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Base requests

Requests

Nuclei offers extensive support for various features related to HTTP protocol. Raw and Model based HTTP requests are supported, along with options Non-RFC client requests support too. Payloads can also be specified and raw requests can be transformed based on payload values along with many more capabilities that are shown later on this Page.

HTTP Requests start with a request block which specifies the start of the requests for the template.

# Start the requests for the template right here
requests:

Method

Request method can be GET, POST, PUT, DELETE, etc depending on the needs.

# Method is the method for the request
method: GET

Redirects

Redirection conditions can be specified per each template. By default, redirects are not followed. However, if desired, they can be enabled with redirects: true in request details. 10 redirects are followed at maximum by default which should be good enough for most use cases. More fine grained control can be exercised over number of redirects followed by using max-redirects field.

An example of the usage:

requests:
  - method: GET
    path:
      - "{{BaseURL}}/login.php"
    redirects: true
    max-redirects: 3

Warning

Currently redirects are defined per template, not per request.

Path

The next part of the requests is the path of the request path. Dynamic variables can be placed in the path to modify its behavior on runtime.

Variables start with {{ and end with }} and are case-sensitive.

{{BaseURL}} - This will replace on runtime in the request by the original URL as specified in the target file.

{{Hostname}} - Hostname variable is replaced by the hostname of the target on runtime.

Some sample dynamic variable replacement examples:

path: "{{BaseURL}}/.git/config"
# This path will be replaced on execution with BaseURL
# If BaseURL is set to  https://abc.com then the
# path will get replaced to the following: https://abc.com/.git/config

Multiple paths can also be specified in one request which will be requested for the target.

Headers

Headers can also be specified to be sent along with the requests. Headers are placed in form of key/value pairs. An example header configuration looks like this:

# headers contains the headers for the request
headers:
  # Custom user-agent header
  User-Agent: Some-Random-User-Agent
  # Custom request origin
  Origin: https://google.com

Body

Body specifies a body to be sent along with the request. For instance:

# Body is a string sent along with the request
body: "{\"some random JSON\"}"

# Body is a string sent along with the request
body: "admin=test"

Session

To maintain cookie based browser like session between multiple requests, you can simply use cookie-reuse: true in your template, Useful in cases where you want to maintain session between series of request to complete the exploit chain and to perform authenticated scans.

# cookie-reuse accepts boolean input and false as default
cookie-reuse: true

Request Condition

Request condition allows to check for condition between multiple requests for writing complex checks and exploits involving multiple HTTP request to complete the exploit chain.

with DSL matcher, it can be utilized by adding req-condition: true and numbers as suffix with respective attributes, status_code_1, status_code_3, andbody_2 for example.

    req-condition: true
    matchers:
      - type: dsl
        dsl:
          - "status_code_1 == 404 && status_code_2 == 200 && contains((body_2), 'secret_string')"

Example HTTP Template

The final template file for the .git/config file mentioned above is as follows:

id: git-config

info:
  name: Git Config File
  author: Ice3man
  severity: medium
  description: Searches for the pattern /.git/config on passed URLs.

requests:
  - method: GET
    path:
      - "{{BaseURL}}/.git/config"
    matchers:
      - type: word
        words:
          - "[core]"

RAW HTTP requests

Another way to create request is using raw requests which comes with more flexibility and support of DSL helper functions, like the following ones (as of now it's suggested to leave the Host header as in the example with the variable {{Hostname}}), All the Matcher, Extractor capabilities can be used with RAW requests in same the way described above.

requests:
  - raw:
    - |
        POST /path2/ HTTP/1.1
        Host: {{Hostname}}
        Content-Length: 1
        Origin: https://www.google.com
        Content-Type: application/x-www-form-urlencoded
        User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_5) AppleWebKit/537.36 (KHTML, like Gecko)
        Accept-Language: en-US,en;q=0.9

        a=test&b=pd

Requests can be fine tuned to perform the exact tasks as desired. Nuclei requests are fully configurable meaning you can configure and define each and every single thing about the requests that will be sent to the target servers.

RAW request format also supports various helper functions letting us do run time manipulation with input. An example of the using a helper function in the header.

    raw:
      - |
        GET /manager/html HTTP/1.1
        Host: {{Hostname}}
        Authorization: Basic {{base64('username:password')}} # Helper function to encode input at run time.
        User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0
        Accept-Language: en-US,en;q=0.9
        Connection: close

HTTP Fuzzing

Info

Nuclei engine supports fuzzing module that allow to run various type of payloads in multiple format, It's possible to define placeholders with simple keywords (or using brackets {{helper_function(variable)}} in case mutator functions are needed), and perform sniper, pitchfork and clusterbomb attacks. The wordlist for these attacks needs to be defined during the request definition under the Payload field, with a name matching the keyword, Nuclei supports both file based and in template wordlist support and Finally all DSL functionalities are fully available and supported, and can be used to manipulate the final values.

