feat(auto_source): add support for auto_source feature (#676)

Gemfile

@@ -4,19 +4,21 @@ source 'https://rubygems.org'
 
 git_source(:github) { |repo_name| "https://github.com/#{repo_name}" }
 
-gem 'html2rss'
+gem 'html2rss', '~> 0.14'
 gem 'html2rss-configs', github: 'html2rss/html2rss-configs'
 
 # Use these instead of the two above (uncomment them) when developing locally:
 # gem 'html2rss', path: '../html2rss'
 # gem 'html2rss-configs', path: '../html2rss-configs'
 
+gem 'base64'
 gem 'erubi'
 gem 'parallel'
 gem 'rack-cache'
 gem 'rack-timeout'
 gem 'rack-unreloader'
 gem 'roda'
+gem 'ssrf_filter'
 gem 'tilt'
 
 gem 'puma', require: false
@@ -33,7 +35,10 @@ group :development do
 end
 
 group :test do
+  gem 'climate_control'
+  gem 'rack-test'
   gem 'rspec'
   gem 'simplecov', require: false
   gem 'vcr'
+  gem 'webmock'
 end

Gemfile.lock

@@ -11,8 +11,14 @@ GEM
     addressable (2.8.7)
       public_suffix (>= 2.0.2, < 7.0)
     ast (2.4.2)
+    base64 (0.2.0)
+    bigdecimal (3.1.8)
     byebug (11.1.3)
+    climate_control (1.2.0)
     concurrent-ruby (1.3.4)
+    crack (1.0.0)
+      bigdecimal
+      rexml
     crass (1.0.6)
     diff-lcs (1.5.1)
     docile (1.4.1)
@@ -25,6 +31,7 @@ GEM
       faraday (>= 1, < 3)
     faraday-net_http (3.3.0)
       net-http
+    hashdiff (1.1.1)
     html2rss (0.14.0)
       addressable (~> 2.7)
       faraday (> 2.0.1, < 3.0)
@@ -75,6 +82,8 @@ GEM
     rack (3.1.7)
     rack-cache (1.17.0)
       rack (>= 0.4)
+    rack-test (2.1.0)
+      rack (>= 1.3)
     rack-timeout (0.7.0)
     rack-unreloader (2.1.0)
     rainbow (3.1.1)
@@ -132,13 +141,18 @@ GEM
       simplecov_json_formatter (~> 0.1)
     simplecov-html (0.12.3)
     simplecov_json_formatter (0.1.4)
+    ssrf_filter (1.1.2)
     thor (1.3.2)
     tilt (2.4.0)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
     unicode-display_width (2.5.0)
     uri (0.13.1)
     vcr (6.2.0)
+    webmock (3.24.0)
+      addressable (>= 2.8.0)
+      crack (>= 0.3.2)
+      hashdiff (>= 0.4.0, < 2.0.0)
     yard (0.9.36)
     zeitwerk (2.6.18)
 
@@ -151,13 +165,16 @@ PLATFORMS
   x86_64-linux
 
 DEPENDENCIES
+  base64
   byebug
+  climate_control
   erubi
-  html2rss
+  html2rss (~> 0.14)
   html2rss-configs!
   parallel
   puma
   rack-cache
+  rack-test
   rack-timeout
   rack-unreloader
   rake
@@ -169,8 +186,10 @@ DEPENDENCIES
   rubocop-rspec
   rubocop-thread_safety
   simplecov
+  ssrf_filter
   tilt
   vcr
+  webmock
   yard
 
 BUNDLED WITH

README.md

@@ -45,9 +45,16 @@ services:
         target: /app/config/feeds.yml
         read_only: true
     environment:
-      - RACK_ENV=production
-      - HEALTH_CHECK_USERNAME=health
-      - HEALTH_CHECK_PASSWORD=please-set-YOUR-OWN-veeeeeery-l0ng-aNd-h4rd-to-gue55-Passw0rd!
+      RACK_ENV: production
+      HEALTH_CHECK_USERNAME: health
+      HEALTH_CHECK_PASSWORD: please-set-YOUR-OWN-veeeeeery-l0ng-aNd-h4rd-to-gue55-Passw0rd!
+      # AUTO_SOURCE_ENABLED: true
+      # AUTO_SOURCE_USERNAME: foobar
+      # AUTO_SOURCE_PASSWORD: A-Unique-And-Long-Password-For-Your-Own-Instance
+      ## to allow just requests originating from the local host
+      # AUTO_SOURCE_ALLOWED_ORIGINS: 127.0.0.1:3000
+      ## to allow multiple origins, seperate those via comma:
+      # AUTO_SOURCE_ALLOWED_ORIGINS: example.com,h2r.host.tld
   watchtower:
     image: containrrr/watchtower
     volumes:
@@ -66,6 +73,31 @@ The [watchtower](https://containrrr.dev/watchtower/) service automatically pulls
 
 The `docker-compose.yml` above contains a service description for watchtower.
 
