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Gracefully handle invalid EBML headers

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This commit is contained in:
Vanilagy
2025-08-13 09:46:27 +02:00
parent 7e546c2cc7
commit 16c8a6c255
2 changed files with 63 additions and 13 deletions
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src/matroska/ebml.ts
+25 -6
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@@ -379,7 +379,7 @@ export class EBMLWriter {
const MAX_VAR_INT_SIZE = 8;
export const MIN_HEADER_SIZE = 2; // 1-byte ID and 1-byte size
export const MAX_HEADER_SIZE = 4 + MAX_VAR_INT_SIZE; // 4-byte ID and 8-byte size
export const MAX_HEADER_SIZE = 2 * MAX_VAR_INT_SIZE; // 8-byte ID and 8-byte size
export class EBMLReader {
pos = 0;
@@ -411,9 +411,13 @@ export class EBMLReader {
const { view, offset } = this.reader.getViewAndOffset(this.pos, this.pos + 1);
const firstByte = view.getUint8(offset);
if (firstByte === 0) {
return null; // Invalid VINT
}
let width = 1;
let mask = 0x80;
while ((firstByte & mask) === 0 && width < 8) {
while ((firstByte & mask) === 0) {
width++;
mask >>= 1;
}
@@ -426,10 +430,14 @@ export class EBMLReader {
const { view, offset } = this.reader.getViewAndOffset(this.pos, this.pos + 1);
const firstByte = view.getUint8(offset);
if (firstByte === 0) {
return null; // Invalid VINT
}
// Find the position of VINT_MARKER, which determines the width
let width = 1;
let mask = 1 << 7;
while ((firstByte & mask) === 0 && width < MAX_VAR_INT_SIZE) {
while ((firstByte & mask) === 0) {
width++;
mask >>= 1;
}
@@ -509,8 +517,11 @@ export class EBMLReader {
readElementId() {
const size = this.readVarIntSize();
const id = this.readUnsignedInt(size);
if (size === null) {
return null;
}
const id = this.readUnsignedInt(size);
return id;
}
@@ -538,6 +549,10 @@ export class EBMLReader {
readElementHeader() {
const id = this.readElementId();
if (id === null) {
return null;
}
const size = this.readElementSize();
return { id, size };
@@ -548,13 +563,17 @@ export class EBMLReader {
const loadChunkSize = 2 ** 20; // 1 MiB
const idsSet = new Set(ids);
while (this.pos < until - MAX_HEADER_SIZE) {
if (!this.reader.rangeIsLoaded(this.pos, this.pos + MAX_HEADER_SIZE)) {
while (this.pos <= until - MIN_HEADER_SIZE) {
if (!this.reader.rangeIsLoaded(this.pos, Math.min(this.pos + MAX_HEADER_SIZE, until))) {
await this.reader.loadRange(this.pos, Math.min(this.pos + loadChunkSize, until));
}
const elementStartPos = this.pos;
const elementHeader = this.readElementHeader();
if (!elementHeader) {
break;
}
if (idsSet.has(elementHeader.id)) {
return elementStartPos;
}