Payloads are defined using variable name and can be referenced in the request in between § § or {{ }} marker.

An example of the using payloads with local wordlist:

    # HTTP Intruder fuzzing using local wordlist.

    payloads:
      paths: params.txt
      header: local.txt

An example of the using payloads with in template wordlist support:

    # HTTP Intruder fuzzing using in template wordlist.

    payloads:
      password:
        - admin
        - guest
        - password

Note:- be careful while selecting attack type, as unexpected input will break the template.

For example, if you used clusterbomb or pitchfork as attack type and defined only one variable in the payload section, template will fail to compile, as clusterbomb or pitchfork expect more than one variable to use in the template.

Attack mode

Nuclei engine supports multiple attack types, including sniper which generally used to fuzz single parameter, clusterbomb and pitchfork for fuzzing multiple parameters which works same as classical burp intruder.

Type sniper pitchfork clusterbomb
Support

sniper

The sniper attack uses only one payload set, and it replaces only one position at a time. It loops through the payload set, first replacing only the first marked position with the payload and leaving all other positions to their original value. After its done with the first position, it continues with the second position.

pitchfork

The pitchfork attack type uses one payload set for each position. It places the first payload in the first position, the second payload in the second position, and so on.

It then loops through all payload sets at the same time. The first request uses the first payload from each payload set, the second request uses the second payload from each payload set, and so on.

clusterbomb

The cluster bomb attack tries all different combinations of payloads. It still puts the first payload in the first position, and the second payload in the second position. But when it loops through the payload sets, it tries all combinations.

It then loops through all payload sets at the same time. The first request uses the first payload from each payload set, the second request uses the second payload from each payload set, and so on.

This attack type is useful for a brute-force attack. Load a list of commonly used usernames in the first payload set, and a list of commonly used passwords in the second payload set. The cluster bomb attack will then try all combinations.

More details here.

An example of the using using clusterbomb attack to fuzz.

requests:
  - raw:
      - |
        POST /?file={{path}} HTTP/1.1
        User-Agent: {{header}}
        Host: {{Hostname}}

    payloads:
      path: helpers/wordlists/prams.txt
      header: helpers/wordlists/header.txt
    attack: clusterbomb # Defining HTTP fuzz attack type

Unsafe HTTP Requests

Nuclei supports rawhttp for complete request control and customization allowing any kind of malformed requests for issues like HTTP request smuggling, Host header injection, CRLF with malformed characters and more.

rawhttp library is disabled by default and can be enabled by including unsafe: true in the request block.

Here is an example of HTTP request smuggling detection template using rawhttp.

requests:
  - raw:
    - |+
        POST / HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/x-www-form-urlencoded
        Content-Length: 150
        Transfer-Encoding: chunked

        0

        GET /post?postId=5 HTTP/1.1
        User-Agent: a"/><script>alert(1)</script>
        Content-Type: application/x-www-form-urlencoded
        Content-Length: 5

        x=1
    - |+
        GET /post?postId=5 HTTP/1.1
        Host: {{Hostname}}

    unsafe: true # Enables rawhttp client
    matchers:
      - type: dsl
        dsl:
          - 'contains(body, "<script>alert(1)</script>")'

Advance Fuzzing

We’ve enriched nuclei to allow advanced fuzzing of web servers. Users can now use multiple options to tune HTTP fuzzing workflows.

Pipelining

HTTP Pipelining support has been added which allows multiple HTTP requests to be sent on the same connection inspired from http-desync-attacks-request-smuggling-reborn.

Before running HTTP pipelining based templates, make sure the running target supports HTTP Pipeline connection, otherwise nuclei engine fallbacks to standard HTTP request engine.

If you want to confirm the given domain or list of subdomains supports HTTP Pipelining, httpx has a flag -pipeline to do so.

An example configuring showing pipelining attributes of nuclei.

    unsafe: true
    pipeline: true
    pipeline-max-connections: 40
    pipeline-max-workers: 25000

An example template demonstrating pipelining capabilities of nuclei has been provided below-

id: pipeline-testing
info:
  name: pipeline testing
  author: pdteam
  severity: info

requests:

  - raw:
      - |+
        GET /§path§ HTTP/1.1
        Host: {{Hostname}}
        Accept: application/json, text/plain, */*
        Referer: {{BaseURL}}

    payloads:
      path: path_wordlist.txt
    attack: sniper
    unsafe: true
    pipeline: true
    pipeline-max-connections: 40
    pipeline-max-workers: 25000

    matchers:
      - type: status
        part: header
        status:
          - 200

Connection pooling

While the earlier versions of nuclei did not do connection pooling, users can now configure templates to either use HTTP connection pooling or not. This allows for faster scanning based on requirement.

To enable connection pooling in the template, threads attribute can be defined with respective number of threads you wanted to use in the payloads sections.

