(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 <C_CkCert.h>
#include <C_CkBinData.h>
#include <C_CkPrivateKey.h>
#include <C_CkHttp.h>
#include <C_CkCrypt2.h>
#include <C_CkDateTime.h>
#include <C_CkStringBuilder.h>
#include <C_CkRsa.h>
#include <C_CkHttpRequest.h>
#include <C_CkHttpResponse.h>
#include <C_CkJsonObject.h>

void ChilkatSample(void)
    {
    HCkCert cert;
    BOOL success;
    HCkBinData bdPrivKey;
    HCkPrivateKey privKey;
    HCkHttp http;
    HCkCrypt2 crypt;
    const char *payload;
    const char *payloadDigest;
    HCkDateTime dt;
    const char *httpMethod;
    const char *reqPath;
    HCkStringBuilder sbStringToSign;
    HCkPrivateKey signingPrivKey;
    HCkRsa rsa;
    const char *b64Signature;
    HCkStringBuilder sbAuthHdrVal;
    HCkStringBuilder sbDigestHdrVal;
    HCkHttpRequest req;
    HCkHttpResponse resp;
    HCkJsonObject json;
    const char *kty;
    const char *n;
    const char *e;
    const char *use;
    const char *alg;
    const char *x5t;
    const char *access_token;
    int expires_in;
    const char *scope;
    const char *token_type;
    const char *client_id;
    int i;
    int count_i;

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

    cert = CkCert_Create();
    success = CkCert_LoadFromFile(cert,"qa_data/certs_and_keys/ING/example_client_tls.cer");
    if (success == FALSE) {
        printf("%s\n",CkCert_lastErrorText(cert));
        CkCert_Dispose(cert);
        return;
    }

    bdPrivKey = CkBinData_Create();
    success = CkBinData_LoadFile(bdPrivKey,"qa_data/certs_and_keys/ING/example_client_tls.key");
    if (success == FALSE) {
        printf("Failed to load example_client_tls.key\n");
        CkCert_Dispose(cert);
        CkBinData_Dispose(bdPrivKey);
        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.

    privKey = CkPrivateKey_Create();
    success = CkPrivateKey_LoadAnyFormat(privKey,bdPrivKey,"");
    if (success == FALSE) {
        printf("%s\n",CkPrivateKey_lastErrorText(privKey));
        CkCert_Dispose(cert);
        CkBinData_Dispose(bdPrivKey);
        CkPrivateKey_Dispose(privKey);
        return;
    }

    // Associate the private key with the certificate.
    success = CkCert_SetPrivateKey(cert,privKey);
    if (success == FALSE) {
        printf("%s\n",CkCert_lastErrorText(cert));
        CkCert_Dispose(cert);
        CkBinData_Dispose(bdPrivKey);
        CkPrivateKey_Dispose(privKey);
        return;
    }

    http = CkHttp_Create();

    success = CkHttp_SetSslClientCert(http,cert);
    if (success == FALSE) {
        printf("%s\n",CkHttp_lastErrorText(http));
        CkCert_Dispose(cert);
        CkBinData_Dispose(bdPrivKey);
        CkPrivateKey_Dispose(privKey);
        CkHttp_Dispose(http);
        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
    crypt = CkCrypt2_Create();
    CkCrypt2_putHashAlgorithm(crypt,"SHA256");
    CkCrypt2_putEncodingMode(crypt,"base64");
    payload = "grant_type=client_credentials";
    payloadDigest = CkCrypt2_hashStringENC(crypt,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")  
    dt = CkDateTime_Create();
    CkDateTime_SetFromCurrentSystemTime(dt);
    // The desire date/time format is the "RFC822" format.
    CkHttp_SetRequestHeader(http,"Date",CkDateTime_getAsRfc822(dt,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`

    httpMethod = "POST";
    reqPath = "/oauth2/token";

    sbStringToSign = CkStringBuilder_Create();
    CkStringBuilder_Append(sbStringToSign,"(request-target): ");
    CkStringBuilder_Append(sbStringToSign,httpMethod);
    CkStringBuilder_ToLowercase(sbStringToSign);
    CkStringBuilder_Append(sbStringToSign," ");
    CkStringBuilder_AppendLine(sbStringToSign,reqPath,FALSE);

    CkStringBuilder_Append(sbStringToSign,"date: ");
    CkStringBuilder_AppendLine(sbStringToSign,CkDateTime_getAsRfc822(dt,FALSE),FALSE);

