Section:

Digitally Sign PDF Files - Go Sample Code

Requirements
View Demo
Server SDK
Package: Digital Signature

Sample code to use Apryse SDK's high-level digital signature API for digitally signing and/or certifying PDF files; provided in Python, C++, C#, Java, Node.js (JavaScript), PHP, Ruby and VB.

Learn more about our Server SDK and PDF Digital Signature Library.

Implementation steps

To apply and validate digital signatures with Apryse Server SDK:

Step 1: Follow get started with Server SDK in your preferred language or framework
Step 2: Add the sample code provided in this guide. Make note of directions at top of code samples.

To use this feature in production, your license key will need the Digital Signature Package. Trial keys already include all packages.

1//---------------------------------------------------------------------------------------
2// Copyright (c) 2001-2024 by Apryse Software Inc. All Rights Reserved.
3// Consult LICENSE.txt regarding license information.
4//---------------------------------------------------------------------------------------
5
6////----------------------------------------------------------------------------------------------------------------------
7//// This sample demonstrates the basic usage of the high-level digital signatures API in PDFNet.
8////
9//// The following steps reflect typical intended usage of the digital signatures API:
10////
11////  0.  Start with a PDF with or without form fields in it that one would like to lock (or, one can add a field, see (1)).
12////  
13////  1.  EITHER: 
14////      (a) Call doc.CreateDigitalSignatureField, optionally providing a name. You receive a DigitalSignatureField.
15////      -OR-
16////      (b) If you didn't just create the digital signature field that you want to sign/certify, find the existing one within the 
17////      document by using PDFDoc.DigitalSignatureFieldIterator or by using PDFDoc.GetField to get it by its fully qualified name.
18////  
19////  2.  Create a signature widget annotation, and pass the DigitalSignatureField that you just created or found. 
20////      If you want it to be visible, provide a Rect argument with a non-zero width or height, and don't set the
21////      NoView and Hidden flags. [Optionally, add an appearance to the annotation when you wish to sign/certify.]
22////      
23////  [3. (OPTIONAL) Add digital signature restrictions to the document using the field modification permissions (SetFieldPermissions) 
24////      or document modification permissions functions (SetDocumentPermissions) of DigitalSignatureField. These features disallow 
25////      certain types of changes to be made to the document without invalidating the cryptographic digital signature once it
26////      is signed.]
27////      
28////  4.  Call either CertifyOnNextSave or SignOnNextSave. There are three overloads for each one (six total):
29////      a.  Taking a PKCS //12 keyfile path and its password
30////      b.  Taking a buffer containing a PKCS //12 private keyfile and its password
31////      c.  Taking a unique identifier of a signature handler registered with the PDFDoc. This overload is to be used
32////          in the following fashion: 
33////          i)      Extend and implement a new SignatureHandler. The SignatureHandler will be used to add or 
34////                  validate/check a digital signature.
35////          ii)     Create an instance of the implemented SignatureHandler and register it with PDFDoc with 
36////                  pdfdoc.AddSignatureHandler(). The method returns a SignatureHandlerId.
37////          iii)    Call SignOnNextSaveWithCustomHandler/CertifyOnNextSaveWithCustomHandler with the SignatureHandlerId.
38////      NOTE: It is only possible to sign/certify one signature per call to the Save function.
39////  
40////  5.  Call pdfdoc.Save(). This will also create the digital signature dictionary and write a cryptographic signature to it.
41////      IMPORTANT: If there are already signed/certified digital signature(s) in the document, you must save incrementally
42////      so as to not invalidate the other signature(s). 
43////
44//// Additional processing can be done before document is signed. For example, UseSignatureHandler() returns an instance
45//// of SDF dictionary which represents the signature dictionary (or the /V entry of the form field). This can be used to
46//// add additional information to the signature dictionary (e.g. Name, Reason, Location, etc.).
47////
48//// Although the steps above describes extending the SignatureHandler class, this sample demonstrates the use of
49//// StdSignatureHandler (a built-in SignatureHandler in PDFNet) to sign a PDF file.
50////----------------------------------------------------------------------------------------------------------------------
51
52package main
53import (
54    "fmt"
55    "strconv"
56    "flag"
57    "testing"
58    . "github.com/ApryseSDK/pdftron-go/v2"
59)
60
61var licenseKey string
62var modulePath string
63
64func init() {
65    flag.StringVar(&licenseKey, "license", "", "License key for Apryse SDK")
66    flag.StringVar(&modulePath, "modulePath", "", "Module path for Apryse SDK")
67}
68
69func VerifySimple(inDocpath string, inPublicKeyFilePath string) bool{
70    doc := NewPDFDoc(inDocpath)
71    fmt.Println("==========")
72    opts := NewVerificationOptions(VerificationOptionsE_compatibility_and_archiving)
73
74    // Add trust root to store of trusted certificates contained in VerificationOptions.
