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phab/src/infrastructure/query/policy/PhabricatorPolicyAwareQuery.php
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PhabricatorPolicyAwareQuery.php
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<?php
/**
* A @{class:PhabricatorQuery} which filters results according to visibility
* policies for the querying user. Broadly, this class allows you to implement
* a query that returns only objects the user is allowed to see.
*
* $results = id(new ExampleQuery())
* ->setViewer($user)
* ->withConstraint($example)
* ->execute();
*
* Normally, you should extend @{class:PhabricatorCursorPagedPolicyAwareQuery},
* not this class. @{class:PhabricatorCursorPagedPolicyAwareQuery} provides a
* more practical interface for building usable queries against most object
* types.
*
* NOTE: Although this class extends @{class:PhabricatorOffsetPagedQuery},
* offset paging with policy filtering is not efficient. All results must be
* loaded into the application and filtered here: skipping `N` rows via offset
* is an `O(N)` operation with a large constant. Prefer cursor-based paging
* with @{class:PhabricatorCursorPagedPolicyAwareQuery}, which can filter far
* more efficiently in MySQL.
*
* @task config Query Configuration
* @task exec Executing Queries
* @task policyimpl Policy Query Implementation
*/
abstract class PhabricatorPolicyAwareQuery extends PhabricatorOffsetPagedQuery {
private $viewer;
private $parentQuery;
private $rawResultLimit;
private $capabilities;
private $workspace = array();
private $policyFilteredPHIDs = array();
private $canUseApplication;
/**
* Should we continue or throw an exception when a query result is filtered
* by policy rules?
*
* Values are `true` (raise exceptions), `false` (do not raise exceptions)
* and `null` (inherit from parent query, with no exceptions by default).
*/
private $raisePolicyExceptions;
/* -( Query Configuration )------------------------------------------------ */
/**
* Set the viewer who is executing the query. Results will be filtered
* according to the viewer's capabilities. You must set a viewer to execute
* a policy query.
*
* @param PhabricatorUser The viewing user.
* @return this
* @task config
*/
final public function setViewer(PhabricatorUser $viewer) {
$this->viewer = $viewer;
return $this;
}
/**
* Get the query's viewer.
*
* @return PhabricatorUser The viewing user.
* @task config
*/
final public function getViewer() {
return $this->viewer;
}
/**
* Set the parent query of this query. This is useful for nested queries so
* that configuration like whether or not to raise policy exceptions is
* seamlessly passed along to child queries.
*
* @return this
* @task config
*/
final public function setParentQuery(PhabricatorPolicyAwareQuery $query) {
$this->parentQuery = $query;
return $this;
}
/**
* Get the parent query. See @{method:setParentQuery} for discussion.
*
* @return PhabricatorPolicyAwareQuery The parent query.
* @task config
*/
final public function getParentQuery() {
return $this->parentQuery;
}
/**
* Hook to configure whether this query should raise policy exceptions.
*
* @return this
* @task config
*/
final public function setRaisePolicyExceptions($bool) {
$this->raisePolicyExceptions = $bool;
return $this;
}
/**
* @return bool
* @task config
*/
final public function shouldRaisePolicyExceptions() {
return (bool)$this->raisePolicyExceptions;
}
/**
* @task config
*/
final public function requireCapabilities(array $capabilities) {
$this->capabilities = $capabilities;
return $this;
}
/* -( Query Execution )---------------------------------------------------- */
/**
* Execute the query, expecting a single result. This method simplifies
* loading objects for detail pages or edit views.
*
* // Load one result by ID.
* $obj = id(new ExampleQuery())
* ->setViewer($user)
* ->withIDs(array($id))
* ->executeOne();
* if (!$obj) {
* return new Aphront404Response();
* }
*
* If zero results match the query, this method returns `null`.
* If one result matches the query, this method returns that result.
*
* If two or more results match the query, this method throws an exception.
* You should use this method only when the query constraints guarantee at
* most one match (e.g., selecting a specific ID or PHID).
*
* If one result matches the query but it is caught by the policy filter (for
* example, the user is trying to view or edit an object which exists but
* which they do not have permission to see) a policy exception is thrown.
