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buflab/bufbomb.c
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200
buflab/bufbomb.c
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#include <stdio.h>
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#include <stdlib.h>
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#include <ctype.h>
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#ifdef __linux__
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#define _alloca alloca
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#endif
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int getbuf(void);
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void test(void);
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int cookie=0x11223344;
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unsigned long rand1_h,rand1_l,rand_div;
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/* 产生一个0~divv-1之间的随机数，同时更新随机数种子 */
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void GenerateRandomNumber(unsigned long divv)
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{
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long long x = rand1_h;
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x *= 0x6AC690C5;
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x += rand1_l;
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rand1_h = (unsigned long)x;
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rand1_l = (unsigned long)(x>>32);
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if (divv==0) return;
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rand_div = rand1_h % divv;
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}
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/* 输入16进制字符串，并转换为对应的字符串，以\0结束 */
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char*getxs(char*dest)
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{
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int c;
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int even =1; /* Have read even number of digits */
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int otherd =0; /* Other hex digit of pair */
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char*sp = dest;
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while ((c = getchar()) != EOF && c !='\n' && c != '\r') {
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if (isxdigit(c)) {
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int val;
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if ('0'<= c && c <='9')
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val = c -'0';
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else if ('A'<= c && c <='F')
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val = c -'A'+10;
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else
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val = c -'a'+10;
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if (even) {
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otherd = val;
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even =0;
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}
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else {
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*sp++= otherd *16+ val;
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even =1;
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}
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}
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}
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*sp++='\0';
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return dest;
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}
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/* 获取一行输入字符串 */
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int getbuf(void)
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{
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char buf[12];
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getxs(buf);
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return 1;
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}
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/* 主测试程序 */
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void test(void)
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{
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int val;
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char *localbuf;
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volatile int bird = 0xdeadbeef; //金丝雀保护机制
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GenerateRandomNumber(23);
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localbuf = (char *)_alloca(rand_div+1); //在栈上分配随机空间
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localbuf[0] = 'l';
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val = getbuf();
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/* 检测是否栈被破坏 */
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if (bird == 0xdeadbeef) {
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printf("鸟还活着！\n");
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}
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else
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printf("不妙！鸟被杀死，栈已经被你破坏了！\n");
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if (val == cookie) {
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printf("不错哦，缓冲区溢出成功，而且getbuf返回 0X%08X\n", val);
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}
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else if (val == 1) {
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printf("缓冲区没有溢出.....攻击失败，请重来吧\n");
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}
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else {
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printf("不对哦，虽然缓冲区溢出成功，但是getbuf返回 0X%08X\n", val);
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}
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}
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/* 第1只木马，只需要修改返回地址，即可进入 */
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void Trojan1(void)
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{
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printf("恭喜你！你已经成功偷偷运行了第1只木马!\n");
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printf("通过第1只木马测试\n");
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exit(0);
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}
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/* 第2只木马，不仅需要修改返回地址，而且要修改栈中返回的结果 */
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void Trojan2(int val)
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{
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if (val == cookie) {
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printf("不错哦！第2只木马运行了，而且通行密码是正确的！(0X%08X)\n", val);
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} else
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printf("需要加油！虽然第2只木马运行了，但是通行密码是不正确的！(0X%08X)\n", val);
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if (val == cookie)
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printf("通过第2只木马测试\n");
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exit(0);
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}
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/* 第3只木马，本关任务是构造特定的机器代码放置在栈内，然后将返回地址置为该段特定代码的入口。此段代码负责将global_value设置为想要的cookie值 */
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/* 汇编指令程序：
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MOV EAX,cookie
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MOV global_val,EAX
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PUSH Trojan3
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RET
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0: a1 e4 c1 04 08 MOV EAX,0x804c1e4
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5: a3 ec c1 04 08 MOV 0x804c1ec,EAX
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a: 68 eb 8c 04 08 PUSH $0x8048ceb
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f: c3 RET
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*/
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int global_value = 0;
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void Trojan3(int val)
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{
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if (global_value == cookie) {
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printf("厉害！第3只木马运行了，而且你修改了全局变量正确！global_value = 0X%08X\n", global_value);
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} else
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printf("差一点！第3只木马运行了，但是全局变量修改错误！global_value = 0X%08X\n", global_value);
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if (global_value == cookie)
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printf("通过第3只木马测试\n");
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exit(0);
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}
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/* 第4只木马，本关任务是构造特定的机器代码放置在栈内，然后将返回地址置为该段特定代码的入口。此段代码负责将global_value设置为想要的cookie值，需要正常返回 */
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/* 汇编指令程序：
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MOV EAX,cookie
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MOV global_val,EAX
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PUSH Trojan3
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RET
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0: a1 e4 c1 04 08 MOV EAX,0x804c1e4
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5: a3 ec c1 04 08 MOV 0x804c1ec,EAX
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a: 68 eb 8c 04 08 PUSH $0x8048ceb
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f: c3 RET
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*/
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void Trojan4(int val)
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{
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if (global_value == cookie) {
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printf("厉害！第4只木马运行了，而且你修改了全局变量正确！global_value = 0X%08X\n", global_value);
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} else
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printf("差一点！第4只木马运行了，但是全局变量不对！global_value = 0X%08X\n", global_value);
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if (global_value == cookie)
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printf("通过第4只木马测试\n");
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return; // 正常返回，需要修复栈
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}
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/* 主程序，依据学号，随机生成cookie值 */
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int main(int argc, char *argv[])
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{
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int i;
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char *MyRandomBuffer;
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printf("\t2018超级缓冲区炸弹，欢迎你！\n");
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printf("============================\n");
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if (argc == 1)
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{
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printf("使用方法：%s 学号后6位 [学号后6位] [学号后6位] ...\n",argv[0]);
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printf("你需要输入攻击字符串，以便种入木马，一旦出错，哇哈哈....\n");
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printf("请以十六进制形式输入攻击字符串，例如00 aa bb cc等等\n");
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return 0;
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}
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printf("欢迎你前来挑战！ %s \n",argv[1]);
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/*依据学号，初始化一个随机数发生器*/
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rand1_h = (unsigned long)atoi(argv[1]);
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rand1_l=0x29A;
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GenerateRandomNumber(0);
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for (i=2;i<argc;i++)
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{
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rand1_l = (unsigned long)atoi(argv[i]);
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GenerateRandomNumber(0);
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}
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cookie = (int)rand1_h;
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printf("你的通行密码是0X%08X\n",cookie);
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printf("============================\n");
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printf("请输入攻击字符串（十六进制串）：");
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GenerateRandomNumber(512);
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MyRandomBuffer = (char *)_alloca(rand_div+1); //在栈上分配随机空间
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MyRandomBuffer[0] = 'h';
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test();
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return 0;
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}
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