66 lines
3.5 KiB
Markdown
66 lines
3.5 KiB
Markdown
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# pywidevine
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Widevine CDM (Content Decryption Module) implementation in Python.
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## Disclaimer
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1. This project requires the use of a Google provisioned private key and Client Identification blob.
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2. Neither of them are provided by this project.
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3. Public test provisions are available to use for testing this project.
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4. License Servers have the ability to block requests from test provisions.
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5. This project does not condone piracy or any action against the terms of the DRM systems.
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6. All efforts in this project have been the result of Reverse Engineering and Trial & Error.
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## Protocol
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*Credit*: w3.org
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### Web Server
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This may be an API/Server in front of a License Server. For example, Netflix's Custom MSL-based API front.
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This is evident by their custom Service Certificate which would only be needed if they had to read the License.
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### Net, Media Stack and MediaKeySession
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These generally refer to the Encrypted Media Extensions API on Browsers.
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Under the assumption of the Android Widevine ecosystem, you can think of `Net` as the Application Code, `Media Stack`
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as the OEM Crypto Library, and `MediaKeySession` as a Session. The orange wrapper titled `Browser` is effectively the
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Application as a whole, while `Platform` (in Green at the bottom) would be the OS or Other libraries.
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## Key and Output Security
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*Licenses, Content Keys, and Decrypted Data is not secure in this CDM implementation.*
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The Content Decryption Module is meant to do all downloading, decrypting, and decoding of content, not just license
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acquisition. This Python implementation only does License Acquisition within the CDM.
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The section of which a 'Decrypt Frame' call is made would be more of a 'Decrypt File' in this implementation. Just
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returning the original file in plain text defeats the point of the DRM. Even if 'Decrypt File' was somehow secure, the
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Content Keys used to decrypt the files are already exposed to the caller anyway, allowing them to manually decrypt.
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An attack on a 'Decrypt Frame' system would be analogous to doing an HDMI capture or similar attack. This is because it
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would require re-encoding the video by splicing each individual frame with the right frame-rate, syncing to audio, and
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more.
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While a 'Decrypt Video' system would be analogous to downloading a Video and passing it through a script. Not much of
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an attack if at all. The only protection against a system like this would be monitoring the provision and acquisitions
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of licenses and prevent them. This can be done by revoking the device provision, or the user or their authorization to
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the service.
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There isn't any immediate way to secure either Key or Decrypted information within a Python environment that is not
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Hardware backed. Even if obfuscation or some other form of Security by Obscurity was used, this is a Software-based
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Content Protection Module (in Python no less) with no hardware backed security. It would be incredibly trivial to break
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any sort of protection against retrieving the original video data.
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Though, it's not impossible. Google's Chrome Browser CDM is a simple library extension file programmed in C++ that has
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been improving its security using math and obscurity for years. It's getting harder and harder to break with its latest
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versions only being beaten by Brute-force style methods. However, they have a huge team of very skilled workers, and
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making a CDM in C++ has immediate security benefits and a lot of methods to obscure and obfuscate the code.
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## License
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[GNU General Public License, Version 3.0](LICENSE)
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