Tweaked LDAP TLS Implementation

- Moved the ldap function out to our separate service for easier
  testing.
- Added testing for the option.
- Moved tls_insecure part back up above connection start as found more
  reliable there.

Done a lot of real-connection testing during this review.
Used wireshare to ensure TLS connection does take place.
Found LDAP_TLS_INSECURE=false can action unreliably, restarting php-fpm
helped.
Tested both trusted and untrusted certificates.

app/Auth/Access/Ldap.php

@@ -31,6 +31,14 @@ class Ldap
         return ldap_set_option($ldapConnection, $option, $value);
     }
 
+    /**
+     * Start TLS on the given LDAP connection.
+     */
+    public function startTls($ldapConnection): bool
+    {
+        return ldap_start_tls($ldapConnection);
+    }
+
     /**
      * Set the version number for the given ldap connection.
      * @param $ldapConnection

app/Auth/Access/LdapService.php

@@ -187,6 +187,12 @@ class LdapService extends ExternalAuthService
             throw new LdapException(trans('errors.ldap_extension_not_installed'));
         }
 
+        // Disable certificate verification.
+        // This option works globally and must be set before a connection is created.
+        if ($this->config['tls_insecure']) {
+            $this->ldap->setOption(null, LDAP_OPT_X_TLS_REQUIRE_CERT, LDAP_OPT_X_TLS_NEVER);
+        }
+
         $serverDetails = $this->parseServerString($this->config['server']);
         $ldapConnection = $this->ldap->connect($serverDetails['host'], $serverDetails['port']);
 
@@ -199,19 +205,12 @@ class LdapService extends ExternalAuthService
             $this->ldap->setVersion($ldapConnection, $this->config['version']);
         }
 
-	// Check if TLS_INSECURE is set. The handle is set to NULL due to the nature of
-        // the LDAP_OPT_X_TLS_REQUIRE_CERT option. It can only be set globally and not per handle.
-	if ($this->config['tls_insecure']) {
-	    // Setting also ignored?
-            $this->ldap->setOption($ldapConnection, LDAP_OPT_X_TLS_REQUIRE_CERT, LDAP_OPT_X_TLS_NEVER);
-	}
-
+        // Start and verify TLS if it's enabled
         if ($this->config['start_tls']) {
-	    // "&& $this->config['tls_cacertfile']" this condition was removed because:
-	    // This ldap option is totally ignored by PHP. (bug: https://bugs.php.net/bug.php?id=73558)
-	    // If we set 'TLS_CACERT /config/ca/bundle.pem' into /etc/openldap/ldap.conf and restart php, ldap_start_tls works. 
-	    //$this->ldap->setOption($ldapConnection, LDAP_OPT_X_TLS_CACERTFILE, $this->config['tls_cacertfile']);
-	    ldap_start_tls($ldapConnection);
+            $started = $this->ldap->startTls($ldapConnection);
+            if (!$started) {
+                throw new LdapException('Could not start TLS connection');
+            }
         }
 
         $this->ldapConnection = $ldapConnection;

phpunit.xml

@@ -36,6 +36,7 @@
         <server name="AUTH_METHOD" value="standard"/>
         <server name="DISABLE_EXTERNAL_SERVICES" value="true"/>
         <server name="AVATAR_URL" value=""/>
+        <server name="LDAP_START_TLS" value="false"/>
         <server name="LDAP_VERSION" value="3"/>
         <server name="SESSION_SECURE_COOKIE" value="null"/>
         <server name="STORAGE_TYPE" value="local"/>

tests/Auth/LdapTest.php

@@ -4,6 +4,7 @@ use BookStack\Auth\Access\LdapService;
 use BookStack\Auth\Role;
 use BookStack\Auth\Access\Ldap;
 use BookStack\Auth\User;
+use BookStack\Exceptions\LdapException;
 use Mockery\MockInterface;
 use Tests\BrowserKitTest;
 
@@ -40,6 +41,14 @@ class LdapTest extends BrowserKitTest
         $this->mockUser = factory(User::class)->make();
     }
 
+    protected function runFailedAuthLogin()
+    {
+        $this->commonLdapMocks(1, 1, 1, 1, 1);
+        $this->mockLdap->shouldReceive('searchAndGetEntries')->times(1)
+            ->andReturn(['count' => 0]);
+        $this->post('/login', ['username' => 'timmyjenkins', 'password' => 'cattreedog']);
+    }
+
     protected function mockEscapes($times = 1)
     {
         $this->mockLdap->shouldReceive('escape')->times($times)->andReturnUsing(function($val) {
@@ -550,6 +559,22 @@ class LdapTest extends BrowserKitTest
         ]);
     }
 
+    public function test_start_tls_called_if_option_set()
+    {
+        config()->set(['services.ldap.start_tls' => true]);
+        $this->mockLdap->shouldReceive('startTls')->once()->andReturn(true);
+        $this->runFailedAuthLogin();
+    }
+
+    public function test_connection_fails_if_tls_fails()
+    {
+        config()->set(['services.ldap.start_tls' => true]);
+        $this->mockLdap->shouldReceive('startTls')->once()->andReturn(false);
+        $this->commonLdapMocks(1, 1, 0, 0, 0);
+        $this->post('/login', ['username' => 'timmyjenkins', 'password' => 'cattreedog']);
+        $this->assertResponseStatus(500);
+    }
+
     public function test_ldap_attributes_can_be_binary_decoded_if_marked()
     {
         config()->set(['services.ldap.id_attribute' => 'BIN;uid']);
@@ -640,12 +665,7 @@ class LdapTest extends BrowserKitTest
     {
         $log = $this->withTestLogger();
         config()->set(['logging.failed_login.message' => 'Failed login for %u']);
-
-        $this->commonLdapMocks(1, 1, 1, 1, 1);
-        $this->mockLdap->shouldReceive('searchAndGetEntries')->times(1)
-            ->andReturn(['count' => 0]);
-
-        $this->post('/login', ['username' => 'timmyjenkins', 'password' => 'cattreedog']);
+        $this->runFailedAuthLogin();
         $this->assertTrue($log->hasWarningThatContains('Failed login for timmyjenkins'));
     }
 }