(C++) ING Open Banking OAuth2 Client Credentials

Demonstrates how to get an access token for the ING Open Banking APIs using client credentials.

For more information, see https://developer.ing.com/openbanking/get-started/openbanking

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#include <CkCert.h>
#include <CkBinData.h>
#include <CkPrivateKey.h>
#include <CkHttp.h>
#include <CkCrypt2.h>
#include <CkDateTime.h>
#include <CkStringBuilder.h>
#include <CkRsa.h>
#include <CkHttpRequest.h>
#include <CkHttpResponse.h>
#include <CkJsonObject.h>

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

    CkCert cert;
    bool success = cert.LoadFromFile("qa_data/certs_and_keys/ING/example_client_tls.cer");
    if (success == false) {
        std::cout << cert.lastErrorText() << "\r\n";
        return;
    }

    CkBinData bdPrivKey;
    success = bdPrivKey.LoadFile("qa_data/certs_and_keys/ING/example_client_tls.key");
    if (success == false) {
        std::cout << "Failed to load example_client_tls.key" << "\r\n";
        return;
    }

    // The OAuth 2.0 client_id for these certificates is e77d776b-90af-4684-bebc-521e5b2614dd. 
    // Please note down this client_id since you will need it in the next steps to call the API.

    CkPrivateKey privKey;
    success = privKey.LoadAnyFormat(bdPrivKey,"");
    if (success == false) {
        std::cout << privKey.lastErrorText() << "\r\n";
        return;
    }

    // Associate the private key with the certificate.
    success = cert.SetPrivateKey(privKey);
    if (success == false) {
        std::cout << cert.lastErrorText() << "\r\n";
        return;
    }

    CkHttp http;

    success = http.SetSslClientCert(cert);
    if (success == false) {
        std::cout << http.lastErrorText() << "\r\n";
        return;
    }

    // Calculate the Digest and add the "Digest" header.  Do the equivalent of this:
    // payload="grant_type=client_credentials"
    // payloadDigest=`echo -n "$payload" | openssl dgst -binary -sha256 | openssl base64`
    // digest=SHA-256=$payloadDigest
    CkCrypt2 crypt;
    crypt.put_HashAlgorithm("SHA256");
    crypt.put_EncodingMode("base64");
    const char *payload = "grant_type=client_credentials";
    const char *payloadDigest = crypt.hashStringENC(payload);

    // Calculate the current date/time and add the Date header.  
    // reqDate=$(LC_TIME=en_US.UTF-8 date -u "+%a, %d %b %Y %H:%M:%S GMT")  
    CkDateTime dt;
    dt.SetFromCurrentSystemTime();
    // The desire date/time format is the "RFC822" format.
    http.SetRequestHeader("Date",dt.getAsRfc822(false));

    // Calculate signature for signing your request
    // Duplicate the following code:

    // 	httpMethod="post"
    // 	reqPath="/oauth2/token"
    // 	signingString="(request-target): $httpMethod $reqPath
    // 	date: $reqDate
    // 	digest: $digest"
    // 	signature=`printf "$signingString" | openssl dgst -sha256 -sign "${certPath}example_client_signing.key" -passin "pass:changeit" | openssl base64 -A`

    const char *httpMethod = "POST";
    const char *reqPath = "/oauth2/token";

    CkStringBuilder sbStringToSign;
    sbStringToSign.Append("(request-target): ");
    sbStringToSign.Append(httpMethod);
    sbStringToSign.ToLowercase();
    sbStringToSign.Append(" ");
    sbStringToSign.AppendLine(reqPath,false);

    sbStringToSign.Append("date: ");
    sbStringToSign.AppendLine(dt.getAsRfc822(false),false);

    sbStringToSign.Append("digest: SHA-256=");
    sbStringToSign.Append(payloadDigest);

    CkPrivateKey signingPrivKey;
    success = signingPrivKey.LoadPemFile("qa_data/certs_and_keys/ING/example_client_signing.key");
    if (success == false) {
        std::cout << signingPrivKey.lastErrorText() << "\r\n";
        return;
    }

    CkRsa rsa;
    success = rsa.ImportPrivateKeyObj(signingPrivKey);
    if (success == false) {
        std::cout << rsa.lastErrorText() << "\r\n";
        return;
    }

    rsa.put_EncodingMode("base64");
    const char *b64Signature = rsa.signStringENC(sbStringToSign.getAsString(),"SHA256");

