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feat(flv-demuxer): skip invalid tag by size check. #61

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feat(flv-demuxer): skip invalid tag by size check. #61

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51 changes: 37 additions & 14 deletions src/demux/flv-demuxer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -296,6 +296,7 @@ class FLVDemuxer {
offset += 4;
}

let lastValidOffset = offset;
while (offset < chunk.byteLength) {
this._dispatch = true;

Expand All @@ -309,18 +310,31 @@ class FLVDemuxer {
let tagType = v.getUint8(0);
let dataSize = v.getUint32(0, !le) & 0x00FFFFFF;

if (offset + 11 + dataSize + 4 > chunk.byteLength) {
// data not enough for parsing actual data body
break;
}

// unsupported tag? try to figure it out!
if (tagType !== 8 && tagType !== 9 && tagType !== 18) {
Log.w(this.TAG, `Unsupported tag type ${tagType}, skipped`);
// consume the whole tag (skip it)
offset += 11 + dataSize + 4;
// not possible for a tag. should be a wrong byte, skip.
if (offset + 11 + dataSize + 4 > chunk.byteLength) {
offset += 1;
continue;
}

const tagSize = v.getUint32(11 + dataSize, !le);
if (tagSize === 11 + dataSize) {
Log.w(this.TAG, `Consumed an unsupported tag with type ${tagType} of size ${dataSize}`);
offset += 11 + dataSize + 4;
continue;
}

// not a valid tag. should be a wrong byte, skip.
offset += 1;
continue;
}

// not enough for a tag, stop and wait.
if (offset + 11 + dataSize + 4 > chunk.byteLength) {
break;
}

let ts2 = v.getUint8(4);
let ts1 = v.getUint8(5);
let ts0 = v.getUint8(6);
Expand All @@ -330,7 +344,20 @@ class FLVDemuxer {

let streamId = v.getUint32(7, !le) & 0x00FFFFFF;
if (streamId !== 0) {
Log.w(this.TAG, 'Meet tag which has StreamID != 0!');
// invalid tag, should be skipped.
offset += 1;
continue;
}

let prevTagSize = v.getUint32(11 + dataSize, !le);
if (prevTagSize !== 11 + dataSize) {
// invalid tag, should skipped.
offset += 1;
continue;
}

if (lastValidOffset !== offset) {
Log.w(this.TAG, `Skipped ${offset - lastValidOffset} bytes of invalid data`);
}

let dataOffset = offset + 11;
Expand All @@ -347,12 +374,8 @@ class FLVDemuxer {
break;
}

let prevTagSize = v.getUint32(11 + dataSize, !le);
if (prevTagSize !== 11 + dataSize) {
Log.w(this.TAG, `Invalid PrevTagSize ${prevTagSize}`);
}

offset += 11 + dataSize + 4; // tagBody + dataSize + prevTagSize
lastValidOffset = offset;
}

// dispatch parsed frames to consumer (typically, the remuxer)
Expand Down