Adding AES-256 and AES-256-CTR encryption methods

[jvary]

Description

Adding AES-256 and AES-256-CTR encryption methods (full segment, as AES-128)

Context

Need stronger encryption scheme than AES-128 for CCTV scenario, in the short-mid term.

See more context & informal addendum to rfc8216 at :
https://mailarchive.ietf.org/arch/msg/hls-interest/RZBgatOvI4W0M0J5cShuXWzdigg/

Are there any points in the code the reviewer needs to double check?

• I have very little experience in JavaScript/TypeScript, please assume that everything is wrong language wise :-)
• Error handling
• Everything crypto related

Limitations

• Does not enforce the presence of explicit IV in AES-256 & AES-256-CTR (when the rfc informal proposal stated they SHALL be present, and different for each segment).
• AES-256 & AES-256-CTR will only work with WebCrypto, not the JavaScript implementation.
• Range access ‘adjustment’ is not implemented for CTR mode (don’t re-compute nonce counter based on block offset)

Checklist

• changes have been done against master branch, and PR does not conflict
• new unit / functional tests have been added (whenever applicable)
• API or design changes are documented in API.md
  - Not an official change yet?

[jvary]

Test playlist can be found here:

https://jvaryhlstests.blob.core.windows.net/hlstestdata/playlist_encrypted.m3u8
(can't commit it to integration test, because default still software decryption, which will not work)

[avelad]

Note: This functionality has already been added to ShakaPlayer and will appear in version 5.0

[robwalch]

(can't commit it to integration test, because default still software decryption, which will not work)

• Depends on Use WebCrypto by default for AES decryption #6015

Please rebase once #6015 is merged.

[robwalch]

@jvary, #6015 has been merged. Thanks for waiting.

[jvary]

@jvary, #6015 has been merged. Thanks for waiting.

@robwalch : rebased and added playlist in integration.