Test fallback SHA1PRNG uses full width seeds

(cherry picked from commit 82575d5df1d80691a9bc96ec1af2c6c32e3426f8)

Bug: 6642616
Change-Id: I922316853eca6fc80c4c5e329864f3a93fc0af4f

1 files changed, 29 insertions, 0 deletions

diff --git a/luni/src/test/java/org/apache/harmony/security/tests/provider/crypto/SHA1PRNG_SecureRandomTest.java b/luni/src/test/java/org/apache/harmony/security/tests/provider/crypto/SHA1PRNG_SecureRandomTest.java
index ffdbe92..0db5ee1 100644
--- a/luni/src/test/java/org/apache/harmony/security/tests/provider/crypto/SHA1PRNG_SecureRandomTest.java
+++ b/luni/src/test/java/org/apache/harmony/security/tests/provider/crypto/SHA1PRNG_SecureRandomTest.java
@@ -17,6 +17,8 @@
 
 package org.apache.harmony.security.tests.provider.crypto;
 
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
 import java.security.NoSuchAlgorithmException;
 import java.security.NoSuchProviderException;
 import java.security.SecureRandom;
@@ -400,4 +402,31 @@ public class SHA1PRNG_SecureRandomTest extends TestCase {
             assertFalse("sequences are equal i=" + i, b);
         }
     }
+
+    public void testSeedIsFullLength() throws Exception {
+        Class<?> srClass = Class.forName(
+                "org.apache.harmony.security.provider.crypto.SHA1PRNG_SecureRandomImpl");
+        Field seedField = srClass.getDeclaredField("seed");
+        seedField.setAccessible(true);
+
+        Method nextBytesMethod = srClass.getDeclaredMethod("engineNextBytes", byte[].class);
+        nextBytesMethod.setAccessible(true);
+
+        byte[] bytes = new byte[1];
+
+        // Iterate 8 times to make sure the probability of a false positive is
+        // extremely rare.
+        for (int i = 0; i < 8; i++) {
+            Object sr = srClass.newInstance();
+            nextBytesMethod.invoke(sr, bytes);
+            int[] seed = (int[]) seedField.get(sr);
+
+            // If the first integer is not zero, it is fixed.
+            if (seed[0] != 0) {
+                return; // Success
+            }
+        }
+
+        fail("Fallback SHA1PRNG_SecureRandomImpl should not clobber seed internally");
+    }
 }