(C) Duplicate openssl req -newkey rsa:2048 -nodes -keyout mydomain.pem -out mydomain.csr

Demonstrates how to duplicate this OpenSSL command:

openssl req -newkey rsa:2048 -nodes -keyout mydomain.pem -out mydomain.csr

This command creates 2 files:

1. mydomain.csr: this is the file to send to DigiCert or Let's Encrypt (or any other CA)
2. mydomain.pem: this is the private key of the domain.

The second file is needed to pair with the certificate that will later be received from the CA.

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#include <C_CkRsa.h>
#include <C_CkPrivateKey.h>
#include <C_CkXml.h>
#include <C_CkAsn.h>
#include <C_CkBinData.h>

void ChilkatSample(void)
    {
    HCkRsa rsa;
    BOOL success;
    HCkPrivateKey privKey;
    HCkXml privKeyXml;
    const char *keyModulus;
    HCkAsn asnRoot;
    HCkAsn asnCertReqInfo;
    HCkAsn asnCertSubject;
    HCkAsn asnTemp;
    HCkAsn asnPubKeyInfo;
    HCkAsn asnPubKeyAlgId;
    HCkAsn asnRsaKey;
    const char *rsaKeyDerBase64;
    HCkBinData bdDer;
    HCkBinData bdSig;
    HCkAsn asnAlgId;
    const char *csrBase64;

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

    rsa = CkRsa_Create();

    // Generate a 2048-bit key.  Chilkat RSA supports
    // key sizes ranging from 512 bits to 8192 bits.
    success = CkRsa_GenerateKey(rsa,2048);
    if (success != TRUE) {
        printf("%s\n",CkRsa_lastErrorText(rsa));
        CkRsa_Dispose(rsa);
        return;
    }

    privKey = CkRsa_ExportPrivateKeyObj(rsa);

    // Save the private key to unencrypted PKCS8 PEM
    success = CkPrivateKey_SavePkcs8PemFile(privKey,"mydomain.pem");

    // (alternatively) Save the private key to encrypted PKCS8 PEM
    success = CkPrivateKey_SavePkcs8EncryptedPemFile(privKey,"myPassword","mydomain_enc.pem");

    // We'll need the private key's modulus for the CSR.
    // The modulus is not something that needs to be protected.  Most people don't realize
    // that a public key is actually just a subset of the private key.  The public parts of
    // an RSA private key are the modulus and exponent.  The exponent is always 65537.
    privKeyXml = CkXml_Create();
    success = CkXml_LoadXml(privKeyXml,CkPrivateKey_getXml(privKey));

    // Get the modulus in base64 format:
    keyModulus = CkXml_getChildContent(privKeyXml,"Modulus");

    // --------------------------------------------------------------------------------
    // Now build the CSR using Chilkat's ASN.1 API.
    // The keyModulus will be embedded within the ASN.1.

    // A new ASN.1 object is automatically a SEQUENCE.
    // Given that the CSR's root item is a SEQUENCE, we can use
    // this as the root of our CSR.
    asnRoot = CkAsn_Create();

    // Beneath the root, we have a SEQUENCE (the certificate request info), 
    // another SEQUENCE (the algorithm identifier), and a BITSTRING (the signature data)

    success = CkAsn_AppendSequence(asnRoot);
    success = CkAsn_AppendSequence(asnRoot);

    // ----------------------------------
    // Build the Certificate Request Info
    // ----------------------------------
    asnCertReqInfo = CkAsn_GetSubItem(asnRoot,0);
    success = CkAsn_AppendInt(asnCertReqInfo,0);

    // Build the Subject part of the Certificate Request Info
    asnCertSubject = CkAsn_AppendSequenceR(asnCertReqInfo);

    // Add each subject part..
    asnTemp = CkAsn_AppendSetR(asnCertSubject);
    success = CkAsn_AppendSequence2(asnTemp);
    // AppendSequence2 updates the internal reference to the newly appended SEQUENCE.
    // The OID and printable string are added to the SEQUENCE.
    success = CkAsn_AppendOid(asnTemp,"2.5.4.6");
    success = CkAsn_AppendString(asnTemp,"printable","US");
    CkAsn_Dispose(asnTemp);

    asnTemp = CkAsn_AppendSetR(asnCertSubject);
    success = CkAsn_AppendSequence2(asnTemp);
    success = CkAsn_AppendOid(asnTemp,"2.5.4.8");
    success = CkAsn_AppendString(asnTemp,"utf8","Utah");
    CkAsn_Dispose(asnTemp);

    asnTemp = CkAsn_AppendSetR(asnCertSubject);
    success = CkAsn_AppendSequence2(asnTemp);
    success = CkAsn_AppendOid(asnTemp,"2.5.4.7");
    success = CkAsn_AppendString(asnTemp,"utf8","Lindon");
    CkAsn_Dispose(asnTemp);

