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The Pappy Intercepting Proxy

Project description

The Pappy Proxy

Introduction

The Pappy (Proxy Attack Proxy ProxY) Proxy is an intercepting proxy for performing web application security testing. Its features are often similar, or straight up rippoffs from Burp Suite. However, Burp Suite is neither open source nor a command line tool, thus making a proxy like Pappy inevitable. The project is still in its early stages, so there are bugs and only the bare minimum features, but it should be able to do some cool stuff soon (I’m already using it for realtm work).

Contributing

I am taking any and all feature requests. If you’ve used Burp and had any inconvenience with it, tell me about it and I’ll do everything in my power to make sure Pappy doesn’t have those issues. Or even better, if you want Burp to do something that it doesn’t already, let me know so that I can [STRIKEOUT:use it to stomp them into the dust] improve my project.

If you’re brave and want to try and contribute code, please let me know. Right now the codebase is a giant clusterfun which I have refactored a few times already, but I would be more than happy to find a stable part of the codebase that you can contribute to.

How to Use It

Installation

Pappy supports OS X and Linux (sorry Windows). Installation requires pip or some other command that can handle a setup.py with requirements. Once the requirements are installed, you can check that it installed correctly by running pappy -l to start the proxy.

$ git clone https://github.com/roglew/pappy-proxy.git
$ cd pappy-proxy
$ pip install .

Quickstart

Pappy projects take up an entire directory. While a full directory may seem like a dumb idea compared to storing everything in a zip file, future releases will do fun stuff like generate attack scripts or other files that need to be used by other programs on a regular basis. To start a project, do something like:

$ mkdir test_project
$ cd test_project
$ pappy
Copying default config to directory
Proxy is listening on port 8000
itsPappyTime> exit
$ ls
data.db            project_config.json  project_config.pyc
$

And that’s it! The proxy will by default be running on port 8000 and bound to localhost (to keep the hackers out). You can modify the port/interface in config.json. You can list all your intercepted requests with ls, view a full request with vfq <reqid> or view a full response with vfs <reqid>. No you can’t delete them yet. I’m working on it.

Lite Mode

If you don’t want to dirty up a directory, you can run Pappy in “lite” mode. Pappy will use the default configuration settings and will create a temporary datafile in /tmp to use. When you quit, the file will be deleted. If you want to run Pappy in line mode, run Pappy with either -l or --lite.

Example:

$ pappy -l
Temporary datafile is /tmp/tmpw4mGv2
Proxy is listening on port 8000
itsPappyTime> quit
Deleting temporary datafile
$

Adding The CA Cert to Your Browser

In order for Pappy to view data sent using HTTPS, you need to add a generated CA cert (certificate.crt) to your browser. Certificates are generated using the gencerts command and are by default stored in the same directory as pappy.py. This allows Pappy to act as a CA and MITM HTTPS connections. I believe that Firefox and Chrome ignore keychain/system certs, so you will have to install the CA cert to the browsers instead of (or in addition to) adding the cert to your keychain.

Firefox

You can add the CA cert to Firefox by going to Preferences -> Advanced -> View Certificates -> Authorities -> Import and selecting the certificate.crt file in the certs directory.

Chrome

You can add the CA cert to Chrome by going to Settings -> Show advanced settings -> HTTPS/SSL -> Manage Certificates -> Authorities -> Import and selecting the certificate.crt file in the certs directory.

Safari

For Safari (on macs, obviously), you need to add the CA cert to your system keychain. You can do this by double clicking on the CA cert and following the prompts.

Internet Explorer

I didn’t search too hard for instructions on this (since Pappy doesn’t support windows) and I don’t own a Windows machine to try this, so if you have trouble, I’m not the one to ask. According to Google you can double-click the cert to install it to the system, or you can do Tools -> Content -> Certificates -> Trusted Root Certificates -> Import.

Configuration

Configuration for each project is done in the config.json file. The file is a JSON-formatted dictionary that contains settings for the proxy. The following fields can be used to configure the proxy:

Key Value
data_file The file where requests and images will be stored
debug_dir (optional) Where connection debug info should be stored. If not present, debug info is not saved to a file.
cert_dir Where the CA cert and the private key for the CA cert are stored
proxy_listeners A list of dicts which describe which ports the proxy will listen on. Each item is a dict with “port” and “interface” values which determine which port and interface to listen on. For example, if port=8000 and the interface is 127.0.0.1, the proxy will only accept connections from localhost on port 8000. To accept connections from anywhere, set the interface to 0.0.0.0.

