content: /*
   * Copyright 1999-2017 Alibaba Group Holding Ltd.
   *
   * 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.alibaba.druid.wall.spi;
  
  import com.alibaba.druid.DbType;
  import com.alibaba.druid.sql.ast.SQLObject;
  import com.alibaba.druid.sql.ast.expr.SQLIdentifierExpr;
  import com.alibaba.druid.sql.ast.expr.SQLPropertyExpr;
  import com.alibaba.druid.sql.ast.expr.SQLVariantRefExpr;
  import com.alibaba.druid.sql.ast.statement.*;
  import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlOutFileExpr;
  import com.alibaba.druid.sql.dialect.mysql.ast.statement.*;
  import com.alibaba.druid.sql.dialect.mysql.visitor.MySqlASTVisitor;
  import com.alibaba.druid.wall.WallProvider;
  import com.alibaba.druid.wall.WallVisitor;
  import com.alibaba.druid.wall.spi.WallVisitorUtils.WallTopStatementContext;
  import com.alibaba.druid.wall.violation.ErrorCode;
  import com.alibaba.druid.wall.violation.IllegalSQLObjectViolation;
  
  public class MySqlWallVisitor extends WallVisitorBase implements WallVisitor, MySqlASTVisitor {
      public MySqlWallVisitor(WallProvider provider) {
          super(provider);
      }
  
      @Override
      public DbType getDbType() {
          return DbType.mysql;
      }
  
      @Override
      public boolean visit(MySqlSelectQueryBlock x) {
          WallVisitorUtils.checkSelect(this, x);
          return true;
      }
  
      @Override
      public boolean visit(MySqlDeleteStatement x) {
          WallVisitorUtils.checkReadOnly(this, x.getFrom());
          return visit((SQLDeleteStatement) x);
      }
  
      @Override
      public boolean visit(MySqlUpdateStatement x) {
          return visit((SQLUpdateStatement) x);
      }
  
      @Override
      public boolean visit(MySqlInsertStatement x) {
          return visit((SQLInsertStatement) x);
      }
  
      public boolean visit(SQLIdentifierExpr x) {
          return true;
      }
  
      public boolean visit(SQLPropertyExpr x) {
          if (x.getOwner() instanceof SQLVariantRefExpr) {
              SQLVariantRefExpr varExpr = (SQLVariantRefExpr) x.getOwner();
              SQLObject parent = x.getParent();
              String varName = varExpr.getName();
              if (varName.equalsIgnoreCase("@@session") || varName.equalsIgnoreCase("@@global")) {
                  if (!(parent instanceof SQLSelectItem) && !(parent instanceof SQLAssignItem)) {
                      violations.add(new IllegalSQLObjectViolation(ErrorCode.VARIANT_DENY,
                              "variable in condition not allow", toSQL(x)));
                      return false;
                  }
  
                  if (!checkVar(x.getParent(), x.getName())) {
                      boolean isTop = WallVisitorUtils.isTopNoneFromSelect(this, x);
                      if (!isTop) {
                          boolean allow = true;
                          if (isDeny(varName)
                                  && (WallVisitorUtils.isWhereOrHaving(x) || WallVisitorUtils.checkSqlExpr(varExpr))) {
                              allow = false;
                          }
  
                          if (!allow) {
                              violations.add(new IllegalSQLObjectViolation(ErrorCode.VARIANT_DENY,
                                      "variable not allow : " + x.getName(),
                                      toSQL(x)));
                          }
                      }
                  }
                  return false;
              }
          }
  
          WallVisitorUtils.check(this, x);
          return true;
      }
  
      public boolean checkVar(SQLObject parent, String varName) {
          if (varName == null) {
              return false;
          }
  
          if (varName.equals("?")) {
              return true;
          }
  
          if (!config.isVariantCheck()) {
              return true;
          }
  
          if (varName.startsWith("@@")) {
              if (!(parent instanceof SQLSelectItem) && !(parent instanceof SQLAssignItem)) {
                  return false;
              }
  
              varName = varName.substring(2);
          }
  
          if (config.getPermitVariants().contains(varName)) {
              return true;
          }
  
          return false;
      }
  
      public boolean isDeny(String varName) {
          if (varName.startsWith("@@")) {
              varName = varName.substring(2);
          }
  
          varName = varName.toLowerCase();
          return config.getDenyVariants().contains(varName);
      }
  
      public boolean visit(SQLVariantRefExpr x) {
          String varName = x.getName();
          if (varName == null) {
              return false;
          }
  
          if (varName.startsWith("@@") && !checkVar(x.getParent(), x.getName())) {
              final WallTopStatementContext topStatementContext = WallVisitorUtils.getWallTopStatementContext();
              if (topStatementContext != null
                      && (topStatementContext.fromSysSchema() || topStatementContext.fromSysTable())) {
                  return false;
              }
  
              boolean isTop = WallVisitorUtils.isTopNoneFromSelect(this, x);
              if (!isTop) {
                  boolean allow = true;
                  if (isDeny(varName) && (WallVisitorUtils.isWhereOrHaving(x) || WallVisitorUtils.checkSqlExpr(x))) {
                      allow = false;
                  }
  
                  if (!allow) {
                      violations.add(new IllegalSQLObjectViolation(ErrorCode.VARIANT_DENY, "variable not allow : "
                              + x.getName(), toSQL(x)));
                  }
              }
          }
  
          return false;
      }
  
      @Override
      public boolean visit(MySqlOutFileExpr x) {
          if (!config.isSelectIntoOutfileAllow() && !WallVisitorUtils.isTopSelectOutFile(x)) {
              violations.add(new IllegalSQLObjectViolation(ErrorCode.INTO_OUTFILE, "into out file not allow", toSQL(x)));
          }
  
          return true;
      }
  
      @Override
      public boolean isDenyTable(String name) {
          if (!config.isTableCheck()) {
              return false;
          }
  
          return !this.provider.checkDenyTable(name);
      }
  
      @Override
      public boolean visit(MySqlCreateTableStatement x) {
          WallVisitorUtils.check(this, x);
          return true;
      }
  }
  