From 5f4358573fb9436aa1278c8100704d8098b63987 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?netop=3A//=E3=82=A6=E3=82=A8=E3=83=8F?= <1288356+NetOperatorWibby@users.noreply.github.com> Date: Tue, 20 Oct 2020 12:10:17 -0500 Subject: [PATCH] Proofreading and copy edits --- README.md | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/README.md b/README.md index a2727be..e09d176 100644 --- a/README.md +++ b/README.md @@ -1,28 +1,33 @@ # Widevine L3 Decryptor -[Widevine](https://www.widevine.com/solutions/widevine-drm) is a Google-Owned DRM system that's in use by many popular streaming services (Netflix, Spotify, ...) to protect media contnet from being downloaded. +[Widevine](https://www.widevine.com/solutions/widevine-drm) is a Google-owned DRM system that's in use by many popular streaming services (Netflix, Spotify, &c) to prevent media content from being downloaded. But Widevine's least secure security level, L3, as used in most browsers and PCs, is implemented 100% in software (i.e no hardware TEEs), thereby making it reversible and bypassable. -This Chrome extension demonstates how it's possible to bypass Widevine DRM by hijacking calls to the browser's [Encrypted Media Extensions (EME)](https://www.html5rocks.com/en/tutorials/eme/basics/) and decrypting all Widevine content keys transferred - effectively turning it into a clearkey DRM. +This Chrome extension demonstates how it's possible to bypass Widevine DRM by hijacking calls to the browser's [Encrypted Media Extensions (EME)](https://www.html5rocks.com/en/tutorials/eme/basics) and decrypting all Widevine content keys transferred - effectively turning it into a clearkey DRM. ## Usage -To see this concept in action, just load the extnesion in developer mode and browse to any website that plays Widevine-protected content, such as https://bitmovin.com/demos/drm. +To see this concept in action, just load the extension in Developer Mode and browse to any website that plays Widevine-protected content, such as https://bitmovin.com/demos/drm. -Keys will be logged in plaintext to the javascript console: +Keys will be logged in plaintext to the javascript console. -`WidevineDecryptor: Found key: 100b6c20940f779a4589152b57d2dacb (KID=eb676abbcb345e96bbcf616630f1a3da) -` +e.g: + +``` +WidevineDecryptor: Found key: 100b6c20940f779a4589152b57d2dacb (KID=eb676abbcb345e96bbcf616630f1a3da) +``` Decrypting the media itself is then just a matter of using a tool that can decrypt MPEG-CENC streams, like `ffmpeg`. e.g: -`ffmpeg -decryption_key 100b6c20940f779a4589152b57d2dacb -i encrypted_media.mp4 -codec copy decrypted_media.mp4` +``` +ffmpeg -decryption_key 100b6c20940f779a4589152b57d2dacb -i encrypted_media.mp4 -codec copy decrypted_media.mp4 +``` ## How In the context of browsers the actual decryption of the media is usually done inside a proprietary binary (`widevinecdm.dll`, known as the Content Decryption Module or CDM) only after receiving the license from a license server with an encrypted key in it. -This binary is usually heavily obfuscated and makes use of third-party solutions that claim to offer software "protection" such as [Arxan](https://digital.ai/application-protection) or [Whitecryption](https://www.intertrust.com/products/application-shielding/). +This binary is usually heavily obfuscated and makes use of third-party solutions that claim to offer software "protection" such as [Arxan](https://digital.ai/application-protection) or [Whitecryption](https://www.intertrust.com/products/application-shielding). Some reversing job on that binary can then be done to extract the secret keys and mimic the key decryption algorithm from the license response. @@ -30,5 +35,4 @@ Some reversing job on that binary can then be done to extract the secret keys an This PoC was done to further show that code obfuscation, anti-debugging tricks, whitebox cryptography algorithms and other methods of security-by-obscurity will eventually by defeated anyway, and are, in a way, pointless. ## Legal Desclaimer -This is for educational purposes only. Downloading copyrighted matirials from streaming services may violate their Terms Of Service. Use at your own risk. - +This is for educational purposes only. Downloading copyrighted materials from streaming services may violate their Terms of Service. **Use at your own risk.**