8 files changed, 198 insertions, 0 deletions
diff --git a/app/controllers/help_controller.rb b/app/controllers/help_controller.rb
index 572915a4930..38f379dbf4f 100644
--- a/app/controllers/help_controller.rb
+++ b/app/controllers/help_controller.rb
@@ -57,6 +57,10 @@ class HelpController < ApplicationController
   def shortcuts
   end
 
+  def instance_configuration
+    @instance_configuration = InstanceConfiguration.new
+  end
+
   def ui
     @user = User.new(id: 0, name: 'John Doe', username: '@johndoe')
   end
diff --git a/app/helpers/instance_configuration_helper.rb b/app/helpers/instance_configuration_helper.rb
new file mode 100644
index 00000000000..cee319f20bc
--- /dev/null
+++ b/app/helpers/instance_configuration_helper.rb
@@ -0,0 +1,18 @@
+module InstanceConfigurationHelper
+  def instance_configuration_cell_html(value, &block)
+    return '-' unless value.to_s.presence
+
+    block_given? ? yield(value) : value
+  end
+
+  def instance_configuration_host(host)
+    @instance_configuration_host ||= instance_configuration_cell_html(host).capitalize
+  end
+
+  # Value must be in bytes
+  def instance_configuration_human_size_cell(value)
+    instance_configuration_cell_html(value) do |v|
+      number_to_human_size(v, strip_insignificant_zeros: true, significant: false)
+    end
+  end
+end
diff --git a/app/models/instance_configuration.rb b/app/models/instance_configuration.rb
new file mode 100644
index 00000000000..b30b707e5fe
--- /dev/null
+++ b/app/models/instance_configuration.rb
@@ -0,0 +1,71 @@
+require 'resolv'
+
+class InstanceConfiguration
+  SSH_ALGORITHMS = %w(DSA ECDSA ED25519 RSA).freeze
+  SSH_ALGORITHMS_PATH = '/etc/ssh/'.freeze
+  CACHE_KEY = 'instance_configuration'.freeze
+  EXPIRATION_TIME = 24.hours
+
+  def settings
+    @configuration ||= Rails.cache.fetch(CACHE_KEY, expires_in: EXPIRATION_TIME) do
+      { ssh_algorithms_hashes: ssh_algorithms_hashes,
+        host: host,
+        gitlab_pages: gitlab_pages,
+        gitlab_ci: gitlab_ci }.deep_symbolize_keys
+    end
+  end
+
+  private
+
+  def ssh_algorithms_hashes
+    SSH_ALGORITHMS.map { |algo| ssh_algorithm_hashes(algo) }.compact
+  end
+
+  def host
+    Settings.gitlab.host
+  end
+
+  def gitlab_pages
+    Settings.pages.to_h.merge(ip_address: resolv_dns(Settings.pages.host))
+  end
+
+  def resolv_dns(dns)
+    Resolv.getaddress(dns)
+  rescue Resolv::ResolvError
+  end
+
+  def gitlab_ci
+    Settings.gitlab_ci
+            .to_h
+            .merge(artifacts_max_size: { value: Settings.artifacts.max_size&.megabytes,
+                                         default: 100.megabytes })
+  end
+
+  def ssh_algorithm_file(algorithm)
+    File.join(SSH_ALGORITHMS_PATH, "ssh_host_#{algorithm.downcase}_key.pub")
+  end
+
+  def ssh_algorithm_hashes(algorithm)
+    content = ssh_algorithm_file_content(algorithm)
+    return unless content.present?
+
+    { name: algorithm,
+      md5: ssh_algorithm_md5(content),
+      sha256: ssh_algorithm_sha256(content) }
+  end
+
+  def ssh_algorithm_file_content(algorithm)
+    file = ssh_algorithm_file(algorithm)
+    return unless File.exist?(file)
+
+    File.read(file)
+  end
+
+  def ssh_algorithm_md5(ssh_file_content)
+    OpenSSL::Digest::MD5.hexdigest(ssh_file_content).scan(/../).join(':')
+  end
+
+  def ssh_algorithm_sha256(ssh_file_content)
+    OpenSSL::Digest::SHA256.hexdigest(ssh_file_content)
+  end
+end
diff --git a/app/views/help/index.html.haml b/app/views/help/index.html.haml
index c25eae63eec..d0c2e0b1d69 100644
--- a/app/views/help/index.html.haml
+++ b/app/views/help/index.html.haml
@@ -11,6 +11,7 @@
       %span= Gitlab::VERSION
       %small= link_to Gitlab::REVISION, Gitlab::COM_URL + namespace_project_commits_path('gitlab-org', 'gitlab-ce', Gitlab::REVISION)
       = version_status_badge
+
   %p.slead
     GitLab is open source software to collaborate on code.
     %br
@@ -23,6 +24,7 @@
     Used by more than 100,000 organizations, GitLab is the most popular solution to manage git repositories on-premises.
