Synchronize Mac init and JNI code.

Macs are inherently *not* thread safe, but
before this change they can crash in native code
if used across multiple threads.

Author: prbprbprb

common/src/main/java/org/conscrypt/OpenSSLMac.java

@@ -141,7 +141,7 @@ protected byte[] engineDoFinal() {
     protected abstract byte[] doFinal();
 
     @Override
-    protected void engineReset() {
+    protected synchronized void engineReset() {
         if (!initialized) {
             return;
         }
@@ -163,36 +163,35 @@ public Hmac(long evpMd, int size) {
         }
 
         @Override
-        protected void initContext(byte[] keyBytes) {
+        protected synchronized void initContext(byte[] keyBytes) {
             NativeRef.HMAC_CTX ctxLocal = new NativeRef.HMAC_CTX(NativeCrypto.HMAC_CTX_new());
             NativeCrypto.HMAC_Init_ex(ctxLocal, keyBytes, evpMd);
             this.ctx = ctxLocal;
         }
 
         @Override
-        protected void resetContext() {
+        protected synchronized void resetContext() {
             final NativeRef.HMAC_CTX ctxLocal = ctx;
             NativeCrypto.HMAC_Reset(ctxLocal);
         }
 
         @Override
-        protected void engineUpdate(byte[] input, int offset, int len) {
+        protected synchronized void engineUpdate(byte[] input, int offset, int len) {
             final NativeRef.HMAC_CTX ctxLocal = ctx;
             NativeCrypto.HMAC_Update(ctxLocal, input, offset, len);
         }
 
         @Override
-        protected void updateDirect(long ptr, int len) {
+        protected synchronized void updateDirect(long ptr, int len) {
             final NativeRef.HMAC_CTX ctxLocal = ctx;
             NativeCrypto.HMAC_UpdateDirect(ctxLocal, ptr, len);
         }
 
         @Override
-        protected byte[] doFinal() {
+        protected synchronized byte[] doFinal() {
             final NativeRef.HMAC_CTX ctxLocal = ctx;
             return NativeCrypto.HMAC_Final(ctxLocal);
         }
-
     }
 
     public static final class HmacMD5 extends Hmac {
@@ -239,32 +238,32 @@ public AesCmac() {
         }
 
         @Override
-        protected void initContext(byte[] keyBytes) {
+        protected synchronized void initContext(byte[] keyBytes) {
             NativeRef.CMAC_CTX ctxLocal = new NativeRef.CMAC_CTX(NativeCrypto.CMAC_CTX_new());
             NativeCrypto.CMAC_Init(ctxLocal, keyBytes);
             this.ctx = ctxLocal;
         }
 
         @Override
-        protected void resetContext() {
+        protected synchronized void resetContext() {
             final NativeRef.CMAC_CTX ctxLocal = ctx;
             NativeCrypto.CMAC_Reset(ctxLocal);
         }
 
         @Override
-        protected void updateDirect(long ptr, int len) {
+        protected synchronized void updateDirect(long ptr, int len) {
             final NativeRef.CMAC_CTX ctxLocal = ctx;
             NativeCrypto.CMAC_UpdateDirect(ctxLocal, ptr, len);
         }
 
         @Override
-        protected byte[] doFinal() {
+        protected synchronized byte[] doFinal() {
             final NativeRef.CMAC_CTX ctxLocal = ctx;
             return NativeCrypto.CMAC_Final(ctxLocal);
         }
 
         @Override
-        protected void engineUpdate(byte[] input, int offset, int len) {
+        protected synchronized void engineUpdate(byte[] input, int offset, int len) {
             final NativeRef.CMAC_CTX ctxLocal = ctx;
             NativeCrypto.CMAC_Update(ctxLocal, input, offset, len);
         }

common/src/test/java/org/conscrypt/MacTest.java

@@ -195,6 +195,27 @@ public void test(final Provider provider, final String algorithm) throws Excepti
             });
     }
 
+    @Test
+    public void threadAbuse() {
+        newMacServiceTester().run((provider, algorithm) -> {
+            final byte[] b1 = new byte[2048];
+            final byte[] b2 = new byte[2048];
+            final byte[] b3 = new byte[2048];
+            final Mac mac = Mac.getInstance(algorithm, provider);
+            final SecretKeySpec key = findAnyKey(algorithm);
+
+            if (key != null) {
+                TestUtils.stressTest(32, 32, () -> {
+                    mac.init(key);
+                    mac.update(b1);
+                    mac.update(b2);
+                    mac.update(b3);
+                    mac.reset();
+                });
+            }
+        });
+    }
+
     @Test
     public void invalidCmacKeySizeThrows() throws Exception {
         // TODO(prb): extend to other Macs, deal with inconsistencies between providers.