Different Digital Signature section on PDF file

[rossinicolas]

Hi @vbuch , now a day, i'm using FortifyApp client in our web application to access to Token certificate that i'm using to sign the PDF files. Previously, i'm adding placeholder with node-signpdf library (plainAddPlaceholder helper). we are making multiple signatures in this way, without any ploblem, but, if i use an external tools to add a new sign, like xolidosign, CryptoId or other similar the /Type/Sig section had different order than the produced by node-signpdf. There's an example of the issue that i have:

• using node-signpdf `<< /Type /Sig /Filter /Adobe.PPKLite /SubFilter /adbe.pkcs7.detached /ByteRange [0 8327 24713 894]
  /Contents <3082059406092a864886f70d010702a082058...> /Reason (FD) /M (D:20221213114802Z) /ContactInfo (informatica@jus.gov.ar) /Name (Firma Digital) /Location (Poder Judicial)

  `

• using external tools: <</Contents <308208a406092a864886f70d010702a0...>/Filter/Adobe.PPKLite/Type/Sig/ByteRange [0 7912 37914 1624 ] /SubFilter/adbe.pkcs7.detached/Reason()/Location()/ContactInfo()/M(D:20221213120145-03'00')>>

summary, /Contents tag is in different order, so, depending on the method used, acrobat is show me all the sign or just the last one. TIA.

[vbuch]

Thou you are not asking any question, I think this answers them: https://github.com/vbuch/node-signpdf/blob/cef8915064d3862e2e08f5fa9e6e09687a468d42/README.md?plain=1#L61

Here is where this requirement comes from: https://github.com/vbuch/node-signpdf/blob/4cedc49fffa4d4bbac2bd855b78555a9cff64e4d/src/signpdf.js#L57

Basically, because we are not parsing anything as a structure from the file, but just moving a cursor withing strings, we introduce that limitation. If you want this to work, you would have to rework it not to do findByteRange() but rather get the whole Sig as a structure and work with it.

As usually, PRs are welcome.

[rossinicolas]

Thou you are not asking any question, I think this answers them:

https://github.com/vbuch/node-signpdf/blob/cef8915064d3862e2e08f5fa9e6e09687a468d42/README.md?plain=1#L61

Here is where this requirement comes from:

https://github.com/vbuch/node-signpdf/blob/4cedc49fffa4d4bbac2bd855b78555a9cff64e4d/src/signpdf.js#L57

Basically, because we are not parsing anything as a structure from the file, but just moving a cursor withing strings, we introduce that limitation. If you want this to work, you would have to rework it not to do findByteRange() but rather get the whole Sig as a structure and work with it.

As usually, PRs are welcome.

Yes, i understood the Requirement but i don't know why that's different than a pdf files signed using Acrobat Reader for example. That's a big problem in our implementation bacause if an enduser upload a file firstly signed by Acrobat and make a second Sign using node-signpdf, the pdf file just show me the last Sign when i open it in Acrobat, losing the first one.

[stale[bot]]

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