75    opts.AddTrustedCertificate(inPublicKeyFilePath, uint16(VerificationOptionsE_default_trust | VerificationOptionsE_certification_trust))
76
77    result := doc.VerifySignedDigitalSignatures(opts)
78        
79    if result == PDFDocE_unsigned{
80        fmt.Println("Document has no signed signature fields.")
81        return false
82        // e_failure == bad doc status, digest status, or permissions status
83        // (i.e. does not include trust issues, because those are flaky due to being network/config-related)
84    }else if result == PDFDocE_failure{
85        fmt.Println("Hard failure in verification on at least one signature.")
86        return false
87    }else if result == PDFDocE_untrusted{
88        fmt.Println("Could not verify trust for at least one signature.")
89        return false
90    }else if result == PDFDocE_unsupported{
91        // If necessary, call GetUnsupportedFeatures on VerificationResult to check which
92        // unsupported features were encountered (requires verification using 'detailed' APIs)
93        fmt.Println("At least one signature contains unsupported features.")
94        return false
95        // unsigned sigs skipped; parts of document may be unsigned (check GetByteRanges on signed sigs to find out)
96    }else if result == PDFDocE_verified{
97        fmt.Println("All signed signatures in document verified.")
98        return true
99    }else{
100        fmt.Println("unrecognized document verification status")
101        return false
102    }
103}
104
105func VerifyAllAndPrint(inDocpath string, inPublicKeyFilePath string) bool{
106    doc := NewPDFDoc(inDocpath)
107    fmt.Println("==========")
108    opts := NewVerificationOptions(VerificationOptionsE_compatibility_and_archiving)
109    
110    // Trust the public certificate we use for signing.
111    trustedCertFile := NewMappedFile(inPublicKeyFilePath)
112    fileSz := trustedCertFile.FileSize()
113    fileReader := NewFilterReader(trustedCertFile)
114    trustedCertBuf := fileReader.Read(fileSz)
115    trustedCertBytes := make([]byte, int(trustedCertBuf.Size()))
116    for i := 0; i < int(trustedCertBuf.Size()); i ++ {
117        trustedCertBytes[i] = trustedCertBuf.Get(i)
118    }
119    opts.AddTrustedCertificate(&trustedCertBytes[0], int64(len(trustedCertBytes)), uint16(VerificationOptionsE_default_trust | VerificationOptionsE_certification_trust))
120
121    // Iterate over the signatures and verify all of them.
122    digsigFitr := doc.GetDigitalSignatureFieldIterator()
123    verificationStatus := true
124    for (digsigFitr.HasNext()){
125        curr := digsigFitr.Current()
126        result := curr.Verify(opts)
127        if result.GetVerificationStatus(){
128            fmt.Printf("Signature verified, objnum: %d\n", curr.GetSDFObj().GetObjNum())
129        }else{
130            fmt.Printf("Signature verification failed, objnum: %d\n", curr.GetSDFObj().GetObjNum())
131            verificationStatus = false
132        }
133        digest_algorithm := result.GetDigestAlgorithm()
134        if digest_algorithm == DigestAlgorithmE_SHA1{
135            fmt.Println("Digest algorithm: SHA-1")
136        }else if digest_algorithm == DigestAlgorithmE_SHA256{
137            fmt.Println("Digest algorithm: SHA-256")
138        }else if digest_algorithm == DigestAlgorithmE_SHA384{
139            fmt.Println("Digest algorithm: SHA-384")
140        }else if digest_algorithm == DigestAlgorithmE_SHA512{
141            fmt.Println("Digest algorithm: SHA-512")
142        }else if digest_algorithm == DigestAlgorithmE_RIPEMD160{
143            fmt.Println("Digest algorithm: RIPEMD-160")
144        }else if digest_algorithm == DigestAlgorithmE_unknown_digest_algorithm{
145            fmt.Println("Digest algorithm: unknown")
146        }else{
147            //unrecognized document status
148        }
149        fmt.Printf("Detailed verification result: \n\t%s\n\t%s\n\t%s\n\t%s\n", 
150            result.GetDocumentStatusAsString(),
151            result.GetDigestStatusAsString(),
152            result.GetTrustStatusAsString(),
153            result.GetPermissionsStatusAsString())
154            
155        changes := result.GetDisallowedChanges()
156        for i := 0; i < int(changes.Size()); i++ {
157            fmt.Printf("\tDisallowed change: %s, objnum: %d\n", changes.Get(i).GetTypeAsString(), changes.Get(i).GetObjNum())
158        }
159
160        // Get and print all the detailed trust-related results, if they are available.
