Fix Error 500 when viewing a blob with binary characters after the 1024-byte mark

Here was the problem:

1. When determining whether a given blob is viewable text, gitlab_git reads the first 1024 bytes and checks with Linguist whether it is a text or binary file.
2. If the blob is text, GitLab will attempt to display it.
3. However, if the text has binary characters after the first 1024 bytes, then GitLab will attempt to load the entire contents, but the encoding will be ASCII-8BIT since there are binary characters.
4. The Error 500 results when GitLab attempts to display a mix UTF-8 and ASCII-8BIT.

To fix this, we load as much data as we are willing to display so that the detection will work properly. Requires
an update to gitlab_git: gitlab-org/gitlab_git!86

Closes #13826

CHANGELOG

@@ -18,6 +18,7 @@ v 8.9.0 (unreleased)
   - Reduce number of fog gem dependencies
   - Remove project notification settings associated with deleted projects
   - Fix 404 page when viewing TODOs that contain milestones or labels in different projects
+  - Fix Error 500 when viewing a blob with binary characters after the 1024-byte mark
   - Redesign navigation for project pages
   - Fix groups API to list only user's accessible projects
   - Redesign account and email confirmation emails

Gemfile.lock

@@ -284,7 +284,7 @@ GEM
       posix-spawn (~> 0.3)
     gitlab_emoji (0.3.1)
       gemojione (~> 2.2, >= 2.2.1)
-    gitlab_git (10.1.0)
+    gitlab_git (10.1.3)
       activesupport (~> 4.0)
       charlock_holmes (~> 0.7.3)
       github-linguist (~> 4.7.0)
@@ -408,7 +408,7 @@ GEM
       mime-types (>= 1.16, < 4)
     mail_room (0.7.0)
     method_source (0.8.2)
-    mime-types (2.99.1)
+    mime-types (2.99.2)
     mimemagic (0.3.0)
     mini_portile2 (2.1.0)
     minitest (5.7.0)

app/helpers/blob_helper.rb

@@ -116,7 +116,7 @@ module BlobHelper
   end
 
   def blob_text_viewable?(blob)
-    blob && blob.text? && !blob.lfs_pointer?
+    blob && blob.text? && !blob.lfs_pointer? && !blob.only_display_raw?
   end
 
   def blob_size(blob)

app/models/blob.rb

@@ -24,7 +24,7 @@ class Blob < SimpleDelegator
   end
 
   def only_display_raw?
-    size && size > 5.megabytes
+    size && truncated?
   end
 
   def svg?

app/models/repository.rb

@@ -446,7 +446,7 @@ class Repository
 
   def blob_at(sha, path)
     unless Gitlab::Git.blank_ref?(sha)
-      Gitlab::Git::Blob.find(self, sha, path)
+      Blob.decorate(Gitlab::Git::Blob.find(self, sha, path))
     end
   end
 

app/views/projects/diffs/_diffs.html.haml

@@ -24,6 +24,7 @@
     - diff_commit = commit_for_diff(diff_file)
     - blob = project.repository.blob_for_diff(diff_commit, diff_file)
     - next unless blob
+    - blob.load_all_data!(project.repository) unless blob.only_display_raw?
 
     = render 'projects/diffs/file', i: index, project: project,
       diff_file: diff_file, diff_commit: diff_commit, blob: blob, diff_refs: diff_refs

app/views/projects/diffs/_file.html.haml

@@ -49,6 +49,8 @@
         = render "projects/diffs/parallel_view", diff_file: diff_file, project: project, blob: blob, index: i
       - else
         = render "projects/diffs/text_file", diff_file: diff_file, index: i
+    - elsif blob.only_display_raw?
+      .nothing-here-block This file is too large to display.
     - elsif blob.image?
       - old_file = project.repository.prev_blob_for_diff(diff_commit, diff_file)
       = render "projects/diffs/image", diff_file: diff_file, old_file: old_file, file: blob, index: i, diff_refs: diff_refs

spec/controllers/blob_controller_spec.rb

@@ -38,6 +38,11 @@ describe Projects::BlobController do
       let(:id) { 'invalid-branch/README.md' }
       it { is_expected.to respond_with(:not_found) }
     end
+
+    context "binary file" do
+      let(:id) { 'binary-encoding/encoding/binary-1.bin' }
+      it { is_expected.to respond_with(:success) }
+    end
   end
 
   describe 'GET show with tree path' do

spec/controllers/projects/commit_controller_spec.rb

@@ -2,6 +2,8 @@ require 'rails_helper'
 
 describe Projects::CommitController do
   describe 'GET show' do
+    render_views
+
     let(:project) { create(:project) }
 
     before do
@@ -27,6 +29,16 @@ describe Projects::CommitController do
       end
     end
 
+    it 'handles binary files' do
+      get(:show,
+          namespace_id: project.namespace.to_param,
+          project_id: project.to_param,
+          id: TestEnv::BRANCH_SHA['binary-encoding'],
+          format: "html")
+
+      expect(response).to be_success
+    end
+
     def go(id:)
       get :show,
         namespace_id: project.namespace.to_param,

spec/support/test_env.rb

@@ -16,6 +16,7 @@ module TestEnv
     'master'           => '5937ac0',
     "'test'"           => 'e56497b',
     'orphaned-branch'  => '45127a9',
+    'binary-encoding'  => '7b1cf43',
   }
 
   # gitlab-test-fork is a fork of gitlab-fork, but we don't necessarily