(C) Get RSA Key Modulus from .cer or .key

Demonstrates how to get the RSA key modulus from either the certificate (.cer) or RSA key (.key). OpenSSL commands to do the same would be:

openssl x509 -inform DER -in "test.cer"  -modulus -noout 

openssl pkcs8 -inform DER -in​ "test.key"​ -outform PEM -passin pass:"12345​678a​"
   | openssl rsa -inform PEM -modulus -noout 

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#include <C_CkPrivateKey.h>
#include <C_CkXml.h>
#include <C_CkBinData.h>
#include <C_CkCert.h>
#include <C_CkPublicKey.h>

void ChilkatSample(void)
    {
    HCkPrivateKey privKey;
    const char *password;
    BOOL success;
    HCkXml xml;
    const char *modulus;
    HCkBinData binDat;
    const char *hexModulus;
    HCkCert cert;
    HCkPublicKey pubKey;

    privKey = CkPrivateKey_Create();

    password = "12345678a";
    success = CkPrivateKey_LoadPkcs8EncryptedFile(privKey,"qa_data/certs/test_12345678a.key",password);
    if (success != TRUE) {
        printf("%s\n",CkPrivateKey_lastErrorText(privKey));
        CkPrivateKey_Dispose(privKey);
        return;
    }

    xml = CkXml_Create();
    CkXml_LoadXml(xml,CkPrivateKey_getXml(privKey));

    // The XML contains the parts of the key in base64.
    printf("Private Key XML:\n");
    printf("%s\n",CkXml_getXml(xml));

    // We can get the base64 modulus like this:
    modulus = CkXml_getChildContent(xml,"Modulus");
    printf("base64 modulus = %s\n",modulus);

    // To convert to hex:
    binDat = CkBinData_Create();
    CkBinData_AppendEncoded(binDat,modulus,"base64");
    hexModulus = CkBinData_getEncoded(binDat,"hex");
    printf("hex modulus = %s\n",hexModulus);

    // Now get the modulus from the cert:
    cert = CkCert_Create();

    success = CkCert_LoadFromFile(cert,"qa_data/certs/test_12345678a.cer");
    if (success != TRUE) {
        printf("%s\n",CkCert_lastErrorText(cert));
        CkPrivateKey_Dispose(privKey);
        CkXml_Dispose(xml);
        CkBinData_Dispose(binDat);
        CkCert_Dispose(cert);
        return;
    }

    // The cert contains the public key, which is composed of the
    // modulus + exponent (for RSA keys).
    pubKey = CkCert_ExportPublicKey(cert);

    CkXml_LoadXml(xml,CkPublicKey_getXml(pubKey));
    printf("Public Key XML:\n");
    printf("%s\n",CkXml_getXml(xml));

    // Proceed in the same way as before....
    modulus = CkXml_getChildContent(xml,"Modulus");
    printf("base64 modulus = %s\n",modulus);

    // To convert to hex:
    CkBinData_Clear(binDat);
    CkBinData_AppendEncoded(binDat,modulus,"base64");
    hexModulus = CkBinData_getEncoded(binDat,"hex");
    printf("hex modulus = %s\n",hexModulus);

    CkPublicKey_Dispose(pubKey);


    CkPrivateKey_Dispose(privKey);
    CkXml_Dispose(xml);
    CkBinData_Dispose(binDat);
    CkCert_Dispose(cert);

    }