java - 如何子类化 BasicPermission 以添加操作

Question

我想创建 BasicPermission 的子类来添加操作，根据 java 文档，这应该是可能的:

Subclasses may implement actions on top of BasicPermission, if desired.

这是我的初步尝试:

public class BasicPermissionWithActions extends BasicPermission {

String        actions;
String[]      actionList;
String        name;

public BasicPermissionWithActions(String name, String actions) {
    super(name, actions);
    this.actions = actions;
    this.actionList = actions.split("\\,");
    this.name = name;
}

private static final long serialVersionUID = 7608854273379948062L;

@Override
public boolean implies(Permission p) {
    // name and class check can be done by super
    if (!super.implies(p))
        return false;

    // now check actions
    String requestedActions = p.getActions();
    String[] requestedActionList = requestedActions.split("\\,");
    for (String requestedAction : requestedActionList) {
        if (!hasRequestedAction(requestedAction))
            return false;
    }

    return true;
}

private boolean hasRequestedAction(String requestedAction) {
    for (String action : actionList) {
        if (action.equals(requestedAction))
            return true;
    }
    return false;
}

@Override
public String getActions() {
    return actions;
}

@Override
public int hashCode() {
    final int prime = 31;
    int result = super.hashCode();
    result = prime * result + ((actions == null) ? 0 : actions.hashCode());
    result = prime * result + ((name == null) ? 0 : name.hashCode());
    return result;
}

@Override
public boolean equals(Object obj) {
    if (this == obj)
        return true;
    if (!super.equals(obj))
        return false;
    if (getClass() != obj.getClass())
        return false;
    BasicPermissionWithActions other = (BasicPermissionWithActions) obj;
    if (actions == null) {
        if (other.actions != null)
            return false;
    } else if (!actions.equals(other.actions))
        return false;
    if (name == null) {
        if (other.name != null)
            return false;
    } else if (!name.equals(other.name))
        return false;
    return true;
}

@Override
public String toString() {
    return "(\"" + this.getClass().getName() + "\" \"" + name + "\" \"" + actions + "\")"; 
}

策略文件中的一个条目用于使用此权限授予访问权限(在本例中，我指定了一个不足以允许所需操作的权限):

grant principal sample.principal.SampleGroup "TestGroup" {
  permission BasicPermissionWithActions "*", "read";
};

以及检查权限的代码:

        rep.getAccessControlContext().checkPermission(new BasicPermissionWithActions(getName(), "write"));

我预计此检查会失败，因为该策略仅指定了读取操作。然而检查却悄然通过。

问题是，每当策略文件中的权限具有名称“*”时，就不会检查操作。在 Debug模式下运行显示BasicPermissionWithActions.implies 方法从未被调用。

如果我忽略策略文件中的权限，我会按预期收到安全异常，但无法执行操作。

Answer 1

该问题与 PermissionCollection 有关。 BasicPermission 实现了自己的 PermissionCollection 以提高性能。不幸的是，这个实现做了一些简化的假设，破坏了子类的语义。具体来说，它实现了“*”的快捷方式，绕过 Permission.implies 方法并始终返回 true。

解决方案是实现一个自定义 PermissionCollection，它只需调用其成员的 Permission.implies 方法:

    private class CustomPermissionCollection extends PermissionCollection {

    private static final long serialVersionUID = 5654758059940546018L;

    Collection<Permission> perms = new ArrayList<Permission>();

    @Override
    public void add(Permission permission) {
        perms.add(permission);
    }

    @Override
    public boolean implies(Permission permission) {
        for (Permission p : perms) {
            if (p.implies(permission))
                return true;
        }
        return false;
    }

    @Override
    public Enumeration<Permission> elements() {
        return Collections.enumeration(perms);
    }

}

并在 BasicPermissionWithActions 的 newPermissionCollection 方法中返回此值

@Override
public PermissionCollection newPermissionCollection() {
    return new CustomPermissionCollection();
}