(Java) 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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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkPdf pdf = new CkPdf();

    // Load a PDF that has cryptographic signatures to be validated
    boolean success = pdf.LoadFile("qa_data/pdf/sign_testing_1/helloSigned2.pdf");
    if (success == false) {
        System.out.println(pdf.lastErrorText());
        return;
        }

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

    // Iterate over each signature and validate each.
    int numSignatures = pdf.get_NumSignatures();
    boolean validated = false;
    int i = 0;
    while (i < numSignatures) {
        validated = pdf.VerifySignature(i,sigInfo);
        System.out.println("Signature " + i + " validated: " + validated);
        System.out.println(sigInfo.emit());
        i = i+1;
        }

    System.out.println("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.

    CkJsonObject json = new CkJsonObject();

    // 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

    CkDtObj unauthAttrTimestampTokenTstInfoGenTime = new CkDtObj();
    CkDtObj signingTime = new CkDtObj();
    CkDtObj authAttrSigningTimeUtctime = new CkDtObj();
    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;
    boolean unauthAttrTimestampTokenTimestampSignatureVerified;
    String unauthAttrTimestampTokenTstInfoTsaPolicyId;
    String unauthAttrTimestampTokenTstInfoMessageImprintHashAlg;
    String unauthAttrTimestampTokenTstInfoMessageImprintDigest;
    boolean 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");
    boolean 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");
    boolean 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.put_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.put_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.put_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.put_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.put_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.put_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.put_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.put_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;
        }
  }
}