161        if result.HasTrustVerificationResult(){
162            trustVerificationResult := result.GetTrustVerificationResult()
163            var msg string
164            if trustVerificationResult.WasSuccessful(){
165                msg = "Trust verified."
166            } else {
167                msg = "Trust not verifiable."
168            }
169            fmt.Println(msg)
170            fmt.Println(trustVerificationResult.GetResultString())
171            
172            tmpTimeTv := trustVerificationResult.GetTimeOfTrustVerification()
173            
174            trustVerificationTimeEnum := trustVerificationResult.GetTimeOfTrustVerificationEnum()
175            
176            if trustVerificationTimeEnum == VerificationOptionsE_current{
177                fmt.Println("Trust verification attempted with respect to current time (as epoch time): " + strconv.Itoa(int(tmpTimeTv)))
178            }else if trustVerificationTimeEnum == VerificationOptionsE_signing{
179                fmt.Println("Trust verification attempted with respect to signing time (as epoch time): " + strconv.Itoa(int(tmpTimeTv)))
180            }else if trustVerificationTimeEnum == VerificationOptionsE_timestamp{
181                fmt.Println("Trust verification attempted with respect to secure embedded timestamp (as epoch time): " + strconv.Itoa(int(tmpTimeTv)))
182            }else{
183                //unrecognized time enum value
184            }
185
186            if trustVerificationResult.GetCertPath().Size() == 0{
187                fmt.Println("Could not print certificate path.")
188            }else{
189                fmt.Println("Certificate path:")
190                certPath := trustVerificationResult.GetCertPath()
191                for i := 0; i < int(certPath.Size()); i ++{
192                    fmt.Println("\tCertificate:")
193                    fmt.Println("\t\tIssuer names:")
194                    issuerDn := certPath.Get(i).GetIssuerField().GetAllAttributesAndValues()
195                    for j := 0; j < int(issuerDn.Size()); j ++{ 
196                        fmt.Println("\t\t\t" + issuerDn.Get(j).GetStringValue())
197                    }
198                    fmt.Println("\t\tSubject names:")
199                    subjectDn := certPath.Get(i).GetSubjectField().GetAllAttributesAndValues()
200                    for k := 0; k < int(subjectDn.Size()); k ++{
201                        fmt.Println("\t\t\t" + subjectDn.Get(k).GetStringValue())
202                    }
203                    fmt.Println("\t\tExtensions:")
204                    for m := 0; m < int(certPath.Get(i).GetExtensions().Size()); m ++{
205                        fmt.Println("\t\t\t" + certPath.Get(i).GetExtensions().Get(m).ToString())
206                    }
207                }
208            }        
209        }else{
210            fmt.Println("No detailed trust verification result available.")
211        
212            unsupportedFeatures := result.GetUnsupportedFeatures()
213            if unsupportedFeatures.Size() > 0 {
214                fmt.Println("Unsupported features:")
215                for i := 0; i < int(unsupportedFeatures.Size()); i ++{
216                    fmt.Println("\t" + unsupportedFeatures.Get(i))
217                }
218            }
219        }
220        fmt.Println("==========")
221        
222        digsigFitr.Next()
223    }
224    return verificationStatus
225}
226
227func CertifyPDF(inDocpath string,
228    inCertFieldName string ,
229    inPrivateKeyFilePath string,
230    inKeyfilePassword string,
231    inAppearanceImagePath string,
232    inOutpath string){
233    
234    fmt.Println("================================================================================")
235    fmt.Println("Certifying PDF document")
236
237    // Open an existing PDF
238    doc := NewPDFDoc(inDocpath)
239
240    if doc.HasSignatures(){
241        fmt.Println("PDFDoc has signatures")
242    }else{
243        fmt.Println("PDFDoc has no signatures")
244    }
245    page1 := doc.GetPage(1)
246
247    // Create a text field that we can lock using the field permissions feature.
