Look inside the box

This tool is just the latest implementation that breaks the encryption and obfuscation layers that Dropbox applies to their modified Python interpreter. It's based on work the author did many, many moons ago as well as public work done by others. For more information please see the blogpost.

Updates

May, 2019

Initial release.

October, 2019

The code was updated to regenerate the opcode database using Python 3.7. It now also checks for the version of uncompyle6 being installed (>= 3.5.x) such that it gives an error when uncompyle6 is installed but is very outdated. Several bugs were fixed in the generation of the opcode mapping. Thanks to @slinkinone for sending me e-mails and helping me out with debugging some of the issues.

Requirements

Have a recent Python 3.x installation for the unpacking.
Make sure that uncompyle6 is installed. You can do this with:

pip3 install uncompyle6

For regenerating the opcode database make sure that the Python version installed is 3.7. Please note that there's already a version of this opcode database mapping included so it shouldn't be necessary to rerun it.

Usage

Run the included fetchdeps.sh bash script. This will fetch the Python source code as well as download the latest version of the Dropbox for Linux tarball. The Python source code is only needed if one wants to regenerate the opcode database.
Please note that Python 3.7 is a requirement for BOTH of the following calls to work as changes were made to >=3.8 underlying code types etc.
Execute the following to unpack, decrypt and decompile most of the Dropbox Python source code. It will extract to a default directory named out:

python3 unpacker.py --dropbox-zip `find . -name python-packages-37.zip`

To regenerate the opcode mapping database use something like this.

find . -name python-packages-37.zip | xargs python3.7 gendb.py --python-dir tmp/Python-3.7.4/ --db opcode.db --dropbox-zip

To patch the ZIP file in the Dropbox distribution and rewrite the pyc files such that the SHA-256 hashes in there are known SHA-256 hashes use the following to rewrite and inject code into the zip.

python3 patchzip.py --dropbox-zip `find . -name python-packages-37.zip` --output-zip out.zip
mv out.zip ~/.dropbox-dist/dropbox-lnx_64-71.4.108/python-packages-37.zip
~/.dropbox-dist/dropbox-lnx_64-71.4.108/dropbox

To dump the contents of the opcode mapping run the following.

python3 checkdb.py --db opcodemap.db

That will yield something like the following:

...
| ============================== | ======= | ======= |
| OPCODE                         |  PYTHON | DROPBOX |
| ============================== | ======= | ======= |
| POP_TOP                        |       1 |      24 |
| ROT_TWO                        |       2 |       1 |
| ROT_THREE                      |       3 |      83 |
| DUP_TOP                        |       4 |      66 |
| UNARY_POSITIVE                 |      10 |      77 |
...

To set the environment variables to enable hidden Dropbox functionality see the setenv.py script. For more information on this please see the blogpost again. Modify at will and then use it like this to setup the environment and run dropbox.