[SOLVED] AES-128 encryption using a DASH MPD manifest file

[StanP]

Hi there

I need help understanding how to decrypt a video. (all URLs at the end)

My original question was here, but larley (thanks) suggested in his answer that this was a (I quote) "rare occurence of AES-128 encryption using a DASH manifest file", and I should start a new thread.

I updated the steps and details below according to some additional things I tried out after his answer. But I still can't figure out how to finalise this.

What I've done so far :

- found the MPD url and downloaded the manifest XML.

- Also downloaded the desired (encrypted) audio and video streams using yt-dlp (also tried dash-mpd-cli, both worked).
These are already sitting on my disk now and need to be decrypted.
Or maybe they need to be decrypted as chunks while being downloaded, I don't know (and wouldn't know how to do that).

- didn't find any PSSH nor explicit licence url, so I just tried out some random things :
I went to cdrm-project.com and entered the url found at "keyUriTemplate" in the manifest XML (first one for audio, along with its kid param.) and some headers that I could make out, leaving the PSSH field blank.

Upon "Send" it returned :

Cached PSSH

PSSH:

Time:Wed Jan 3 17:08:02 2024

    b8d35746ec9e9f5c3ebfc5ec945ebf42:78531faef00ddfcf9dfe029812c9f40f

First I tried to use this as a decryption id:key pair with mp4decrypt it didn't work (didn't get any error, but a 0 byte output file).

Then, since larley pointed out that it could be AES-128, I searched the forum a bit and found a thread explaining how to find the key in browser's dev tools (it was about a HLS stream but I just followed the key part).

So I looked for requests to the "key delivery" URL and their responses.
This is what I found (sorry french UI) :

[Attachment 78373 - Click to enlarge]

Converted to HEX :

Base64: 9CrjgG+fUx2fsUlmCQ7gTQ==
HEX: f42ae3806f9f531d9fb14966090ee04d

I then tried different id:key combinations with mp4decrypt, to no avail. (again, either "wrong id (or key)" error, or no error but 0 byte output file)

If someone could just give the last hint(s) I'm missing that would be greatly appreciated.


Video URL (public access) :
https://community.claris.com/en/s/engage/claris-engage-recordings?vtui__catalogId=a5NV...y0000000EB3MAM

MPD URL :
https://appiniummediacentralusa-usct.streaming.media.azure.net/02f4acb1-7193-422d-8d0f...ncryption=cbc)

Headers I used on cdrm-project :

accept: "*/*"
Accept-Language: "fr,fr-FR;q=0.8,en-US;q=0.5,en;q=0.3"
Accept-Encoding: "gzip, deflate, br"
Origin: "https://community.claris.com"
Connection: keep-alive
Referer: "https://community.claris.com"
Sec-Fetch-Dest: empty
Sec-Fetch-Mode: cors
Sec-Fetch-Site: cross-site

[2nHxWW6GkN1l916N3ayz8HQoi]

This has nothing to do with DRM. It's just plain old AES-128 only disguised as a mpd manifest. It surprised me that N_m3u8 fails at this just because it's not m3u8. Here's your video, subtitles included:
https://www.transfernow.net/dl/20240414SWWWir6A

[StanP]

OK thousand thanks for that but could you please explain what you did, exactly ?

I realise I stated in my original post that "I was a complete newb to this" but didn't repeat it here.

I have no idea how to grab "plain old AES-128 only disguised as a mpd manifest" as you put it.
If you could just direct me to where I could find the info here, that would be great.

Firslty because there's a few other videos I want to grab from that source, and I'd rather do it by myself and second because I'm very much interested in understanding the process.

[2nHxWW6GkN1l916N3ayz8HQoi]

could you please explain what you did

Well, as I told you: "N_m3u8 fails at this just because it's not m3u8". So why not build your own local m3u8? Keep in mind, I dunno if there is some hidden m3u8 provided by them already. I tried editing some variables in that mpd path of yours with no luck.

First, download the encrypted content using their manifest. You do not want to decrypt them using N_m3u8 or merge them. Make sure you grab your wanted quality for both audio/video since we'll be working with that.

N_m3u8DL-RE.exe https://appiniummediacentralusa-usct.streaming.media.azure.net/02f4acb1-7193-422d-8d0f-a8b2f5cd36d2/9f891697-3e16-4a91-8e3a-73392daf.ism/manifest(format=mpd-time-csf,encryption=cbc) --skip-merge

In the N_m3u8 output folder you're gonna have 2 folders containing the fragments for video and audio separated. Rename the 2 folders with their long names to simply audio or video. In the new video folder rename _init.mp4 to 0000a.mp4 and 0000.m4s to 0000b.m4s . Do the same for audio.

