(C#) 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.

Chilkat.Pdf pdf = new Chilkat.Pdf();

// Load a PDF that has cryptographic signatures to be validated
bool success = pdf.LoadFile("qa_data/pdf/sign_testing_1/helloSigned2.pdf");
if (success == false) {
    Debug.WriteLine(pdf.LastErrorText);
    return;
}

// Each time we verify a signature, information about the signature is written into
// sigInfo (replacing whatever sigInfo previously contained).
Chilkat.JsonObject sigInfo = new Chilkat.JsonObject();
sigInfo.EmitCompact = false;

// Iterate over each signature and validate each.
int numSignatures = pdf.NumSignatures;
bool validated = false;
int i = 0;
while (i < numSignatures) {
    validated = pdf.VerifySignature(i,sigInfo);
    Debug.WriteLine("Signature " + Convert.ToString(i) + " validated: " + Convert.ToString(validated));
    Debug.WriteLine(sigInfo.Emit());
    i = i + 1;
}

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.

Chilkat.JsonObject json = 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

Chilkat.DtObj unauthAttrTimestampTokenTstInfoGenTime = new Chilkat.DtObj();
Chilkat.DtObj signingTime = new Chilkat.DtObj();
Chilkat.DtObj authAttrSigningTimeUtctime = new Chilkat.DtObj();
int intVal;
string strVal;
string issuerCN;
string serial;
string certSerialNumber;
string certIssuerCN;
string certDigestAlgOid;
string certDigestAlgName;
string contentType;
string messageDigest;
string signingAlgOid;
string signingAlgName;
string authAttr1_2_840_113583_1_1_8Der;
string authAttrContentTypeName;
string authAttrContentTypeOid;
string authAttrMessageDigestName;
string authAttrMessageDigestDigest;
string unauthAttrTimestampTokenName;
string unauthAttrTimestampTokenDer;
bool unauthAttrTimestampTokenTimestampSignatureVerified;
string unauthAttrTimestampTokenTstInfoTsaPolicyId;
string unauthAttrTimestampTokenTstInfoMessageImprintHashAlg;
string unauthAttrTimestampTokenTstInfoMessageImprintDigest;
bool unauthAttrTimestampTokenTstInfoMessageImprintDigestMatches;
string unauthAttrTimestampTokenTstInfoSerialNumber;
int j;
int count_j;
string authAttrSigningTimeName;
string authAttrSigningCertificateName;
string authAttrSigningCertificateDer;

validated = json.BoolOf("validated");
string signatureDictionary_Contents = json.StringOf("signatureDictionary./Contents");
string signatureDictionary_Filter = json.StringOf("signatureDictionary./Filter");
string signatureDictionary_M = json.StringOf("signatureDictionary./M");
string signatureDictionary_Name = json.StringOf("signatureDictionary./Name");
string signatureDictionary_Prop_Build_App_Name = json.StringOf("signatureDictionary./Prop_Build./App./Name");
int signatureDictionary_Prop_Build_App_R = json.IntOf("signatureDictionary./Prop_Build./App./R");
string signatureDictionary_Prop_Build_App_REx = json.StringOf("signatureDictionary./Prop_Build./App./REx");
bool signatureDictionary_Prop_Build_App_TrustedMode = json.BoolOf("signatureDictionary./Prop_Build./App./TrustedMode");
string signatureDictionary_Prop_Build_Filter_Date = json.StringOf("signatureDictionary./Prop_Build./Filter./Date");
string signatureDictionary_Prop_Build_Filter_Name = json.StringOf("signatureDictionary./Prop_Build./Filter./Name");
int signatureDictionary_Prop_Build_Filter_R = json.IntOf("signatureDictionary./Prop_Build./Filter./R");
int signatureDictionary_Prop_Build_Filter_V = json.IntOf("signatureDictionary./Prop_Build./Filter./V");
string signatureDictionary_Prop_Build_PubSec_Date = json.StringOf("signatureDictionary./Prop_Build./PubSec./Date");
bool signatureDictionary_Prop_Build_PubSec_NonEFontNoWarn = json.BoolOf("signatureDictionary./Prop_Build./PubSec./NonEFontNoWarn");
int signatureDictionary_Prop_Build_PubSec_R = json.IntOf("signatureDictionary./Prop_Build./PubSec./R");
string signatureDictionary_SubFilter = json.StringOf("signatureDictionary./SubFilter");
string signatureDictionary_Type = json.StringOf("signatureDictionary./Type");
i = 0;
int count_i = json.SizeOfArray("signatureDictionary./ByteRange");
while (i < count_i) {
    json.I = i;
    intVal = json.IntOf("signatureDictionary./ByteRange[i]");
    i = i + 1;
}

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;
}

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;
}

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;
}

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;
    }

    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;
    }

    i = i + 1;
}

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;
}