Fixes for Azure-MySQL connections

Azure has a couple of differences from stock mysql.
First, it always sends a "switch auth" packet back from the first auth
request.  If you google "azure mysql handshake" you'll find a bunch of
other libraries that had to deal with this.

Second, it's rather persnickitty with the response to this; if we send
the response a byte or so at a time azure just closes our connection.

src/main/java/com/github/shyiko/mysql/binlog/BinaryLogClient.java

@@ -46,6 +46,7 @@
 import com.github.shyiko.mysql.binlog.network.protocol.PacketChannel;
 import com.github.shyiko.mysql.binlog.network.protocol.ResultSetRowPacket;
 import com.github.shyiko.mysql.binlog.network.protocol.command.AuthenticateCommand;
+import com.github.shyiko.mysql.binlog.network.protocol.command.AuthenticateNativePasswordCommand;
 import com.github.shyiko.mysql.binlog.network.protocol.command.Command;
 import com.github.shyiko.mysql.binlog.network.protocol.command.DumpBinaryLogCommand;
 import com.github.shyiko.mysql.binlog.network.protocol.command.DumpBinaryLogGtidCommand;
@@ -722,8 +723,40 @@ private void authenticate(GreetingPacket greetingPacket) throws IOException {
                 ErrorPacket errorPacket = new ErrorPacket(bytes);
                 throw new AuthenticationException(errorPacket.getErrorMessage(), errorPacket.getErrorCode(),
                     errorPacket.getSqlState());
+            } else if (authenticationResult[0] == (byte) 0xFE) {
+                switchAuthentication(authenticationResult);
+            } else {
+                throw new AuthenticationException("Unexpected authentication result (" + authenticationResult[0] + ")");
+            }
+        }
+    }
+
+    private void switchAuthentication(byte[] authenticationResult) throws IOException {
+        /*
+            Azure-MySQL likes to tell us to switch authentication methods, even though
+            we haven't advertised that we support any.  It uses this for some-odd
+            reason to send the real password scramble.
+        */
+        ByteArrayInputStream buffer = new ByteArrayInputStream(authenticationResult);
+        buffer.read(1);
+
+        String authName = buffer.readZeroTerminatedString();
+        if ("mysql_native_password".equals(authName)) {
+            String scramble = buffer.readZeroTerminatedString();
+
+            Command switchCommand = new AuthenticateNativePasswordCommand(scramble, password);
+            channel.writeBuffered(switchCommand, 3);
+            byte[] authResult = channel.read();
+
+            if (authResult[0] != (byte) 0x00) {
+                byte[] bytes = Arrays.copyOfRange(authResult, 1, authResult.length);
+                ErrorPacket errorPacket = new ErrorPacket(bytes);
+                throw new AuthenticationException(errorPacket.getErrorMessage(), errorPacket.getErrorCode(),
+                    errorPacket.getSqlState());
             }
-            throw new AuthenticationException("Unexpected authentication result (" + authenticationResult[0] + ")");
+            return;
+        } else {
+            throw new AuthenticationException("Unsupported authentication type: " + authName);
         }
     }
 

src/main/java/com/github/shyiko/mysql/binlog/network/protocol/PacketChannel.java

@@ -71,6 +71,21 @@ public void write(Command command, int packetNumber) throws IOException {
         outputStream.flush();
     }
 
+    /*
+       Azure's MySQL has bizarre network properties that force us to write an
+       auth-response challenge in one shot, lest their hair catch on fire and
+       forcibly disconnect us.
+     */
+    public void writeBuffered(Command command, int packetNumber) throws IOException {
+        byte[] body = command.toByteArray();
+        ByteArrayOutputStream buffer = new ByteArrayOutputStream();
+        buffer.writeInteger(body.length, 3); // packet length
+        buffer.writeInteger(packetNumber, 1);
+        buffer.write(body, 0, body.length);
+        buffer.flush();
+        socket.getOutputStream().write(buffer.toByteArray());
+    }
+
     public void write(Command command) throws IOException {
         write(command, 0);
     }

src/main/java/com/github/shyiko/mysql/binlog/network/protocol/command/AuthenticateCommand.java

@@ -79,7 +79,7 @@ public byte[] toByteArray() throws IOException {
     /**
      * see mysql/sql/password.c scramble(...)
      */
-    private static byte[] passwordCompatibleWithMySQL411(String password, String salt) {
+    public static byte[] passwordCompatibleWithMySQL411(String password, String salt) {
         MessageDigest sha;
         try {
             sha = MessageDigest.getInstance("SHA-1");

src/main/java/com/github/shyiko/mysql/binlog/network/protocol/command/AuthenticateNativePasswordCommand.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2013 Stanley Shyiko
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.github.shyiko.mysql.binlog.network.protocol.command;
+
+import java.io.IOException;
+
+/**
+ * @author <a href="mailto:ben.osheroff@gmail.com">Ben Osheroff</a>
+ */
+public class AuthenticateNativePasswordCommand implements Command {
+    private final String scramble, password;
+
+    public AuthenticateNativePasswordCommand(String scramble, String password) {
+        this.scramble = scramble;
+        this.password = password;
+    }
+    @Override
+    public byte[] toByteArray() throws IOException {
+        return AuthenticateCommand.passwordCompatibleWithMySQL411(password, scramble);
+    }
+}