(C) Walmart Partner API Authentication (Generate a Signature for a Request)

Demonstrates how to generate a signature for a Walmart Partner REST API call.

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#include <C_CkDateTime.h>
#include <C_CkStringBuilder.h>
#include <C_CkPrivateKey.h>
#include <C_CkRsa.h>

void ChilkatSample(void)
    {
    BOOL success;
    const char *consumerId;
    const char *baseUrl;
    const char *privateEncodedStr;
    const char *httpMethod;
    HCkDateTime dt;
    BOOL bLocal;
    int timeStampVal;
    HCkStringBuilder sbStringToSign;
    HCkPrivateKey privKey;
    HCkRsa rsa;
    const char *signatureString;

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

    consumerId = "b68d2a72....";
    baseUrl = "https://marketplace.walmartapis.com/v2/feeds";
    // This is your Base64 encoded private key
    privateEncodedStr = "MIICeAIBADANBgkqhkiG9w0BAQEFAA......";
    httpMethod = "GET";

    // We need a timestamp in decimal string form representing the number of milliseconds since Jan 01 1970 UTC.
    dt = CkDateTime_Create();
    // Set bLocal = TRUE for a timestamp in the local timezone.  Set bLocal = FALSE for a UTC timestamp.
    bLocal = FALSE;
    // This gets the timestamp in seconds, not milliseconds.
    timeStampVal = CkDateTime_GetAsUnixTime(dt,bLocal);

    // Build the string to sign.
    sbStringToSign = CkStringBuilder_Create();
    CkStringBuilder_Append(sbStringToSign,consumerId);
    CkStringBuilder_Append(sbStringToSign,"\n");
    CkStringBuilder_Append(sbStringToSign,baseUrl);
    CkStringBuilder_Append(sbStringToSign,"\n");
    CkStringBuilder_Append(sbStringToSign,httpMethod);
    CkStringBuilder_Append(sbStringToSign,"\n");
    CkStringBuilder_AppendInt(sbStringToSign,timeStampVal);
    // We add three zero's so that the timestamp value is in milliseconds.
    // We don't care about accuracy down to less than a second.
    // All the server cares about is that the request was signed at the current date/time
    // within some reasonable margin of error (to account for systems having clocks
    // that may be slightly different).
    CkStringBuilder_Append(sbStringToSign,"000\n");

    privKey = CkPrivateKey_Create();
    // Load the private key into a private key object.
    // Note: Technically the private key is not PEM because it lacks the header/footer strings
    // used for PEM.  However, the LoadPem method will still accept it and load it correctly.
    success = CkPrivateKey_LoadPem(privKey,privateEncodedStr);
    if (success != TRUE) {
        printf("%s\n",CkPrivateKey_lastErrorText(privKey));
        CkDateTime_Dispose(dt);
        CkStringBuilder_Dispose(sbStringToSign);
        CkPrivateKey_Dispose(privKey);
        return;
    }

    rsa = CkRsa_Create();
    success = CkRsa_ImportPrivateKeyObj(rsa,privKey);
    if (success != TRUE) {
        printf("%s\n",CkRsa_lastErrorText(rsa));
        CkDateTime_Dispose(dt);
        CkStringBuilder_Dispose(sbStringToSign);
        CkPrivateKey_Dispose(privKey);
        CkRsa_Dispose(rsa);
        return;
    }

    // We want a base64 signature string.
    CkRsa_putEncodingMode(rsa,"base64");

    signatureString = CkRsa_signStringENC(rsa,CkStringBuilder_getAsString(sbStringToSign),"SHA256");
    if (CkRsa_getLastMethodSuccess(rsa) != TRUE) {
        printf("%s\n",CkRsa_lastErrorText(rsa));
        CkDateTime_Dispose(dt);
        CkStringBuilder_Dispose(sbStringToSign);
        CkPrivateKey_Dispose(privKey);
        CkRsa_Dispose(rsa);
        return;
    }

    printf("Signature String: %s\n",signatureString);


    CkDateTime_Dispose(dt);
    CkStringBuilder_Dispose(sbStringToSign);
    CkPrivateKey_Dispose(privKey);
    CkRsa_Dispose(rsa);

    }