248    annot1 := TextWidgetCreate(doc, NewRect(143.0, 440.0, 350.0, 460.0), "asdf_test_field")
249    page1.AnnotPushBack(annot1)
250
251    // Create a new signature form field in the PDFDoc. The name argument is optional;
252    // leaving it empty causes it to be auto-generated. However, you may need the name for later.
253    // Acrobat doesn"t show digsigfield in side panel if it's without a widget. Using a
254    // Rect with 0 width and 0 height, or setting the NoPrint/Invisible flags makes it invisible. 
255    certificationSigField := doc.CreateDigitalSignatureField(inCertFieldName)
256    widgetAnnot := SignatureWidgetCreate(doc, NewRect(143.0, 287.0, 219.0, 306.0), certificationSigField)
257    page1.AnnotPushBack(widgetAnnot)
258
259    // (OPTIONAL) Add an appearance to the signature field.
260    img := ImageCreate(doc.GetSDFDoc(), inAppearanceImagePath)
261    widgetAnnot.CreateSignatureAppearance(img)
262
263    // Add permissions. Lock the random text field.
264    fmt.Println("Adding document permissions.")
265    certificationSigField.SetDocumentPermissions(DigitalSignatureFieldE_annotating_formfilling_signing_allowed)
266    
267    // Prepare to lock the text field that we created earlier.
268    fmt.Println("Adding field permissions.")
269    testField := NewVectorString()
270    testField.Add("asdf_test_field")
271    certificationSigField.SetFieldPermissions(DigitalSignatureFieldE_include, testField)
272
273    certificationSigField.CertifyOnNextSave(inPrivateKeyFilePath, inKeyfilePassword)
274
275    // (OPTIONAL) Add more information to the signature dictionary.
276    certificationSigField.SetLocation("Vancouver, BC")
277    certificationSigField.SetReason("Document certification.")
278    certificationSigField.SetContactInfo("www.pdftron.com")
279
280    // Save the PDFDoc. Once the method below is called, PDFNet will also sign the document using the information provided.
281    doc.Save(inOutpath, uint(0))
282
283    fmt.Println("================================================================================")
284}
285
286func SignPDF(inDocpath string, 
287    inApprovalFieldName string, 
288    inPrivateKeyFilePath string, 
289    inKeyfilePassword string, 
290    inAppearanceImgPath string, 
291    inOutpath string){
292    
293    fmt.Println("================================================================================")
294    fmt.Println("Signing PDF document")
295
296    // Open an existing PDF
297    doc := NewPDFDoc(inDocpath)
298
299    // Retrieve the unsigned approval signature field.
300    foundApprovalField := doc.GetField(inApprovalFieldName)
301    foundApprovalSignatureDigsigField := NewDigitalSignatureField(foundApprovalField)
302    
303    // (OPTIONAL) Add an appearance to the signature field.
304    img := ImageCreate(doc.GetSDFDoc(), inAppearanceImgPath)
305    foundApprovalSignatureWidget := NewSignatureWidget(foundApprovalField.GetSDFObj())
306    foundApprovalSignatureWidget.CreateSignatureAppearance(img)
307
308    // Prepare the signature and signature handler for signing.
309    foundApprovalSignatureDigsigField.SignOnNextSave(inPrivateKeyFilePath, inKeyfilePassword)
310
311    // The actual approval signing will be done during the following incremental save operation.
312    doc.Save(inOutpath, uint(SDFDocE_incremental))
313
314    fmt.Println("================================================================================")
315}
316
317func ClearSignature(inDocpath string,
318    inDigsigFieldName string,
319    inOutpath string){
320
321    fmt.Println("================================================================================")
322    fmt.Println("Clearing certification signature")
323
324    doc := NewPDFDoc(inDocpath)
325
326    digsig := NewDigitalSignatureField(doc.GetField(inDigsigFieldName))
327    
328    fmt.Println("Clearing signature: " + inDigsigFieldName)
329    digsig.ClearSignature()
330
331    if !digsig.HasCryptographicSignature(){
332        fmt.Println("Cryptographic signature cleared properly.")
333    }
334    // Save incrementally so as to not invalidate other signatures from previous saves.
335    doc.Save(inOutpath, uint(SDFDocE_incremental))
336
337    fmt.Println("================================================================================")
338}
339
340func PrintSignaturesInfo(inDocpath string){
341    fmt.Println("================================================================================")
342    fmt.Println("Reading and printing digital signature information")
343
344    doc := NewPDFDoc(inDocpath)
345    if !doc.HasSignatures(){
346        fmt.Println("Doc has no signatures.")
