如何在Linux中使用C或Shell检查密码？ [英] How to check password in Linux by using C or shell?

问题描述

我有一个用C编写的程序在嵌入式Linux上运行，有时它想检查系统用户的密码。

I have a program written in C running on a embedded Linux, sometimes it want to check the password of a system user.

1. 如果我可以得到 / etc / passwd 的地穴盐，则可以使用crypt（）进行检查


2. 是否有任何shell脚本可以帮助我检查密码？如check_passwd用户名密码，那么它返回的值是正确还是不正确？
   谢谢！

1. If I can get the crypt salt of /etc/passwd, I can use crypt() to check the correction of user password.
2. Is there any script of shell can help me check the password? Such as check_passwd username password, then it return a value for correct or incorrect? Thanks!

推荐答案

我最近一直在解决相同的任务。这是C函数的示例（与-lcrypt链接）。请注意，您需要具有对/ etc / passwd和/ etc / shadow文件的读取权限。

I had been solving the same task recently. Here is an example of C function (link with -lcrypt). Note that you need to have read permissions for files /etc/passwd and /etc/shadow.

#include <sys/types.h>
#include <pwd.h>
#include <shadow.h>
#include <crypt.h>
#include <string.h>
#include <stdio.h>

/// @return 0 - password is correct, otherwise no
int CheckPassword( const char* user, const char* password )
{
    struct passwd* passwdEntry = getpwnam( user );
    if ( !passwdEntry )
    {
        printf( "User '%s' doesn't exist\n", user );
        return 1;
    }

    if ( 0 != strcmp( passwdEntry->pw_passwd, "x" ) )
    {
        return strcmp( passwdEntry->pw_passwd, crypt( password, passwdEntry->pw_passwd ) );
    }
    else
    {
        // password is in shadow file
        struct spwd* shadowEntry = getspnam( user );
        if ( !shadowEntry )
        {
            printf( "Failed to read shadow entry for user '%s'\n", user );
            return 1;
        }

        return strcmp( shadowEntry->sp_pwdp, crypt( password, shadowEntry->sp_pwdp ) );
    }
}

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