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密码源代码

tag-icon • tag-icon root c passwd setuid uid
密码源代码

我正在尝试看看passwd 和 gpasswd 程序的源代码。这些工具会检查设置为零的有效 UID 以成功完成执行。但我是 C 菜鸟，找不到检查进程是否由 UID == 0 运行的代码行。我将不胜感激任何提示或解决方案。

答案1

如果您指的是 的“shadow-utils”实现passwd，您会发现测试这里：

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

在 中gpasswd，测试被定义​​为两个阶段；第一的UID 已存储：

    /*
     * 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 ();

然后用在宏观amroot​：

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

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