale(:anon, limits))
{:ok, _pid} =
LimiterSupervisor.add_or_return_limiter(user_bucket_name(name), get_scale(:user, limits))
:ok
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end
defp attach_identity(base, %{mode: :user, conn_info: conn_info}),
do: "user:#{base}:#{conn_info}"
defp attach_identity(base, %{mode: :anon, conn_info: conn_info}),
do: "ip:#{base}:#{conn_info}"
defp user_bucket_name(bucket_name_root), do: "user:#{bucket_name_root}" |> String.to_atom()
defp anon_bucket_name(bucket_name_root), do: "anon:#{bucket_name_root}" |> String.to_atom()
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end