*
* @return mixed Single result, or null.
* @task exec
*/
final public function executeOne() {
$this->setRaisePolicyExceptions(true);
try {
$results = $this->execute();
} catch (Exception $ex) {
$this->setRaisePolicyExceptions(false);
throw $ex;
}
if (count($results) > 1) {
throw new Exception('Expected a single result!');
}
if (!$results) {
return null;
}
return head($results);
}
/**
* Execute the query, loading all visible results.
*
* @return list<PhabricatorPolicyInterface> Result objects.
* @task exec
*/
final public function execute() {
if (!$this->viewer) {
throw new Exception('Call setViewer() before execute()!');
}
$parent_query = $this->getParentQuery();
if ($parent_query && ($this->raisePolicyExceptions === null)) {
$this->setRaisePolicyExceptions(
$parent_query->shouldRaisePolicyExceptions());
}
$results = array();
$filter = $this->getPolicyFilter();
$offset = (int)$this->getOffset();
$limit = (int)$this->getLimit();
$count = 0;
if ($limit) {
$need = $offset + $limit;
} else {
$need = 0;
}
$this->willExecute();
do {
if ($need) {
$this->rawResultLimit = min($need - $count, 1024);
} else {
$this->rawResultLimit = 0;
}
if ($this->canViewerUseQueryApplication()) {
try {
$page = $this->loadPage();
} catch (PhabricatorEmptyQueryException $ex) {
$page = array();
}
} else {
$page = array();
}
if ($page) {
$maybe_visible = $this->willFilterPage($page);
} else {
$maybe_visible = array();
}
if ($this->shouldDisablePolicyFiltering()) {
$visible = $maybe_visible;
} else {
$visible = $filter->apply($maybe_visible);
$policy_filtered = array();
foreach ($maybe_visible as $key => $object) {
if (empty($visible[$key])) {
$phid = $object->getPHID();
if ($phid) {
$policy_filtered[$phid] = $phid;
}
}
}
$this->addPolicyFilteredPHIDs($policy_filtered);
}
if ($visible) {
$this->putObjectsInWorkspace($this->getWorkspaceMapForPage($visible));
$visible = $this->didFilterPage($visible);
}
$removed = array();
foreach ($maybe_visible as $key => $object) {
if (empty($visible[$key])) {
$removed[$key] = $object;
}
}
$this->didFilterResults($removed);
foreach ($visible as $key => $result) {
++$count;
// If we have an offset, we just ignore that many results and start
// storing them only once we've hit the offset. This reduces memory
// requirements for large offsets, compared to storing them all and
// slicing them away later.
if ($count > $offset) {
$results[$key] = $result;
}
if ($need && ($count >= $need)) {
// If we have all the rows we need, break out of the paging query.
break 2;
}
}
if (!$this->rawResultLimit) {
// If we don't have a load count, we loaded all the results. We do
// not need to load another page.
break;
}
if (count($page) < $this->rawResultLimit) {
// If we have a load count but the unfiltered results contained fewer
// objects, we know this was the last page of objects; we do not need
// to load another page because we can deduce it would be empty.
break;
}
$this->nextPage($page);
} while (true);
$results = $this->didLoadResults($results);
return $results;
}
private function getPolicyFilter() {
$filter = new PhabricatorPolicyFilter();
$filter->setViewer($this->viewer);
$capabilities = $this->getRequiredCapabilities();
$filter->requireCapabilities($capabilities);
$filter->raisePolicyExceptions($this->shouldRaisePolicyExceptions());
return $filter;
}
protected function getRequiredCapabilities() {
if ($this->capabilities) {
return $this->capabilities;
}
return array(
PhabricatorPolicyCapability::CAN_VIEW,
);
}
protected function applyPolicyFilter(array $objects, array $capabilities) {
if ($this->shouldDisablePolicyFiltering()) {
return $objects;
}
$filter = $this->getPolicyFilter();
$filter->requireCapabilities($capabilities);
return $filter->apply($objects);
}
protected function didRejectResult(PhabricatorPolicyInterface $object) {
$this->getPolicyFilter()->rejectObject(
$object,
$object->getPolicy(PhabricatorPolicyCapability::CAN_VIEW),
PhabricatorPolicyCapability::CAN_VIEW);
}
public function addPolicyFilteredPHIDs(array $phids) {
$this->policyFilteredPHIDs += $phids;
if ($this->getParentQuery()) {
$this->getParentQuery()->addPolicyFilteredPHIDs($phids);
}
return $this;
}
/**
* Return a map of all object PHIDs which were loaded in the query but
* filtered out by policy constraints. This allows a caller to distinguish
* between objects which do not exist (or, at least, were filtered at the
* content level) and objects which exist but aren't visible.
