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feat: parse key attributes for Widevine HLS #88

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merged 3 commits into from
Jun 25, 2019
Merged

feat: parse key attributes for Widevine HLS #88

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d035bae
parse new key attributes for Widevine HLS support
alex-barstow Jun 20, 2019
4512442
edit comment
alex-barstow Jun 20, 2019
a2de055
edit comment, add link to Widevine/HLS spec, add tests
alex-barstow Jun 21, 2019
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53 changes: 53 additions & 0 deletions src/parser.js
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
import Stream from './stream';
import LineStream from './line-stream';
import ParseStream from './parse-stream';
import decodeB64ToUint8Array from './utils/decode';

/**
* A parser for M3U8 files. The current interpretation of the input is
Expand Down Expand Up @@ -49,6 +50,9 @@ export default class Parser extends Stream {
'CLOSED-CAPTIONS': {},
'SUBTITLES': {}
};
// This is the Widevine UUID from DASH IF IOP. The same exact string is
// used in MPDs with Widevine encrypted streams.
const widevineUuid = 'urn:uuid:edef8ba9-79d6-4ace-a3c8-27dcd51d21ed';
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this is from the spec?

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@misteroneill misteroneill Jun 20, 2019 •
edited
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Yeah, I had the same question. It's in the spec doc... 🤷‍♂

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Yep, and the same string is used for mpds (see mpd-parser)

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Might be useful to add a comment and link to the widevine hls extension spec

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@misteroneill misteroneill Jun 20, 2019 •
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I know nothing about this really, but is this a universally valid UUID?
Answered my own question.

// group segments into numbered timelines delineated by discontinuities
let currentTimeline = 0;

Expand Down Expand Up @@ -143,6 +147,55 @@ export default class Parser extends Stream {
});
return;
}

// check if the content is encrypted for Widevine
// Widevine/HLS spec: https://storage.googleapis.com/wvdocs/Widevine_DRM_HLS.pdf
if (entry.attributes.KEYFORMAT === widevineUuid) {
const VALID_METHODS = ['SAMPLE-AES', 'SAMPLE-AES-CTR', 'SAMPLE-AES-CENC'];

if (VALID_METHODS.indexOf(entry.attributes.METHOD) === -1) {
this.trigger('warn', {
message: 'invalid key method provided for Widevine'
});
return;
}

if (entry.attributes.METHOD === 'SAMPLE-AES-CENC') {
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This case is fine just deprecated?

Maybe we should group the ones that exit early?

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Just logging a warning should be fine. The spec didn't replace 'SAMPLE-AES-CENC' with 'SAMPLE-AES-CTR' all that long ago so there's likely still a good amount of content out there using the former. I could group the early exits together, but that would require separating the two METHOD validation blocks. I don't feel strongly either way.

this.trigger('warn', {
message: 'SAMPLE-AES-CENC is deprecated, please use SAMPLE-AES-CTR instead'
});
}

if (entry.attributes.URI.substring(0, 23) !== 'data:text/plain;base64,') {
this.trigger('warn', {
message: 'invalid key URI provided for Widevine'
});
return;
}

if (!(entry.attributes.KEYID && entry.attributes.KEYID.substring(0, 2) === '0x')) {
this.trigger('warn', {
message: 'invalid key ID provided for Widevine'
});
return;
}

// if Widevine key attributes are valid, store them as `contentProtection`
// on the manifest to emulate Widevine tag structure in a DASH mpd
this.manifest.contentProtection = {
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should we call this out specifically as widevine since it isn't standard hls?

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I guess the mpd parser calls it this as well?

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You mean renaming contentProtection to widevine? We could, but that would require an additional change in VHS (and perhaps elsewhere), which already expects contentProtection. Calling it contentProtection maintains greater parity with mpd-parser.

'com.widevine.alpha': {
attributes: {
schemeIdUri: entry.attributes.KEYFORMAT,
// remove '0x' from the key id string
keyId: entry.attributes.KEYID.substring(2)
},
// decode the base64-encoded PSSH box
pssh: decodeB64ToUint8Array(entry.attributes.URI.split(',')[1])
}
};
return;
}

if (!entry.attributes.METHOD) {
this.trigger('warn', {
message: 'defaulting key method to AES-128'
Expand Down
11 changes: 11 additions & 0 deletions src/utils/decode.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
import window from 'global/window';

export default function decodeB64ToUint8Array(b64Text) {
const decodedString = window.atob(b64Text || '');
const array = new Uint8Array(decodedString.length);

for (let i = 0; i < decodedString.length; i++) {
array[i] = decodedString.charCodeAt(i);
}
return array;
}
111 changes: 111 additions & 0 deletions test/m3u8.test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -896,6 +896,7 @@ QUnit.test('parses prefixed with 0x or 0X #EXT-X-KEY:IV tags', function(assert)
0x90abcdef
]), 'parsed an IV value with 0X');
});

// #EXT-X-START
QUnit.test('parses EXT-X-START tags', function(assert) {
const manifest = '#EXT-X-START:TIME-OFFSET=1.1\n';
Expand Down Expand Up @@ -1173,6 +1174,116 @@ QUnit.test('parses FORCED attribute', function(assert) {
'parsed FORCED attribute');
});

