Introduce better credential and error checking to `rake gitlab:ldap:check`

It was previously possible for invalid credential errors to go unnoticed
in this task. Users would believe everything was configured correctly and
then sign in would fail with 'invalid credentials'. This adds a specific
bind check, plus catches errors connecting to the server. Also, specs :)

9 files changed, 226 insertions, 78 deletions

diff --git a/changelogs/unreleased/ldap_check_bind.yml b/changelogs/unreleased/ldap_check_bind.yml
new file mode 100644
index 00000000000..daff8103a07
--- /dev/null
+++ b/changelogs/unreleased/ldap_check_bind.yml
@@ -0,0 +1,4 @@
+---
+title: Introduce better credential and error checking to `rake gitlab:ldap:check`
+merge_request: 6601
+author: 
diff --git a/doc/administration/auth/ldap.md b/doc/administration/auth/ldap.md
index bf7814875bf..fd23047f027 100644
--- a/doc/administration/auth/ldap.md
+++ b/doc/administration/auth/ldap.md
@@ -35,6 +35,10 @@ of one hour.
 To enable LDAP integration you need to add your LDAP server settings in
 `/etc/gitlab/gitlab.rb` or `/home/git/gitlab/config/gitlab.yml`.
 
+There is a Rake task to check LDAP configuration. After configuring LDAP
+using the documentation below, see [LDAP check Rake task](../raketasks/check.md#ldap-check)
+for information on the LDAP check Rake task.
+
 >**Note**: In GitLab EE, you can configure multiple LDAP servers to connect to
 one GitLab server.
 
diff --git a/doc/raketasks/check_repos_output.png b/doc/administration/img/raketasks/check_repos_output.png
index 1f632566b00..1f632566b00 100644
--- a/doc/raketasks/check_repos_output.png
+++ b/doc/administration/img/raketasks/check_repos_output.png
diff --git a/doc/administration/raketasks/check.md b/doc/administration/raketasks/check.md
new file mode 100644
index 00000000000..d1d2fed4861
--- /dev/null
+++ b/doc/administration/raketasks/check.md
@@ -0,0 +1,97 @@
+# Check Rake Tasks
+
+## Repository Integrity
+
+Even though Git is very resilient and tries to prevent data integrity issues,
+there are times when things go wrong. The following Rake tasks intend to
+help GitLab administrators diagnose problem repositories so they can be fixed.
+
+There are 3 things that are checked to determine integrity.
+
+1. Git repository file system check ([git fsck](https://git-scm.com/docs/git-fsck)).
+   This step verifies the connectivity and validity of objects in the repository.
+1. Check for `config.lock` in the repository directory.
+1. Check for any branch/references lock files in `refs/heads`.
+
+It's important to note that the existence of `config.lock` or reference locks
+alone do not necessarily indicate a problem. Lock files are routinely created
+and removed as Git and GitLab perform operations on the repository. They serve
+to prevent data integrity issues. However, if a Git operation is interrupted these
+locks may not be cleaned up properly.
+
+The following symptoms may indicate a problem with repository integrity. If users
+experience these symptoms you may use the rake tasks described below to determine
+exactly which repositories are causing the trouble.
+
+- Receiving an error when trying to push code - `remote: error: cannot lock ref`
+- A 500 error when viewing the GitLab dashboard or when accessing a specific project.
+
+### Check all GitLab repositories
+
+This task loops through all repositories on the GitLab server and runs the
+3 integrity checks described previously.
+
+**Omnibus Installation**
+
+```
+sudo gitlab-rake gitlab:repo:check
+```
+
+**Source Installation**
+
+```bash
+sudo -u git -H bundle exec rake gitlab:repo:check RAILS_ENV=production
+```
+
+### Check repositories for a specific user
+
+This task checks all repositories that a specific user has access to. This is important
+because sometimes you know which user is experiencing trouble but you don't know
+which project might be the cause.
+
+If the rake task is executed without brackets at the end, you will be prompted
+to enter a username.
+
+**Omnibus Installation**
+
+```bash
+sudo gitlab-rake gitlab:user:check_repos
+sudo gitlab-rake gitlab:user:check_repos[<username>]
+```
+
+**Source Installation**
+
+```bash
+sudo -u git -H bundle exec rake gitlab:user:check_repos RAILS_ENV=production
+sudo -u git -H bundle exec rake gitlab:user:check_repos[<username>] RAILS_ENV=production
+```
+
+Example output:
+
+![gitlab:user:check_repos output](../img/raketasks/check_repos_output.png)
+
+## LDAP Check
+
+The LDAP check Rake task will test the bind_dn and password credentials
+(if configured) and will list a sample of LDAP users. This task is also
+executed as part of the `gitlab:check` task, but can run independently
+using the command below.
+
+**Omnibus Installation**
+
+```
+sudo gitlab-rake gitlab:ldap:check
+```
+
+**Source Installation**
+
+```bash
+sudo -u git -H bundle exec rake gitlab:ldap:check RAILS_ENV=production
+```
+
+By default, the task will return a sample of 100 LDAP users. Change this
+limit by passing a number to the check task:
+
+```bash
+rake gitlab:ldap:check[50]
+```
diff --git a/doc/raketasks/check.md b/doc/raketasks/check.md
index 3ff3fee6a40..f7f6a40cd04 100644
--- a/doc/raketasks/check.md
+++ b/doc/raketasks/check.md
@@ -1,63 +1,3 @@
 # Check Rake Tasks
 
