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Support for Licenses with a 128-byte Session Key #20
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Could you send a License Response in Base64 for me to take a look? What version of Chrome are you on, and is it beta or stable? |
Sure, This is from the newest Chrome CDM version, pretty sure it was like that too on the previous version. Chrome version: 107.0.5304.88 and CDM: 4.10.2557.0 |
Yeah I can confirm that is only 128 bytes somehow. All Chrome CDMs v4.10.2449.0 and older do 256 bytes like normal. I wonder if v4.10.2540.0 is like this as well, as that reportedly uses the same private key. |
I think I also had seen this on 4.10.2449.0, is probably a slight different key request/response approach on Chrome only, I've only noticed it on Licenses generated by Chrome. The license request for this license was not crafted by me or using your project. But is an interesting change nevertheless. |
We aren't referring to the License, we are referring to the Session Key within the license.
This would be unrelated. You are likely not passing the correct value back to the CDM. Another user had this similar mistake see #25
You don't need to Base64 decode it, Pywidevine does that for you. |
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I've noticed that on Chrome license's responses, the session key which is normally 256 bytes long to match the length of the device private key, now is 128 bytes. It seems to suggest it is decrypted with a less secure private key (very unlikely) or the device private key is used elsewhere and differently.
I am not sure if I am missing anything or I am misunderstanding, but has this been noted or researched? or maybe this is on web based CDM's only? Padding the session key is not an option that works.
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