Connection: Close header can not be used in HTTP connection pooling template, otherwise engine will fail and fallback to standard HTTP requests with pooling.

An example template using HTTP connection pooling-

id: fuzzing-example
info:
  name: Connection pooling example
  author: pdteam
  severity: info

requests:

  - raw:
      - |
        GET /protected HTTP/1.1
        Host: {{Hostname}}
        Authorization: Basic {{base64('admin:§password§')}}
        User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0
        Accept-Language: en-US,en;q=0.9

    payloads:
      password: password.txt
    threads: 40
    attack: sniper

    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200

      - type: word
        words:
          - "Unique string"
        part: body    

Smuggling

HTTP Smuggling is a class of Web-Attacks recently made popular by Portswigger’s Research into the topic. For an in-depth overview, please visit the article linked above.

In the open source space, detecting http smuggling is difficult particularly due to the requests for detection being malformed by nature. Nuclei is able to reliably detect HTTP Smuggling vulnerabilities utilising the rawhttp engine.

The most basic example of a HTTP Smuggling vulnerability is CL.TE Smuggling. An example template to detect a CE.TL HTTP Smuggling vulnerability is provided below using the unsafe: true attribute for rawhttp based requests.

id: CL.TE-http-smuggling

info:
  name: HTTP request smuggling, basic CL.TE vulnerability
  author: pdteam
  severity: info
  lab: https://portswigger.net/web-security/request-smuggling/lab-basic-cl-te

requests:
  - raw:
    - |+
      POST / HTTP/1.1
      Host: {{Hostname}}
      Connection: keep-alive
      Content-Type: application/x-www-form-urlencoded
      Content-Length: 6
      Transfer-Encoding: chunked

      0

      G      
    - |+
      POST / HTTP/1.1
      Host: {{Hostname}}
      Connection: keep-alive
      Content-Type: application/x-www-form-urlencoded
      Content-Length: 6
      Transfer-Encoding: chunked

      0

      G

    unsafe: true
    matchers:
      - type: word
        words:
          - 'Unrecognized method GPOST'

More examples are available in template-examples section for smuggling templates.

Race conditions

Race Conditions are another class of bugs not easily automated via traditional tooling. Burp Suite introduced a Gate mechanism to Turbo Intruder where all the bytes for all the requests are sent expect the last one at once which is only sent together for all requests synchronizing the send event.

We have implemented Gate mechanism in nuclei engine and allow them run via templates which makes the testing for this specfic bug class simple and portable.

To enable race condition check within template, race attribute can be set to true and race_count defines the number of simultaneous request you want to initiate.

Below is an example template where the same request is repeated for 10 times using the gate logic.

id: race-condition-testing

info:
  name: Race condition testing
  author: pdteam
  severity: info

requests:
  - raw:
      - |
        POST /coupons HTTP/1.1
        Host: {{Hostname}}
        Pragma: no-cache
        Cache-Control: no-cache, no-transform
        User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:47.0) Gecko/20100101 Firefox/47.0

        promo_code=20OFF        

    race: true
    race_count: 10

    matchers:
      - type: status
        part: header
        status:
          - 200

You can simply replace the POST request with any suspected vulnerable request and change the race_count as per your need and it's ready to run.

nuclei -t race.yaml -target https://api.target.com

Multi request race condition testing

For the scenario when multiple requests needs to be sent in order to exploit the race condition, we can make use of threads.

    threads: 5
    race: true

threads is a total number of request you wanted make with the template to perform race condition testing.

Below is an example template where multiple (5) unique request will be sent at the same time using the gate logic.

id: multi-request-race

info:
  name: Race condition testing with multiple requests
  author: pd-team
  severity: info

requests:
  - raw:  
      - |
        POST / HTTP/1.1
        Pragma: no-cache
        Host: {{Hostname}}
        Cache-Control: no-cache, no-transform
        User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:47.0) Gecko/20100101 Firefox/47.0

        id=1

      - |
        POST / HTTP/1.1
        Pragma: no-cache
        Host: {{Hostname}}
        Cache-Control: no-cache, no-transform
        User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:47.0) Gecko/20100101 Firefox/47.0

        id=2

      - |
        POST / HTTP/1.1
        Pragma: no-cache
        Host: {{Hostname}}
        Cache-Control: no-cache, no-transform
        User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:47.0) Gecko/20100101 Firefox/47.0

        id=3

      - |
        POST / HTTP/1.1
        Pragma: no-cache
        Host: {{Hostname}}
        Cache-Control: no-cache, no-transform
        User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:47.0) Gecko/20100101 Firefox/47.0

        id=4

      - |
        POST / HTTP/1.1
        Pragma: no-cache
        Host: {{Hostname}}
        Cache-Control: no-cache, no-transform
        User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:47.0) Gecko/20100101 Firefox/47.0

        id=5

    threads: 5
    race: true