(VB.NET) Validate PDF Signatures

See more PDF Signatures Examples

This example demonstrates how to validate the signatures in a PDF and also shows how to get information from each signature.

Note: This example requires Chilkat v9.5.0.85 or greater.

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' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim pdf As New Chilkat.Pdf

' Load a PDF that has cryptographic signatures to be validated
Dim success As Boolean = pdf.LoadFile("qa_data/pdf/sign_testing_1/helloSigned2.pdf")
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If


' Each time we verify a signature, information about the signature is written into
' sigInfo (replacing whatever sigInfo previously contained).
Dim sigInfo As New Chilkat.JsonObject
sigInfo.EmitCompact = False

' Iterate over each signature and validate each.
Dim numSignatures As Integer = pdf.NumSignatures
Dim validated As Boolean = False
Dim i As Integer = 0
While i < numSignatures
    validated = pdf.VerifySignature(i,sigInfo)
    Debug.WriteLine("Signature " & i & " validated: " & validated)
    Debug.WriteLine(sigInfo.Emit())
    i = i + 1
End While

Debug.WriteLine("Finished.")


' When VerifySignature validates a signature, a lot of information is deposited into the JSON sigInfo object.
' The information can vary depending on what was included in the signature (for example, various authenticated attributes
' and unauthenticated attributes may or may not be included).
' Here is a sample of the information you'll see.
' 
' The following online tool can be used to generate code to parse any given JSON.
' Generate Parsing Code from JSON

