sudo_pppoe.c

一个在LINUX下运行的东西

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <signal.h>
#include <errno.h>
#define g_print printf


 int ruid,euid;
void be_root()
{
  ruid=getuid();
  euid=geteuid();
  if(ruid == euid) {
   g_print("Warning: This program wasn't marked setuid in the filesystem.\n");
   return;
  }
  if(setuid(euid) == -1) {
    g_print("Failed to be euid -> %d !!\n",euid);
  }
  else{
   g_print("be_euid:I think I done.Real uid = %d, effective uid = %d pid = %d\n", getuid(), geteuid(),getpid());
  }
}

void be_user()
{
 /*
 if(seteuid(euid)==-1){
  g_print("Failed to noraml euid !!\n");
  }
 else{
 g_print("Real uid = %d, effective uid = %d pid = %d\n", getuid(), geteuid(),getpid());
 }
 */
 g_print("be_user:euid = %d ,ruid = %d \n",geteuid(),getuid());
if(setuid(ruid)==-1){
  g_print("Failed to noraml user !!\n");
  }
 else{
 g_print("be_user :Real uid = %d, effective uid = %d ,pid = %d\n", getuid(), geteuid(),getpid());
 }

}

 char *getexedir(void)
{
 static char str[1024]={0};
 char tmp[32]={0};
 int len=0;
 sprintf(tmp,"/proc/%d/exe",getpid());
 if((len=readlink(tmp,str,1024))<0)perror("readlink():");
 len--;
 while(len>=0){
 	if(str[len]=='/'){
 		str[len]=0;
 		return str;
 	 }
 		else
 		 str[len]=0;
 	 len--;
 	}
 	
 return NULL;
}

int main(int argc ,char **argv)
{
 int pid=0;

 signal(SIGCHLD ,SIG_IGN);
 if((pid=fork())==0)
 {
  char *str = getexedir();
  char *file = NULL;
 	L :
         file = malloc (strlen(str)+256);
 	if(file==NULL){
 	 fprintf(stderr,"malloc():%s .\n",strerror(errno));
 	 goto L;
  }
 	sprintf(file,"%s/gtk-pppoe",str);
 	be_root();
 	execl(file,"gtk-pppoe",argv[1],NULL);
 	fprintf(stderr,"%s :execl():%s !\n",argv[0],strerror(errno));
	free(file);
 	}
 	else //be_user();
 	 g_print("Proc pid = %d euid = %d ,ruid = %d \n",getpid(),geteuid(),getuid());
 return 0;

}