Add unit tests and checks when setting DEFAULT to be ThreadSafe

This commit improves the way SecureRandom algorithms (LibCryptoRng and its alias DEFAULT) are registered and adds unit tests.

1. Check that DEFAULT points to LibCryptoRng before setting it to be ThreadSafe. This is to mitigate risks that a future code change uses a different non-ThreadSafe algorithm for the DEFAULT alias.
2. Add unit tests checking that both LibCryptoRng and DEFAULT are ThreadSafe.

src/com/amazon/corretto/crypto/provider/AmazonCorrettoCryptoProvider.java

@@ -121,9 +121,24 @@ private void buildServiceMap() {
               singletonMap("ThreadSafe", "true"),
               "DEFAULT")
           .setSelfTest(LibCryptoRng.SPI.SELF_TEST);
-      // Following line is a workaround to ensure that the SecureRandom service
-      // is seens as ThreadSafe by SecureRandom, when using the alias name DEFAULT
-      setProperty("SecureRandom.DEFAULT ThreadSafe", "true");
+
+      // Following lines are a workaround to ensure that the SecureRandom service
+      // is seen as ThreadSafe by SecureRandom, when using the alias name DEFAULT
+      // See https://bugs.openjdk.org/browse/JDK-8329754
+
+      // We add additional tests to confirm the DEFAULT algorithm is actually ThreadSafe
+      // This is to prevent issues in case a future code change set DEFAULT to a non-ThreadSafe
+      // algorithm
+
+      // Get the name of the algorithm pointed by the alias name DEFAULT
+      String algorithmUsedForDEFAULT = getProperty("Alg.Alias.SecureRandom.DEFAULT");
+      // If this alias exists and the algorithm pointed by it is thread safe, then mark DEFAULT
+      // ThreadSafe
+      if (algorithmUsedForDEFAULT != null
+          && "true"
+              .equals(getProperty("SecureRandom." + algorithmUsedForDEFAULT + " ThreadSafe"))) {
+        setProperty("SecureRandom.DEFAULT ThreadSafe", "true");
+      }
     }
 
     addSignatures();

tst/com/amazon/corretto/crypto/provider/test/TestProviderInstallation.java

@@ -89,4 +89,18 @@ public void testSerialization() throws Exception {
       result.assertHealthy();
     }
   }
+
+  /**
+   * Check that the SecureRandom algorithm `LibCryptoRng` and its alias `DEFAULT` are both marked
+   * thread safe
+   */
+  @Test
+  public void testSecureRandomThreadSafe() {
+    assertEquals(
+        "true",
+        AmazonCorrettoCryptoProvider.INSTANCE.getProperty("SecureRandom.LibCryptoRng ThreadSafe"));
+    assertEquals(
+        "true",
+        AmazonCorrettoCryptoProvider.INSTANCE.getProperty("SecureRandom.DEFAULT ThreadSafe"));
+  }
 }