    asnTemp = CkAsn_AppendSetR(asnCertSubject);
    success = CkAsn_AppendSequence2(asnTemp);
    success = CkAsn_AppendOid(asnTemp,"2.5.4.10");
    success = CkAsn_AppendString(asnTemp,"utf8","DigiCert Inc.");
    CkAsn_Dispose(asnTemp);

    asnTemp = CkAsn_AppendSetR(asnCertSubject);
    success = CkAsn_AppendSequence2(asnTemp);
    success = CkAsn_AppendOid(asnTemp,"2.5.4.11");
    success = CkAsn_AppendString(asnTemp,"utf8","DigiCert");
    CkAsn_Dispose(asnTemp);

    asnTemp = CkAsn_AppendSetR(asnCertSubject);
    success = CkAsn_AppendSequence2(asnTemp);
    success = CkAsn_AppendOid(asnTemp,"2.5.4.3");
    success = CkAsn_AppendString(asnTemp,"utf8","example.digicert.com");
    CkAsn_Dispose(asnTemp);

    CkAsn_Dispose(asnCertSubject);

    // Build the Public Key Info part of the Certificate Request Info
    asnPubKeyInfo = CkAsn_AppendSequenceR(asnCertReqInfo);

    asnPubKeyAlgId = CkAsn_AppendSequenceR(asnPubKeyInfo);
    success = CkAsn_AppendOid(asnPubKeyAlgId,"1.2.840.113549.1.1.1");
    success = CkAsn_AppendNull(asnPubKeyAlgId);
    CkAsn_Dispose(asnPubKeyAlgId);

    // The public key itself is a BIT STRING, but the bit string is composed of ASN.1
    // for the RSA public key.  We'll first build the RSA ASN.1 for the public key
    // (containing the 2048 bit modulus and exponent), and encoded it to DER, and then add
    // the DER bytes as a BIT STRING (as a sub-item of asnPubKeyInfo)

    // This is already a SEQUENCE..
    asnRsaKey = CkAsn_Create();

    // The RSA modulus is a big integer.
    success = CkAsn_AppendBigInt(asnRsaKey,keyModulus,"base64");
    success = CkAsn_AppendInt(asnRsaKey,65537);

    rsaKeyDerBase64 = CkAsn_getEncodedDer(asnRsaKey,"base64");

    // Now add the RSA key DER as a BIT STRING.
    success = CkAsn_AppendBits(asnPubKeyInfo,rsaKeyDerBase64,"base64");
    CkAsn_Dispose(asnPubKeyInfo);

    // The last part of the certificate request info is an empty context-specific constructed item
    // with a tag equal to 0.
    success = CkAsn_AppendContextConstructed(asnCertReqInfo,0);

    // Get the DER of the asnCertReqInfo.  
    // This will be signed using the RSA private key.
    bdDer = CkBinData_Create();
    success = CkAsn_WriteBd(asnCertReqInfo,bdDer);

    // Add the signature to the ASN.1
    bdSig = CkBinData_Create();
    success = CkRsa_SignBd(rsa,bdDer,"SHA1",bdSig);
    success = CkAsn_AppendBits(asnRoot,CkBinData_getEncoded(bdSig,"base64"),"base64");

    CkAsn_Dispose(asnCertReqInfo);

    // ----------------------------------
    // Finally, add the algorithm identifier, which is the 2nd sub-item under the root.
    // ----------------------------------
    asnAlgId = CkAsn_GetSubItem(asnRoot,1);
    success = CkAsn_AppendOid(asnAlgId,"1.2.840.113549.1.1.5");
    success = CkAsn_AppendNull(asnAlgId);
    CkAsn_Dispose(asnAlgId);

    // Write the CSR to a DER encoded binary file:
    success = CkAsn_WriteBinaryDer(asnRoot,"qa_output/mydomain.csr");
    if (success != TRUE) {
        printf("%s\n",CkAsn_lastErrorText(asnRoot));
        CkRsa_Dispose(rsa);
        CkXml_Dispose(privKeyXml);
        CkAsn_Dispose(asnRoot);
        CkAsn_Dispose(asnRsaKey);
        CkBinData_Dispose(bdDer);
        CkBinData_Dispose(bdSig);
        return;
    }

    // It is also possible to get the CSR in base64 format:
    csrBase64 = CkAsn_getEncodedDer(asnRoot,"base64");

    printf("Base64 CSR:\n");
    printf("%s\n",csrBase64);

    CkPrivateKey_Dispose(privKey);


    CkRsa_Dispose(rsa);
    CkXml_Dispose(privKeyXml);
    CkAsn_Dispose(asnRoot);
    CkAsn_Dispose(asnRsaKey);
    CkBinData_Dispose(bdDer);
    CkBinData_Dispose(bdSig);

    }