[SWPUCTF 2021 新生赛]re1

Problem: [SWPUCTF 2021 新生赛]re1

思路

• 解题大致思路

EXP

• 具体攻击代码
• 用IDA打开，F5查看伪代码

int __fastcall main(int argc, const char **argv, const char **envp)
{
  char Str2[1008]; // [rsp+20h] [rbp-60h] BYREF
  char Str1[1000]; // [rsp+410h] [rbp+390h] BYREF
  int i; // [rsp+7FCh] [rbp+77Ch]

  _main();
  strcpy(Str2, "{34sy_r3v3rs3}");
  printf("please put your flag:");
  scanf("%s", Str1);
  for ( i = 0; i <= 665; ++i )
  {
    if ( Str1[i] == 101 )
      Str1[i] = 51;
  }
  for ( i = 0; i <= 665; ++i )
  {
    if ( Str1[i] == 97 )
      Str1[i] = 52;
  }
  if ( strcmp(Str1, Str2) )
    printf("you are wrong,see again!");
  else
    printf("you are right!");
  system("pause");
  return 0;
}
​
            
AI代码解释
            
                
            
        

解题脚本：

#include "stdio.h"

int main(){
	
	char flag[]="{34sy_r3v3rs3}";
	int i=0;
	for(i=0;i<20;i++){
		if(flag[i]==51)
			flag[i]=101;
		if(flag[i]==52)
			flag[i]=97;
	}
	printf("%s",flag);
} 
//{easy_reverse}
​
            
AI代码解释
            
                
            
        

总结

• 对该题的考点总结
• 最总flag：NSSCTF{easy_reverse}