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Scott Bailey
Scott Bailey

Reputation: 71

iTextPdf and iTextSharp - Malformed PDF causes hang

I recently received a PDF which causes the application to hang when loading in both iText Java and iTextSharp.

Upvotes: 2

Views: 443

Answers (1)

Scott Bailey
Scott Bailey

Reputation: 71

The problem was that the PDF had incremental updates and the additional trailer had a Prev entry pointing to its own cross-reference table. This causes an infinite loop in PdfReader.ReadXref().

My proposed solution is as follows.

while (true) {
    PdfNumber prev = (PdfNumber)trailer2.Get(PdfName.PREV);
    if (prev == null)
        break;
    // Add check to prevent infinite loop
    if (prev.LongValue == startxref)
        throw new InvalidPdfException("trailer Prev points to its own cross-reference section.");
    // end added check
    tokens.Seek(prev.LongValue);
    trailer2 = ReadXrefSection();
}

Apologies to StackOverflow for this not actually being a question, but I can't afford the time to satisfy the iText requirements for a pull request for two lines of code.

Upvotes: 4

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