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check for cycles during indirect reference resolution (#1097)

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Co-authored-by: Jan Sutter <jan@suttermail.de>
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jan-sutter 2025-07-20 18:12:55 +02:00 committed by GitHub
parent 3b318e1944
commit e636212ec8
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GPG Key ID: B5690EEEBB952194
1 changed files with 19 additions and 10 deletions
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29
src/UglyToad.PdfPig/PdfExtensions.cs
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@ -66,7 +66,7 @@
{
var filter = filters[i];
totalMaxEstSize *= GetEstimatedSizeMultiplier(filter);
transform = filter.Decode(transform, stream.StreamDictionary, filterProvider, i);
if (i < filters.Count - 1 && transform.Length > totalMaxEstSize)
@ -93,9 +93,9 @@
{
var filter = filters[i];
totalMaxEstSize *= GetEstimatedSizeMultiplier(filter);
transform = filter.Decode(transform, stream.StreamDictionary, filterProvider, i);
if (i < filters.Count - 1 && transform.Length > totalMaxEstSize)
{
// Try to prevent malicious decompression, leading to OOM issues
@ -122,16 +122,16 @@
/// Returns an equivalent token where any indirect references of child objects are
/// recursively traversed and resolved.
/// </summary>
internal static T? Resolve<T>(this T? token, IPdfTokenScanner scanner) where T : IToken
internal static T? Resolve<T>(this T? token, IPdfTokenScanner scanner, List<long>? visited = null) where T : IToken
{
return (T?)ResolveInternal(token, scanner);
return (T?)ResolveInternal(token, scanner, visited ?? []);
}
private static IToken? ResolveInternal(this IToken? token, IPdfTokenScanner scanner)
private static IToken? ResolveInternal(this IToken? token, IPdfTokenScanner scanner, List<long> visited)
{
if (token is StreamToken stream)
{
return new StreamToken(Resolve(stream.StreamDictionary, scanner), stream.Data);
return new StreamToken(Resolve(stream.StreamDictionary, scanner, visited), stream.Data);
}
if (token is DictionaryToken dict)
@ -139,8 +139,17 @@
var resolvedItems = new Dictionary<NameToken, IToken>();
foreach (var kvp in dict.Data)
{
var value = kvp.Value is IndirectReferenceToken reference ? scanner.Get(reference.Data)?.Data : kvp.Value;
resolvedItems[NameToken.Create(kvp.Key)] = ResolveInternal(value, scanner);
var value = kvp.Value;
if (kvp.Value is IndirectReferenceToken reference)
{
if (visited.Contains(reference.Data.ObjectNumber))
{
continue;
}
value = scanner.Get(reference.Data)?.Data;
visited.Add(reference.Data.ObjectNumber);
}
resolvedItems[NameToken.Create(kvp.Key)] = ResolveInternal(value, scanner, visited);
}
return new DictionaryToken(resolvedItems);
@ -152,7 +161,7 @@
for (int i = 0; i < arr.Length; i++)
{
var value = arr.Data[i] is IndirectReferenceToken reference ? scanner.Get(reference.Data)?.Data : arr.Data[i];
resolvedItems.Add(ResolveInternal(value, scanner));
resolvedItems.Add(ResolveInternal(value, scanner, visited));
}
return new ArrayToken(resolvedItems);
}