passwd源代码

Question

我想看看passwd和gpasswd程序的源代码。这些工具检查有效的UID设置为零，以成功地完成执行。但我是C的新手，无法找到检查进程是否由UID == 0运行的代码行。如有任何提示或解决办法，我将不胜感激。

Answer 1

如果您指的是passwd的“影子-实用程序”实现，您将找到测试这里：

    /*
     * The program behaves differently when executed by root than when
     * executed by a normal user.
     */
    amroot = (getuid () == 0);

在gpasswd中，测试分为两个阶段:第一个阶段是UID存储在：

    /*
     * Make a note of whether or not this command was invoked by root.
     * This will be used to bypass certain checks later on. Also, set
     * the real user ID to match the effective user ID. This will
     * prevent the invoker from issuing signals which would interfere
     * with this command.
     */
    bywho = getuid ();

然后在这个amroot宏中使用：

/* Indicate if gpasswd was called by root */
#define amroot  (0 == bywho)