' {
'   "validated": true,
'   "signatureDictionary": {         <--- This is the contents of the PDF Signature Dictionary for this signature.
'     "/ByteRange": [
'       0,
'       154682,
'       170512,
'       3233
'     ],
'     "/Contents": "<hex_data>",
'     "/Filter": "/Adobe.PPKLite",        <--- The meaning of the Signature Dictionary entries are defined in the PDF format specification document.
'     "/M": "D:20201006110216-05'00'",
'     "/Name": "yubikey rsa 1024 authentication",
'     "/Prop_Build": {
'       "/App": {
'         "/Name": "/Adobe#20Acrobat#20Pro#20DC",
'         "/OS": [
'           "/Win"
'         ],
'         "/R": 1313792,
'         "/REx": "2020.012.20048",
'         "/TrustedMode": true
'       },
'       "/Filter": {
'         "/Date": "Sep 11 2020 16:30:54",
'         "/Name": "/Adobe.PPKLite",
'         "/R": 131104,
'         "/V": 2
'       },
'       "/PubSec": {
'         "/Date": "Sep 11 2020 16:30:54",
'         "/NonEFontNoWarn": true,
'         "/R": 131105
'       }
'     },
'     "/SubFilter": "/adbe.pkcs7.detached",
'     "/Type": "/Sig"
'   },
'   "pkcs7": {          <--- This is the content of the CMS signature.
'     "verify": {
'       "certs": [      <--- Each signing certificate is listed here (by issuer common name and signing cert's serail number (in hex))
'         {
'           "issuerCN": "yubikey rsa 1024 authentication",
'           "serial": "66BE58138D761E92BC594A722932657BE26D421F"
'         }
'       ],
'       "digestAlgorithms": [
'         "sha256"
'       ],
'       "signerInfo": [     <--- contains data from each SignerInfo
'         {
'           "cert": {
'             "serialNumber": "66BE58138D761E92BC594A722932657BE26D421F",
'             "issuerCN": "yubikey rsa 1024 authentication",
'             "digestAlgOid": "2.16.840.1.101.3.4.2.1",
'             "digestAlgName": "SHA256"
'           },
'           "contentType": "1.2.840.113549.1.7.1",
'           "messageDigest": "btQOuSEvC31mdRFHtyEUPw8R9NuKfk0XPcQ6Lcmn6pk=",
'           "signingAlgOid": "1.2.840.113549.1.1.11",
'           "signingAlgName": "RSA-SHA256-PKCSV-1_5",
'           "authAttr": {     <--- CMS authenticated attributes are contained here.
'             "1.2.840.113583.1.1.8": {
'               "der": "MAA="
'             },
'             "1.2.840.113549.1.9.3": {
'               "name": "contentType",
'               "oid": "1.2.840.113549.1.7.1"
'             },
'             "1.2.840.113549.1.9.4": {
'               "name": "messageDigest",
'               "digest": "btQOuSEvC31mdRFHtyEUPw8R9NuKfk0XPcQ6Lcmn6pk="
'             }
'           },
'           "unauthAttr": {    <--- CMS unauthenticated attributes are contained here.
'             "1.2.840.113549.1.9.16.2.14": {
'               "name": "timestampToken",
'               "der": "MIIOvAYJKo ... Es/70g=",
'               "verify": {
'                 "digestAlgorithms": [
'                   "sha256"
'                 ],
'                 "signerInfo": [
'                   {
'                     "cert": {
'                       "serialNumber": "04CD3F8568AE76C61BB0FE7160CCA76D",
'                       "issuerCN": "DigiCert SHA2 Assured ID Timestamping CA",
'                       "digestAlgOid": "2.16.840.1.101.3.4.2.1",
'                       "digestAlgName": "SHA256"
'                     },
'                     "contentType": "1.2.840.113549.1.9.16.1.4",
'                     "signingTime": "201006160423Z",
'                     "messageDigest": "Atv5Rj3kidB8IR6CplYiX3o6De/k8SC6JJ6uUPAGO0g=",
'                     "signingAlgOid": "1.2.840.113549.1.1.1",
'                     "signingAlgName": "RSA-PKCSV-1_5",
'                     "authAttr": {
'                       "1.2.840.113549.1.9.3": {
'                         "name": "contentType",
'                         "oid": "1.2.840.113549.1.9.16.1.4"
'                       },
'                       "1.2.840.113549.1.9.5": {
'                         "name": "signingTime",
'                         "utctime": "201006160423Z"
'                       },
'                       "1.2.840.113549.1.9.16.2.12": {
'                         "name": "signingCertificate",
'                         "der": "MBowGDAWBBQDJb1QXtqWMC3CL0+gHkwovig0xQ=="
'                       },
'                       "1.2.840.113549.1.9.4": {
'                         "name": "messageDigest",
'                         "digest": "Atv5Rj3kidB8IR6CplYiX3o6De/k8SC6JJ6uUPAGO0g="
'                       }
'                     }
'                   }
'                 ]
'               },
'               "timestampSignatureVerified": true,
'               "tstInfo": {
'                 "tsaPolicyId": "2.16.840.1.114412.7.1",
'                 "messageImprint": {
'                   "hashAlg": "sha256",
'                   "digest": "gLJtrRWUSDfjzDkF1MfWG1wyHA6FrUJLkWMGRG+eMlA=",
'                   "digestMatches": true
'                 },
'                 "serialNumber": "00CE57E1113970607EF63B1D1160545321",
'                 "genTime": "20201006160423Z"
'               }
'             }
'           }
'         }
'       ],
'       "pkcs7": {
'         "verify": {
'           "certs": [
'             {
'               "issuerCN": "DigiCert SHA2 Assured ID Timestamping CA",
'               "serial": "04CD3F8568AE76C61BB0FE7160CCA76D"
'             },
'             {
'               "issuerCN": "DigiCert Assured ID Root CA",
'               "serial": "0AA125D6D6321B7E41E405DA3697C215"
'             }
'           ]
'         }
'       }
'     }
'   }
' }


' **** The point of this code is to show how to get at each desired piece of information contained in the signature.
' **** If your signature contains additional information not shown here, then you can use the online tool to generate the parse code.
' **** It is likely you're only interested in a few items of information, and therefore you wouldn't copy all of this code, but might
' **** choose to use bits and pieces to get the information you find important.

Dim json As New Chilkat.JsonObject

' Imagine that the "json" object contains the information obtained by validating a signature...
' The code below was generated using the online tool:  Generate Parsing Code from JSON



Dim unauthAttrTimestampTokenTstInfoGenTime As New Chilkat.DtObj
Dim signingTime As New Chilkat.DtObj
Dim authAttrSigningTimeUtctime As New Chilkat.DtObj
Dim intVal As Integer
Dim strVal As String
Dim issuerCN As String
Dim serial As String
Dim certSerialNumber As String
Dim certIssuerCN As String
Dim certDigestAlgOid As String
Dim certDigestAlgName As String
Dim contentType As String
Dim messageDigest As String
Dim signingAlgOid As String
Dim signingAlgName As String
Dim authAttr1_2_840_113583_1_1_8Der As String
Dim authAttrContentTypeName As String
Dim authAttrContentTypeOid As String
Dim authAttrMessageDigestName As String
Dim authAttrMessageDigestDigest As String
Dim unauthAttrTimestampTokenName As String
Dim unauthAttrTimestampTokenDer As String
Dim unauthAttrTimestampTokenTimestampSignatureVerified As Boolean
Dim unauthAttrTimestampTokenTstInfoTsaPolicyId As String
Dim unauthAttrTimestampTokenTstInfoMessageImprintHashAlg As String
Dim unauthAttrTimestampTokenTstInfoMessageImprintDigest As String
Dim unauthAttrTimestampTokenTstInfoMessageImprintDigestMatches As Boolean
Dim unauthAttrTimestampTokenTstInfoSerialNumber As String
Dim j As Integer
Dim count_j As Integer
Dim authAttrSigningTimeName As String
Dim authAttrSigningCertificateName As String
Dim authAttrSigningCertificateDer As String

