#399

backend/app/models/post.rb

@@ -17,6 +17,7 @@ class Post < ApplicationRecord
   MAX_SVG_DIMENSION = 4_096
   MAX_SVG_PIXELS = 16_777_216
   THUMBNAIL_PROCESS_TIMEOUT = 5.seconds
+  RASTER_THUMBNAIL_FORMATS = ['jpeg', 'png', 'gif', 'webp'].freeze
 
   def self.resized_thumbnail_attachment(upload, content_type: nil)
     upload.rewind
@@ -225,9 +226,23 @@ class Post < ApplicationRecord
   end
 
   def self.image_for_thumbnail_upload(bytes, content_type: nil)
-    return decode_raster_thumbnail(bytes) unless svg_content_type?(content_type) || svg_document_bytes?(bytes)
+    if svg_content_type?(content_type) || svg_document_bytes?(bytes)
+      return decode_svg_thumbnail(bytes)
+    end
 
-    decode_svg_thumbnail(bytes)
+    raise MiniMagick::Error, 'サムネイル画像の形式が不正です．' unless raster_thumbnail_bytes?(bytes)
+
+    decode_raster_thumbnail(bytes)
+  end
+
+  def self.raster_thumbnail_bytes?(bytes)
+    raster_thumbnail_format(bytes).present?
+  end
+
+  def self.remote_thumbnail_image_bytes?(bytes, content_type: nil)
+    return true if svg_content_type?(content_type) || svg_document_bytes?(bytes)
+
+    raster_thumbnail_bytes?(bytes)
   end
 
   def self.svg_content_type?(content_type)
@@ -254,6 +269,18 @@ class Post < ApplicationRecord
     MiniMagick::Image.read(sanitised_svg_bytes(bytes))
   end
 
+  def self.raster_thumbnail_format(bytes)
+    binary = bytes.to_s.b
+    return 'jpeg' if binary.start_with?("\xFF\xD8\xFF".b)
+    return 'png' if binary.start_with?("\x89PNG\r\n\x1A\n".b)
+    return 'gif' if binary.start_with?('GIF87a'.b) || binary.start_with?('GIF89a'.b)
+    return 'webp' if binary.bytesize >= 12 &&
+                     binary.start_with?('RIFF'.b) &&
+                     binary.byteslice(8, 4) == 'WEBP'
+
+    nil
+  end
+
   def self.sanitised_svg_bytes(bytes)
     parse_options =
         Nokogiri::XML::ParseOptions::STRICT |
@@ -354,6 +381,7 @@ class Post < ApplicationRecord
                        :svg_content_type?,
                        :decode_raster_thumbnail,
                        :decode_svg_thumbnail,
+                       :raster_thumbnail_format,
                        :sanitised_svg_bytes,
                        :svg_uses_disallowed_features?,
                        :external_svg_reference?,

backend/app/services/post_create_plan.rb

@@ -12,6 +12,7 @@ class PostCreatePlan
     direct_tag_specs, tag_sections = parse_direct_tag_specs
     default_tag_specs = build_default_tag_specs(direct_tag_specs)
     snapshot_tag_specs = merge_tag_specs(direct_tag_specs + default_tag_specs)
+    validate_new_tag_specs!(snapshot_tag_specs)
     post_tag_specs = expand_parent_tag_specs(snapshot_tag_specs)
     video_ms = normalise_video_ms(snapshot_tag_specs)
     validate_video_sections!(video_ms, tag_sections)
@@ -103,6 +104,31 @@ class PostCreatePlan
     default_tag_specs
   end
 
+  def validate_new_tag_specs! specs
+    Array(specs).each do |spec|
+      next if existing_tags_by_name.key?(spec[:name])
+
+      validate_new_tag_spec!(spec)
+    end
+  end
+
+  def validate_new_tag_spec! spec
+    tag_name = TagName.new(name: spec[:name])
+    tag = Tag.new(category: spec[:category], tag_name:)
+    return if tag_name.valid? && tag.valid?
+
+    post = Post.new
+    tag_name.errors[:name].each do |message|
+      post.errors.add :tags, "#{ spec[:name] }: #{ message }"
+    end
+    tag.errors.each do |error|
+      next if error.attribute == :tag_name
+
+      post.errors.add :tags, "#{ spec[:name] }: #{ error.message }"
+    end
+    raise ActiveRecord::RecordInvalid, post
+  end
+
   def expand_parent_tag_specs snapshot_tag_specs
     existing_snapshot_tags = snapshot_tag_specs.filter_map { existing_tags_by_name[_1[:name]] }
     expanded_parent_specs =

backend/app/services/post_thumbnail_upload_validator.rb

@@ -11,10 +11,15 @@ class PostThumbnailUploadValidator
     end
     raise InvalidUpload, 'thumbnail file size が大きすぎます．' if thumbnail.size > MAX_THUMBNAIL_BYTES
     raise InvalidUpload, 'サムネイル画像の形式が不正です．' unless allowed_content_type?(thumbnail.content_type)
-    raise InvalidUpload, 'サムネイル画像の形式が不正です．' if Post.svg_document_bytes?(thumbnail.read)
+    bytes = thumbnail.read
-    thumbnail.rewind
+    raise InvalidUpload, 'サムネイル画像の形式が不正です．' if Post.svg_document_bytes?(bytes)
+    unless Post.raster_thumbnail_bytes?(bytes)
+      raise InvalidUpload, 'サムネイル画像の形式が不正です．'
+    end
 
-    attachment = Post.resized_thumbnail_attachment(thumbnail, content_type: thumbnail.content_type)
+    attachment = Post.resized_thumbnail_attachment(
+        StringIO.new(bytes),
+        content_type: thumbnail.content_type)
     attachment[:io].close if attachment[:io].respond_to?(:close)
   rescue MiniMagick::Error, Timeout::Error
     raise InvalidUpload, 'サムネイル画像の変換に失敗しました．'

backend/app/services/preview/thumbnail_fetcher.rb

@@ -32,7 +32,9 @@ module Preview
     def self.fetch_image_response(raw_url)
       uri, = UrlSafety.validate(raw_url)
       response = HttpFetcher.fetch(uri.to_s)
-      unless allowed_remote_image_content_type?(response.content_type) || Post.svg_document_bytes?(response.body)
+      unless Post.remote_thumbnail_image_bytes?(
+                 response.body,
+                 content_type: response.content_type)
         raise GenerationFailed, 'サムネール画像が見つかりませんでした．'
       end
 
@@ -55,7 +57,9 @@ module Preview
       return nil if url.blank?
 
       response = HttpFetcher.fetch(url)
-      return nil unless allowed_remote_image_content_type?(response.content_type)
+      return nil unless Post.remote_thumbnail_image_bytes?(
+                            response.body,
+                            content_type: response.content_type)
 
       response.body
     rescue HttpFetcher::FetchTimeout