+## How to use automatic feed generation
+
+> [!NOTE]
+> This feature is disabled by default.
+
+To enable the `auto_source` feature, comment in the env variables in the `docker-compose.yml` file from above and change the values accordingly:
+
+```yaml
+environment:
+  ## … snip ✁
+  AUTO_SOURCE_ENABLED: true
+  AUTO_SOURCE_USERNAME: foobar
+  AUTO_SOURCE_PASSWORD: A-Unique-And-Long-Password-For-Your-Own-Instance
+  ## to allow just requests originating from the local host
+  AUTO_SOURCE_ALLOWED_ORIGINS: 127.0.0.1:3000
+  ## to allow multiple origins, seperate those via comma:
+  # AUTO_SOURCE_ALLOWED_ORIGINS: example.com,h2r.host.tld
+  ## … snap ✃
+```
+
+Restart the container and open <http://127.0.0.1:3000/auto_source>.
+When asked, enter your username and password.
+
+Then enter the URL of a website and click on the _Generate_ button.
+
 ## How to use the included configs
 
 html2rss-web comes with many feed configs out of the box. [See the file list of all configs.](https://github.com/html2rss/html2rss-configs/tree/master/lib/html2rss/configs)
@@ -85,7 +117,7 @@ To build your own RSS feed, you need to create a _feed config_.\
 That _feed config_ goes into the file `feeds.yml`.\
 Check out the [`example` feed config](https://github.com/html2rss/html2rss-web/blob/master/config/feeds.yml#L9).
 
-Please refer to [html2rss' README for a description of _the feed config and its options_](https://github.com/html2rss/html2rss#the-feed-config-and-its-options). html2rss-web is just a small web application that depends on html2rss.
+Please refer to [html2rss' README for a description of _the feed config and its options_](https://github.com/html2rss/html2rss#the-feed-config-and-its-options). html2rss-web is just a small web application that builds on html2rss.
 
 ## Versioning and releases
 
@@ -112,15 +144,23 @@ If you're going to host a public instance, _please, please, please_:
 
 ### Supported ENV variables
 
-| Name                           | Description                      |
-| ------------------------------ | -------------------------------- |
-| `PORT`                         | default: 3000                    |
-| `RACK_ENV`                     | default: 'development'           |
-| `RACK_TIMEOUT_SERVICE_TIMEOUT` | default: 15                      |
-| `WEB_CONCURRENCY`              | default: 2                       |
-| `WEB_MAX_THREADS`              | default: 5                       |
-| `HEALTH_CHECK_USERNAME`        | default: auto-generated on start |
-| `HEALTH_CHECK_PASSWORD`        | default: auto-generated on start |
+| Name                           | Description                        |
+| ------------------------------ | ---------------------------------- |
+| `BASE_URL`                     | default: '<http://localhost:3000>' |
+| `LOG_LEVEL`                    | default: 'warn'                    |
+| `HEALTH_CHECK_USERNAME`        | default: auto-generated on start   |
+| `HEALTH_CHECK_PASSWORD`        | default: auto-generated on start   |
+|                                |                                    |
+| `AUTO_SOURCE_ENABLED`          | default: false                     |
+| `AUTO_SOURCE_USERNAME          | no default                         |
+| `AUTO_SOURCE_PASSWORD          | no default                         |
+| `AUTO_SOURCE_ALLOWED_ORIGINS`  | no default.                        |
+|                                |                                    |
+| `PORT`                         | default: 3000                      |
+| `RACK_ENV`                     | default: 'development'             |
+| `RACK_TIMEOUT_SERVICE_TIMEOUT` | default: 15                        |
+| `WEB_CONCURRENCY`              | default: 2                         |
+| `WEB_MAX_THREADS`              | default: 5                         |
 
 ### Runtime monitoring via `GET /health_check.txt`
 

app.rb

@@ -2,7 +2,6 @@
 
 require 'roda'
 require 'rack/cache'
-
 require_relative 'roda/roda_plugins/basic_auth'
 
 module Html2rss
@@ -12,12 +11,9 @@ module Web
     #
     # It is built with [Roda](https://roda.jeremyevans.net/).
     class App < Roda
-      # TODO: move to helper
-      def self.development?
-        ENV['RACK_ENV'] == 'development'
-      end
+      CONTENT_TYPE_RSS = 'application/xml'
 
-      def development? = self.class.development?
+      def self.development? = ENV['RACK_ENV'] == 'development'
 
       opts[:check_dynamic_arity] = false
       opts[:check_arity] = :warn
@@ -33,16 +29,16 @@ def development? = self.class.development?
         csp.script_src :self
         csp.connect_src :self
         csp.img_src :self
-        csp.font_src :self
+        csp.font_src :self, 'data:'
         csp.form_action :self
         csp.base_uri :none
-        csp.frame_ancestors :none
+        csp.frame_ancestors :self
+        csp.frame_src :self
         csp.block_all_mixed_content
       end
 
       plugin :default_headers,
              'Content-Type' => 'text/html',
-             'X-Frame-Options' => 'deny',
              'X-Content-Type-Options' => 'nosniff',
              'X-XSS-Protection' => '1; mode=block'
 