*
* @return map<phid, phid> Map of object PHIDs which were filtered
* by policies.
* @task exec
*/
public function getPolicyFilteredPHIDs() {
return $this->policyFilteredPHIDs;
}
/* -( Query Workspace )---------------------------------------------------- */
/**
* Put a map of objects into the query workspace. Many queries perform
* subqueries, which can eventually end up loading the same objects more than
* once (often to perform policy checks).
*
* For example, loading a user may load the user's profile image, which might
* load the user object again in order to verify that the viewer has
* permission to see the file.
*
* The "query workspace" allows queries to load objects from elsewhere in a
* query block instead of refetching them.
*
* When using the query workspace, it's important to obey two rules:
*
* **Never put objects into the workspace which the viewer may not be able
* to see**. You need to apply all policy filtering //before// putting
* objects in the workspace. Otherwise, subqueries may read the objects and
* use them to permit access to content the user shouldn't be able to view.
*
* **Fully enrich objects pulled from the workspace.** After pulling objects
* from the workspace, you still need to load and attach any additional
* content the query requests. Otherwise, a query might return objects without
* requested content.
*
* Generally, you do not need to update the workspace yourself: it is
* automatically populated as a side effect of objects surviving policy
* filtering.
*
* @param map<phid, PhabricatorPolicyInterface> Objects to add to the query
* workspace.
* @return this
* @task workspace
*/
public function putObjectsInWorkspace(array $objects) {
assert_instances_of($objects, 'PhabricatorPolicyInterface');
$viewer_phid = $this->getViewer()->getPHID();
// The workspace is scoped per viewer to prevent accidental contamination.
if (empty($this->workspace[$viewer_phid])) {
$this->workspace[$viewer_phid] = array();
}
$this->workspace[$viewer_phid] += $objects;
return $this;
}
/**
* Retrieve objects from the query workspace. For more discussion about the
* workspace mechanism, see @{method:putObjectsInWorkspace}. This method
* searches both the current query's workspace and the workspaces of parent
* queries.
*
* @param list<phid> List of PHIDs to retrieve.
* @return this
* @task workspace
*/
public function getObjectsFromWorkspace(array $phids) {
$viewer_phid = $this->getViewer()->getPHID();
$results = array();
foreach ($phids as $key => $phid) {
if (isset($this->workspace[$viewer_phid][$phid])) {
$results[$phid] = $this->workspace[$viewer_phid][$phid];
unset($phids[$key]);
}
}
if ($phids && $this->getParentQuery()) {
$results += $this->getParentQuery()->getObjectsFromWorkspace($phids);
}
return $results;
}
/**
* Convert a result page to a `<phid, PhabricatorPolicyInterface>` map.
*
* @param list<PhabricatorPolicyInterface> Objects.
* @return map<phid, PhabricatorPolicyInterface> Map of objects which can
* be put into the workspace.
* @task workspace
*/
protected function getWorkspaceMapForPage(array $results) {
$map = array();
foreach ($results as $result) {
$phid = $result->getPHID();
if ($phid !== null) {
$map[$phid] = $result;
}
}
return $map;
}
/* -( Policy Query Implementation )---------------------------------------- */
/**
* Get the number of results @{method:loadPage} should load. If the value is
* 0, @{method:loadPage} should load all available results.
*
* @return int The number of results to load, or 0 for all results.
* @task policyimpl
*/
final protected function getRawResultLimit() {
return $this->rawResultLimit;
}
/**
* Hook invoked before query execution. Generally, implementations should
* reset any internal cursors.
