Cloudflare blocks sign PDF

[MichalY-WizSoft]

• Generate PDF using JSPDF
• Merge PDFs using PDF-MERGER
• Add signature placeholder using pdflibAddPlaceholder
• Sign the PDF
• Try to upload to system -> Cloudflare blocks with WAF alerts
• When switching to plainAddPlaceholder, the upload works but the signature is not visible in Adobe Reader

• what the difrent and how to do not block and visible in Adobe Reader ?

Attachments

• [signed_pdflib.pdf] - PDF signed with pdflibAddPlaceholder
• [signed_plain.pdf] - PDF signed with plainAddPlaceholder
• [cloudflare_block.png] - Screenshot of Cloudflare WAF block

signed_plain.pdf
signed_pdflib.pdf

const signPdf = async (pdfBuffer, signer) => {
    try {
        const pdfWithPlaceholder = await plainAddPlaceholder({
            pdfBuffer,
            reason: 'Digital Invoice Signature',
            contactInfo: 'Wizsoft',
            name: 'Wizsoft Digital Signature',
            location: 'Israel',
            signingTime: new Date().toISOString(),
            signatureLength: 8192,
            subFilter: 'adbe.pkcs7.detached',
            appName: 'Wizsoft Digital Signature System',
            widgetRect: [0, 0, 595, 842]
        });    
        return signpdf.sign(pdfWithPlaceholder, signer);
    } catch (err) {
        throw {message:`signature faild, error : ${err}`};
    }
}

const signPdfLib = async (pdfBuffer,  signer) =>{
    try {
        let pdfDoc = await PDFDocument.load(pdfBuffer);
        await pdflibAddPlaceholder({
            pdfDoc: pdfDoc,
            reason: 'Digital Invoice Signature',
            contactInfo: '',
            name: 'Digital Signature',
            location: 'Israel',
            signingTime: new Date().toISOString(),
            signatureLength: 8192,
            subFilter: 'adbe.pkcs7.detached',
        });
        pdfWithPlaceholder = await Buffer.from(await pdfDoc.save({useObjectStreams: false }), 'arraybuffer');
        return signpdf.sign(pdfWithPlaceholder, signer)                    
    } catch (err) {
        throw {message:`signature faild, error : ${err}`};
    }
}

[dhensby]

Have you spoken to cloudflare?

[MichalY-WizSoft]

I’m trying to contact them as well.

Previously, I used to work with :
const { plainAddPlaceholder } = require('node-signpdf/dist/helpers');
However, I had to switch because I needed to upload a PDF version that wasn’t supported, and this library is now deprecated.

What has changed between the libraries?
Is there an alternative way to create a VALID Adobe signature that is also visible in Adobe Reader, while still using plainAddPlaceholder in a way that Cloudflare does not block?

[dhensby]

We don't know specifically what cloudflare is blocking or what they don't like. Is it specifically to do with the content of the PDF? With the signature? With that particular instance of a signature?

I'm not intimately familiar with the exact differences, but I don't see why they should produce vastly different signatures that would make cloudflare think there's embedded PHP, command injections, etc in them.

Have you looked at the PDF files in a text editor to see what is different?

[MichalY-WizSoft]

I noticed that in pdflibAddPlaceholder, a long string with various characters is embedded in the signature.

How does this information help me?

[dhensby]

That stream doesn't look well formed to me, it should be binary data but it's made up of ASCII, which is unusual.

I suspect there's some encoding problem somewhere which is corrupting something. I don't know what exactly, you'll have to debug what is going on.

You aren't following the example for pdf-lib, so maybe that's a problem too?

const signPdfLib = async (pdfBuffer,  signer) =>{
    try {
        const pdfDoc = await PDFDocument.load(pdfBuffer);
       pdflibAddPlaceholder({
            pdfDoc: pdfDoc,
            reason: 'Digital Invoice Signature',
            contactInfo: '',
            name: 'Digital Signature',
            location: 'Israel',
            signingTime: new Date().toISOString(),
            signatureLength: 8192,
            subFilter: 'adbe.pkcs7.detached',
        });
        pdfWithPlaceholder = await pdfDoc.save();
        return signpdf.sign(pdfWithPlaceholder, signer)                    
    } catch (err) {
        throw {message:`signature faild, error : ${err}`};
    }
}

[MichalY-WizSoft]

If I follow the example, I encounter an error:
"PDF expected as Buffer"

This happens because pdfDoc.save returns a Uint8Array, while signpdf.sign expects a Buffer.

Am I missing something in the process?

[dhensby]

Then do this

const signPdfLib = async (pdfBuffer,  signer) =>{
    try {
        const pdfDoc = await PDFDocument.load(pdfBuffer);
       pdflibAddPlaceholder({
            pdfDoc: pdfDoc,
            reason: 'Digital Invoice Signature',
            contactInfo: '',
            name: 'Digital Signature',
            location: 'Israel',
            signingTime: new Date().toISOString(),
            signatureLength: 8192,
            subFilter: 'adbe.pkcs7.detached',
        });
        pdfWithPlaceholder = await pdfDoc.save();
-        return signpdf.sign(pdfWithPlaceholder, signer)
+        return signpdf.sign(Buffer.from(pdfWithPlaceholder), signer)
    } catch (err) {
        throw {message:`signature faild, error : ${err}`};
    }
}

[MichalY-WizSoft]

Thank you for the quick response - I really appreciate it!

I’ve encountered an issue: if I don’t use pdfDoc.save({ useObjectStreams: false }), I get the following error:
"No ByteRangeStrings found within PDF buffer."

[dhensby]

ok, and if you add that in?

[MichalY-WizSoft]

Yes,

The document was signed, but it’s still being blocked by Cloudflare.
I suspected it (useObjectStreams: false) might be the cause.

[MichalY-WizSoft]

Is there a way to add a placeholder using plainAddPlaceholder so that the signature will be visible in Adobe Reader?

[dhensby]

Yep - it seems there's a compatibility issue with lib-pdf and this lib at the moment, then. Perhaps something changed under the hood with pdf-lib in a version and we've not kept up.

[MichalY-WizSoft]

If I use this function.
the process completes successfully and Cloudflare does not block it. However,
I do not receive the validation in Acrobat.
I’ve attached an image of what I expect to see.
Do you know why this is happening and how to fix it?
Thank you in advance for your help!

const signPdfLib = async (pdfBuffer, signer) => {
    try {
        const pdfWithPlaceholder = await plainAddPlaceholder({
            pdfBuffer: pdfBuffer,
            reason: 'Digital Invoice Signature',
            contactInfo: 'Wizsoft',
            name: 'Wizsoft Digital Signature',
            location: 'Israel',
            signingTime: new Date().toISOString(),
            signatureLength: 8192,
            subFilter: 'adbe.pkcs7.detached',
            appName: 'Wizsoft Digital Signature System',
            widgetRect: [0, 0, 595, 842]
        });

        return signpdf.sign(pdfWithPlaceholder, signer);
    } catch (err) {
        throw {message:`signature faild, error : ${err}`};
    }
}