Fix GCMSIVBlockCipher processing

Author: peterdettman

core/src/main/java/org/bouncycastle/crypto/modes/GCMSIVBlockCipher.java

@@ -935,8 +935,8 @@ void updateHash(final byte[] pBuffer,
                  gHASH(theReverse);
 
                  /* Adjust counters */
-                 numProcessed += mySpace;
-                 myRemaining -= mySpace;
+                 numProcessed += BUFLEN;
+                 myRemaining -= BUFLEN;
              }
 
              /* If we have remaining data */

core/src/test/java/org/bouncycastle/crypto/test/GCMSIVTest.java

@@ -80,6 +80,15 @@ void testSIVCipher(final GCMSIVBlockCipher pCipher,
             pCipher.doFinal(myOutput, 0);
             isTrue("Encryption mismatch", Arrays.areEqual(myExpected, myOutput));
 
+            if (myData.length >= 2)
+            {
+                /* Repeat processing checking processBytes with non-empty internal buffer */
+                pCipher.processByte(myData[0], null, 0);
+                pCipher.processBytes(myData, 1, myData.length - 1, null, 0);
+                pCipher.doFinal(myOutput, 0);
+                isTrue("Encryption mismatch", Arrays.areEqual(myExpected, myOutput));
+            }
+
             /* Re-initialise the cipher */
             pCipher.init(false, myParams);
             pCipher.processBytes(myOutput, 0, myOutput.length, null, 0);