ID3 metadata COMM frame with size<4 decoding error

[ZuZuK]

Issue description

I found some *.mp3 tracks where ID3 metadata contains COMM frame with frameSize=1. In that case Id3Decoder throws NegativeArraySizeException on parsing such frame.
As I understand it's not illegal to set such data into COMM so player can just skip such frame as it's frameSize is only 1 byte. Other players have no problems with playing such files.

Reproduction steps

Just play track with such metadata

Link to test content

https://www.dropbox.com/s/qdsxgi8s462jql9/BAD_COMM_SAMPLE.mp3?dl=0

Version of ExoPlayer being used

2.3.1

Device(s) and version(s) of Android being used

Any device. I've tested on Emulator 6.0 and on Google Pixel 7.1.2

A full bug report captured from the device

Exo code problem and possible fix

This bug occurs because according to ID3 specification COMM frame should contains encoding byte and then language iso (3 bytes). So ID3Decoder (in method decodeCommentFrame) gets byte for encoding, then gets 3 bytes for language iso even if frameSize is less than 4 bytes. Then it is creating byte-array with size=frameSize-4. Then it crashes obviously.

My possible fix is to modify COMM frame decoding condition into ID3Decoder.decodeFrame

from

else if (frameId0 == 'C' && frameId1 == 'O' && frameId2 == 'M'
          && (frameId3 == 'M' || majorVersion == 2)) {
        frame = decodeCommentFrame(id3Data, frameSize);
      }

to

else if (frameId0 == 'C' && frameId1 == 'O' && frameId2 == 'M'
          && (frameId3 == 'M' || majorVersion == 2) && frameSize > 4) {
        frame = decodeCommentFrame(id3Data, frameSize);
      }

but maybe it's better to modify CommentFrame to contains some default language and empty content for example. don't know...

maybe it makes sense to check every frame on it's minimum frameSize to prevent such crashes in other frames decoding code

[ojw28]

Fixed in dev-v2.