Help with wv decryption

[ohadk84]

Hi,
Having issue decrypting license data.
I'm able to receive the license data from the server (after providing correct headers and fresh authorization code) but the data cannot be decrypted.
the format I'm receiving is:

{
"licenseData": [
"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxx="
],
"keyData": [
{
"keyID": "A99D7A68D53139CA3CBC693B1C52A810",
"startTime": "2024-01-18T00:00:00Z",
"endTime": "2025-01-17T00:00:00Z",
"eventId": "54"
}
],
"identityCookie": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx ==",
"idCookieExpiration": "2024-05-12T19:41:39Z",
"domainID": "xxxxxxxxxxxx",
"deviceID": "xxxxxxxxxxxxx",
"householdRef": "xxxxxx",
"keysHorizon": "2024-02-13T03:41:39Z"
}

(hidden the personal data with xxxx)

I'm using my own CDM but when trying to decrypt the 'licenseData' value with:
wvdecrypt.update_license(license_b64)

I get: "Incorrect decryption."

when running l3.py (with some necassary modification) I get:
license response status: <Response [200]>

unable to parse license - check protobufs

Would appreciate any help.
Thanks.

[ElCap]

did you replace the license challenge in the request with your own?
are you sure that youre extracting the licenseData value properly?
print out license_b64 and it should be CAIS....

[ohadk84]

I have seen that the license challange always remains the same in this video. the Authorization Token is being changed so I took a fresh one.

[ElCap]

The license challenge is generated from your cdm so unless you have the private key for Chrome cdm you won't be able to decrypt the license response from the browsers license challenge. You need to generate the license challenge from your cdm and replace the one in the request data.

[ohadk84]

actually its a mobile app, not available on pc browser.
so how do I get my own license challenge? can you explain a bit?

[ElCap]

assuming that youre using wks-keys and the challenge in the request is in base64 format heres the line that you need to generate the challenge

challenge_b64 = base64.b64encode(wvdecrypt.get_challenge()).decode('utf-8')

then you need insert it into the right spot of the request data


Check out the stickied threads - they have a lot of info

[ohadk84]

you mean the cdm files from Frida? device_private_key and device_client_id_blob? I have them.
but how do I send it as a license challenge? l3.py should do it automatically?
btw, I took these keys from a different device than the one I copied the request details from if it matters.

[ElCap]

sorry i edited my response above as i re-read your original post where you have your cdm files

[ohadk84]

assuming that youre using wks-keys and the challenge in the request is in base64 format heres the line that you need to generate the challenge

challenge_b64 = base64.b64encode(wvdecrypt.get_challenge()).decode('utf-8')

then you need insert it into the right spot of the request data


Check out the stickied threads - they have a lot of info

WOW! you are a life saver! it worked! thanks a lot!!!