Description
I am testing the TSA feature (set_tsa and not set_ltv) with a dompdf generated pdf, after the signing I load again the PDF with "$pdfDoc = PDFDoc::from_string($pdfSigned);" doing this several times with the same input sometimes $pdfDoc returns true;
The error is related to "xref tag not found at position", I checked the signed pdf buffer and in some cases the xref_pos size is different, when using TSA feature sometimes it adds 4 chars to the xref_pos, this is an example of PDF signed with TSA and checked correctly with startxref 17394:
endobj
xref
0 2
0000000000 65535 f
0000001723 00000 n
5 2
0000001335 00000 n
0000001613 00000 n
10 3
0000001476 00000 n
0000001501 00000 n
0000001822 00000 n
trailer
<</Size 13/Root 1 0 R/Info 5 0 R/ID[<1a3d216a394bb6ba74fb5cc1fd4391fe> <1a3d216a394bb6ba74fb5cc1fd4391fe>]/Prev 984>>
startxref
17394
%%EOF
'
and this is the same PDF signed again that reports startxref 17398 bytes:
endobj
xref
0 2
0000000000 65535 f
0000001723 00000 n
5 2
0000001335 00000 n
0000001613 00000 n
10 3
0000001476 00000 n
0000001501 00000 n
0000001822 00000 n
trailer
<</Size 13/Root 1 0 R/Info 5 0 R/ID[<454c825cf55cc68453eea7ab2eb1315b> <454c825cf55cc68453eea7ab2eb1315b>]/Prev 984>>
startxref
17398
%%EOF
'
In the second case the function "public static function get_xref_1_4" xref_line starts in "obj\n" instead of "xref\n" and the code reports the "xref tag not found at position".
I could fix the code to detect this 4 bytes shift when searching the xref anchor but the bug itself is probably upstream when applying the TSA signature, as the documents have the same exact sizes with different signatures, any ideas?.
I have repeat the test several times without set_tsa, or with set_ltv and it only triggers with set_tsa, I am testing with the digicert timestap service.
Cheers
Jacq