How to decrypt AES-128 encrypted m3u8 video files?

问题:

I trying to decrypt AES-128 encrypted m3u8 video files such as this one :

the m3u8 file :

#EXTM3U
#EXT-X-MEDIA-SEQUENCE:0
#EXT-X-ALLOW-CACHE:NO
#EXT-X-VERSION:2
#EXT-X-FAXS-CM:MII6lAYJKoZIhvcNAQcCoII6hTCCOoECAQExCzAJBgUrDgMCGgUAM... very long key...
#EXT-X-KEY:METHOD=AES-128,URI="faxs://faxs.adobe.com",IV=0X99b74007b6254e4bd1c6e03631cad15b
#EXT-X-TARGETDURATION:8
#EXTINF:8,
video.mp4Frag1Num0.ts
#EXTINF:8,
video.mp4Frag1Num1.ts
...

I've tried with openssl :

openssl aes-128-cbc -d -kfile key.txt -iv 99b74007b6254e4bd1c6e03631cad15b -nosalt -in video_enc.ts -out video_dec.ts

key.txt contains the very long key -->

bad decrypt
1074529488:error:06065064:digital envelope routines:EVP_DecryptFinal_ex:bad decrypt:evp_enc.c:539:

What am-I doing wrong ?

回答1:

In order to decrypt encrypted video stream you need encryption key. This key is not part of the stream. It should be obtained separately.

EXT-X-FAXS-CM header contains DRM meta-data and not the key.

This is excert from Adobe Media Server developer guide: The Adobe Access Server protected variant playlist also needs to include the #EXT-X-FAXS-CM tag. The value of #EXT-X-FAXS-CM tag in variant playlist is the relative URI referring to the DRM metadata of one of the individual streams.At the client, the #EXT-X-FAXS-CM tag in variant playlist will be used to create the DRM session. The same DRM session will be used for all encrypted M3U8 files inside the variant playlist.

Full guide can be found here: http://help.adobe.com/en_US/adobemediaserver/devguide/WS5262178513756206-4b6aabd1378392bb59-7fe8.html

There is also mention that faxs://faxs.adobe.com URI is for local key serving. So key obtained locally from a device.

回答2:

This might be a bit of a hack, but given a URL to an .m3u8 file, it will download and decrypt the files that make up the stream:

#!/usr/bin/env bash
curl "$1" -s | awk 'BEGIN {c=0} $0 ~ "EXT-X-KEY" {urlpos=index($0,"URI=")+5; ivpos=index($0,"IV="); keyurl=substr($0, urlpos, ivpos-urlpos-2); iv=substr($0, ivpos+5); print "key=`curl -s '\''"keyurl"'\'' | hexdump -C | head -1 | sed \"s/00000000//;s/|.*//;s/ //g\"`"; print "iv="iv} $0 !~ "-KEY" && $0 ~ "http" {printf("curl -s '\''"$0"'\'' | openssl aes-128-cbc -K $key -iv $iv -d >seg%05i.ts\n", c++)}' | bash

This script generates a second script that extracts keys and initialization vectors and uses them to decrypt while downloading. It needs curl, awk, hexdump, sed, and openssl to run. It'll probably choke on an unencrypted stream, or on a stream that uses something other than AES-128 (is any other encryption supported?).

You'll get a bunch of files: seg00000.ts, seg00001.ts, etc. Use tsMuxeR (https://www.videohelp.com/software/tsMuxeR) to merge these into a single file (simple concatenation didn't work for me...it's what I tried first):

(echo "MUXOPT --no-pcr-on-video-pid --new-audio-pes --vbr  --vbv-len=500"; (echo -n "V_MPEG4/ISO/AVC, "; for i in seg*.ts; do echo -n "\"$i\"+"; done; echo ", fps=30, insertSEI, contSPS, track=258") | sed "s/+,/,/"; (echo -n "A_AAC, "; for i in seg*.ts; do echo -n "\"$i\"+"; done; echo ", track=257") | sed "s/+,/,/") >video.meta
tsMuxeR video.meta video.ts

(Track IDs and framerate may need adjustment...get the values to use by passing one of the downloaded files to tsMuxeR.)

Then use ffmpeg to remux to something a bit more widely understood:

ffmpeg -i video.ts -vcodec copy -acodec copy video.m4v

回答3:

Even through this file includes AES encrypted data, openssl don't know the m3u8 format. However FFmpeg might be able to handle it.

回答4:

While some of the bash scripts in the existing answers get you part (or even all) of the way, depending which site you're trying to download from, you might hit other obstacles (different auth method, custom license server mount, etc.)

I've found streamlink to be the most robust solution for this, which also lets you stream directly (rather than download), if that's what you're after, and it has all the site-specific work already done for you for a long list of sites (see plugins section, but keep in mind it's under active development and the latest release was in June, so for some of the newer ones you'll have to git clone and install from source).