[PDFBOX-3256] Trailer Validation error PDF/A1-b

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Not A Problem
• Affects Version/s: 2.0.0
• Component/s: Preflight
• Assignee: Unassigned
• Reporter: Davide Silvestri
• Created: 01/Mar/16 13:55
• Updated: 13/Mar/16 11:24
• Resolved: 13/Mar/16 09:17

Description

According to PDF specifications "File identifiers are defined by the optional ID entry in a PDF file’s trailer dictionary (see Section 3.4.4, “File Trailer”; see also implementation note 162 in Appendix H). The value of this entry is an array of two byte strings. The first byte string is a permanent identifier based on the contents of the file at the time it was originally created and does not change when the file is incrementally updated. The second byte string is a changing identifier based on the file’s contents at the time it was last updated."
We are having a problem validating a PDF/A1-b when preflight checks first and last trailer. TrailerValidationProcess.java compares IDs in the compareIds function checking that both values remain the same in the first and last trailer, but it checks both the first byte AND the second byte of the trailer into the cycle (line 206). Being the second byte a changing item when the file is updated (eg. with a digital signature), we have this error in validation "1.4.6.: Trailer Syntax error, ID is different in the first and the last trailer" even if the first item remains the same and so the PDF/A1-b compliance should be verified.
Please can you help me with this issue?
Thank you very much.
Davide