Before we move on we're gonna need 2 important things to decrypt hls aes 128: the key and the iv. The key you already found and we'll be using the hex value:

So I looked for requests to the "key delivery" URL and their responses.
This is what I found (sorry french UI) :

[Attachment 78373 - Click to enlarge]

Converted to HEX :

Base64: 9CrjgG+fUx2fsUlmCQ7gTQ==
HEX: f42ae3806f9f531d9fb14966090ee04d

For the iv, download the mpd and save it as xml. Use VS Code or any other formatting tool to make it look neat. Then in it, you'll find:

<sea:CryptoPeriod keyUriTemplate="https://appiniummediacentralusa.keydelivery.centralus.media.azure.net/?kid=f7f79bd5-91a2-4747-a61d-cee302b17c1b" IV="0x40E9F39B386D74F22185F092C7836FDE"/>

So the iv is 0x40E9F39B386D74F22185F092C7836FDE . Now we have the wanted content (but encrypted), the key, and the iv. Time to generate the most basic m3u8. I don't think you can even play it in VLC or any other media player, however, you only need it to be valid enough so that it can be parsed by N_m3u8. I coded a short script that does that. Put the script outside the video and audio folders and run it.

import os


def generate_m3u8(directory, iv_value):
    fragments = sorted([f for f in os.listdir(directory)])
    with open(f"{directory}.m3u8", "w") as f:
        f.write("#EXTM3U\n")
        f.write("#EXT-X-VERSION:3\n")
        f.write("#EXT-X-MEDIA-SEQUENCE:1\n")

        f.write(f'#EXT-X-KEY:METHOD=AES-128,URI="random_irrelevant_path",IV={iv_value}\n')
        for fragment in fragments:
            f.write(f"#EXTINF:0,\n")
            f.write(f"{directory}/{fragment}\n")
        f.write("#EXT-X-ENDLIST")


def generate_master_m3u8(video_dir, audio_dir):
    with open("master.m3u8", "w") as f:
        f.write(f"#EXTM3U\n")
        f.write(f"#EXT-X-STREAM-INF:BANDWIDTH=2\n{video_dir}.m3u8\n")
        f.write(f"#EXT-X-STREAM-INF:BANDWIDTH=1\n{audio_dir}.m3u8\n")


v_dir = "video"
a_dir = "audio"
iv_val = "0x40E9F39B386D74F22185F092C7836FDE"

generate_master_m3u8(v_dir, a_dir)
generate_m3u8(v_dir, iv_val)
generate_m3u8(a_dir, iv_val)

If you notice, the variable iv_val was initialized using the iv extracted from the MPD. Now, all it takes is running this final command. Make sure you check both boxes for video/audio tracks.

N_m3u8DL-RE.exe master.m3u8 --custom-hls-key f42ae3806f9f531d9fb14966090ee04d -M format=mkv

You can now delete the previously encrypted fragments and the generated m3u8s. The solution is boring, cheap, and very tedious. But I don't know any other way. I didn't care that much to actually search for a smarter way but I know there is definitely one. You should search for tools that can convert mpd manifests to m3u8s either locally or from a URL. Or N_m3u8 has some specific parameters that I don't know. Or if other tools can actually decrypt hls aes 128 if it's in an MPD manifest.

[Novia]

https://github.com/Tontonnow/N_m3u8DL-RE/actions/runs/8680287173

download this

key must set

N_m3u8DL-RE.exe https://appiniummediacentralusa-usct.streaming.media.azure.net/02f4acb1-7193-422d-8d0f-a8b2f5cd36d2/9f891697-3e16-4a91-8e3a-73392daf.ism/manifest(format=mpd-time-csf,encryption=cbc)  --custom-hls-key 9CrjgG+fUx2fsUlmCQ7gTQ== -M format=mkv

[Attachment 78378 - Click to enlarge]


[Attachment 78377 - Click to enlarge]

[white_snake]

Well, as I told you: "N_m3u8 fails at this just because it's not m3u8". So why not build your own local m3u8? Keep in mind, I dunno if there is some hidden m3u8 provided by them already. I tried editing some variables in that mpd path of yours with no luck.

Great write-up, as usual.

https://github.com/Tontonnow/N_m3u8DL-RE/actions/runs/8680287173

Following command worked perfectly, well done.

N_m3u8DL-RE.exe https://appiniummediacentralusa-usct.streaming.media.azure.net/02f4acb1-7193-422d-8d0f-a8b2f5cd36d2/9f891697-3e16-4a91-8e3a-73392daf.ism/manifest(format=mpd-time-csf,encryption=cbc) -M format=mkv --custom-hls-key f42ae3806f9f531d9fb14966090ee04d --custom-range 0-10

[mister_ nex]

https://github.com/Tontonnow/N_m3u8DL-RE/actions/runs/8680287173

Please tell me how to get N_m3u8DL-RE.exe
I can't find the link

[LittleSoldier]

https://github.com/Tontonnow/N_m3u8DL-RE/actions/runs/8680287173

Please tell me how to get N_m3u8DL-RE.exe
I can't find the link

Check in this Repo
1. https://github.com/nilaoda/N_m3u8DL-RE
2. https://github.com/Tontonnow/N_m3u8DL-RE/

Or Direct File
N_m3u8DL-RE.zip

[mister_ nex]

LittleSoldier
Thank you for the tip
Everything was found, I just didn’t look carefully

2nHxWW6GkN1l916N3ayz8HQoi
Му gratitude to you for, as always, an informative theoretical guide.

