Late binding: support children of Signature

The way Signature is a class of SignatureSpi allows you to register a
provider that returns a direct child of Signature. Support that by
checking if it's a subclass before trying to wrap it in SignatureImpl.

Bug: 12971079
Change-Id: I76b03f0962fe1b6ae95f205588c17d54b4bf504c

1 files changed, 6 insertions, 1 deletions

diff --git a/luni/src/main/java/java/security/Signature.java b/luni/src/main/java/java/security/Signature.java
index e70898b..24f5298 100644
--- a/luni/src/main/java/java/security/Signature.java
+++ b/luni/src/main/java/java/security/Signature.java
@@ -25,6 +25,7 @@ import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.Set;
 import org.apache.harmony.security.fortress.Engine;
+import org.apache.harmony.security.fortress.Engine.SpiAndProvider;
 
 /**
  * {@code Signature} is an engine class which is capable of creating and
@@ -171,7 +172,8 @@ public abstract class Signature extends SignatureSpi {
             throw new NoSuchAlgorithmException("Unknown algorithm: " + algorithm);
         }
 
-        if (tryAlgorithm(null, provider, algorithm) == null) {
+        SpiAndProvider spiAndProvider = tryAlgorithm(null, provider, algorithm);
+        if (spiAndProvider == null) {
             if (provider == null) {
                 throw new NoSuchAlgorithmException("No provider found for " + algorithm);
             } else {
@@ -179,6 +181,9 @@ public abstract class Signature extends SignatureSpi {
                         + " does not provide " + algorithm);
             }
         }
+        if (spiAndProvider.spi instanceof Signature) {
+            return (Signature) spiAndProvider.spi;
+        }
         return new SignatureImpl(algorithm, provider);
     }