(Unicode C) Create a JWS Using ECDSA P-256 SHA-256

Creates and validates a JSON Web Signature (JWS) that uses ECDSA P-256 SHA-256

Note: This example requires Chilkat v9.5.0.66 or greater.

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#include <C_CkStringBuilderW.h>
#include <C_CkPrivateKeyW.h>
#include <C_CkJsonObjectW.h>
#include <C_CkJwsW.h>
#include <C_CkPublicKeyW.h>

void ChilkatSample(void)
    {
    HCkStringBuilderW sbJwk;
    HCkPrivateKeyW eccKey;
    BOOL success;
    HCkJsonObjectW jwsProtHdr;
    HCkJwsW jws;
    int signatureIndex;
    BOOL bIncludeBom;
    const wchar_t *payloadStr;
    const wchar_t *jwsCompact;
    HCkJwsW jws2;
    HCkPublicKeyW eccPubKey;
    int v;
    HCkJsonObjectW joseHeader;

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

    // Note: This example requires Chilkat v9.5.0.66 or greater.

    // Use the following ECC key loaded from JWK format.
    sbJwk = CkStringBuilderW_Create();
    CkStringBuilderW_Append(sbJwk,L"{\"kty\":\"EC\",");
    CkStringBuilderW_Append(sbJwk,L"\"crv\":\"P-256\",");
    CkStringBuilderW_Append(sbJwk,L"\"x\":\"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU\",");
    CkStringBuilderW_Append(sbJwk,L"\"y\":\"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0\",");
    CkStringBuilderW_Append(sbJwk,L"\"d\":\"jpsQnnGQmL-YBIffH1136cspYG6-0iY7X1fCE9-E9LI\"");
    CkStringBuilderW_Append(sbJwk,L"}");

    eccKey = CkPrivateKeyW_Create();
    // Note: This example loads the ECDSA key from JWK format.  Any format can be loaded
    // into the private key object. (See the online reference documentation..)
    success = CkPrivateKeyW_LoadJwk(eccKey,CkStringBuilderW_getAsString(sbJwk));
    if (success != TRUE) {
        wprintf(L"%s\n",CkPrivateKeyW_lastErrorText(eccKey));
        CkStringBuilderW_Dispose(sbJwk);
        CkPrivateKeyW_Dispose(eccKey);
        return;
    }

    // Create the JWS Protected Header
    jwsProtHdr = CkJsonObjectW_Create();
    CkJsonObjectW_AppendString(jwsProtHdr,L"alg",L"ES256");

    jws = CkJwsW_Create();

    // Set the protected header:
    signatureIndex = 0;
    CkJwsW_SetProtectedHeader(jws,signatureIndex,jwsProtHdr);

    // Set the ECC key:
    CkJwsW_SetPrivateKey(jws,signatureIndex,eccKey);

    // Set the payload.
    bIncludeBom = FALSE;
    payloadStr = L"In our village, folks say God crumbles up the old moon into stars.";
    CkJwsW_SetPayload(jws,payloadStr,L"utf-8",bIncludeBom);

    // Create the JWS
    // By default, the compact serialization is used.
    jwsCompact = CkJwsW_createJws(jws);
    if (CkJwsW_getLastMethodSuccess(jws) != TRUE) {
        wprintf(L"%s\n",CkJwsW_lastErrorText(jws));
        CkStringBuilderW_Dispose(sbJwk);
        CkPrivateKeyW_Dispose(eccKey);
        CkJsonObjectW_Dispose(jwsProtHdr);
        CkJwsW_Dispose(jws);
        return;
    }

    wprintf(L"JWS: %s\n",jwsCompact);

    // Note: ECC signatures use random values, so the output will be different each time a signature is produced.
    // sample output:
    // JWS: eyJhbGciOiJFUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.J6EGTNkeuEjehHHBu0SOKzifm8r35wbx49A5964pxzB7gannyZZPMkK7vmlaPJ-K8Xmm8cZsQySAPC12Xd8avw

    // Now load the JWS, validate, and recover the original text.
    jws2 = CkJwsW_Create();

    // Load the JWS.
    success = CkJwsW_LoadJws(jws2,jwsCompact);

    eccPubKey = CkPrivateKeyW_GetPublicKey(eccKey);

    // Set the ECC public key used for validation.
    signatureIndex = 0;
    CkJwsW_SetPublicKey(jws2,signatureIndex,eccPubKey);
    CkPublicKeyW_Dispose(eccPubKey);

    // Validate the 1st (and only) signature at index 0..
    v = CkJwsW_Validate(jws2,signatureIndex);
    if (v < 0) {
        // Perhaps Chilkat was not unlocked or the trial expired..
        wprintf(L"Method call failed for some other reason.\n");
        wprintf(L"%s\n",CkJwsW_lastErrorText(jws2));
        CkStringBuilderW_Dispose(sbJwk);
        CkPrivateKeyW_Dispose(eccKey);
        CkJsonObjectW_Dispose(jwsProtHdr);
        CkJwsW_Dispose(jws);
        CkJwsW_Dispose(jws2);
        return;
    }

    if (v == 0) {
        wprintf(L"Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.\n");
        CkStringBuilderW_Dispose(sbJwk);
        CkPrivateKeyW_Dispose(eccKey);
        CkJsonObjectW_Dispose(jwsProtHdr);
        CkJwsW_Dispose(jws);
        CkJwsW_Dispose(jws2);
        return;
    }

    // If we get here, the signature was validated..
    wprintf(L"Signature validated.\n");

    // Recover the original content:
    wprintf(L"%s\n",CkJwsW_getPayload(jws2,L"utf-8"));

    // Examine the protected header:
    joseHeader = CkJwsW_GetProtectedHeader(jws2,signatureIndex);
    if (CkJwsW_getLastMethodSuccess(jws2) != TRUE) {
        wprintf(L"No protected header found at the given index.\n");
        CkStringBuilderW_Dispose(sbJwk);
        CkPrivateKeyW_Dispose(eccKey);
        CkJsonObjectW_Dispose(jwsProtHdr);
        CkJwsW_Dispose(jws);
        CkJwsW_Dispose(jws2);
        return;
    }

    CkJsonObjectW_putEmitCompact(joseHeader,FALSE);

    wprintf(L"Protected (JOSE) header:\n");
    wprintf(L"%s\n",CkJsonObjectW_emit(joseHeader));
    CkJsonObjectW_Dispose(joseHeader);

    // Output:

    // Signature validated.
    // In our village, folks say God crumbles up the old moon into stars.
    // Protected (JOSE) header:
    // { 
    //   "alg": "ES256"
    // }


    CkStringBuilderW_Dispose(sbJwk);
    CkPrivateKeyW_Dispose(eccKey);
    CkJsonObjectW_Dispose(jwsProtHdr);
    CkJwsW_Dispose(jws);
    CkJwsW_Dispose(jws2);

    }