347        fmt.Println("================================================================================")
348        return
349    }else{
350        fmt.Println("Doc has signatures.")
351    }
352
353    fitr := doc.GetFieldIterator()
354    for fitr.HasNext(){
355        current := fitr.Current()
356        if (current.IsLockedByDigitalSignature()){
357            fmt.Println("==========\nField locked by a digital signature")
358        }else{
359            fmt.Println("==========\nField not locked by a digital signature")
360        }
361        fmt.Println("Field name: " + current.GetName())
362        fmt.Println("==========")
363        
364        fitr.Next()
365    }
366
367    fmt.Println("====================\nNow iterating over digital signatures only.\n====================")
368
369    digsigFitr := doc.GetDigitalSignatureFieldIterator()
370    for digsigFitr.HasNext(){
371        current := digsigFitr.Current()
372        fmt.Println("==========")
373        fmt.Println("Field name of digital signature: " + NewField(current.GetSDFObj()).GetName())
374
375        digsigfield := current
376        if !digsigfield.HasCryptographicSignature(){
377            fmt.Println("Either digital signature field lacks a digital signature dictionary, " +
378                "or digital signature dictionary lacks a cryptographic Contents entry. " +
379                "Digital signature field is not presently considered signed.\n" +
380                "==========")
381            digsigFitr.Next()
382            continue
383        }
384        certCount := digsigfield.GetCertCount()
385        fmt.Println("Cert count: " + strconv.Itoa(int(certCount)))
386        for i := uint(0); i < certCount; i ++{
387            cert := digsigfield.GetCert(i)
388            fmt.Println("Cert //" + strconv.Itoa(int(i)) + " size: " + strconv.Itoa(int(cert.Size())))
389        }
390        subfilter := digsigfield.GetSubFilter()
391
392        fmt.Println("Subfilter type: " + strconv.Itoa(int(subfilter)))
393
394        if subfilter != DigitalSignatureFieldE_ETSI_RFC3161{
395            fmt.Println("Signature's signer: " + digsigfield.GetSignatureName())
396
397            signingTime := digsigfield.GetSigningTime()
398            if signingTime.IsValid(){
399                fmt.Println("Signing time is valid.")
400            }
401            fmt.Println("Location: " + digsigfield.GetLocation())
402            fmt.Println("Reason: " + digsigfield.GetReason())
403            fmt.Println("Contact info: " + digsigfield.GetContactInfo())
404        }else{
405            fmt.Println("SubFilter == e_ETSI_RFC3161 (DocTimeStamp; no signing info)")
406        }
407        if digsigfield.HasVisibleAppearance(){
408            fmt.Println("Visible")
409        }else{
410            fmt.Println("Not visible")
411        }
412        digsigDocPerms := digsigfield.GetDocumentPermissions()
413        lockedFields := digsigfield.GetLockedFields()
414        for i := 0; i < int(lockedFields.Size()); i ++{
415            fmt.Println("This digital signature locks a field named: " + lockedFields.Get(i))
416        }
417        if digsigDocPerms == DigitalSignatureFieldE_no_changes_allowed{
418            fmt.Println("No changes to the document can be made without invalidating this digital signature.")
419        }else if digsigDocPerms == DigitalSignatureFieldE_formfilling_signing_allowed{
420            fmt.Println("Page template instantiation, form filling, and signing digital signatures are allowed without invalidating this digital signature.")
421        }else if digsigDocPerms == DigitalSignatureFieldE_annotating_formfilling_signing_allowed{
422            fmt.Println("Annotating, page template instantiation, form filling, and signing digital signatures are allowed without invalidating this digital signature.")
423        }else if digsigDocPerms == DigitalSignatureFieldE_unrestricted{
424            fmt.Println("Document not restricted by this digital signature.")
425        }else{
426            fmt.Println("Unrecognized digital signature document permission level.")
427        }
428        fmt.Println("==========")
429        digsigFitr.Next()
430    }
431
432    fmt.Println("================================================================================")
433}
434
435func CustomSigningAPI(doc_path string,
436        cert_field_name string,
437        private_key_file_path string,
438        keyfile_password string,
439        public_key_file_path string,
440        appearance_image_path string,
441        digest_algorithm_type PdftronCryptoDigestAlgorithmType,
442        PAdES_signing_mode bool,
443        output_path string){
444    fmt.Println("================================================================================")
445    fmt.Println("Custom signing PDF document")
446
447    doc := NewPDFDoc(doc_path)
448
449    page1 := doc.GetPage(1)
450
451    digsig_field := doc.CreateDigitalSignatureField(cert_field_name)
452    widgetAnnot := SignatureWidgetCreate(doc, NewRect(143.0, 287.0, 219.0, 306.0), digsig_field)
453    page1.AnnotPushBack(widgetAnnot)
454
455    // (OPTIONAL) Add an appearance to the signature field.
