suspiciousoctalescaperule.java

检查Java程序漏洞

package net.sourceforge.pmd.rules;

import net.sourceforge.pmd.AbstractRule;
import net.sourceforge.pmd.RuleContext;
import net.sourceforge.pmd.ast.ASTLiteral;

public class SuspiciousOctalEscapeRule extends AbstractRule
{
   public Object visit(ASTLiteral node, Object data)
   {
      RuleContext ctx = (RuleContext) data;
      String image = node.getImage();
      if (image != null && image.startsWith("\"")) // make sure it's a string literal
      {
         // trim quotes
         String s = image.substring(1, image.length() - 1);

         // process escape sequences
         int offset = 0;
         for (int slash = s.indexOf('\\', offset);
              slash != -1 && slash < s.length() - 1;
              slash = s.indexOf('\\', offset))
         {
            String escapeSequence = s.substring(slash+1);
            char first = escapeSequence.charAt(0);
            if (isOctal(first))
            {
               if (escapeSequence.length() > 1)
               {
                  char second = escapeSequence.charAt(1);
                  if (isOctal(second))
                  {
                     if (escapeSequence.length() > 2)
                     {
                        char third = escapeSequence.charAt(2);
                        if (isOctal(third))
                        {
                           // this is either a three digit octal escape or a two-digit
                           // octal escape followed by an octal digit. the value of
                           // the first digit in the sequence determines which is the
                           // case
                           if (first != '0' && first != '1' && first != '2' && first != '3')
                           {
                              // VIOLATION: it's a two-digit octal escape followed by
                              // an octal digit -- legal but very confusing!
                              ctx.getReport().addRuleViolation(createRuleViolation(ctx, node.getBeginLine()));
                           }
                           else
                           {
                              // if there is a 4th decimal digit, it could never be part of
                              // the escape sequence, which is confusing
                              if (escapeSequence.length() > 3)
                              {
                                 char fourth = escapeSequence.charAt(3);
                                 if (isDecimal(fourth))
                                 {
                                    ctx.getReport().addRuleViolation(createRuleViolation(ctx, node.getBeginLine()));
                                 }
                              }
                           }

                        }
                        else if (isDecimal(third))
                        {
                           // this is a two-digit octal escape followed by a decimal digit
                           // legal but very confusing
                           ctx.getReport().addRuleViolation(createRuleViolation(ctx, node.getBeginLine()));
                        }
                     }
                  }
                  else if (isDecimal(second))
                  {
                     // this is a one-digit octal escape followed by a decimal digit
                     // legal but very confusing
                     ctx.getReport().addRuleViolation(createRuleViolation(ctx, node.getBeginLine()));
                  }
               }
            }

            offset = slash + 1;
         }
      }

      return super.visit(node, data);
   }

   private boolean isOctal(char c)
   {
      switch (c)
      {
      case '0':
      case '1':
      case '2':
      case '3':
      case '4':
      case '5':
      case '6':
      case '7':
         return true;
      default:
         return false;
      }
   }

   private boolean isDecimal(char c)
   {
      switch (c)
      {
      case '0':
      case '1':
      case '2':
      case '3':
      case '4':
      case '5':
      case '6':
      case '7':
      case '8':
      case '9':
         return true;
      default:
         return false;
      }
   }
}