A very simple (and incomplete!) implementation of scep protocol for nodejs.

The function that responds to requests must be something like this:

var node_scep = require('scep'); /* With the GET method, the message part is either plain text, or Distinguished Encoding Rules (DER)-encoded PKCS#7 converted to Base64. If the POST method is supported, content that would be sent in Base64 encoding with GET might be sent in binary format with POST instead. */

function pkiclient(req, res){ var operation = req.query && req.query.operation; tlog('pkiclient op=' + operation); /* operation = GetCACert, GetNextCACert, or (optional) GetCACaps: message can be omitted, or can be set to a name that identifies the CA. */

/*
 { operation: 'GetCACert',
 message: 'EnrollmentCAInstance' }
 */
switch(operation){
    case 'GetCACert':
        var crt = ...;// the certificate.pem in der format
        res.setHeader('Content-Type', 'application/x-x509-ca-cert');
        res.setHeader('Content-Length', crt.length);
        res.send(crt);
        break;
/*
 { operation: 'GetCACaps',
 message: 'EnrollmentCAInstance' }
 */

/*
{ operation: 'PKIOperation',
    message: 'MIAG...AAAAAAA=' }
*/
/*
 message is a SCEP pkiMessage structure, based on PKCS#7 and encoded with DER and Base64.
 the pkiMessage structure can be of these types:
 PKCSReq: PKCS#10 CSR
 GetCertInitial: polling for CSR granting status
 GetCert or GetCRL: certificate or CRL retrieval
 */
    case 'PKIOperation':
        var p7sign = new Buffer(req.query.message, 'base64');
        var input = {
            req  : p7sign,
            cert : '/path/of/certificate.pem',
            key  : '/path/of/key.pem'
        };

        var csr = node_scep.extract_csr(input);
        var opt = {
            csr  : csr,
            days : 365,
            caCert : input.cert,
            caKey : input.key,
            outform : 'der'
        };
        //this function call the line command:
        //openssl x509 -req -days 365 -in input.csr -CA cert.pem -CAkey key.pem -CAcreateserial -out out.der -outform der
        openssl.generateCrt(opt, function(err, crt){
            if(err){
                log(err);
                return res.send(500);
            }
            input.crt = crt;//this is a buffer
            var pkcs7 = node_scep.encode_res(input);
            res.setHeader('Content-Type', 'application/x-pki-message');
            res.setHeader('Content-Length', pkcs7.length);
            res.send(pkcs7);
        });
        break;
    default:
        res.send(200);
}

}