Signing PDF files with Go

This PDF signing library is written in Go. The library is in development, might not work for all PDF files and the API might change, bug reports, contributions and suggestions are welcome.

See also our PDFSigner, a more advanced digital signature server that is using this project.

From the command line

Usage of ./pdfsign:
  -certType string
        Type of the certificate (CertificationSignature, ApprovalSignature, UsageRightsSignature, TimeStampSignature) (default "CertificationSignature")
  -contact string
        Contact information for signatory
  -location string
        Location of the signatory
  -name string
        Name of the signatory
  -reason string
        Reason for signing
  -tsa string
        URL for Time-Stamp Authority (default "https://freetsa.org/tsr")

Example usage:
        ./pdfsign -name "Jon Doe" sign input.pdf output.pdf certificate.crt private_key.key [chain.crt]
        ./pdfsign -certType "CertificationSignature" -name "Jon Doe" sign input.pdf output.pdf certificate.crt private_key.key [chain.crt]
        ./pdfsign -certType "TimeStampSignature" input.pdf output.pdf
        ./pdfsign verify input.pdf

As library

import "github.com/digitorus/pdf"

input_file, err := os.Open(input)
if err != nil {
    return err
}
defer input_file.Close()

output_file, err := os.Create(output)
if err != nil {
    return err
}
defer output_file.Close()

finfo, err := input_file.Stat()
if err != nil {
    return err
}
size := finfo.Size()

rdr, err := pdf.NewReader(input_file, size)
if err != nil {
    return err
}

err = sign.Sign(input_file, output_file, rdr, size, sign.SignData{
    Signature: sign.SignDataSignature{
        Info: sign.SignDataSignatureInfo{
            Name:        "John Doe",
            Location:    "Somewhere on the globe",
            Reason:      "My season for siging this document",
            ContactInfo: "How you like",
            Date:        time.Now().Local(),
        },
        CertType:   sign.CertificationSignature,
        DocMDPPerm: sign.AllowFillingExistingFormFieldsAndSignaturesPerms,
    },
    Signer:            privateKey,         // crypto.Signer
    DigestAlgorithm:   crypto.SHA256,      // hash algorithm for the digest creation
    Certificate:       certificate,        // x509.Certificate
    CertificateChains: certificate_chains, // x509.Certificate.Verify()
    TSA: sign.TSA{
        URL: "https://freetsa.org/tsr",
        Username: "",
        Password: "",
    },

    // The follow options are likely to change in a future release
    //
    // cache revocation data when bulk signing
    RevocationData:     revocation.InfoArchival{}, 
    // custom revocation lookup
    RevocationFunction: sign.DefaultEmbedRevocationStatusFunction,
})
if err != nil {
    log.Println(err)
} else {
    log.Println("Signed PDF written to " + output)
}