Flow 12 --- ML-DSA-65 ➜ SLH-DSA-SHA2-128S Detached-JWS Re-sign (Streaming)

/*
 * Copyright 2025 ANKATech Solutions Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
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package co.ankatech.ankasecure.sdk.examples;

import co.ankatech.ankasecure.sdk.AuthenticatedSdk;
import co.ankatech.ankasecure.sdk.model.ResignResult;
import co.ankatech.ankasecure.sdk.model.SignResult;
import co.ankatech.ankasecure.sdk.model.VerifySignatureResult;
import co.ankatech.ankasecure.sdk.util.FileIO;

import java.nio.file.Path;
import java.text.MessageFormat;
import java.util.Properties;

import static co.ankatech.ankasecure.sdk.examples.ExampleUtil.*;

/**
 * Scenario 12 — ML-DSA-65 → SLH-DSA-SHA2-128S Streaming Re-sign (Detached JWS).
 *
 * <p>This scenario migrates a detached JWS signature from an ML-DSA-65 key to a
 * SLH-DSA-SHA2-128S key, fully server-side &mdash; no payload re-upload.</p>
 *
 * <p>The SDK is data-plane-only: it does not create keys. This scenario operates
 * on the <strong>pre-provisioned granted cross-kid pair</strong> of the
 * demo playground &mdash; source {@code cli-resign3-source}
 * ({@code ML-DSA-65}) and target {@code cli-resign3-target}
 * ({@code SLH-DSA-SHA2-128S}). The playground actor holds the cross-kid
 * RESIGN grant on this pair plus the atomic sign/verify grants on each endpoint.</p>
 *
 * <ol>
 *   <li>Resolve the granted {@code ML-DSA-65} source and {@code SLH-DSA-SHA2-128S} target kids.</li>
 *   <li>Stream-sign a file under the source.</li>
 *   <li>Re-sign the existing detached JWS on the server
 *       (ML-DSA-65 &rarr; SLH-DSA-SHA2-128S).</li>
 *   <li>Stream-verify the new SLH-DSA signature.</li>
 * </ol>
 *
 * <p><b>Implementation notes (Java&nbsp;21+):</b></p>
 * <ul>
 *   <li>All filesystem work relies on {@link java.nio.file.Path}.</li>
 *   <li>UTF-8 encoding is enforced explicitly for deterministic behaviour.</li>
 *   <li>Temporary artefacts reside under <kbd>temp_files/</kbd>.</li>
 * </ul>
 *
 * <p><b>Thread-safety:</b> the class is stateless and immutable.</p>
 *
 * @see ExampleUtil
 * @see ExamplePlaygroundKeys
 * @see AuthenticatedSdk
 */
public final class ExampleScenario12 {

    /** No instantiation &mdash; this class only exposes {@link #main(String[])}. */
    private ExampleScenario12() { }

    /**
     * Runs the ML-DSA-65 to SLH-DSA-SHA2-128S streaming re-sign scenario.
     *
     * <p>Loads CLI properties, authenticates against ANKASecure&copy;,
     * and delegates to the scenario logic. On any unrecoverable error
     * the JVM terminates via
     * {@link ExampleUtil#fatal(String, Throwable)}.</p>
     *
     * @param args command-line arguments (ignored)
     */
    public static void main(final String[] args) {

        System.out.println("===== SCENARIO 12 START =====");
        System.out.println("""
                Purpose :
                  * Migrate a detached ML-DSA-65 signature to SLH-DSA-SHA2-128S
                  * Uses the pre-provisioned granted cross-kid pair
                    (cli-resign3-source / cli-resign3-target)
                Steps   :
                  1) Resolve granted ML-DSA-65 source + SLH-DSA-SHA2-128S target kids
                  2) Stream-sign payload under source
                  3) Re-sign on server
                  4) Verify SLH-DSA signature
                --------------------------------------------------------------""");

        try {
            prepareWorkingDir();

            Properties            props      = loadProperties();
            AuthenticatedSdk      sdk        = authenticate(props);
            ExamplePlaygroundKeys playground = ExamplePlaygroundKeys.from(props, sdk);

            runScenario(sdk, playground);

        } catch (Exception ex) {
            fatal("Scenario 12 failed", ex);
        }

        System.out.println("===== SCENARIO 12 END =====");
    }

    /* ====================================================================== */
    /**
     * Executes Scenario&nbsp;12 on the granted cross-kid pair.
     *
     * @param sdk        an authenticated {@link AuthenticatedSdk} instance
     * @param playground the pre-provisioned playground key resolver; must not be {@code null}
     * @throws Exception if any step fails
     */
    private static void runScenario(final AuthenticatedSdk sdk,
                                    final ExamplePlaygroundKeys playground) throws Exception {

        /* -- working paths -------------------------------------------------- */
        Path dataFile = TEMP_DIR.resolve("scenario12_data.txt");
        Path oldSig   = TEMP_DIR.resolve("scenario12_mldsa.sig");
        Path newSig   = TEMP_DIR.resolve("scenario12_slhdsa.sig");

        /* 1 -- payload ------------------------------------------------------ */
        FileIO.writeUtf8(dataFile,
                "Scenario-12 - ML-DSA-65 -> SLH-DSA-SHA2-128S streaming re-sign demo.");
        System.out.println("[1] Data file ready          -> " + dataFile.toAbsolutePath());

        /* 2 -- resolve granted cross-kid pair (data-plane SDK: no key creation) */
        final String oldKid = playground.requireKid("cli-resign3-source"); // ML-DSA-65
        final String newKid = playground.requireKid("cli-resign3-target"); // SLH-DSA-SHA2-128S
        System.out.println("[2] Source kid (ML-DSA-65)            -> " + oldKid);
        System.out.println("[2] Target kid (SLH-DSA-SHA2-128S)    -> " + newKid);

        /* 3 -- stream-sign under ML-DSA-65 source --------------------------- */
        SignResult oldMeta = sdk.signFileStream(oldKid, dataFile, oldSig);
        System.out.println("[3] ML-DSA signature stored  -> " + oldSig.toAbsolutePath());
        printSignMeta(oldMeta);

        /* 4 ── server re-sign (stream) ----------------------------------- */
        ResignResult reMeta = sdk.resignFileStream(
                oldSig,     // existing detached JWS header+sig
                newKid,     // replacement key
                dataFile,   // payload to sign
                newSig);    // output file
        System.out.println("[4] New signature written    -> " + newSig.toAbsolutePath());
        printResignMeta(reMeta);

        /* 5 ── stream-verify new JWS ------------------------------------- */
        VerifySignatureResult verMeta = sdk.verifySignatureStream(dataFile, newSig);
        System.out.println(MessageFormat.format(
                "[5] Signature valid?         -> {0}", verMeta.isValid()));
        printVerifyMeta(verMeta);

        System.out.println(verMeta.isValid()
                ? "[6] SUCCESS - SLH-DSA-SHA2-128S JWS verified."
                : "[6] FAILURE - verification failed.");
    }
}