MXS-1628: Respond with correct error to malformed packets

If the client sent a malformed authentication response packet, MaxScale
would interpret that as failed authentication.

include/maxscale/authenticator.h

@@ -99,6 +99,7 @@ typedef struct mxs_authenticator
 #define MXS_AUTH_INCOMPLETE 4 /**< Authentication is not yet complete */
 #define MXS_AUTH_SSL_INCOMPLETE 5 /**< SSL connection is not yet complete */
 #define MXS_AUTH_NO_SESSION 6
+#define MXS_AUTH_BAD_HANDSHAKE 7 /**< Malformed client packet */
 
 /** Return values for the loadusers entry point */
 #define MXS_AUTH_LOADUSERS_OK    0 /**< Users loaded successfully */

server/modules/authenticator/MySQLAuth/mysql_auth.c

@@ -475,26 +475,36 @@ mysql_auth_set_client_data(
     if (client_auth_packet_size > MYSQL_AUTH_PACKET_BASE_SIZE)
     {
         /* Should have a username */
-        char *first_letter_of_username = (char *)(client_auth_packet + MYSQL_AUTH_PACKET_BASE_SIZE);
-        int user_length = strlen(first_letter_of_username);
+        uint8_t* name = client_auth_packet + MYSQL_AUTH_PACKET_BASE_SIZE;
+        uint8_t* end = client_auth_packet + sizeof(client_auth_packet);
+        int user_length = 0;
 
-        ss_dassert(client_auth_packet_size > (MYSQL_AUTH_PACKET_BASE_SIZE + user_length)
-                   && user_length <= MYSQL_USER_MAXLEN);
+        while (name < end && *name)
+        {
+            name++;
+            user_length++;
+        }
+
+        if (name == end)
+        {
+            // The name is not null terminated
+            return MXS_AUTH_BAD_HANDSHAKE;
+        }
 
         if (client_auth_packet_size > (MYSQL_AUTH_PACKET_BASE_SIZE + user_length + 1))
         {
             /* Extra 1 is for the terminating null after user name */
             packet_length_used = MYSQL_AUTH_PACKET_BASE_SIZE + user_length + 1;
             /* We should find an authentication token next */
             /* One byte of packet is the length of authentication token */
-            memcpy(&client_data->auth_token_len,
-                   client_auth_packet + packet_length_used, 1);
+            client_data->auth_token_len = client_auth_packet[packet_length_used];
 
             if (client_auth_packet_size >
                 (packet_length_used + client_data->auth_token_len))
             {
-                /* Packet is large enough for authentication token */
-                if (NULL != (client_data->auth_token = (uint8_t *)MXS_MALLOC(client_data->auth_token_len)))
+                client_data->auth_token = (uint8_t*)MXS_MALLOC(client_data->auth_token_len);
+
+                if (client_data->auth_token)
                 {
                     /* The extra 1 is for the token length byte, just extracted*/
                     memcpy(client_data->auth_token,
@@ -510,9 +520,13 @@ mysql_auth_set_client_data(
             else
             {
                 /* Packet was too small to contain authentication token */
-                return MXS_AUTH_FAILED;
+                return MXS_AUTH_BAD_HANDSHAKE;
             }
         }
+        else
+        {
+            return MXS_AUTH_BAD_HANDSHAKE;
+        }
     }
     return MXS_AUTH_SUCCEEDED;
 }

server/modules/protocol/MySQL/MySQLClient/mysql_client.c

@@ -1132,6 +1132,10 @@ mysql_client_auth_error_handling(DCB *dcb, int auth_val, int packet_number)
         modutil_send_mysql_err_packet(dcb, packet_number, 0, 1045, "28000", fail_str);
         break;
 
+    case MXS_AUTH_BAD_HANDSHAKE:
+        modutil_send_mysql_err_packet(dcb, packet_number, 0, 1045, "08S01", "Bad handshake");
+        break;
+
     default:
         MXS_DEBUG("%lu [gw_read_client_event] authentication failed. fd %d, "
                   "state unrecognized.", pthread_self(), dcb->fd);