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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]; var filter = filters[i];
totalMaxEstSize *= GetEstimatedSizeMultiplier(filter); totalMaxEstSize *= GetEstimatedSizeMultiplier(filter);
transform = filter.Decode(transform, stream.StreamDictionary, filterProvider, i); transform = filter.Decode(transform, stream.StreamDictionary, filterProvider, i);
if (i < filters.Count - 1 && transform.Length > totalMaxEstSize) if (i < filters.Count - 1 && transform.Length > totalMaxEstSize)
@ -93,9 +93,9 @@
{ {
var filter = filters[i]; var filter = filters[i];
totalMaxEstSize *= GetEstimatedSizeMultiplier(filter); totalMaxEstSize *= GetEstimatedSizeMultiplier(filter);
transform = filter.Decode(transform, stream.StreamDictionary, filterProvider, i); transform = filter.Decode(transform, stream.StreamDictionary, filterProvider, i);
if (i < filters.Count - 1 && transform.Length > totalMaxEstSize) if (i < filters.Count - 1 && transform.Length > totalMaxEstSize)
{ {
// Try to prevent malicious decompression, leading to OOM issues // 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 /// Returns an equivalent token where any indirect references of child objects are
/// recursively traversed and resolved. /// recursively traversed and resolved.
/// </summary> /// </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) 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) if (token is DictionaryToken dict)
@ -139,8 +139,17 @@
var resolvedItems = new Dictionary<NameToken, IToken>(); var resolvedItems = new Dictionary<NameToken, IToken>();
foreach (var kvp in dict.Data) foreach (var kvp in dict.Data)
{ {
var value = kvp.Value is IndirectReferenceToken reference ? scanner.Get(reference.Data)?.Data : kvp.Value; var value = kvp.Value;
resolvedItems[NameToken.Create(kvp.Key)] = ResolveInternal(value, scanner); 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); return new DictionaryToken(resolvedItems);
@ -152,7 +161,7 @@
for (int i = 0; i < arr.Length; i++) for (int i = 0; i < arr.Length; i++)
{ {
var value = arr.Data[i] is IndirectReferenceToken reference ? scanner.Get(reference.Data)?.Data : arr.Data[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); return new ArrayToken(resolvedItems);
} }