-## Repository Integrity
-
-Even though Git is very resilient and tries to prevent data integrity issues,
-there are times when things go wrong. The following Rake tasks intend to
-help GitLab administrators diagnose problem repositories so they can be fixed.
-
-There are 3 things that are checked to determine integrity.
-
-1. Git repository file system check ([git fsck](https://git-scm.com/docs/git-fsck)).
-   This step verifies the connectivity and validity of objects in the repository.
-1. Check for `config.lock` in the repository directory.
-1. Check for any branch/references lock files in `refs/heads`.
-
-It's important to note that the existence of `config.lock` or reference locks
-alone do not necessarily indicate a problem. Lock files are routinely created
-and removed as Git and GitLab perform operations on the repository. They serve
-to prevent data integrity issues. However, if a Git operation is interrupted these
-locks may not be cleaned up properly.
-
-The following symptoms may indicate a problem with repository integrity. If users
-experience these symptoms you may use the rake tasks described below to determine
-exactly which repositories are causing the trouble.
-
-- Receiving an error when trying to push code - `remote: error: cannot lock ref`
-- A 500 error when viewing the GitLab dashboard or when accessing a specific project.
-
-### Check all GitLab repositories
-
-This task loops through all repositories on the GitLab server and runs the
-3 integrity checks described previously.
-
-```
-# omnibus-gitlab
-sudo gitlab-rake gitlab:repo:check
-
-# installation from source
-bundle exec rake gitlab:repo:check RAILS_ENV=production
-```
-
-### Check repositories for a specific user
-
-This task checks all repositories that a specific user has access to. This is important
-because sometimes you know which user is experiencing trouble but you don't know
-which project might be the cause.
-
-If the rake task is executed without brackets at the end, you will be prompted
-to enter a username.
-
-```bash
-# omnibus-gitlab
-sudo gitlab-rake gitlab:user:check_repos
-sudo gitlab-rake gitlab:user:check_repos[<username>]
-
-# installation from source
-bundle exec rake gitlab:user:check_repos RAILS_ENV=production
-bundle exec rake gitlab:user:check_repos[<username>] RAILS_ENV=production
-```
-
-Example output:
-
-![gitlab:user:check_repos output](check_repos_output.png)
+This document was moved to [administration/raketasks/check](../administration/raketasks/check.md).
diff --git a/lib/gitlab/ldap/config.rb b/lib/gitlab/ldap/config.rb
index f9bb5775323..6ea069d26df 100644
--- a/lib/gitlab/ldap/config.rb
+++ b/lib/gitlab/ldap/config.rb
@@ -92,6 +92,10 @@ module Gitlab
         options['timeout'].to_i
       end
 
+      def has_auth?
+        options['password'] || options['bind_dn']
+      end
+
       protected
 
       def base_config
@@ -122,10 +126,6 @@ module Gitlab
           }
         }
       end
-
-      def has_auth?
-        options['password'] || options['bind_dn']
-      end
     end
   end
 end
diff --git a/lib/tasks/gitlab/check.rake b/lib/tasks/gitlab/check.rake
index 2ae48a970ce..35c4194e87c 100644
--- a/lib/tasks/gitlab/check.rake
+++ b/lib/tasks/gitlab/check.rake
@@ -760,7 +760,7 @@ namespace :gitlab do
   end
 
   namespace :ldap do
-    task :check, [:limit] => :environment do |t, args|
+    task :check, [:limit] => :environment do |_, args|
       # Only show up to 100 results because LDAP directories can be very big.
       # This setting only affects the `rake gitlab:check` script.
       args.with_defaults(limit: 100)
@@ -768,7 +768,7 @@ namespace :gitlab do
       start_checking "LDAP"
 
       if Gitlab::LDAP::Config.enabled?
-        print_users(args.limit)
+        check_ldap(args.limit)
       else
         puts 'LDAP is disabled in config/gitlab.yml'
       end
@@ -776,21 +776,42 @@ namespace :gitlab do
       finished_checking "LDAP"
     end
 
