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Poor Validation One(失效的数据认证 1)

题介绍

需要实现空手套白狼,不花钱购买到第三个商品(巨魔)

功能实现

点击页面购买按钮 ,获得请求包

POST /challenges/ca0e89caf3c50dbf9239a0b3c6f6c17869b2a1e2edc3aa6f029fd30925d66c7e HTTP/1.1


megustaAmount=0&trollAmount=1&rageAmount=-100&notBadAmount=0
对应后端实现代码 src/main/java/servlets/module/challenge/PoorValidation1.java

int megustaAmount = Integer.parseInt(request.getParameter("megustaAmount")); //所有输入进行了强制转换成int  但没有校验是否是正数
int trollAmount = Integer.parseInt(request.getParameter("trollAmount"));  //购买巨魔的商品的数量
int rageAmount = Integer.parseInt(request.getParameter("rageAmount"));
int notBadAmount = Integer.parseInt(request.getParameter("notBadAmount"));

//Working out costs
int megustaCost = megustaAmount * 30;
int trollCost = trollAmount * 3000;
int rageCost = rageAmount * 45;
int notBadCost = notBadAmount * 15;

htmlOutput = new String();

//Work Out Final Cost
int finalCost = megustaCost + rageCost + notBadCost + trollCost;  //计算最终的费用

//Output Order
htmlOutput = "<h3 class='title'>" + bundle.getString("poorValidation.orderComplete")+ "</h3>"
        + "<p>" + bundle.getString("poorValidation.orderComplete.message")+ "<br></p>"
        + "<p>" + bundle.getString("poorValidation.orderTotal")+ " <a><strong>$" + finalCost + "</strong></a></p>";
if (finalCost <= 0 && trollAmount > 0) //最终费用小于等于0, 并且巨魔的费用大于1 则表示通关
{
    htmlOutput += "<br><p>" + bundle.getString("poorValidation.freeTrolls")+ " - " + Hash.generateUserSolution(levelSolution, currentUser) + "</p>";
}

解题步骤

购买的数量没有校验是否是负数,因此只需要保证巨魔商品为正数,其他商品数量为负数,总价格小于0即可

总结

对用户收入的数据进行校验是非常重要的,本题已经进行了部分校验,但由于校验不充分,没有考虑到负数情况,进而造成漏洞
校验一定要充分,确保输入数据,在系统可用情况下的最小集合

汉化说明

添加汉化文件

src/main/resources/i18n/challenges/poorValidation/poorValidationStrings_zh.properties

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