server: Avoid Null pointer at DomainChecker and enhance AssignVMCmd (#4279)

When executing request assignVirtualMachine with null domainID and a valid projectID then a NullPointerException happens at DomainChecker.java.

Command example:

assign virtualmachine virtualmachineid=vmID projectid=projectID account=admin
The NullPointerException that is thrown at DomainChecker is handled at AssignVMCmd.java#L142, resulting in the following log message: Failed to move vm null.

Author: GabrielBrascher

api/src/main/java/org/apache/cloudstack/api/command/admin/vm/AssignVMCmd.java

@@ -138,8 +138,14 @@ public void execute() {
             e.printStackTrace();
             throw new ServerApiException(ApiErrorCode.INTERNAL_ERROR, e.getMessage());
         } catch (Exception e) {
-            e.printStackTrace();
-            throw new ServerApiException(ApiErrorCode.INTERNAL_ERROR, "Failed to move vm " + e.getMessage());
+            s_logger.error("Failed to move vm due to: " + e.getStackTrace());
+            if (e.getMessage() != null) {
+                throw new ServerApiException(ApiErrorCode.INTERNAL_ERROR, "Failed to move vm due to " + e.getMessage());
+            } else if (e.getCause() != null) {
+                throw new ServerApiException(ApiErrorCode.INTERNAL_ERROR, "Failed to move vm due to " + e.getCause());
+            } else {
+                throw new ServerApiException(ApiErrorCode.INTERNAL_ERROR, "Failed to move vm");
+            }
         }
 
     }

server/src/main/java/com/cloud/acl/DomainChecker.java

@@ -106,6 +106,11 @@ public boolean checkAccess(Account caller, Domain domain) throws PermissionDenie
         if (caller.getState() != Account.State.enabled) {
             throw new PermissionDeniedException(caller + " is disabled.");
         }
+
+        if (domain == null) {
+            throw new PermissionDeniedException(String.format("Provided domain is NULL, cannot check access for account [uuid=%s, name=%s]", caller.getUuid(), caller.getAccountName()));
+        }
+
         long domainId = domain.getId();
 
         if (_accountService.isNormalUser(caller.getId())) {

server/src/main/java/com/cloud/vm/UserVmManagerImpl.java

@@ -6133,6 +6133,10 @@ public UserVm moveVMToUser(final AssignVMCmd cmd) throws ResourceAllocationExcep
             throw new InvalidParameterValueException("The new account owner " + cmd.getAccountName() + " is disabled.");
         }
 
+        if (cmd.getProjectId() != null && cmd.getDomainId() == null) {
+            throw new InvalidParameterValueException("Please provide a valid domain ID; cannot assign VM to a project if domain ID is NULL.");
+        }
+
         //check caller has access to both the old and new account
         _accountMgr.checkAccess(caller, null, true, oldAccount);
         _accountMgr.checkAccess(caller, null, true, newAccount);