Metadata in pictures embedded(!) in docx files

by Asbjørn Reglund Thorsen

Motivation

This blog post startet naturally after finishing a previous blog post on Are you leaking metadata? Here's a simple example to make your own tool to check!. When you make a word document, I guess you often use images you have taken with your smart phone og camera? All these files contain metadata. What happens to the metadata when these images are imported into e.g. a word document? Is it possible to extract the images from a given word document? Are the pictures metadata still present?

Modern cameras and phones often writes a lot of metadata embedded in the pictures, e.g. GPS coordinates from where the picture was taken

I would like to raise the question: if washing documents of metadata is, or should be important to you, should you also wash images and files imported into your docx files?

In this blog post I will show how you easily can extract metadata from embedded JPG files in a docx document. I will also give you some Ruby code if you want to give it a go.

It is also possible to do this for pptx and maybe other files too, however I will only show the docx example just to show the concept.

Unzipping

I made a simple word docx file containing some text and a picture I know contains GPS-coordinates in the metadata. Lets do a little experiment. Lets unzip a word docx file and look at the content being extracted:

I saved the docx document and entered the directory with my terminal:

So it's possible to unzip docx files and look at the internals of the document. A quick search for where the JPG files are stored using my terminal:

I could only find one picture in the extracted data which makes sense since I only imported one picture to the document. The picture was renamed to image1.JPG by word and it was put in a folder /word/media/. Extracting metadata from this file with exiftool:

The picture still contained the original metadata. Above is a truncated version of the results.

In an earlier blog post I wrote about writing your own tool to collect metadata. You use this small program to download docx files from NASA and see if there are pictures embedded in them with interesting data.

Automated extraction of metadata in embedded files

Lets say you have run the google-dork.rb like this:

 ruby google-dork.rb nasa.gov docx 1

This will download approximately 60 docx files to your /tmp folder. Lets make a ruby program and extract the data we are looking for and present it in an html file.

Step 1 - Glob through docx files

First we need to run through all the docx files we have downloaded into /tmp. I made a unpack folder inside /tmp to unpack the docx files:

def loop_over_files
  Dir.glob("/tmp/*.docx") do |file|
    unzip_file(file,'/tmp/unpack')
  end
end

Step 2 - Unzip the files

Next we need to unzip all the docx files, however for each file that is unzipped all the folders and files will have the same name and we need to clear the folder after the document is processed to make room for the next document.

1x-192-157-203-225:metadata asbjornt$ ls /tmp/unpack/
[Content_Types].xml rels docProps word
1x-192-157-203-225:metadata asbjornt$

You need to install rubyzip to run the code below.

gem install rubyzip

The method for unzipping the files:

def unzip_file (file, destination)
  puts "Unzipping #{file}"
  clean_up("/tmp/unpack/")
  Zip::File.open(file) do |zip_file|
    zip_file.each do |f|
      f_path = File.join(destination, f.name)
      FileUtils.mkdir_p(File.dirname(f_path))
      f.extract(f_path)
    end
  end
end

Step 3 - Clean the unpack folder

I need to clean the unpack folder to make room for the next folders and files containing the same names in the extracted files and folders:

def clean_up(dir)
  puts "Cleaning up"
  FileUtils.remove_dir(dir)
  unless File.directory?(dir)
    FileUtils.mkdir_p(dir)
  end
end

Step 4 - Extracting the data

To extract the metadata we need to find where the pictures are stored, and for docx files the image files is stored in the /tmp/unpack/word/media/ folder. We need a method for extracting the metadata from the images:

def extract_data
  puts "Extracting metadata"
  path = "/tmp/unpack/word/media/"
  $html_file.write("<html><meta charset=\"UTF-8\"><title>Metadata in embedded pictures</title><body>")

  Dir.glob("#{path}/*.jpg") do |file|
    puts "Running exiftool on #{file}"
    $html_file.write("<br/><br/>")
    $html_file.write("<table border=\"solid\"><th>Key</th><th>Value</th>")
    e = Exiftool.new(file)
    data = e.to_hash

    for key in data.keys()
      $html_file.write("<tr><td>#{key}</td><td>#{data[key]}</td></tr>")
    end
  end
end

Results

This is a truncated version of the html result page generated by the small Ruby program. As you can see there are GPS findings. It's easy to get google maps to reveal the location:

https://www.google.com/maps/@59.8937806,10.6450333,13z

Putting it all together

The complete code should look like this:

#!/usr/bin/ruby
require 'exiftool'
require 'zip'
require 'fileutils'

def loop_over_files
  Dir.glob("/tmp/*.docx") do |file|
    unzip_file(file,'/tmp/unpack')
  end
end

def unzip_file (file, destination)
  puts "Unzipping #{file}"
  clean_up("/tmp/unpack/")
  Zip::File.open(file) do |zip_file|
    zip_file.each do |f|
      f_path = File.join(destination, f.name)
      FileUtils.mkdir_p(File.dirname(f_path))
      f.extract(f_path)
    end
  end
  extract_data()
end

def extract_data
  puts "Extracting metadata"
  path = "/tmp/unpack/word/media/"
  $html_file.write("<html><meta charset=\"UTF-8\"><title>Metadata in embedded pictures</title><body>")

  Dir.glob("#{path}/*.jpg") do |file|
    puts "Running exiftool on #{file}"
    $html_file.write("<br/><br/>")
    $html_file.write("<table border=\"solid\"><th>Key</th><th>Value</th>")
    e = Exiftool.new(file)
    data = e.to_hash

    for key in data.keys()
      $html_file.write("<tr><td>#{key}</td><td>#{data[key]}</td></tr>")
    end
  end
end

def clean_up(dir)
puts "Cleaning up"
  FileUtils.remove_dir(dir)
  unless File.directory?(dir)
    FileUtils.mkdir_p(dir)
  end
end

$html_file = File.open("/tmp/metadata_embedded_pic.html", "a")

loop_over_files()
$html_file.close

Run the code like this:

ruby extract_embedded.rb

Open the newly generated html file in your browser, it should be located in

/tmp/metadata_embedded_pic.html

Github

Get the code from github:

git clone https://github.com/reglund/metadata.git

Have fun!