Ensure users are able to edit the page after changing the content model

It is possible for page restrictions to be dependent upon the content
model a page. The best example of this is user JavaScript and CSS
subpages. This adds a Title::setContentModel() function which allows
mocking a Title's content model for the purpose of permission checks.

EditPage and Special:ChangeContentModel were updated to ensure the user
can edit the page with the newly proposed content model before making
the change.

Title::$mContentModel was made private to make sure nothing else mucks
around with it. There were no uses outside of Title anyways.

Bug: T145316
Change-Id: I28c46f408cadf65ed1868401cd00dc15e5acd2fe

diff --git a/includes/EditPage.php b/includes/EditPage.php
index 7e4e411..41b9865 100644 (file)
--- a/includes/EditPage.php
+++ b/includes/EditPage.php
@@ -1838,8 +1838,17 @@ class EditPage {
                        } elseif ( !$wgUser->isAllowed( 'editcontentmodel' ) ) {
                                $status->setResult( false, self::AS_NO_CHANGE_CONTENT_MODEL );
                                return $status;
-
                        }
+                       // Make sure the user can edit the page under the new content model too
+                       $titleWithNewContentModel = clone $this->mTitle;
+                       $titleWithNewContentModel->setContentModel( $this->contentModel );
+                       if ( !$titleWithNewContentModel->userCan( 'editcontentmodel', $wgUser )
+                               || !$titleWithNewContentModel->userCan( 'edit', $wgUser )
+                       ) {
+                               $status->setResult( false, self::AS_NO_CHANGE_CONTENT_MODEL );
+                               return $status;
+                       }
+
                        $changingContentModel = true;
                        $oldContentModel = $this->mTitle->getContentModel();
                }

diff --git a/includes/Title.php b/includes/Title.php
index 3475b26..16c715d 100644 (file)
--- a/includes/Title.php
+++ b/includes/Title.php
@@ -91,7 +91,13 @@ class Title implements LinkTarget {
         * @var bool|string ID of the page's content model, i.e. one of the
         *   CONTENT_MODEL_XXX constants
         */
-       public $mContentModel = false;
+       private $mContentModel = false;
+
+       /**
+        * @var bool If a content model was forced via setContentModel()
+        *   this will be true to avoid having other code paths reset it
+        */
+       private $mForcedContentModel = false;
 
        /** @var int Estimated number of revisions; null of not loaded */
        private $mEstimateRevisions;
@@ -467,9 +473,9 @@ class Title implements LinkTarget {
                        if ( isset( $row->page_latest ) ) {
                                $this->mLatestID = (int)$row->page_latest;
                        }
-                       if ( isset( $row->page_content_model ) ) {
+                       if ( !$this->mForcedContentModel && isset( $row->page_content_model ) ) {
                                $this->mContentModel = strval( $row->page_content_model );
-                       } else {
+                       } elseif ( !$this->mForcedContentModel ) {
                                $this->mContentModel = false; # initialized lazily in getContentModel()
                        }
                        if ( isset( $row->page_lang ) ) {
@@ -483,7 +489,9 @@ class Title implements LinkTarget {
                        $this->mLength = 0;
                        $this->mRedirect = false;
                        $this->mLatestID = 0;
-                       $this->mContentModel = false; # initialized lazily in getContentModel()
+                       if ( !$this->mForcedContentModel ) {
+                               $this->mContentModel = false; # initialized lazily in getContentModel()
+                       }
                }
        }
 
@@ -921,8 +929,9 @@ class Title implements LinkTarget {
         * @return string Content model id
         */
        public function getContentModel( $flags = 0 ) {
-               if ( ( !$this->mContentModel || $flags === Title::GAID_FOR_UPDATE ) &&
-                       $this->getArticleID( $flags )
+               if ( !$this->mForcedContentModel
+                       && ( !$this->mContentModel || $flags === Title::GAID_FOR_UPDATE )
+                       && $this->getArticleID( $flags )
                ) {
                        $linkCache = LinkCache::singleton();
                        $linkCache->addLinkObj( $this ); # in case we already had an article ID
@@ -946,6 +955,22 @@ class Title implements LinkTarget {
                return $this->getContentModel() == $id;
        }
 
+       /**
+        * Set a proposed content model for the page for permissions
+        * checking. This does not actually change the content model
+        * of a title!
+        *
+        * Additionally, you should make sure you've checked
+        * ContentHandler::canBeUsedOn() first.
+        *
+        * @since 1.28
+        * @param string $model CONTENT_MODEL_XXX constant
+        */
+       public function setContentModel( $model ) {
+               $this->mContentModel = $model;
+               $this->mForcedContentModel = true;
+       }
+
        /**
         * Get the namespace text
         *

diff --git a/includes/specials/SpecialChangeContentModel.php b/includes/specials/SpecialChangeContentModel.php
index b37c475..4fb1b53 100644 (file)
--- a/includes/specials/SpecialChangeContentModel.php
+++ b/includes/specials/SpecialChangeContentModel.php
@@ -156,10 +156,20 @@ class SpecialChangeContentModel extends FormSpecialPage {
                }
 
                $this->title = Title::newFromText( $data['pagetitle'] );
+               $titleWithNewContentModel = clone $this->title;
+               $titleWithNewContentModel->setContentModel( $data['model'] );
                $user = $this->getUser();
-               // Check permissions and make sure the user has permission to edit the specific page
-               $errors = $this->title->getUserPermissionsErrors( 'editcontentmodel', $user );
-               $errors = wfMergeErrorArrays( $errors, $this->title->getUserPermissionsErrors( 'edit', $user ) );
+               // Check permissions and make sure the user has permission to:
+               $errors = wfMergeErrorArrays(
+                       // edit the contentmodel of the page
+                       $this->title->getUserPermissionsErrors( 'editcontentmodel', $user ),
+                       // edit the page under the old content model
+                       $this->title->getUserPermissionsErrors( 'edit', $user ),
+                       // edit the contentmodel under the new content model
+                       $titleWithNewContentModel->getUserPermissionsErrors( 'editcontentmodel', $user ),
+                       // edit the page under the new content model
+                       $titleWithNewContentModel->getUserPermissionsErrors( 'edit', $user )
+               );
                if ( $errors ) {
                        $out = $this->getOutput();
                        $wikitext = $out->formatPermissionsErrorMessage( $errors );