The following tokens will also be replaced with values:

Token Replaced with
{PAPPYDIR} The directory where Pappy’s files are stored

Generating Pappy’s CA Cert

In order to intercept and modify requests to sites that use HTTPS, you have to generate and install CA certs to your browser. You can do this by running the gencerts command in Pappy. By default, certs are stored in the same directory as Pappy’s script files. However, you can change where Pappy will look for the private key file in the config file. In addition, you can give the gencerts command an argument to have it put the generated certs in a different directory.

Command Description
gencerts [/path/to/put/certs/in] Generate a CA cert that can be added to your browser to let Pappy decrypt HTTPS traffic. Also generates the private key for that cert in the same directory.

Browsing Recorded Requests/Responses

The following commands can be used to view requests and responses

Command Aliases Description
ls [a|<num>] list, ls List requests that are in the current context (see Context section). Has information like the host, target path, and status code. With no arguments, it will print the 25 most recent requests in the current context. If you pass ‘a’ or ‘all’ as an argument, it will print all the requests in the current context. If you pass a number “n” as an argument, it will print the n most recent requests in the current context.
viq <id> [u] view_request_info, viq View additional information about a request. Includes the target port, if SSL was used, and other information. If ‘u’ is given as an additional argument, it will print information on the unmangled version of the request.
vfq <id> [u] view_full_request, vfq [V]iew [F]ull Re[Q]uest, prints the full request including headers and data. If ‘u’ is given as an additional argument, it will print the unmangled version of the request.
vhq <id> [u] view_request_headers, vhq [V]iew [H]eaders of a Re[Q]uest. Prints just the headers of a request. If ‘u’ is given as an additional argument, it will print the unmangled version of the request.
vfs <id> [u] view_full_response, vfs [V]iew [F]ull Re[S]ponse, prints the full response associated with a request including headers and data. If ‘u’ is given as an additional argument, it will print the unmangled version of the response.
vhs <id> [u] view_response_headers, vhs [V]iew [H]eaders of a Re[S]ponse. Prints just the headers of a response associated with a request. If ‘u’ is given as an additional argument, it will print the unmangled version of the response.

The table shown will have the following columns:

Label Description
ID The request ID of that request. Used to identify the request for other commands.
Method The method(/http verb) for the request
Host The host that the request was sent to
Path The path of the request
S-Code The status code of the response
Req Len The length of the data submitted
Rsp Len The length of the data returned in the response
Time The time in seconds it took to complete the request
Mngl If the request or response were mangled with the interceptor. If the request was mangled, the column will show ‘q’. If the response was mangled, the column will show ‘s’. If both were mangled, it will show ‘q/s’.

Context

The context is a set of filters that define which requests are considered “active”. Only requests in the current context are displayed with ls, and eventually contexts will be how Pappy will manage requests for group operations. By default, the context includes every single request that passes through the proxy. You can limit down the current context by applying filters. Filters apply rules such as “the response code must equal 500” or “the host must contain google.com”. Once you apply one or more filters, only requests/responses which pass every active filter will be a part of the current context.

Command Aliases Description
f <filter string> filter, fl, f Add a filter that limits which requests are included in the current context. See the Filter String section for how to create a filter string
fc filter_clear, fc Clears the filters and resets the context to contain all requests and responses. Ignores scope
fls filter_list, fls Print the filters that make up the current context

Filter Strings

Filter strings define a condition that a request/response pair must pass to be part of a context. Most filter strings have the following format:

<field> <comparer> <value>

Where <field> is some part of the request/response, <comparer> is some comparison to <value>. Also if you prefix a comparer with ‘n’ it turns it into a negation. For example, if you wanted a filter that only matches requests to target.org, you could use the following filter string:

host is target.org

field = "host"
comparer = "is"
value = "target.org"

For fields that are a list of key/value pairs (headers, get params, post params, and cookies) you can use the following format:

<field> <comparer1> <value1>[ <comparer2> <value2>]

This is a little more complicated. If you don’t give comparer2/value2, the filter will pass any pair where the key or the value matches comparer1 and value1. If you do give comparer2/value2, the key must match comparer1/value1 and the value must match comparer2/value2 For example:

