linux密码登陆时加入自己登陆验证模块(pam)

1.编译动态库pam_mylogin.so
2.将该动态库拷贝至/lib/x86_64-linux-gnu/security
3.修改/etc/pma.d/login 文件增加如下红色内容：
....
# The PAM configuration file for the Shadow `login' service
#
auth required pam_mylogin.so

# Enforce a minimal delay in case of failure (in microseconds).
# (Replaces the `FAIL_DELAY' setting from login.defs)
# Note that other modules may require another minimal delay. (for example,
# to disable any delay, you should add the nodelay option to pam_unix)
#auth    sufficient      pam_usb.so
auth       optional   pam_faildelay.so  delay=3000000
...
4.修改/etc/pma.d/lightdm文件增加如下红色内容：
....
#%PAM-1.0
auth    requisite       pam_mylogin.so
auth    requisite       pam_nologin.so
auth    sufficient      pam_succeed_if.so user ingroup nopasswdlogin
.....
5.编写文件：pam_mylogin.c 

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <security/pam_appl.h>
#include <security/pam_modules.h>
#include <security/pam_ext.h>
int myloginVerify(pam_handle_t *pamh)
{
 int retval;
 char* pPw;
 char * p = "Password:";
 retval = pam_prompt(pamh,PAM_PROMPT_ECHO_OFF,&pPw,"%s",p);
 printf(">>>>>>>>>pPw=%s\n",pPw);
 if (retval != PAM_SUCCESS) {
        printf("pam_prompt failed!\n");
        return 0;
 }
 char pw[7]="asdfgh";
 printf(">>>>>>>>>pw=%s\n",pw);
 for(int i=0;i<6;i++)
  {
     printf("%d>>>pw[%d]=%c  pPw[%d]=%c\n",i,i,pw[i],i,pPw[i]);
     if(pw[i]!=pPw[i])
      {
        return 0;
      }
   return 1;
  }
}
int Verify(pam_handle_t *pamh)
{
     if(!myloginVerify(pamh))
       return PAM_CONV_ERR;
     return  PAM_SUCCESS;
}
// Authentication API's
PAM_EXTERN int pam_sm_setcred( pam_handle_t *pamh, int flags, int argc, const char **argv ) {
        printf("pam_sm_setcred>>>>>>>\n");
        return PAM_SUCCESS;
}
PAM_EXTERN int pam_sm_authenticate( pam_handle_t *pamh, int flags,int argc, const char **argv ) {
        printf("pam_sm_authenticate>>>>>>>>\n");
        int retval;
        const char* pUsername;
        retval = pam_get_user(pamh, &pUsername, NULL);

        printf("begin call hotdoorpam %s\n", pUsername);
        if (retval != PAM_SUCCESS) {
                printf("pam_get_user failed\n");
                return retval;
        }
        if(!strcasecmp("root",pUsername))
        {
           printf("root user!\n");
        }
        else
        {
          printf("normal user!\n");
        }

    return Verify(pamh);
}
 /* Account Management API's */
PAM_EXTERN int pam_sm_acct_mgmt(pam_handle_t *pamh, int flags, int argc, const char **argv) {
        printf("pam_sm_acct_mgmt>>>>>>>>\n");
        return PAM_SUCCESS;
}

/* Session Management API's */
PAM_EXTERN int pam_sm_open_session(pam_handle_t *pamh, int flags,int argc, const char **argv){
        printf("pam_sm_open_session>>>>>>>>\n");
        return PAM_SUCCESS;
}
PAM_EXTERN int pam_sm_close_session(pam_handle_t *pamh, int flags,int argc, const char **argv){
        printf("pam_sm_close_session>>>>>>>>\n");
        return PAM_SUCCESS;
}
/* Password Management API's */
PAM_EXTERN int pam_sm_chauthtok(pam_handle_t *pamh, int flags,int argc, const char **argv){
        printf("pam_sm_chauthtok>>>>>>>>\n");
        return PAM_SUCCESS;
}

5.编写Makefile文件

  SOURCE = pam_mylogin.c
all:
gcc $(SOURCE) -fPIC -shared -o pam_mylogin.so
clean:
rm pam_mylogin.so pam_mylogin.o