-    def print_users(limit)
-      puts "LDAP users with access to your GitLab server (only showing the first #{limit} results)"
-
+    def check_ldap(limit)
       servers = Gitlab::LDAP::Config.providers
 
       servers.each do |server|
         puts "Server: #{server}"
-        Gitlab::LDAP::Adapter.open(server) do |adapter|
-          users = adapter.users(adapter.config.uid, '*', limit)
-          users.each do |user|
-            puts "\tDN: #{user.dn}\t #{adapter.config.uid}: #{user.uid}"
+
+        begin
+          Gitlab::LDAP::Adapter.open(server) do |adapter|
+            check_ldap_auth(adapter)
+
+            puts "LDAP users with access to your GitLab server (only showing the first #{limit} results)"
+
+            users = adapter.users(adapter.config.uid, '*', limit)
+            users.each do |user|
+              puts "\tDN: #{user.dn}\t #{adapter.config.uid}: #{user.uid}"
+            end
           end
+        rescue Net::LDAP::ConnectionRefusedError, Errno::ECONNREFUSED => e
+          puts "Could not connect to the LDAP server: #{e.message}".color(:red)
         end
       end
     end
+
+    def check_ldap_auth(adapter)
+      auth = adapter.config.has_auth?
+
+      if auth && adapter.ldap.bind
+        message = 'Success'.color(:green)
+      elsif auth
+        message = 'Failed. Check `bind_dn` and `password` configuration values'.color(:red)
+      else
+        message = 'Anonymous. No `bind_dn` or `password` configured'.color(:yellow)
+      end
+
+      puts "LDAP authentication... #{message}"
+    end
   end
 
   namespace :repo do
diff --git a/spec/lib/gitlab/ldap/config_spec.rb b/spec/lib/gitlab/ldap/config_spec.rb
index 835853a83a4..f5ebe703083 100644
--- a/spec/lib/gitlab/ldap/config_spec.rb
+++ b/spec/lib/gitlab/ldap/config_spec.rb
@@ -1,20 +1,51 @@
 require 'spec_helper'
 
 describe Gitlab::LDAP::Config, lib: true do
-  let(:config) { Gitlab::LDAP::Config.new provider }
-  let(:provider) { 'ldapmain' }
+  include LdapHelpers
+
+  let(:config) { Gitlab::LDAP::Config.new('ldapmain') }
 
   describe '#initalize' do
     it 'requires a provider' do
       expect{ Gitlab::LDAP::Config.new }.to raise_error ArgumentError
     end
 
-    it "works" do
+    it 'works' do
       expect(config).to be_a described_class
     end
 
-    it "raises an error if a unknow provider is used" do
+    it 'raises an error if a unknown provider is used' do
       expect{ Gitlab::LDAP::Config.new 'unknown' }.to raise_error(RuntimeError)
     end
   end
+
+  describe '#has_auth?' do
+    it 'is true when password is set' do
+      stub_ldap_config(
+        options: {
+          'bind_dn'  => 'uid=admin,dc=example,dc=com',
+          'password' => 'super_secret'
+        }
+      )
+
+      expect(config.has_auth?).to be_truthy
+    end
+
+    it 'is true when bind_dn is set and password is empty' do
+      stub_ldap_config(
+        options: {
+          'bind_dn'  => 'uid=admin,dc=example,dc=com',
+          'password' => ''
+        }
+      )
+
+      expect(config.has_auth?).to be_truthy
+    end
+
+    it 'is false when password and bind_dn are not set' do
+      stub_ldap_config(options: { 'bind_dn' => nil, 'password' => nil })
+
+      expect(config.has_auth?).to be_falsey
+    end
+  end
 end
diff --git a/spec/tasks/gitlab/check_rake_spec.rb b/spec/tasks/gitlab/check_rake_spec.rb
new file mode 100644
index 00000000000..538ff952bf4
--- /dev/null
+++ b/spec/tasks/gitlab/check_rake_spec.rb
@@ -0,0 +1,51 @@
+require 'rake_helper'
+
+describe 'gitlab:ldap:check rake task' do
+  include LdapHelpers
+
+  before do
+    Rake.application.rake_require 'tasks/gitlab/check'
+
+    stub_warn_user_is_not_gitlab
+  end
+
+  context 'when LDAP is not enabled' do
+    it 'does not attempt to bind or search for users' do
+      expect(Gitlab::LDAP::Config).not_to receive(:providers)
+      expect(Gitlab::LDAP::Adapter).not_to receive(:open)
+
+      run_rake_task('gitlab:ldap:check')
+    end
+  end
+
+  context 'when LDAP is enabled' do
+    let(:ldap) { double(:ldap) }
+    let(:adapter) { ldap_adapter('ldapmain', ldap) }
+
+    before do
+      allow(Gitlab::LDAP::Config)
+        .to receive_messages(
+          enabled?: true,
+          providers: ['ldapmain']
+        )
+      allow(Gitlab::LDAP::Adapter).to receive(:open).and_yield(adapter)
+      allow(adapter).to receive(:users).and_return([])
+    end
+
+    it 'attempts to bind using credentials' do
+      stub_ldap_config(has_auth?: true)
+
+      expect(ldap).to receive(:bind)
+
+      run_rake_task('gitlab:ldap:check')
+    end
+
+    it 'searches for 100 LDAP users' do
+      stub_ldap_config(uid: 'uid')
+
+      expect(adapter).to receive(:users).with('uid', '*', 100)
+
+      run_rake_task('gitlab:ldap:check')
+    end
+  end
+end