Merge pull request #3563 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), 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)
@@ -67,7 +70,7 @@ 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 +82,6 @@ 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 +96,7 @@ 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 +109,6 @@ module Downloads
           end
         end
       end # while
-
-      [src, datums]
     end # def
 
     def fix_twitter_sources(src)
@@ -135,5 +133,27 @@ module Downloads
         src
       end
     end
+
+    private
+
+    # Prevent Cloudflare from potentially mangling the image. See issue #3528.
+    def uncached_url(url, headers = {})
+      url = Addressable::URI.parse(url)
+
+      if is_cloudflare?(url, headers)
+        url.query_values = (url.query_values || {}).merge(danbooru_no_cache: SecureRandom.uuid)
+      end
+
+      url
+    end
+
+    def is_cloudflare?(url, headers = {})
+      Cache.get("is_cloudflare:#{url.origin}", 4.hours) do
+        res = HTTParty.head(url, { headers: headers }.deep_merge(Danbooru.config.httparty_options))
+        raise Error.new("HTTP error code: #{res.code} #{res.message}") unless res.success?
+
+        res.key?("CF-Ray")
+      end
+    end
   end
 end