456    img := ImageCreate(doc.GetSDFDoc(), appearance_image_path)
457    widgetAnnot.CreateSignatureAppearance(img)
458
459    signing_mode := DigitalSignatureFieldE_adbe_pkcs7_detached
460    if PAdES_signing_mode{
461    signing_mode = DigitalSignatureFieldE_ETSI_CAdES_detached
462    }
463    // Create a digital signature dictionary inside the digital signature field, in preparation for signing.
464    digsig_field.CreateSigDictForCustomSigning("Adobe.PPKLite",
465        &signing_mode,
466        7500) // For security reasons, set the contents size to a value greater than but as close as possible to the size you expect your final signature to be, in bytes.
467                // ... or, if you want to apply a certification signature, use CreateSigDictForCustomCertification instead.
468
469    // (OPTIONAL) Set the signing time in the signature dictionary, if no secure embedded timestamping support is available from your signing provider.
470    current_date := NewDate()
471    current_date.SetCurrentTime()
472    digsig_field.SetSigDictTimeOfSigning(current_date)
473
474    doc.Save(output_path, uint(SDFDocE_incremental))
475
476    // Digest the relevant bytes of the document in accordance with ByteRanges surrounding the signature.
477    pdf_digest := digsig_field.CalculateDigest(digest_algorithm_type)
478
479    signer_cert := NewX509Certificate(public_key_file_path)
480
481    // Optionally, you can add a custom signed attribute at this point, such as one of the PAdES ESS attributes.
482    // The function we provide takes care of generating the correct PAdES ESS attribute depending on your digest algorithm.
483    pades_versioned_ess_signing_cert_attribute := DigitalSignatureFieldGenerateESSSigningCertPAdESAttribute(signer_cert, digest_algorithm_type)
484
485    // Generate the signedAttrs component of CMS, passing any optional custom signedAttrs (e.g. PAdES ESS).
486    // The signedAttrs are certain attributes that become protected by their inclusion in the signature.
487    signedAttrs := DigitalSignatureFieldGenerateCMSSignedAttributes(pdf_digest, pades_versioned_ess_signing_cert_attribute)
488
489    // Calculate the digest of the signedAttrs (i.e. not the PDF digest, this time).
490    signedAttrs_digest := DigestAlgorithmCalculateDigest(digest_algorithm_type, signedAttrs)
491
492    ///////////////////////////// custom digest signing starts ////////////////////////////
493    // At this point, you can sign the digest (for example, with HSM). We use our own SignDigest function instead here as an example,
494    // which you can also use for your purposes if necessary as an alternative to the handler/callback APIs (i.e. Certify/SignOnNextSave).
495    signature_value := DigestAlgorithmSignDigest(
496        signedAttrs_digest,
497        digest_algorithm_type,
498        private_key_file_path,
499        keyfile_password)
500    ///////////////////////////// custom digest signing ends ///////////////////////////////
501
502    // Then, load all your chain certificates into a container of X509Certificate.
503    chain_certs := NewVectorX509Certificate()
504
505    // Then, create ObjectIdentifiers for the algorithms you have used.
506    // Here we use digest_algorithm_type (usually SHA256) for hashing, and RSAES-PKCS1-v1_5 (specified in the private key) for signing.
507    digest_algorithm_oid := NewObjectIdentifier(digest_algorithm_type)
508    signature_algorithm_oid := NewObjectIdentifier(ObjectIdentifierE_RSA_encryption_PKCS1)
509
510    // Then, put the CMS signature components together.
511    cms_signature := DigitalSignatureFieldGenerateCMSSignature(
512        signer_cert, chain_certs, digest_algorithm_oid, signature_algorithm_oid,
513        signature_value, signedAttrs)
514
515    // Write the signature to the document.
