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How to Send an HTTP Request Using HTTPClient

Brent Cook edited this page · 15 revisions

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This is an example of how to write a module that uses the HttpClient mixin to send a basic HTTP request.

There are mainly two common methods you will see:

  • send_request_raw - You use this to send a raw HTTP request. Usually, you will want this method if you need something that violates the specification; in most other cases, you should prefer send_request_cgi. If you wish to learn about how this method works, look at the documentation for Rex::Proto::Http::Client#request_raw.

Here's a basic example of how to use send_request_raw:

    send_request_raw({'uri'=>'/index.php'})

Both methods can automatically do the HTTP authentication if the user sets the "USERNAME" and "PASSWORD" advanced options.

Here's a very basic example for send_request_cgi:

    send_request_cgi({
        'method'   => 'GET',
        'uri'      => '/hello_world.php',
        'vars_get' => {
            'param_1' => 'abc',
            'param_2' => '123'
        }
    })

Please note: send_request_raw and send_request_cgi will return a nil if there's a timeout, so please make sure to account for that condition when you handle the return value.

URI Parsing

Before you send a HTTP request, you will most likely have to do some URI parsing. This is a tricky task, because sometimes when you join paths, you may accidentally get double slashes, like this: "/test//index.php". Or for some reason you have a missing slash. These are really commonly made mistakes. So here's how you can handle it safely:

1 - Register your default URI datastore option as 'TARGETURI':

Example:

    register_options(
        [
            OptString.new('TARGETURI', [true, 'The base path to XXX application', '/xxx_v1/'])
        ], self.class)

2 - Load your TARGETURI with target_uri, that way the URI input validation will kick in, and then you get a real URI object:

In this example, we'll just load the path:

    uri = target_uri.path

3 - When you want to join another URI, always use normalize_uri:

Example:

    # Returns: "/xxx_v1/admin/upload.php"
    uri = normalize_uri(uri, 'admin', 'upload.php')

4 - When you're done normalizing the URI, you're ready to use send_request_cgi or send_request_raw

Please note: The normalize_uri method will always follow these rules:

  1. The URI should always begin with a slash.
  2. You will have to decide if you need the trailing slash or not.
  3. There should be no double slashes.

Full Example

    require 'msf/core'

    class Metasploit3 < Msf::Auxiliary

        include Msf::Exploit::Remote::HttpClient

        def initialize(info = {})
            super(update_info(info,
                'Name'           => 'HttpClient Example',
                'Description'    => %q{
                    Do a send_request_cgi()
                },
                'Author'         => [ 'sinn3r' ],
                'License'        => MSF_LICENSE
            ))

            register_options(
                [
                    OptString.new('TARGETURI', [true, 'The base path', '/'])
                ], self.class)
        end


        def run
            uri = target_uri.path

            res = send_request_cgi({
                'method'   => 'GET',
                'uri'      => normalize_uri(uri, 'admin', 'index.phpp'),
                'vars_get' => {
                    'p1' => "This is param 1",
                    'p2' => "This is param 2"
                }
            })

            if res && res.code == 200
                print_good("I got a 200, awesome")
            else
                print_error("No 200, feeling blue")
            end
        end
    end

Common question(s):

1 - Can I use vars_get and vars_post together?

Yes. When you supply a hash to vars_get, basically it means "put all this data in the query string". When you supply a hash to vars_post, it means "put all this data in the body." All of them will be in the same request. You do need to make sure you're using send_request_cgi, of course.

2 - I can't use vars_get or vars_post due to some weird reason, what to do?

Do mention about this problem in the code (as a comment). If you can't use vars_post, you can try the data key instead, which will send your post data raw. Normally, the most common solution to get around vars_get is to leave your stuff in the uri key. msftidy will flag this, but only as an "Info" and not a warning, which means you should still pass msftidy anyway. If this is a common problem, we can always change msftidy.

References

https://github.com/rapid7/metasploit-framework/wiki/How-to-send-an-HTTP-request-using-Rex%3A%3AProto%3A%3AHttp%3A%3AClient

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