    CkStringBuilder sbAuthHdrVal;
    sbAuthHdrVal.Append("Signature keyId=\"e77d776b-90af-4684-bebc-521e5b2614dd\",");
    sbAuthHdrVal.Append("algorithm=\"rsa-sha256\",");
    sbAuthHdrVal.Append("headers=\"(request-target) date digest\",");
    sbAuthHdrVal.Append("signature=\"");
    sbAuthHdrVal.Append(b64Signature);
    sbAuthHdrVal.Append("\"");

    CkStringBuilder sbDigestHdrVal;
    sbDigestHdrVal.Append("SHA-256=");
    sbDigestHdrVal.Append(payloadDigest);

    // Do the following CURL statement:

    // 	curl -i -X POST "${httpHost}${reqPath}" \
    // 	-H 'Accept: application/json' \
    // 	-H 'Content-Type: application/x-www-form-urlencoded' \
    // 	-H "Digest: ${digest}" \
    // 	-H "Date: ${reqDate}" \
    // 	-H "authorization: Signature keyId=\"$keyId\",algorithm=\"rsa-sha256\",headers=\"(request-target) date digest\",signature=\"$signature\"" \
    // 	-d "${payload}" \
    // 	--cert "${certPath}tlsCert.crt" \
    // 	--key "${certPath}tlsCert.key"

    CkHttpRequest req;
    req.AddParam("grant_type","client_credentials");
    req.AddHeader("Accept","application/json");
    req.AddHeader("Date",dt.getAsRfc822(false));
    req.AddHeader("Digest",sbDigestHdrVal.getAsString());
    req.AddHeader("Authorization",sbAuthHdrVal.getAsString());
    CkHttpResponse *resp = http.PostUrlEncoded("https://api.sandbox.ing.com/oauth2/token",req);
    if (http.get_LastMethodSuccess() == false) {
        std::cout << http.lastErrorText() << "\r\n";
        return;
    }

    // If successful, the status code = 200
    std::cout << "Response Status Code: " << resp->get_StatusCode() << "\r\n";
    std::cout << resp->bodyStr() << "\r\n";

    CkJsonObject json;
    json.Load(resp->bodyStr());

    delete resp;

    json.put_EmitCompact(false);
    std::cout << json.emit() << "\r\n";

    // A successful response contains an access token such as:
    // {
    //   "access_token": "eyJhbGc ... bxI_SoPOBH9xmoM",
    //   "expires_in": 905,
    //   "scope": "payment-requests:view payment-requests:create payment-requests:close greetings:view virtual-ledger-accounts:fund-reservation:create virtual-ledger-accounts:fund-reservation:delete virtual-ledger-accounts:balance:view",
    //   "token_type": "Bearer",
    //   "keys": [
    //     {
    //       "kty": "RSA",
    //       "n": "3l3rdz4...04VPkdV",
    //       "e": "AQAB",
    //       "use": "sig",
    //       "alg": "RS256",
    //       "x5t": "3c396700fc8cd709cf9cb5452a22bcde76985851"
    //     }
    //   ],
    //   "client_id": "e77d776b-90af-4684-bebc-521e5b2614dd"
    // }

    // Use this online tool to generate parsing code from sample JSON: 
    // Generate Parsing Code from JSON

    const char *kty = 0;
    const char *n = 0;
    const char *e = 0;
    const char *use = 0;
    const char *alg = 0;
    const char *x5t = 0;

    const char *access_token = json.stringOf("access_token");
    int expires_in = json.IntOf("expires_in");
    const char *scope = json.stringOf("scope");
    const char *token_type = json.stringOf("token_type");
    const char *client_id = json.stringOf("client_id");
    int i = 0;
    int count_i = json.SizeOfArray("keys");
    while (i < count_i) {
        json.put_I(i);
        kty = json.stringOf("keys[i].kty");
        n = json.stringOf("keys[i].n");
        e = json.stringOf("keys[i].e");
        use = json.stringOf("keys[i].use");
        alg = json.stringOf("keys[i].alg");
        x5t = json.stringOf("keys[i].x5t");
        i = i + 1;
    }

    // This example will save the JSON containing the access key to a file so that
    // a subsequent example can load it and then use the access key for a request, such as to create a payment request.
    json.WriteFile("qa_data/tokens/ing_access_token.json");
    }