Fix logged-out Diffusion calls to Conduit

Summary:
Conduit doesn't currently have an analog to "shouldAllowPublic", so the recent policy checks added here caught legitimate Conduit calls when viewing Diffusion as a logged-out user.

Add `shouldAllowPublic()` and set it for all the Diffusion queries.

(More calls probably need this, but we can add it when we hit them.)

Test Plan: Looked at Diffusion as a logged-out user with public access enabled.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D7380

src/applications/conduit/call/ConduitCall.php

@@ -86,11 +86,18 @@ final class ConduitCall {
 
     $this->request->setUser($user);
 
-    if ($this->shouldRequireAuthentication()) {
-      // TODO: As per below, this should get centralized and cleaned up.
+    if (!$this->shouldRequireAuthentication()) {
+      // No auth requirement here.
+    } else {
+
+      $allow_public = $this->handler->shouldAllowPublic() &&
+                      PhabricatorEnv::getEnvConfig('policy.allow-public');
+      if (!$allow_public) {
         if (!$user->isLoggedIn() && !$user->isOmnipotent()) {
+          // TODO: As per below, this should get centralized and cleaned up.
           throw new ConduitException("ERR-INVALID-AUTH");
         }
+      }
 
       // TODO: This would be slightly cleaner by just using a Query, but the
       // Conduit auth workflow requires the Call and User be built separately.

src/applications/conduit/method/ConduitAPIMethod.php

@@ -104,6 +104,10 @@ abstract class ConduitAPIMethod
     return true;
   }
 
+  public function shouldAllowPublic() {
+    return false;
+  }
+
   public function shouldAllowUnguardedWrites() {
     return false;
   }

src/applications/diffusion/conduit/ConduitAPI_diffusion_abstractquery_Method.php

@@ -6,9 +6,14 @@
 abstract class ConduitAPI_diffusion_abstractquery_Method
   extends ConduitAPI_diffusion_Method {
 
+  public function shouldAllowPublic() {
+    return true;
+  }
+
   public function getMethodStatus() {
     return self::METHOD_STATUS_UNSTABLE;
   }
+
   public function getMethodStatusDescription() {
     return pht(
       'See T2784 - migrating diffusion working copy calls to conduit methods. '.