(Node.js) Decrypt S/MIME and Verify S/MIME Signatures

Node.js example to decrypt S/MIME and verify S/MIME signatures. The S/MIME is unwrapped to get the original MIME prior to signing/encrypting.

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOSX, and ARM

var os = require('os');
if (os.platform() == 'win32') {  
    if (os.arch() == 'ia32') {
        var chilkat = require('@chilkat/ck-node21-win-ia32');
    } else {
        var chilkat = require('@chilkat/ck-node21-win64'); 
    }
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node21-arm');
    } else if (os.arch() == 'x86') {
        var chilkat = require('@chilkat/ck-node21-linux32');
    } else {
        var chilkat = require('@chilkat/ck-node21-linux64');
    }
} else if (os.platform() == 'darwin') {
    if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node21-mac-m1');
    } else {
        var chilkat = require('@chilkat/ck-node21-macosx');
    }
}

function chilkatExample() {

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

    var mime = new chilkat.Mime();

    // Load an S/MIME message from a file:
    var success = mime.LoadMimeFile("signedMime.txt");
    if (success !== true) {
        console.log(mime.LastErrorText);
        return;
    }

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

    // We don't want the "unwrap extras".  You'll see what those
    // are in a few moments...
    mime.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.
        console.log(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:
        // signerCert: Cert
        var signerCert = mime.GetSignerCert(0);
        if (mime.LastMethodSuccess == true) {
            console.log("**** 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:
        // encryptCert: Cert
        var encryptCert = mime.GetEncryptCert(0);
        if (mime.LastMethodSuccess == true) {
            console.log("**** Encrypt Cert: " + encryptCert.SubjectCN);

        }

    }

    // Display the unwrapped MIME:
    console.log(mime.GetMime());

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

}

chilkatExample();