(C#) ebay: Add Digital Signature to HTTP Request

See more eBay Examples

Demonstrates how to add a digital signature to an ebay HTTP request.

For more information, see https://developer.ebay.com/develop/guides/digital-signatures-for-apis

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

bool success;

// Note: Ebay provides a Key Management API
// See https://developer.ebay.com/api-docs/developer/key-management/overview.html

// The following test keys can be used: 
// 
// Ed25519 
// 
// Private Key:
// 
// -----BEGIN PRIVATE KEY-----
// MC4CAQAwBQYDK2VwBCIEIJ+DYvh6SEqVTm50DFtMDoQikTmiCqirVv9mWG9qfSnF
// -----END PRIVATE KEY-----

string strPrivateKey = "MC4CAQAwBQYDK2VwBCIEIJ+DYvh6SEqVTm50DFtMDoQikTmiCqirVv9mWG9qfSnF";

// 
// Public Key:
// 
// -----BEGIN PUBLIC KEY-----
// MCowBQYDK2VwAyEAJrQLj5P/89iXES9+vFgrIy29clF9CC/oPPsw3c5D0bs=
// -----END PUBLIC KEY-----

string strPublicKey = "MCowBQYDK2VwAyEAJrQLj5P/89iXES9+vFgrIy29clF9CC/oPPsw3c5D0bs=";

// This example assumes you got a JWE for your given private key from the Ebay Key Management REST API.
// This JWE is just for example:
string strJwe = "eyJ6aXAiOiJERUYiLCJlbmMiOiJBMjU2R0NNIiwidGFnIjoiSXh2dVRMb0FLS0hlS0Zoa3BxQ05CUSIsImFsZyI6IkEyNTZHQ01LVyIsIml2IjoiaFd3YjNoczk2QzEyOTNucCJ9.2o02pR9SoTF4g_5qRXZm6tF4H52TarilIAKxoVUqjd8.3qaF0KJN-rFHHm_P.AMUAe9PPduew09mANIZ-O_68CCuv6EIx096rm9WyLZnYz5N1WFDQ3jP0RBkbaOtQZHImMSPXIHVaB96RWshLuJsUgCKmTAwkPVCZv3zhLxZVxMXtPUuJ-ppVmPIv0NzznWCOU5Kvb9Xux7ZtnlvLXgwOFEix-BaWNomUAazbsrUCbrp514GIea3butbyxXLNi6R9TJUNh8V2uan-optT1MMyS7eMQnVGL5rYBULk.9K5ucUqAu0DqkkhgubsHHw";

Chilkat.StringBuilder sbBody = new Chilkat.StringBuilder();
sbBody.Append("{\"hello\": \"world\"}");

Debug.WriteLine("Body of request:");
Debug.WriteLine(sbBody.GetAsString());

// -------------------------------------------------
// Build the signature base string...

Chilkat.StringBuilder sbSigBase = new Chilkat.StringBuilder();

sbSigBase.Append("\"content-digest\": sha-256=:");
sbSigBase.Append(sbBody.GetHash("sha256","base64","utf-8"));
sbSigBase.Append(":\n");

sbSigBase.Append("\"x-ebay-signature-key\": ");
sbSigBase.Append(strJwe);
sbSigBase.Append("\n");

sbSigBase.Append("\"@method\": POST\n");

// This is the path part of the URL without query params...
sbSigBase.Append("\"@path\": ");
sbSigBase.Append("/verifysignature");
sbSigBase.Append("\n");

// The is the domain, such as "api.ebay.com" w/ port if the port is something unusual.
// In this example, we're testing against a local docker test server (see the info at https://developer.ebay.com/develop/guides/digital-signatures-for-apis)
// Normally, I think it would just be "api.ebay.com" instead of "localhost:8080".
sbSigBase.Append("\"@authority\": ");
sbSigBase.Append("localhost:8080");
sbSigBase.Append("\n");

sbSigBase.Append("\"@signature-params\": ");

Chilkat.StringBuilder sbSigInput = new Chilkat.StringBuilder();
sbSigInput.Append("(\"content-digest\" \"x-ebay-signature-key\" \"@method\" \"@path\" \"@authority\")");
sbSigInput.Append(";created=");

Chilkat.CkDateTime dt = new Chilkat.CkDateTime();
dt.SetFromCurrentSystemTime();
string unixTimeNow = dt.GetAsUnixTimeStr(false);
sbSigInput.Append(unixTimeNow);

sbSigBase.AppendSb(sbSigInput);

// -------------------------------------------------
// Sign the signature base string using the Ed25519 private key

Chilkat.BinData bdPrivKey = new Chilkat.BinData();
bdPrivKey.AppendEncoded(strPrivateKey,"base64");

Chilkat.PrivateKey privKey = new Chilkat.PrivateKey();
success = privKey.LoadAnyFormat(bdPrivKey,"");
if (success == false) {
    Debug.WriteLine(privKey.LastErrorText);
    return;
}

Chilkat.BinData bdToBeSigned = new Chilkat.BinData();
bdToBeSigned.AppendSb(sbSigBase,"utf-8");

Chilkat.EdDSA eddsa = new Chilkat.EdDSA();
string sigBase64 = eddsa.SignBdENC(bdToBeSigned,"base64",privKey);
if (eddsa.LastMethodSuccess == false) {
    Debug.WriteLine(eddsa.LastErrorText);
    return;
}

Debug.WriteLine("sigBase64:");
Debug.WriteLine(sigBase64);

// ----------------------------------------------------------
// Send the JSON POST

Chilkat.Http http = new Chilkat.Http();

http.SetRequestHeader("x-ebay-signature-key",strJwe);

Chilkat.StringBuilder sbContentDigestHdr = new Chilkat.StringBuilder();
sbContentDigestHdr.Append("sha-256=:");
sbContentDigestHdr.Append(sbBody.GetHash("sha256","base64","utf-8"));
sbContentDigestHdr.Append(":");
http.SetRequestHeader("Content-Digest",sbContentDigestHdr.GetAsString());

Chilkat.StringBuilder sbSigHdr = new Chilkat.StringBuilder();
sbSigHdr.Append("sig1=:");
sbSigHdr.Append(sigBase64);
sbSigHdr.Append(":");
http.SetRequestHeader("Signature",sbSigHdr.GetAsString());

sbSigInput.Prepend("sig1=");
http.SetRequestHeader("Signature-Input",sbSigInput.GetAsString());

// Add this header to make eBay actually check the signature.
http.SetRequestHeader("x-ebay-enforce-signature","true");

// Set the OAuth2 access token to add the "Authorization: Bearer <access_token>" to the header.
http.AuthToken = "your_oauth2_access_token";

// The signature base string constructed above is valid if we send this POST to "http://localhost:8080/verifysignature"
// Normally, you'll send your POST to some api.ebay.com endpoint.
string url = "http://localhost:8080/verifysignature";

Chilkat.HttpResponse resp = http.PostJson2("http://localhost:8080/verifysignature","application/json",sbBody.GetAsString());
if (http.LastMethodSuccess == false) {
    Debug.WriteLine(http.LastErrorText);
    return;
}

Debug.WriteLine("Response status code: " + Convert.ToString(resp.StatusCode));
Debug.WriteLine("Response body:");
Debug.WriteLine(resp.BodyStr);