*
* @return void
* @task policyimpl
*/
protected function willExecute() {
return;
}
/**
* Load a raw page of results. Generally, implementations should load objects
* from the database. They should attempt to return the number of results
* hinted by @{method:getRawResultLimit}.
*
* @return list<PhabricatorPolicyInterface> List of filterable policy objects.
* @task policyimpl
*/
abstract protected function loadPage();
/**
* Update internal state so that the next call to @{method:loadPage} will
* return new results. Generally, you should adjust a cursor position based
* on the provided result page.
*
* @param list<PhabricatorPolicyInterface> The current page of results.
* @return void
* @task policyimpl
*/
abstract protected function nextPage(array $page);
/**
* Hook for applying a page filter prior to the privacy filter. This allows
* you to drop some items from the result set without creating problems with
* pagination or cursor updates. You can also load and attach data which is
* required to perform policy filtering.
*
* Generally, you should load non-policy data and perform non-policy filtering
* later, in @{method:didFilterPage}. Strictly fewer objects will make it that
* far (so the program will load less data) and subqueries from that context
* can use the query workspace to further reduce query load.
*
* This method will only be called if data is available. Implementations
* do not need to handle the case of no results specially.
*
* @param list<wild> Results from `loadPage()`.
* @return list<PhabricatorPolicyInterface> Objects for policy filtering.
* @task policyimpl
*/
protected function willFilterPage(array $page) {
return $page;
}
/**
* Hook for performing additional non-policy loading or filtering after an
* object has satisfied all policy checks. Generally, this means loading and
* attaching related data.
*
* Subqueries executed during this phase can use the query workspace, which
* may improve performance or make circular policies resolvable. Data which
* is not necessary for policy filtering should generally be loaded here.
*
* This callback can still filter objects (for example, if attachable data
* is discovered to not exist), but should not do so for policy reasons.
*
* This method will only be called if data is available. Implementations do
* not need to handle the case of no results specially.
*
* @param list<wild> Results from @{method:willFilterPage()}.
* @return list<PhabricatorPolicyInterface> Objects after additional
* non-policy processing.
*/
protected function didFilterPage(array $page) {
return $page;
}
/**
* Hook for removing filtered results from alternate result sets. This
* hook will be called with any objects which were returned by the query but
* filtered for policy reasons. The query should remove them from any cached
* or partial result sets.
*
* @param list<wild> List of objects that should not be returned by alternate
* result mechanisms.
* @return void
* @task policyimpl
*/
protected function didFilterResults(array $results) {
return;
}
/**
* Hook for applying final adjustments before results are returned. This is
* used by @{class:PhabricatorCursorPagedPolicyAwareQuery} to reverse results
* that are queried during reverse paging.
*
* @param list<PhabricatorPolicyInterface> Query results.
* @return list<PhabricatorPolicyInterface> Final results.
* @task policyimpl
*/
protected function didLoadResults(array $results) {
return $results;
}
/**
* Allows a subclass to disable policy filtering. This method is dangerous.
* It should be used only if the query loads data which has already been
* filtered (for example, because it wraps some other query which uses
* normal policy filtering).
*
* @return bool True to disable all policy filtering.
* @task policyimpl
*/
protected function shouldDisablePolicyFiltering() {
return false;
}
/**
* If this query belongs to an application, return the application class name
* here. This will prevent the query from returning results if the viewer can
* not access the application.
*
* If this query does not belong to an application, return `null`.
*
* @return string|null Application class name.
*/
abstract public function getQueryApplicationClass();
/**
* Determine if the viewer has permission to use this query's application.
* For queries which aren't part of an application, this method always returns
* true.
*
* @return bool True if the viewer has application-level permission to
* execute the query.
*/
public function canViewerUseQueryApplication() {
if ($this->canUseApplication === null) {
$class = $this->getQueryApplicationClass();
if (!$class) {
$this->canUseApplication = true;
} else {
$result = id(new PhabricatorApplicationQuery())
->setViewer($this->getViewer())
->withClasses(array($class))
->execute();
$this->canUseApplication = (bool)$result;
}
}
return $this->canUseApplication;
}
}
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