有了shellcode，就可以进行攻击了，但是要有漏洞才行，真实世界中的漏洞很复杂，并且很难发现，因此我专门做一个漏洞来进行攻击。
具体来说就是做一个简单的tcp server，里面包含明显的栈溢出漏洞。
具体如下：
1 /* server.c */ 2 #include <stdio.h> 3 #include <stdlib.h> 4 #include <errno.h> 5 #include <string.h> 6 #include <sys/types.h> 7 #include <netinet/in.h> 8 #include <sys/socket.h> 9 #include <sys/wait.h> 10 #include <arpa/inet.h> 11 void showClientInf(struct sockaddr_in client_addr) { 12 printf("\nThe IP of client is:%s",inet_ntoa(client_addr.sin_addr)); 13 printf("\nThe Port of client is:%d\n",ntohs(client_addr.sin_port)); 14 } 15 unsigned long get_sp(void) 16 { 17 __asm__("movl %esp,%eax"); 18 } 19 void testf() 20 { 21 printf("ttttt\n"); 22 } 23 24 25 void recvastring(int new_fd) 26 { 27 unsigned char buff[100]; 28 int i=0; 29 printf("sp=0x%x,addr=0x%x bytes.\n",get_sp(),&buff); 30 int numbytes = recv(new_fd,buff,1024,0); 31 if(numbytes==-1) 32 { 33 perror("recv"); 34 exit(9); 35 } 36 } 37 int main() { 38 int sockfd,new_fd; 39 struct sockaddr_in my_addr; 40 struct sockaddr_in their_addr; 41 int flag=1,len=sizeof(int); 42 int sin_size; 43 char buff[100]; 44 int numbytes; 45 printf("socket\n"); 46 if((sockfd = socket(AF_INET,SOCK_STREAM,0))==-1) { 47 perror("socket"); 48 exit(1); 49 } 50 my_addr.sin_family = AF_INET; 51 my_addr.sin_port = htons(7777); 52 my_addr.sin_addr.s_addr = INADDR_ANY; 53 bzero(&(my_addr.sin_zero),8); 54 printf("bind\n"); 55 if( setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &flag, len) ==-1) 56 { 57 perror("setsockopt"); 58 exit(1); 59 } 60 if(bind(sockfd,(struct sockaddr *)&my_addr,sizeof(struct sockaddr))==-1) 61 { 62 perror("bind"); 63 exit(1); 64 } 65 printf("listen\n"); 66 if(listen(sockfd,10)==-1) { 67 perror("listen"); 68 exit(1); 69 } 70 printf("server is run...\n"); 71 while(1) { 72 sin_size = sizeof(struct sockaddr_in); 73 printf("accept\n"); 74 if((new_fd = accept(sockfd,(struct sockaddr *) 75 &their_addr,&sin_size))==-1) 76 { 77 perror("accept"); 78 exit(1); 79 } 80 showClientInf(their_addr); 81 if(!fork()) { 82 printf("recv\n"); 83 recvastring(new_fd); 84 printf("close-new_fd 1\n"); 85 close(new_fd); 86 exit(0); 87 } 88 printf("close-new_fd 2\n"); 89 close(new_fd); 90 } 91 printf("close-sockfd\n"); 92 close(sockfd); 93 }
这个核心就是我们关注的recvastring函数，包含明显的栈溢出漏洞。我们专门看一下：
1 void recvastring(int new_fd) 2 { 3 unsigned char buff[100]; 4 int i=0; 5 printf("sp=0x%x,addr=0x%x bytes.\n",get_sp(),&buff); 6 int numbytes = recv(new_fd,buff,1024,0); 7 if(numbytes==-1) 8 { 9 perror("recv"); 10 exit(9); 11 } 12 }
同样编译生成：
bai@ubuntu:/mnt/hgfs/r/stack$ gcc -fno-stack-protector -z execstack -g -o server socketserver.c bai@ubuntu:/mnt/hgfs/r/stack$ ./server socket bind listen server is run... accept