Novia
many thanks for the fork which can recognize AES-128 in DASH manifest file

[StanP]

https://github.com/Tontonnow/N_m3u8DL-RE/actions/runs/8680287173

download this

key must set

N_m3u8DL-RE.exe https://appiniummediacentralusa-usct.streaming.media.azure.net/02f4acb1-7193-422d-8d0f-a8b2f5cd36d2/9f891697-3e16-4a91-8e3a-73392daf.ism/manifest(format=mpd-time-csf,encryption=cbc)  --custom-hls-key 9CrjgG+fUx2fsUlmCQ7gTQ== -M format=mkv

Well, this doesn't work on my side, and actually I already tried it before. (not sure what you mean by "key must set" though)


[Attachment 78380 - Click to enlarge]

I'll try the method that doesn't merge the fragments asap and let you know.

Thanks to you all in the meantime.

[mister_ nex]

Well, this doesn't work on my side, and actually I already tried it before.

Use only this version of the program

https://github.com/Tontonnow/N_m3u8DL-RE/actions/runs/8680287173

you did it

INFO : Extracted, there are 5 streams, with 4 basic streams, 1 audio streams, 0 subtitle streams
INFO : Vid *CENC 1920x1080 | 3947 Kbps | 1_V_video_1 | avc1.640028 | 1898 Segments | ~01h03m14s
INFO : Vid *CENC 1280x720 | 3092 Kbps | 1_V_video_2 | avc1.64001F | 1898 Segments | ~01h03m14s
INFO : Vid *CENC 960x540 | 1392 Kbps | 1_V_video_3 | avc1.64001F | 1898 Segments | ~01h03m14s
INFO : Vid *CENC 640x360 | 937 Kbps | 1_V_video_4 | avc1.64001E | 1898 Segments | ~01h03m14s

but the program should recognize AES-128 instead of CENC

INFO : Extracted, there are 5 streams, with 4 basic streams, 1 audio streams, 0 subtitle streams
INFO : Vid *AES_128 1920x1080 | 3947 Kbps | 1_V_video_1 | avc1.640028 | 1898 Segments | ~01h03m14s
INFO : Vid *AES_128 1280x720 | 3092 Kbps | 1_V_video_2 | avc1.64001F | 1898 Segments | ~01h03m14s
INFO : Vid *AES_128 960x540 | 1392 Kbps | 1_V_video_3 | avc1.64001F | 1898 Segments | ~01h03m14s
INFO : Vid *AES_128 640x360 | 937 Kbps | 1_V_video_4 | avc1.64001E | 1898 Segments | ~01h03m14s

[StanP]

Well, this doesn't work on my side, and actually I already tried it before.

Use only this version of the program

https://github.com/Tontonnow/N_m3u8DL-RE/actions/runs/8680287173

Sorry if I'm being stupid here, but your link doesn't show any downloadable resource.

So I went for the latest release for that repo, that is N_m3u8DL-RE_Beta_win-x64_20240319.zip (found here )

If that's not the same version you're using, then I don't know where to find it.

I also tried with the 3 links provided by LittleSoldier.

No matter which version I try, the console shows

INFO : Vid *CENC 1920x1080 | 3947 Kbps...

(still didn't have time to try 2nHxWW6GkN1l916N3ayz8HQoi's solution, but I'm puzzled by the fact that mister_nex manages to do it with a plain N_m3u8DL-RE command and I can't...)

[StanP]

Well, this doesn't work on my side, and actually I already tried it before.

Use only this version of the program

https://github.com/Tontonnow/N_m3u8DL-RE/actions/runs/8680287173

never mind, I got the right exe, I wasn't logged in to github and the "artifacts" section at the bottom wasn't showing links...
I didn't know this behaviour !

Now with the right exe, AES-128 is correctly detected and the decryption / muxing works !

Thanks again to you all for your help, I was very close since the beginning, but was going in circles because not using the right versions of the tools...

[StanP]

Well, as I told you: "N_m3u8 fails at this just because it's not m3u8". So why not build your own local m3u8? Keep in mind, I dunno if there is some hidden m3u8 provided by them already. I tried editing some variables in that mpd path of yours with no luck.

[...]

I didn't thank you specifically for your very detailed answer and efforts, that was some brilliant workaround.

I guess I won't need it now though, with that version of N_m3u8DL-RE detecting AES-128 ...

[simplemen]

Can anyone help me, how to play mpd dash to ott player.. Any format to playlist. Please