Comment 113 for bug 740506

I don't think we need to check if the byte range covers the entire document. Our job, when verifying the signature, is to use the byte ranges provided in the signature dictionary. It is up to the pdf producer to ensure the byte range covers the entire document (excluding the signature value).

All we need to do is ensure we check all bytes ranges in the ByteRange array. We should also check that each byte range is within the file. eg check that each offset is >= 0 and offset + length <= file size.

While it would be nice to check if the byte range covers the entire document, poppler does not provide any easy way to determine the file offsets of a dictionary value. This makes it difficult to check if the excluded range only covers the signature value.