Bug 309534 – CDMSessionAVContentKeySession::isAnyKeyUsable should check that content key is available

• Status: RESOLVED
• Resolution: FIXED
• Component: Media

[Ruthvik Konda]

`CDMSessionAVContentKeySession::attachContentKeyToSample()` crashes with a debug ASSERT when `[contentKeyRequest() contentKey]` returns nil.

The legacy CDM session's `isAnyKeyUsable()` returns true when key IDs from the `AVContentKeyRequest` match the sample's key IDs, but does not verify that `[request contentKey]` is non-nil.  This allows samples to proceed through `canEnqueueSample()` and reach `attachContentKeyToSample()` before AVFoundation has finished deriving the content key (via `processContentKeyResponse:`).

The modern code path (`CDMInstanceSessionFairPlayStreamingAVFObjC::attachContentKeyToSample`) already handles nil `contentKey` gracefully via an early return.

Stack trace:
0   com.apple.WebCore:  WTFCrashWithInfo
1   com.apple.WebCore:  CDMSessionAVContentKeySession::attachContentKeyToSample
2   com.apple.WebCore:  AudioVideoRendererAVFObjC::attachContentKeyToSampleIfNeeded
3   com.apple.WebCore:  AudioVideoRendererAVFObjC::enqueueSample
4   com.apple.WebKit:  RemoteAudioVideoRendererProxyManager::enqueueSample
[...]

<rdar://171478431>

[Ruthvik Konda]

Pull request: https://github.com/WebKit/WebKit/pull/60234

[EWS]

Committed 309033@main (ec2a9eedd035): <https://commits.webkit.org/309033@main>

Reviewed commits have been landed. Closing PR #60234 and removing active labels.