516    doc.SaveCustomSignature(cms_signature, digsig_field, output_path)
517
518    fmt.Println("================================================================================")
519}
520
521func TimestampAndEnableLTV(inDocpath string,
522    inTsaUrl string,
523    inTrustedCertPath string, 
524    inAppearanceImgPath string,
525    inOutpath string) bool{
526    doc := NewPDFDoc(inDocpath)
527    doctimestampSignatureField := doc.CreateDigitalSignatureField()
528    tstConfig := NewTimestampingConfiguration(inTsaUrl)
529    opts := NewVerificationOptions(VerificationOptionsE_compatibility_and_archiving)
530//   It is necessary to add to the VerificationOptions a trusted root certificate corresponding to 
531//   the chain used by the timestamp authority to sign the timestamp token, in order for the timestamp
532//   response to be verifiable during DocTimeStamp signing. It is also necessary in the context of this 
533//   function to do this for the later LTV section, because one needs to be able to verify the DocTimeStamp 
534//   in order to enable LTV for it, and we re-use the VerificationOptions opts object in that part.
535
536    opts.AddTrustedCertificate(inTrustedCertPath)
537//       By default, we only check online for revocation of certificates using the newer and lighter 
538//   OCSP protocol as opposed to CRL, due to lower resource usage and greater reliability. However, 
539//   it may be necessary to enable online CRL revocation checking in order to verify some timestamps
540//   (i.e. those that do not have an OCSP responder URL for all non-trusted certificates).
541
542    opts.EnableOnlineCRLRevocationChecking(true)
543
544    widgetAnnot := SignatureWidgetCreate(doc, NewRect(0.0, 100.0, 200.0, 150.0), doctimestampSignatureField)
545    doc.GetPage(1).AnnotPushBack(widgetAnnot)
546
547    // (OPTIONAL) Add an appearance to the signature field.
548    img := ImageCreate(doc.GetSDFDoc(), inAppearanceImgPath)
549    widgetAnnot.CreateSignatureAppearance(img)
550
551    fmt.Println("Testing timestamping configuration.")
552    configResult := tstConfig.TestConfiguration(opts)
553    if configResult.GetStatus(){
554        fmt.Println("Success: timestamping configuration usable. Attempting to timestamp.")
555    }else{
556        // Print details of timestamping failure.
557        fmt.Println(configResult.GetString())
558        if configResult.HasResponseVerificationResult(){
559            tstResult := configResult.GetResponseVerificationResult()
560            fmt.Println("CMS digest status: "+ tstResult.GetCMSDigestStatusAsString())
561            fmt.Println("Message digest status: " + tstResult.GetMessageImprintDigestStatusAsString())
562            fmt.Println("Trust status: " + tstResult.GetTrustStatusAsString())
563        }
564        return false
565    }
566
567    doctimestampSignatureField.TimestampOnNextSave(tstConfig, opts)
568
569    // Save/signing throws if timestamping fails.
570    doc.Save(inOutpath, uint(SDFDocE_incremental))
571
572    fmt.Println("Timestamping successful. Adding LTV information for DocTimeStamp signature.")
573
574    // Add LTV information for timestamp signature to document.
575    timestampVerificationResult := doctimestampSignatureField.Verify(opts)
576    if !doctimestampSignatureField.EnableLTVOfflineVerification(timestampVerificationResult){
577        fmt.Println("Could not enable LTV for DocTimeStamp.")
578        return false
579    }
580    doc.Save(inOutpath, uint(SDFDocE_incremental))
581    fmt.Println("Added LTV information for DocTimeStamp signature successfully.")
582
583    return true
584}
585
586func TestDigitalSignatures(t *testing.T){
587    // Initialize PDFNet
588    PDFNetInitialize(licenseKey)
589    
590    result := true
591    inputPath := "../TestFiles/"
592    outputPath := "../TestFiles/Output/"
593    
594    //////////////////////////////////////// TEST 0:
595    // Create an approval signature field that we can sign after certifying.
596    // (Must be done before calling CertifyOnNextSave/SignOnNextSave/WithCustomHandler.)
597    // Open an existing PDF
598    doc := NewPDFDoc(inputPath + "waiver.pdf")
599    widgetAnnotApproval := SignatureWidgetCreate(doc, NewRect(300.0, 287.0, 376.0, 306.0), "PDFTronApprovalSig")
600    page1 := doc.GetPage(1)
601    page1.AnnotPushBack(widgetAnnotApproval)
602    doc.Save(outputPath + "waiver_withApprovalField_output.pdf", uint(SDFDocE_remove_unused))
603
604    //////////////////////////////////////// TEST 1: certify a PDF.