     %br
     Read more about GitLab at #{link_to promo_host, promo_url, target: '_blank', rel: 'noopener noreferrer'}.
+    %p= link_to 'Check the current instance configuration ', help_instance_configuration_url
   %hr
 
 .row.prepend-top-default
diff --git a/app/views/help/instance_configuration.html.haml b/app/views/help/instance_configuration.html.haml
new file mode 100644
index 00000000000..f09e3825a4b
--- /dev/null
+++ b/app/views/help/instance_configuration.html.haml
@@ -0,0 +1,17 @@
+- page_title 'Instance Configuration'
+.wiki.documentation
+  %h1 Instance Configuration
+
+  %p
+    In this page you will find information about the settings that are used in your current instance.
+
+  = render 'help/instance_configuration/ssh_info'
+  = render 'help/instance_configuration/gitlab_pages'
+  = render 'help/instance_configuration/gitlab_ci'
+  %p
+    %strong Table of contents
+
+    %ul
+      = content_for :table_content
+
+  = content_for :settings_content
diff --git a/app/views/help/instance_configuration/_gitlab_ci.html.haml b/app/views/help/instance_configuration/_gitlab_ci.html.haml
new file mode 100644
index 00000000000..7fa8bd086d4
--- /dev/null
+++ b/app/views/help/instance_configuration/_gitlab_ci.html.haml
@@ -0,0 +1,24 @@
+- content_for :table_content do
+  %li= link_to 'GitLab CI', '#gitlab-ci'
+
+- content_for :settings_content do
+  %h2#gitlab-ci
+    GitLab CI
+
+  %p
+    Below are the current settings regarding
+    = succeed('.') { link_to('GitLab CI', 'https://about.gitlab.com/gitlab-ci', target: '_blank') }
+
+  .table-responsive
+    %table
+      %thead
+        %tr
+          %th Setting
+          %th= instance_configuration_host(@instance_configuration.settings[:host])
+          %th Default
+      %tbody
+        %tr
+          - artifacts_size = @instance_configuration.settings[:gitlab_ci][:artifacts_max_size]
+          %td Artifacts maximum size
+          %td= instance_configuration_human_size_cell(artifacts_size[:value])
+          %td= instance_configuration_human_size_cell(artifacts_size[:default])
diff --git a/app/views/help/instance_configuration/_gitlab_pages.html.haml b/app/views/help/instance_configuration/_gitlab_pages.html.haml
new file mode 100644
index 00000000000..bdd77730dcc
--- /dev/null
+++ b/app/views/help/instance_configuration/_gitlab_pages.html.haml
@@ -0,0 +1,35 @@
+- gitlab_pages = @instance_configuration.settings[:gitlab_pages]
+- content_for :table_content do
+  %li= link_to 'GitLab Pages', '#gitlab-pages'
+
+- content_for :settings_content do
+  %h2#gitlab-pages
+    GitLab Pages
+
+  %p
+    Below are the settings for
+    = succeed('.') { link_to('Gitlab Pages', gitlab_pages[:url], target: '_blank') }
+  .table-responsive
+    %table
+      %thead
+        %tr
+          %th Setting
+          %th= instance_configuration_host(@instance_configuration.settings[:host])
+      %tbody
+        %tr
+          %td Domain Name
+          %td
+            %code= instance_configuration_cell_html(gitlab_pages[:host])
+        %tr
+          %td IP Address
+          %td
+            %code= instance_configuration_cell_html(gitlab_pages[:ip_address])
+        %tr
+          %td Port
+          %td
+            %code= instance_configuration_cell_html(gitlab_pages[:port])
+  %br
+
+  %p
+    The maximum size of your Pages site is regulated by the artifacts maximum
+    size which is part of #{succeed('.') { link_to('GitLab CI', '#gitlab-ci') }}
diff --git a/app/views/help/instance_configuration/_ssh_info.html.haml b/app/views/help/instance_configuration/_ssh_info.html.haml
new file mode 100644
index 00000000000..987cc61b3f6
--- /dev/null
+++ b/app/views/help/instance_configuration/_ssh_info.html.haml
@@ -0,0 +1,27 @@
+- ssh_info = @instance_configuration.settings[:ssh_algorithms_hashes]
+- if ssh_info.any?
+  - content_for :table_content do
+    %li= link_to 'SSH host keys fingerprints', '#ssh-host-keys-fingerprints'
+
+  - content_for :settings_content do
+    %h2#ssh-host-keys-fingerprints
+      SSH host keys fingerprints
+
+    %p
+      Below are the fingerprints for the current instance SSH host keys.
+
+    .table-responsive
+      %table
+        %thead
+          %tr
+            %th Algorithm
+            %th MD5
+            %th SHA256
+        %tbody
+          - ssh_info.each do |algorithm|
+            %tr
+              %td= algorithm[:name]
+              %td
+                %code= instance_configuration_cell_html(algorithm[:md5])
+              %td
+                %code= instance_configuration_cell_html(algorithm[:sha256])