QUnit.test('parses Widevine #EXT-X-KEY attributes and attaches to manifest', function(assert) {
const parser = new Parser();

const manifest = [
'#EXTM3U',
'#EXT-X-KEY:METHOD=SAMPLE-AES-CTR,' +
'URI="data:text/plain;base64,AAAAPnBzc2gAAAAA7e+LqXnWSs6jyCfc1R0h7QAAAB4iFnN' +
'oYWthX2NlYzJmNjRhYTc4OTBhMTFI49yVmwY=",KEYID=0x800AACAA522958AE888062B5695DB6BF,' +
'KEYFORMATVERSIONS="1",KEYFORMAT="urn:uuid:edef8ba9-79d6-4ace-a3c8-27dcd51d21ed"',
'#EXTINF:5,',
'ex1.ts',
'#EXT-X-ENDLIST'
].join('\n');

parser.push(manifest);

assert.ok(parser.manifest.contentProtection, 'contentProtection property added');
assert.equal(
parser.manifest.contentProtection['com.widevine.alpha'].attributes.schemeIdUri,
'urn:uuid:edef8ba9-79d6-4ace-a3c8-27dcd51d21ed',
'schemeIdUri set correctly'
);
assert.equal(
parser.manifest.contentProtection['com.widevine.alpha'].attributes.keyId,
'800AACAA522958AE888062B5695DB6BF',
'keyId set correctly'
);
assert.equal(
parser.manifest.contentProtection['com.widevine.alpha'].pssh.byteLength,
62,
'base64 URI decoded to TypedArray'
);
});

QUnit.test('Widevine #EXT-X-KEY attributes not attached to manifest if METHOD is invalid', function(assert) {
const parser = new Parser();

const manifest = [
'#EXTM3U',
'#EXT-X-KEY:METHOD=NONE,' +
'URI="data:text/plain;base64,AAAAPnBzc2gAAAAA7e+LqXnWSs6jyCfc1R0h7QAAAB4iFnN' +
'oYWthX2NlYzJmNjRhYTc4OTBhMTFI49yVmwY=",KEYID=0x800AACAA522958AE888062B5695DB6BF,' +
'KEYFORMATVERSIONS="1",KEYFORMAT="urn:uuid:edef8ba9-79d6-4ace-a3c8-27dcd51d21ed"',
'#EXTINF:5,',
'ex1.ts',
'#EXT-X-ENDLIST'
].join('\n');

parser.push(manifest);

assert.notOk(parser.manifest.contentProtection, 'contentProtection not added');
});

QUnit.test('Widevine #EXT-X-KEY attributes not attached to manifest if URI is invalid', function(assert) {
const parser = new Parser();

const manifest = [
'#EXTM3U',
'#EXT-X-KEY:METHOD=SAMPLE-AES-CTR,' +
'URI="AAAAPnBzc2gAAAAA7e+LqXnWSs6jyCfc1R0h7QAAAB4iFnN' +
'oYWthX2NlYzJmNjRhYTc4OTBhMTFI49yVmwY=",KEYID=0x800AACAA522958AE888062B5695DB6BF,' +
'KEYFORMATVERSIONS="1",KEYFORMAT="urn:uuid:edef8ba9-79d6-4ace-a3c8-27dcd51d21ed"',
'#EXTINF:5,',
'ex1.ts',
'#EXT-X-ENDLIST'
].join('\n');

parser.push(manifest);

assert.notOk(parser.manifest.contentProtection, 'contentProtection not added');
});

QUnit.test('Widevine #EXT-X-KEY attributes not attached to manifest if KEYID is invalid', function(assert) {
const parser = new Parser();

const manifest = [
'#EXTM3U',
'#EXT-X-KEY:METHOD=SAMPLE-AES-CTR,' +
'URI="data:text/plain;base64,AAAAPnBzc2gAAAAA7e+LqXnWSs6jyCfc1R0h7QAAAB4iFnN' +
'oYWthX2NlYzJmNjRhYTc4OTBhMTFI49yVmwY=",KEYID=800AACAA522958AE888062B5695DB6BF,' +
'KEYFORMATVERSIONS="1",KEYFORMAT="urn:uuid:edef8ba9-79d6-4ace-a3c8-27dcd51d21ed"',
'#EXTINF:5,',
'ex1.ts',
'#EXT-X-ENDLIST'
].join('\n');

parser.push(manifest);

assert.notOk(parser.manifest.contentProtection, 'contentProtection not added');
});

QUnit.test('Widevine #EXT-X-KEY attributes not attached to manifest if KEYFORMAT is not Widevine UUID', function(assert) {
const parser = new Parser();

const manifest = [
'#EXTM3U',
'#EXT-X-KEY:METHOD=SAMPLE-AES-CTR,' +
'URI="data:text/plain;base64,AAAAPnBzc2gAAAAA7e+LqXnWSs6jyCfc1R0h7QAAAB4iFnN' +
'oYWthX2NlYzJmNjRhYTc4OTBhMTFI49yVmwY=",KEYID=0x800AACAA522958AE888062B5695DB6BF,' +
'KEYFORMATVERSIONS="1",KEYFORMAT="invalid-keyformat"',
'#EXTINF:5,',
'ex1.ts',
'#EXT-X-ENDLIST'
].join('\n');

parser.push(manifest);

assert.notOk(parser.manifest.contentProtection, 'contentProtection not added');
});

QUnit.module('m3u8s');

QUnit.test('parses static manifests as expected', function(assert) {
Expand Down