605    CertifyPDF(inputPath + "waiver_withApprovalField.pdf",
606            "PDFTronCertificationSig",
607            inputPath + "pdftron.pfx",
608            "password",
609            inputPath + "pdftron.bmp",
610            outputPath + "waiver_withApprovalField_certified_output.pdf")
611    PrintSignaturesInfo(outputPath + "waiver_withApprovalField_certified_output.pdf")
612
613    //////////////////////////////////////// TEST 2: approval-sign an existing, unsigned signature field in a PDF that already has a certified signature field.
614    SignPDF(inputPath + "waiver_withApprovalField_certified.pdf",
615            "PDFTronApprovalSig",
616            inputPath + "pdftron.pfx",
617            "password",
618            inputPath + "signature.jpg",
619            outputPath + "waiver_withApprovalField_certified_approved_output.pdf")
620    PrintSignaturesInfo(outputPath + "waiver_withApprovalField_certified_approved_output.pdf")
621
622    //////////////////////////////////////// TEST 3: Clear a certification from a document that is certified and has an approval signature.
623    ClearSignature(inputPath + "waiver_withApprovalField_certified_approved.pdf",
624            "PDFTronCertificationSig",
625            outputPath + "waiver_withApprovalField_certified_approved_certcleared_output.pdf")
626    PrintSignaturesInfo(outputPath + "waiver_withApprovalField_certified_approved_certcleared_output.pdf")
627
628    //////////////////////////////////////// TEST 4: Verify a document's digital signatures.
629    if !VerifyAllAndPrint(inputPath + "waiver_withApprovalField_certified_approved.pdf", inputPath + "pdftron.cer"){
630        result = false
631    }
632
633    //////////////////////////////////////// TEST 5: Verify a document's digital signatures in a simple fashion using the document API.
634    if !VerifySimple(inputPath + "waiver_withApprovalField_certified_approved.pdf", inputPath + "pdftron.cer"){
635       result = false
636    }
637
638    //////////////////// TEST 6: Custom signing API.
639    // The Apryse custom signing API is a set of APIs related to cryptographic digital signatures
640    // which allows users to customize the process of signing documents. Among other things, this
641    // includes the capability to allow for easy integration of PDF-specific signing-related operations
642    // with access to Hardware Security Module (HSM) tokens/devices, access to cloud keystores, access
643    // to system keystores, etc.
644    CustomSigningAPI(inputPath + "waiver.pdf",
645            "PDFTronApprovalSig",
646            inputPath + "pdftron.pfx",
647            "password",
648            inputPath + "pdftron.cer",
649            inputPath + "signature.jpg",
650            DigestAlgorithmE_SHA256,
651            true,
652            outputPath + "waiver_custom_signed.pdf")
653
654    //////////////////////////////////////// TEST 7: Timestamp a document, then add Long Term Validation (LTV) information for the DocTimeStamp.
655    
656    // // Replace YOUR_URL_OF_TSA with the timestamp authority (TSA) URL to use during timestamping.
657    // // For example, as of July 2024, http://timestamp.globalsign.com/tsa/r6advanced1 was usable.
658    // // Note that this url may not work in the future. A reliable solution requires using your own TSA.
659    // tsaUrl := "YOUR_URL_OF_TSA"
660    //
661    // // Replace YOUR_CERTIFICATE with the trusted root certificate corresponding to the chain used by the timestamp authority.
662    // // For example, as of July 2024, https://secure.globalsign.com/cacert/gstsacasha384g4.crt was usable.
663    // // Note that this certificate may not work in the future. A reliable solution requires using your own TSA certificate.
664    // trustedCertPath := "YOUR_CERTIFICATE";
665    //
666    // if tsaUrl == "YOUR_URL_OF_TSA" {
667    //     fmt.Println("Error: The URL of your timestamp authority was not specified.")
668    //     result = false
669    // } else if trustedCertPath == "YOUR_CERTIFICATE" {
670    //     fmt.Println("Error: The path to your timestamp authority trusted root certificate was not specified.")
671    //     result = false
672    // } else if !TimestampAndEnableLTV(inputPath + "waiver.pdf",
673    //    tsaUrl,
674    //    trustedCertPath,
675    //    inputPath + "signature.jpg",
676    //    outputPath + "waiver_DocTimeStamp_LTV.pdf") {
677    //    result = false
678    // }
679     
680    //////////////////////////////////////// End of tests. ////////////////////////////////////////
681
682    if !result{
683        fmt.Println("Tests FAILED!!!\n==========")
684        PDFNetTerminate()
685        return
686    }
687    PDFNetTerminate()
688    fmt.Println("Tests successful.\n==========")
689}

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