Verify S/MIME Signature

Java example to verify an S/MIME signature and unwrap the S/MIME to get the original MIME prior to signing/encrypting.

Download Chilkat Java Library

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[])
  {
    CkMime mime = new CkMime();

    //  Any string argument automatically begins the 30-day trial.
    boolean success;
    success = mime.UnlockComponent("30-day trial");
    if (success != true) {
        System.out.println("MIME component unlock failed");
        return;
    }

    //  Load an S/MIME message from a file:
    success = mime.LoadMimeFile("signedMime.txt");
    if (success != true) {
        System.out.println(mime.lastErrorText());
        return;
    }

    //  The ContainsEncryptedParts/ContainsSignedParts methods
    //  can be called to determine if the MIME is encrypted and/or signed:
    boolean isEncrypted;
    isEncrypted = mime.ContainsEncryptedParts();
    boolean isSigned;
    isSigned = mime.ContainsSignedParts();

    //  We don't want the "unwrap extras".  You'll see what those
    //  are in a few moments...
    mime.put_UnwrapExtras(false);

    //  To verify the signature, call UnwrapSecurity.  This will
    //  verify the signature(s) and decrypt the S/MIME and restore
    //  the MIME to the unsigned/unencrypted state.
    //  The results of what was found are present in the MIME object's
    //  properties, as well as extra header fields that are added
    //  to the unwrapped MIME.
    success = mime.UnwrapSecurity();
    if (success != true) {
        //  UnwrapSecurity returns _TRUE_ if all signatures were
        //  verified and all parts decrypted.
        System.out.println(mime.lastErrorText());
        return;
    }

    //  The mime.UnwrapExtras property controls whether or not
    //  these additional fields are added to the unwrapped MIME:
    // 
    //  X-NumPartsSigned: 1
    //  X-SignaturesValid: yes
    //  X-NumPartsEncrypted: 1
    //  X-Decrypted: no
    // 
    //  The X-NumPartsSigned/X-SignaturesValid headers are added
    //  if the MIME was signed.
    // 
    //  The X-NumPartsEncrypted/X-Decrypted headers are added
    //  if the MIME was encrypted.
    // 

    //  If the MIME was signed, get the certificate used for signing.
    if (isSigned == true) {
        //  The NumSignerCerts property indicates how many certificates
        //  were used for signing.  This example will assume the value is 1.
        //  To get the 1st signer cert, call GetSignerCert with an index of 0:
        CkCert signerCert;
        signerCert = mime.GetSignerCert(0);
        if (!(signerCert == null )) {
            System.out.println("**** Signer Cert: "
                 + signerCert.subjectCN());
        }

    }

    //  If the MIME was encrypted, get the certificate used for encryption:
    if (isEncrypted == true) {
        //  The NumEncryptCerts property indicates how many certificates
        //  were used for encrypting.  This example will assume the value is 1.
        //  To get the 1st encrypt cert, call GetEncryptCert with an index of 0:
        CkCert encryptCert;
        encryptCert = mime.GetEncryptCert(0);
        if (!(encryptCert == null )) {
            System.out.println("**** Encrypt Cert: "
                 + encryptCert.subjectCN());
        }

    }

    //  Display the unwrapped MIME:
    System.out.println(mime.getMime());

    //  Save the unwrapped MIME to a file:
    mime.SaveMime("unwrappedMime.txt");


  }
}