    CkStringBuilder_Append(sbStringToSign,"digest: SHA-256=");
    CkStringBuilder_Append(sbStringToSign,payloadDigest);

    signingPrivKey = CkPrivateKey_Create();
    success = CkPrivateKey_LoadPemFile(signingPrivKey,"qa_data/certs_and_keys/ING/example_client_signing.key");
    if (success == FALSE) {
        printf("%s\n",CkPrivateKey_lastErrorText(signingPrivKey));
        CkCert_Dispose(cert);
        CkBinData_Dispose(bdPrivKey);
        CkPrivateKey_Dispose(privKey);
        CkHttp_Dispose(http);
        CkCrypt2_Dispose(crypt);
        CkDateTime_Dispose(dt);
        CkStringBuilder_Dispose(sbStringToSign);
        CkPrivateKey_Dispose(signingPrivKey);
        return;
    }

    rsa = CkRsa_Create();
    success = CkRsa_ImportPrivateKeyObj(rsa,signingPrivKey);
    if (success == FALSE) {
        printf("%s\n",CkRsa_lastErrorText(rsa));
        CkCert_Dispose(cert);
        CkBinData_Dispose(bdPrivKey);
        CkPrivateKey_Dispose(privKey);
        CkHttp_Dispose(http);
        CkCrypt2_Dispose(crypt);
        CkDateTime_Dispose(dt);
        CkStringBuilder_Dispose(sbStringToSign);
        CkPrivateKey_Dispose(signingPrivKey);
        CkRsa_Dispose(rsa);
        return;
    }

    CkRsa_putEncodingMode(rsa,"base64");
    b64Signature = CkRsa_signStringENC(rsa,CkStringBuilder_getAsString(sbStringToSign),"SHA256");

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

    sbDigestHdrVal = CkStringBuilder_Create();
    CkStringBuilder_Append(sbDigestHdrVal,"SHA-256=");
    CkStringBuilder_Append(sbDigestHdrVal,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"

    req = CkHttpRequest_Create();
    CkHttpRequest_AddParam(req,"grant_type","client_credentials");
    CkHttpRequest_AddHeader(req,"Accept","application/json");
    CkHttpRequest_AddHeader(req,"Date",CkDateTime_getAsRfc822(dt,FALSE));
    CkHttpRequest_AddHeader(req,"Digest",CkStringBuilder_getAsString(sbDigestHdrVal));
    CkHttpRequest_AddHeader(req,"Authorization",CkStringBuilder_getAsString(sbAuthHdrVal));
    resp = CkHttp_PostUrlEncoded(http,"https://api.sandbox.ing.com/oauth2/token",req);
    if (CkHttp_getLastMethodSuccess(http) == FALSE) {
        printf("%s\n",CkHttp_lastErrorText(http));
        CkCert_Dispose(cert);
        CkBinData_Dispose(bdPrivKey);
        CkPrivateKey_Dispose(privKey);
        CkHttp_Dispose(http);
        CkCrypt2_Dispose(crypt);
        CkDateTime_Dispose(dt);
        CkStringBuilder_Dispose(sbStringToSign);
        CkPrivateKey_Dispose(signingPrivKey);
        CkRsa_Dispose(rsa);
        CkStringBuilder_Dispose(sbAuthHdrVal);
        CkStringBuilder_Dispose(sbDigestHdrVal);
        CkHttpRequest_Dispose(req);
        return;
    }

    // If successful, the status code = 200
    printf("Response Status Code: %d\n",CkHttpResponse_getStatusCode(resp));
    printf("%s\n",CkHttpResponse_bodyStr(resp));

    json = CkJsonObject_Create();
    CkJsonObject_Load(json,CkHttpResponse_bodyStr(resp));

    CkHttpResponse_Dispose(resp);

    CkJsonObject_putEmitCompact(json,FALSE);
    printf("%s\n",CkJsonObject_emit(json));

    // 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

    access_token = CkJsonObject_stringOf(json,"access_token");
    expires_in = CkJsonObject_IntOf(json,"expires_in");
    scope = CkJsonObject_stringOf(json,"scope");
    token_type = CkJsonObject_stringOf(json,"token_type");
    client_id = CkJsonObject_stringOf(json,"client_id");
    i = 0;
    count_i = CkJsonObject_SizeOfArray(json,"keys");
    while (i < count_i) {
        CkJsonObject_putI(json,i);
        kty = CkJsonObject_stringOf(json,"keys[i].kty");
        n = CkJsonObject_stringOf(json,"keys[i].n");
        e = CkJsonObject_stringOf(json,"keys[i].e");
        use = CkJsonObject_stringOf(json,"keys[i].use");
        alg = CkJsonObject_stringOf(json,"keys[i].alg");
        x5t = CkJsonObject_stringOf(json,"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.
    CkJsonObject_WriteFile(json,"qa_data/tokens/ing_access_token.json");


    CkCert_Dispose(cert);
    CkBinData_Dispose(bdPrivKey);
    CkPrivateKey_Dispose(privKey);
    CkHttp_Dispose(http);
    CkCrypt2_Dispose(crypt);
    CkDateTime_Dispose(dt);
    CkStringBuilder_Dispose(sbStringToSign);
    CkPrivateKey_Dispose(signingPrivKey);
    CkRsa_Dispose(rsa);
    CkStringBuilder_Dispose(sbAuthHdrVal);
    CkStringBuilder_Dispose(sbDigestHdrVal);
    CkHttpRequest_Dispose(req);
    CkJsonObject_Dispose(json);

    }