validated = json.BoolOf("validated")
Dim signatureDictionary_Contents As String = json.StringOf("signatureDictionary./Contents")
Dim signatureDictionary_Filter As String = json.StringOf("signatureDictionary./Filter")
Dim signatureDictionary_M As String = json.StringOf("signatureDictionary./M")
Dim signatureDictionary_Name As String = json.StringOf("signatureDictionary./Name")
Dim signatureDictionary_Prop_Build_App_Name As String = json.StringOf("signatureDictionary./Prop_Build./App./Name")
Dim signatureDictionary_Prop_Build_App_R As Integer = json.IntOf("signatureDictionary./Prop_Build./App./R")
Dim signatureDictionary_Prop_Build_App_REx As String = json.StringOf("signatureDictionary./Prop_Build./App./REx")
Dim signatureDictionary_Prop_Build_App_TrustedMode As Boolean = json.BoolOf("signatureDictionary./Prop_Build./App./TrustedMode")
Dim signatureDictionary_Prop_Build_Filter_Date As String = json.StringOf("signatureDictionary./Prop_Build./Filter./Date")
Dim signatureDictionary_Prop_Build_Filter_Name As String = json.StringOf("signatureDictionary./Prop_Build./Filter./Name")
Dim signatureDictionary_Prop_Build_Filter_R As Integer = json.IntOf("signatureDictionary./Prop_Build./Filter./R")
Dim signatureDictionary_Prop_Build_Filter_V As Integer = json.IntOf("signatureDictionary./Prop_Build./Filter./V")
Dim signatureDictionary_Prop_Build_PubSec_Date As String = json.StringOf("signatureDictionary./Prop_Build./PubSec./Date")
Dim signatureDictionary_Prop_Build_PubSec_NonEFontNoWarn As Boolean = json.BoolOf("signatureDictionary./Prop_Build./PubSec./NonEFontNoWarn")
Dim signatureDictionary_Prop_Build_PubSec_R As Integer = json.IntOf("signatureDictionary./Prop_Build./PubSec./R")
Dim signatureDictionary_SubFilter As String = json.StringOf("signatureDictionary./SubFilter")
Dim signatureDictionary_Type As String = json.StringOf("signatureDictionary./Type")
i = 0
Dim count_i As Integer = json.SizeOfArray("signatureDictionary./ByteRange")
While i < count_i
    json.I = i
    intVal = json.IntOf("signatureDictionary./ByteRange[i]")
    i = i + 1
End While
i = 0
count_i = json.SizeOfArray("signatureDictionary./Prop_Build./App./OS")
While i < count_i
    json.I = i
    strVal = json.StringOf("signatureDictionary./Prop_Build./App./OS[i]")
    i = i + 1
End While
i = 0
count_i = json.SizeOfArray("pkcs7.verify.certs")
While i < count_i
    json.I = i
    issuerCN = json.StringOf("pkcs7.verify.certs[i].issuerCN")
    serial = json.StringOf("pkcs7.verify.certs[i].serial")
    i = i + 1
End While
i = 0
count_i = json.SizeOfArray("pkcs7.verify.digestAlgorithms")
While i < count_i
    json.I = i
    strVal = json.StringOf("pkcs7.verify.digestAlgorithms[i]")
    i = i + 1
End While
i = 0
count_i = json.SizeOfArray("pkcs7.verify.signerInfo")
While i < count_i
    json.I = i
    certSerialNumber = json.StringOf("pkcs7.verify.signerInfo[i].cert.serialNumber")
    certIssuerCN = json.StringOf("pkcs7.verify.signerInfo[i].cert.issuerCN")
    certDigestAlgOid = json.StringOf("pkcs7.verify.signerInfo[i].cert.digestAlgOid")
    certDigestAlgName = json.StringOf("pkcs7.verify.signerInfo[i].cert.digestAlgName")
    contentType = json.StringOf("pkcs7.verify.signerInfo[i].contentType")
    messageDigest = json.StringOf("pkcs7.verify.signerInfo[i].messageDigest")
    signingAlgOid = json.StringOf("pkcs7.verify.signerInfo[i].signingAlgOid")
    signingAlgName = json.StringOf("pkcs7.verify.signerInfo[i].signingAlgName")
    authAttr1_2_840_113583_1_1_8Der = json.StringOf("pkcs7.verify.signerInfo[i].authAttr.""1.2.840.113583.1.1.8"".der")
    authAttrContentTypeName = json.StringOf("pkcs7.verify.signerInfo[i].authAttr.""1.2.840.113549.1.9.3"".name")
    authAttrContentTypeOid = json.StringOf("pkcs7.verify.signerInfo[i].authAttr.""1.2.840.113549.1.9.3"".oid")
    authAttrMessageDigestName = json.StringOf("pkcs7.verify.signerInfo[i].authAttr.""1.2.840.113549.1.9.4"".name")
    authAttrMessageDigestDigest = json.StringOf("pkcs7.verify.signerInfo[i].authAttr.""1.2.840.113549.1.9.4"".digest")
