5 files changed, 16 insertions, 5 deletions
diff --git a/activestorage/lib/active_storage/downloader.rb b/activestorage/lib/active_storage/downloader.rb
index 0e7039e104..2aa56a729a 100644
--- a/activestorage/lib/active_storage/downloader.rb
+++ b/activestorage/lib/active_storage/downloader.rb
@@ -10,6 +10,7 @@ module ActiveStorage
     def download_blob_to_tempfile
       open_tempfile do |file|
         download_blob_to file
+        verify_integrity_of file
         yield file
       end
     end
@@ -34,6 +35,12 @@ module ActiveStorage
         file.rewind
       end
 
+      def verify_integrity_of(file)
+        unless Digest::MD5.file(file).base64digest == blob.checksum
+          raise ActiveStorage::IntegrityError
+        end
+      end
+
       def tempfile_extension_with_delimiter
         blob.filename.extension_with_delimiter
       end
diff --git a/activestorage/lib/active_storage/errors.rb b/activestorage/lib/active_storage/errors.rb
index f099b13f5b..bedcd080c4 100644
--- a/activestorage/lib/active_storage/errors.rb
+++ b/activestorage/lib/active_storage/errors.rb
@@ -4,4 +4,8 @@ module ActiveStorage
   class InvariableError < StandardError; end
   class UnpreviewableError < StandardError; end
   class UnrepresentableError < StandardError; end
+
+  # Raised when uploaded or downloaded data does not match a precomputed checksum.
+  # Indicates that a network error or a software bug caused data corruption.
+  class IntegrityError < StandardError; end
 end
diff --git a/activestorage/lib/active_storage/previewer/video_previewer.rb b/activestorage/lib/active_storage/previewer/video_previewer.rb
index 2f28a3d341..50e13d202a 100644
--- a/activestorage/lib/active_storage/previewer/video_previewer.rb
+++ b/activestorage/lib/active_storage/previewer/video_previewer.rb
@@ -9,15 +9,14 @@ module ActiveStorage
     def preview
       download_blob_to_tempfile do |input|
         draw_relevant_frame_from input do |output|
-          yield io: output, filename: "#{blob.filename.base}.png", content_type: "image/png"
+          yield io: output, filename: "#{blob.filename.base}.jpg", content_type: "image/jpeg"
         end
       end
     end
 
     private
       def draw_relevant_frame_from(file, &block)
-        draw ffmpeg_path, "-i", file.path, "-y", "-vcodec", "png",
-          "-vf", "thumbnail", "-vframes", "1", "-f", "image2", "-", &block
+        draw ffmpeg_path, "-i", file.path, "-y", "-vframes", "1", "-f", "image2", "-", &block
       end
 
       def ffmpeg_path
diff --git a/activestorage/lib/active_storage/service.rb b/activestorage/lib/active_storage/service.rb
index 949969fc95..da1af4f745 100644
--- a/activestorage/lib/active_storage/service.rb
+++ b/activestorage/lib/active_storage/service.rb
@@ -3,8 +3,6 @@
 require "active_storage/log_subscriber"
 
 module ActiveStorage
-  class IntegrityError < StandardError; end
-
   # Abstract class serving as an interface for concrete services.
   #
   # The available services are:
diff --git a/activestorage/lib/tasks/activestorage.rake b/activestorage/lib/tasks/activestorage.rake
index 296e91afa1..ac254d717f 100644
--- a/activestorage/lib/tasks/activestorage.rake
+++ b/activestorage/lib/tasks/activestorage.rake
@@ -1,6 +1,9 @@
 # frozen_string_literal: true
 
 namespace :active_storage do
+  # Prevent migration installation task from showing up twice.
+  Rake::Task["install:migrations"].clear_comments
+
   desc "Copy over the migration needed to the application"
   task install: :environment do
     if Rake::Task.task_defined?("active_storage:install:migrations")