Merge pull request #3551 from evazion/fix-3528

Fix #3528: Add method to prevent image-hosting CloudFlare sites from altering the image

app/logical/downloads/file.rb

@@ -26,20 +26,23 @@ module Downloads
     end
 
     def size
-      @source, headers, @data = before_download(@source, @data)
+      url, headers, _ = before_download(@source, @data)
       options = { timeout: 3, headers: headers }.deep_merge(Danbooru.config.httparty_options)
-      res = HTTParty.head(@source, options)
+      res = HTTParty.head(url, options)
       res.content_length
     end
 
     def download!
+      url, headers, @data = before_download(@source, @data)
+
       ::File.open(@file_path, "wb") do |out|
-        @source, @data = http_get_streaming(@source, @data) do |response|
+        http_get_streaming(uncached_url(url), headers) do |response|
           out.write(response)
         end
       end
-      @downloaded_source = @source
+
-      @source = after_download(@source)
+      @downloaded_source = url
+      @source = after_download(url)
     end
 
     def before_download(url, datums)
@@ -52,6 +55,13 @@ module Downloads
       return [url, headers, datums]
     end
 
+    # Prevent transparent proxies (namely Cloudflare) from potentially mangling the image. See issue #3528.
+    def uncached_url(url)
+      url = Addressable::URI.parse(url)
+      url.query_values = (url.query_values || {}).merge(danbooru_no_cache: SecureRandom.uuid)
+      url
+    end
+
     def after_download(src)
       src = fix_twitter_sources(src)
       if options[:referer_url].present?
@@ -67,7 +77,7 @@ module Downloads
       end
     end
 
-    def http_get_streaming(src, datums = {}, options = {}, &block)
+    def http_get_streaming(src, headers = {}, options = {}, &block)
       max_size = options[:max_size] || Danbooru.config.max_file_size
       max_size = nil if max_size == 0 # unlimited
       limit = 4
@@ -79,9 +89,6 @@ module Downloads
           raise Error.new("URL must be HTTP or HTTPS")
         end
 
-        src, headers, datums = before_download(src, datums)
-        url = URI.parse(src)
-
         validate_local_hosts(url)
 
         begin
@@ -96,7 +103,7 @@ module Downloads
 
             @content_type = res["Content-Type"]
 
-            return [src, datums]
+            return
           else
             raise Error.new("HTTP error code: #{res.code} #{res.message}")
           end
@@ -109,8 +116,6 @@ module Downloads
           end
         end
       end # while
-
-      [src, datums]
     end # def
 
     def fix_twitter_sources(src)

test/unit/downloads/art_station_test.rb

@@ -28,6 +28,13 @@ module Downloads
       end
     end
 
+    context "a download for an ArtStation image hosted on CloudFlare" do
+      should "return the original file, not the polished file" do
+        @source = "https://cdnb.artstation.com/p/assets/images/images/003/716/071/large/aoi-ogata-hate-city.jpg?1476754974"
+        assert_downloaded(517_706, @source) # polished size: 502_052
+      end
+    end
+
     context "a download for a https://$artist.artstation.com/projects/$id page" do
       setup do
         @source = "https://dantewontdie.artstation.com/projects/YZK5q"