Filter A:
    cookie contains Session

Filter B:
    cookie contains Session contains 456

Filter C:
    cookie ncontains Ultra

Cookie: SuperSession=abc123
Matches A and C but not B

Cookie: UltraSession=abc123456
Matches both A and B but not C

List of fields

Field Name Aliases Description Format
all all The entire request represented as one string String
host host, domain, hs, dm The target host (ie www.target.com) String
path path, pt The path of the url (ie /path/to/secrets.php) String
body body, data, bd, dt The body (data section) of either the request or the response String
verb verb, vb The HTTP verb of the request (ie GET, POST) String
param param, pm Either the get or post parameters Key/Value
header header, hd An HTTP header (ie User-Agent, Basic-Authorization) in the request or response Key/Value
rawheaders rawheaders, rh The entire header section (as one string) of either the head or the response String
sentcookie sentcookie, sck A cookie sent in a request Key/Value
setcookie setcookie, stck A cookie set by a response Key/Value
statuscode statuscode, sc, responsecode The response code of the response Numeric

List of comparers

Field Name Aliases Description
is is Exact string match
contains contains, ct A contain B is true if B is a substring of A
containsr containsr, ctr A containr B is true if A matches regexp B (NOT IMPLEMENTED)
exists exists, ex A exists B if A is not an empty string (likely buggy)
Leq Leq A Leq B if A’s length equals B (B must be a number)
Lgt Lgt A Lgt B if A’s length is greater than B (B must be a number )
Llt Llt A Llt B if A’s length is less than B (B must be a number)
eq eq A eq B if A = B (A and B must be a number)
gt gt A gt B if A > B (A and B must be a number)
lt lt A lt B if A < B (A and B must be a number)

Scope

Scope is a set of rules to define whether Pappy should mess with a request. You define the scope by setting the context to what you want the scope to be and running scope_save. The scope is saved in data.db and is automatically restored when using the same project directory.

Any requests which don’t match all the filters in the scope will be passed straight to the browser and will not be caught by the interceptor or recorded in the database. This is useful to make sure you don’t accidentally do something like log in to your email through the proxy and have your plaintext username/password stored and accidentally shown to your coworkers.

Command Aliases Description
scope_save scope_save Set the current context to be the scope
sr scope_reset, sr Set the current context to the scope
scope_delete scope_delete Clear the scope (everything’s in scope!)
scope_list scope_list, sls List all the filters that are applied to the scope

Interceptor

This feature is like Burp’s proxy with “Intercept Mode” turned on, except it’s not turned on unless you explicitly turn it on. When the proxy gets a request while in intercept mode, it lets you edit it before it forwards it to the server. In addition, it can stop responses from the server and let you edit them before they get forwarded to the browser. When you run the command, you can pass request and/or response as arguments to say whether you would like to intercept requests and/or responses. Only in-scope requests/responses will be intercepted (see Scope section).

The interceptor will use your EDITOR variable to decide which editor to edit the request/response with. If no editor variable is set, it will default to vi.

To forward a request, edit it, save the file, then quit.

Command Aliases Description
ic <requests,responses,request,response,req,rsp>+ intercept, ic Begins interception mode. Press enter to leave interception mode and return to the command prompt. Pass in request to intercept requests, response to intercept responses, or both to intercept both.
Intercept both requests and responses:
> ic requests responses
> ic req rsp

Intercept just requests:
> ic requests
> ic req

Intercept just responses:
> ic responses
> ic rsp

Be totally useless:
> ic

Repeater

This feature is like Burp’s repeater (yes, really). You choose a request and Pappy will open vim in a split window with your request on the left and the original response on the right. You can make changes to the request and then run “:RepeaterSubmitBuffer” to submit the modified request. The response will be displayed on the right. This command is bound to <leader>f by default, but you can rebind it in your vimrc (I think, dunno if vim will complain if it’s undefined). This command will submit whatever buffer your cursor is in, so make sure it’s in the request buffer.

To drop a request, delete everything, save and quit (ggdG:wq).

When you’re done with repeater, run “:qa!” to avoid having to save changes to nonexistent files.

Command Aliases Description
rp <id> repeater, rp Open the specified request in the repeater
Vim Command Keybinding Action
RepeaterSubmitBuffer f Submit the current buffer, split the windows vertically, and show the result in the right window

Logging

You can watch in real-time what requests are going through the proxy. Verbosisty defaults to 1 which just states when connections are made/lost and some information on what is happening. If verbosity is set to 3, it includes all the data which is sent through the proxy and processed. It will print the raw response from the server, what it decodes it to, etc. Even if you don’t run this command, all the information is stored in the dubug directory (the directory is cleared every start though!)

Command Description
log [verbosity] View the log at the given verbosity. Default verbosity is 1 which just shows connections being made/lost and some other info, verbosity 3 shows full requests/responses as they pass through and are processed by the proxy

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