    unauthAttrTimestampTokenName = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".name")
    unauthAttrTimestampTokenDer = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".der")
    unauthAttrTimestampTokenTimestampSignatureVerified = json.BoolOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".timestampSignatureVerified")
    unauthAttrTimestampTokenTstInfoTsaPolicyId = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".tstInfo.tsaPolicyId")
    unauthAttrTimestampTokenTstInfoMessageImprintHashAlg = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".tstInfo.messageImprint.hashAlg")
    unauthAttrTimestampTokenTstInfoMessageImprintDigest = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".tstInfo.messageImprint.digest")
    unauthAttrTimestampTokenTstInfoMessageImprintDigestMatches = json.BoolOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".tstInfo.messageImprint.digestMatches")
    unauthAttrTimestampTokenTstInfoSerialNumber = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".tstInfo.serialNumber")
    json.DtOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".tstInfo.genTime",False,unauthAttrTimestampTokenTstInfoGenTime)
    j = 0
    count_j = json.SizeOfArray("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.digestAlgorithms")
    While j < count_j
        json.J = j
        strVal = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.digestAlgorithms[j]")
        j = j + 1
    End While
    j = 0
    count_j = json.SizeOfArray("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo")
    While j < count_j
        json.J = j
        certSerialNumber = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].cert.serialNumber")
        certIssuerCN = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].cert.issuerCN")
        certDigestAlgOid = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].cert.digestAlgOid")
        certDigestAlgName = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].cert.digestAlgName")
        contentType = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].contentType")
        json.DtOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].signingTime",False,signingTime)
        messageDigest = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].messageDigest")
        signingAlgOid = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].signingAlgOid")
        signingAlgName = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].signingAlgName")
        authAttrContentTypeName = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].authAttr.""1.2.840.113549.1.9.3"".name")
        authAttrContentTypeOid = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].authAttr.""1.2.840.113549.1.9.3"".oid")
        authAttrSigningTimeName = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].authAttr.""1.2.840.113549.1.9.5"".name")
        json.DtOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].authAttr.""1.2.840.113549.1.9.5"".utctime",False,authAttrSigningTimeUtctime)
        authAttrSigningCertificateName = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].authAttr.""1.2.840.113549.1.9.16.2.12"".name")
        authAttrSigningCertificateDer = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].authAttr.""1.2.840.113549.1.9.16.2.12"".der")
        authAttrMessageDigestName = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].authAttr.""1.2.840.113549.1.9.4"".name")
        authAttrMessageDigestDigest = json.StringOf("pkcs7.verify.signerInfo[i].unauthAttr.""1.2.840.113549.1.9.16.2.14"".verify.signerInfo[j].authAttr.""1.2.840.113549.1.9.4"".digest")
        j = j + 1
    End While
    i = i + 1
End While
i = 0
count_i = json.SizeOfArray("pkcs7.verify.pkcs7.verify.certs")
While i < count_i
    json.I = i
    issuerCN = json.StringOf("pkcs7.verify.pkcs7.verify.certs[i].issuerCN")
    serial = json.StringOf("pkcs7.verify.pkcs7.verify.certs[i].serial")
    i = i + 1
End While