@@ -53,8 +49,9 @@ def development? = self.class.development?
         handle_error(error)
       end
 
-      plugin :hash_branches
+      plugin :hash_branch_view_subdir
       plugin :public
+      plugin :content_for
       plugin :render, escape: true, layout: 'layout'
       plugin :typecast_params
       plugin :basic_auth
@@ -69,7 +66,6 @@ def development? = self.class.development?
 
       route do |r|
         r.public
-
         r.hash_branches('')
 
         r.root { view 'index' }

config.ru

@@ -4,8 +4,6 @@ require 'rubygems'
 require 'bundler/setup'
 require 'rack-timeout'
 
-use Rack::Timeout
-
 dev = ENV.fetch('RACK_ENV', nil) == 'development'
 
 requires = Dir['app/**/*.rb']
@@ -26,6 +24,8 @@ if dev
 
   run Unreloader
 else
+  use Rack::Timeout
+
   require_relative 'app'
   requires.each { |f| require_relative f }
 

helpers/auto_source.rb

@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+require 'addressable'
+require 'base64'
+require 'html2rss'
+require 'ssrf_filter'
+
+module Html2rss
+  module Web
+    ##
+    # Helper methods for handling auto source feature.
+    class AutoSource
+      def self.enabled?        = ENV['AUTO_SOURCE_ENABLED'].to_s == 'true'
+      def self.username        = ENV.fetch('AUTO_SOURCE_USERNAME')
+      def self.password        = ENV.fetch('AUTO_SOURCE_PASSWORD')
+
+      def self.allowed_origins = ENV.fetch('AUTO_SOURCE_ALLOWED_ORIGINS', '')
+                                    .split(',')
+                                    .map(&:strip)
+                                    .reject(&:empty?)
+                                    .to_set
+
+      # @param encoded_url [String] Base64 encoded URL
+      # @return [RSS::Rss]
+      def self.build_auto_source_from_encoded_url(encoded_url)
+        url = Addressable::URI.parse Base64.urlsafe_decode64(encoded_url)
+        request = SsrfFilter.get(url)
+        headers = request.to_hash.transform_values(&:first)
+
+        auto_source = Html2rss::AutoSource.new(url, body: request.body, headers:)
+
+        auto_source.channel.stylesheets << Html2rss::RssBuilder::Stylesheet.new(href: '/rss.xsl', type: 'text/xsl')
+
+        auto_source.build
+      end
+
+      # @param rss [RSS::Rss]
+      # @param default_in_minutes [Integer]
+      # @return [Integer]
+      def self.ttl_in_seconds(rss, default_in_minutes: 60)
+        (rss&.channel&.ttl || default_in_minutes) * 60
+      end
+
+      # @param request [Roda::RodaRequest]
+      # @param response [Roda::RodaResponse]
+      # @param allowed_origins [Set<String>]
+      def self.check_request_origin!(request, response, allowed_origins = AutoSource.allowed_origins)
+        if allowed_origins.empty?
+          response.write 'No allowed origins are configured. Please set AUTO_SOURCE_ALLOWED_ORIGINS.'
+        else
+          origin = Set[request.env['HTTP_HOST'], request.env['HTTP_X_FORWARDED_HOST']].delete(nil)
+          return if allowed_origins.intersect?(origin)
+
+          response.write 'Origin is not allowed.'
+        end
+
+        response.status = 403
+        request.halt
+      end
+    end
+  end
+end

helpers/error_handlers.rb → helpers/handle_error.rb

@@ -1,5 +1,8 @@
 # frozen_string_literal: true
 
+require 'html2rss/configs'
+require_relative '../app/local_config'
+
 module Html2rss
   module Web
     class App
@@ -15,15 +18,21 @@ def handle_error(error) # rubocop:disable Metrics/MethodLength
         when LocalConfig::NotFound,
              Html2rss::Configs::ConfigNotFound
           set_error_response('Feed config not found', 404)
+        when Html2rss::Error
+          set_error_response('Html2rss error', 422)
         else
           set_error_response('Internal Server Error', 500)
         end
 
-        @show_backtrace = ENV.fetch('RACK_ENV', nil) == 'development'
+        @show_backtrace = self.class.development?
         @error = error
+
+        set_view_subdir nil
         view 'error'
       end
 
+      private
+
       def set_error_response(page_title, status)
         @page_title = page_title
         response.status = status

helpers/handle_html2rss_configs.rb

@@ -7,7 +7,7 @@ def handle_html2rss_configs(request, _folder_name, _config_name_with_ext)
         path = RequestPath.new(request)
 
         Html2rssFacade.from_config(path.full_config_name, typecast_params) do |config|
-          response['Content-Type'] = 'text/xml'
+          response['Content-Type'] = CONTENT_TYPE_RSS
           HttpCache.expires(response, config.ttl * 60, cache_control: 'public')
         end
       end