Add kdf module: Key Derivation Function API (JEP 510, final in JDK 25), HKDF, RFC 5869 vectors, interop with Python cryptography and openssl, per-tenant keys

Co-Authored-By: Claude Sonnet 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_017ic4b7rnC7jppGGdHGESvy
2026-10-28 18:07:57 +00:00
parent c93a1fffbb
commit eca73ad544
21 changed files with 995 additions and 0 deletions
@@ -0,0 +1,69 @@
+import javax.crypto.KDF;
+import javax.crypto.SecretKey;
+import javax.crypto.spec.HKDFParameterSpec;
+import java.security.NoSuchAlgorithmException;
+import java.security.Provider;
+import java.security.Security;
+import java.util.Arrays;
+
+/** What the JDK 25 KDF API offers: algorithm names, the three spec shapes, and what each returns. */
+public class ApiTour {
+    public static void main(String[] args) throws Exception {
+        Fx.header("KDF algorithms registered by the providers of this JDK");
+        for (Provider p : Security.getProviders())
+            for (Provider.Service s : p.getServices())
+                if (s.getType().equals("KDF"))
+                    System.out.println(p.getName() + "  " + s.getAlgorithm());
+
+        Fx.header("getInstance: what works and what does not");
+        KDF kdf = KDF.getInstance("HKDF-SHA256");
+        System.out.println("algorithm=" + kdf.getAlgorithm() + " provider=" + kdf.getProviderName() + " parameters=" + kdf.getParameters());
+        for (String bad : new String[] {"HKDF", "HKDF-SHA1", "hkdf-sha256", "PBKDF2WithHmacSHA256", "Argon2"}) {
+            try {
+                KDF.getInstance(bad);
+                System.out.println(bad + " -> available");
+            } catch (NoSuchAlgorithmException e) {
+                System.out.println(bad + " -> NoSuchAlgorithmException: " + e.getMessage());
+            }
+        }
+
+        byte[] ikm = Fx.fill(0x0b, 22), salt = Fx.range(0, 13), info = Fx.range(0xf0, 10);
+
+        Fx.header("Shape 1: extract then expand in one call (the common case)");
+        HKDFParameterSpec both = HKDFParameterSpec.ofExtract().addIKM(ikm).addSalt(salt).thenExpand(info, 42);
+        byte[] okm = kdf.deriveData(both);
+        System.out.println("deriveData  -> byte[" + okm.length + "] " + Fx.hex(okm));
+        SecretKey k = kdf.deriveKey("AES", HKDFParameterSpec.ofExtract().addIKM(ikm).addSalt(salt).thenExpand(info, 32));
+        System.out.println("deriveKey   -> algorithm=" + k.getAlgorithm() + " format=" + k.getFormat() + " bytes=" + k.getEncoded().length);
+
+        Fx.header("Shape 2: extract only (returns the pseudorandom key, PRK)");
+        SecretKey prk = kdf.deriveKey("Generic", HKDFParameterSpec.ofExtract().addIKM(ikm).addSalt(salt).extractOnly());
+        System.out.println("PRK = " + Fx.hex(prk.getEncoded()));
+
+        Fx.header("Shape 3: expand only (you already hold a uniformly random key)");
+        byte[] again = kdf.deriveData(HKDFParameterSpec.expandOnly(prk, info, 42));
+        Fx.check("extractOnly + expandOnly equals the one-call result", Arrays.equals(okm, again));
+
+        Fx.header("The same KDF object can be used again, and gives the same bytes");
+        Fx.check("second call with the same spec is identical", Arrays.equals(okm, kdf.deriveData(both)));
+
+        Fx.header("Several IKM or salt pieces are concatenated in the order added");
+        byte[] split = kdf.deriveData(HKDFParameterSpec.ofExtract()
+                .addIKM(Arrays.copyOfRange(ikm, 0, 10)).addIKM(Arrays.copyOfRange(ikm, 10, 22))
+                .addSalt(salt).thenExpand(info, 42));
+        Fx.check("addIKM(first 10) + addIKM(last 12) == addIKM(all 22)", Arrays.equals(okm, split));
+
+        Fx.header("deriveKey does not check key sizes; Cipher.init does");
+        for (int len : new int[] {16, 24, 32, 20}) {
+            try {
+                SecretKey a = kdf.deriveKey("AES", HKDFParameterSpec.ofExtract().addIKM(ikm).thenExpand(info, len));
+                System.out.println("deriveKey(\"AES\") length " + len + " -> ok, " + a.getEncoded().length + " bytes");
+                javax.crypto.Cipher.getInstance("AES/GCM/NoPadding").init(javax.crypto.Cipher.ENCRYPT_MODE, a);
+                System.out.println("                   Cipher.init -> ok");
+            } catch (Exception e) {
+                System.out.println("                   Cipher.init -> " + e.getClass().getSimpleName() + ": " + e.getMessage());
+            }
+        }
+        Fx.done();
+    }
+}