/*
 * Half open port scanner. Send SYNs, and look for a SYN-ACK. If you see one,
 * the port is listening.
 *
 * The whole point is to evade TCP-wrapper software and other alarm systems
 * which look for a fully established connection. Since this never establishes
 * a connection, its existance isn't logged.
 *
 * Note, this can be detected by things like TCPdump, or other raw network
 * monitors.
 *
 * Runs under SunOS 4.x with NIT. This is a proof-of-concept toy, not a
 * production model. :-)
 *
 * Mike Neuman
 * 12/7/93
 *
 * You can do whatever you want with this code as long as you leave this
 * header intact.
 *
 * Contact information:
 *
 * Mike Neuman (mcn@EnGarde.com) - http://www.engarde.com/~mcn
 */

#include <stdio.h>
#include <netdb.h>
#include <ctype.h>
#include <signal.h>
#include <errno.h>
#include <malloc.h>
#include <setjmp.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/timeb.h>
#include <sys/socket.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <net/nit.h>
#include <sys/fcntlcom.h>

#include <sys/param.h>
#include <sys/dir.h>
#include <net/nit_if.h>
#include <net/nit_pf.h>
#include <net/nit_buf.h>
#include <net/packetfilt.h>
#include <sys/stropts.h>

#include <net/if.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/if_ether.h>
#include <netinet/ip_var.h>
#include <netinet/udp.h>
#include <netinet/udp_var.h>
#include <netinet/tcp.h>
#include <netinet/tcpip.h>
#include <sys/stream.h>
#include <sys/tihdr.h>

#include <rpc/rpc.h>
#include <rpc/pmap_prot.h>
#include <rpc/pmap_clnt.h>

/* RPC makes an rpcdump call, which may be logged by a secure portmapper.
 * If you're paranoid and want to guess at rpc stuff, specify -r
 */

main(argc,argv)
int argc;
char *argv[];

{
  struct sockaddr_in server;
  struct servent *sp;
  struct hostent *hp;
  int c, s, count, userpc=1, sock=RPC_ANYSOCK, minport = 1, maxport = 6001;
  struct pmaplist *head = NULL, *headp=NULL;
  struct timeval timeout;
  register CLIENT *client;
  struct rpcent *rpc;
  unsigned long addr;
  char *hostp;
  extern char *optarg;
  extern int optind;


  /* 1: Parse options, get host addr */
  while ((c = getopt(argc, argv, "rhm:M:")) != -1)
    switch(c) {
      case 'r':
        userpc = 0;
        break;
      case 'm':
        minport = atoi(optarg);
        break;
      case 'M':
        maxport = atoi(optarg);
        break;
      case 'h':
        usage(argv[0]);
        exit(1);
    }
        
  if (optind != argc-1) {
    usage(argv[0]);
    exit(1);
  }

  if (minport > maxport || minport <= 0) {
    fprintf(stderr, "ERROR: minport must be > 0 and <= maxport\n");
    usage(argv[0]);
    exit(1);
  }
  hostp = argv[optind];

  if ((hp=gethostbyname(hostp))==NULL) {
    addr = inet_addr(hostp);
    if (addr == (u_long)-1) {
      fprintf(stderr, "Unknown host '%s'\n", hostp);
      usage(argv[0]);
      exit(1);
    }
    bcopy(&server.sin_addr, &addr, 4);
  } else {
    bzero((char *)&server, sizeof server);
    bcopy(hp->h_addr, (char *)&server.sin_addr, hp->h_length);
    server.sin_family=hp->h_addrtype;
  }

  printf("Connections established for host %s:\n",hostp);

  /* 2: Call rpc and get its ports */
  head=NULL;
  if (userpc) {
    server.sin_port=htons(PMAPPORT);
    timeout.tv_sec=10;
    timeout.tv_usec=0;
    if ((client = clnttcp_create(&server, PMAPPROG,
                                 PMAPVERS, &sock, 50, 500))!=NULL) {
      if (clnt_call(client, PMAPPROC_DUMP, xdr_void, NULL,
                    xdr_pmaplist, &head, timeout) != RPC_SUCCESS)
        head=NULL;
    }
  }

  /* 3: Try each port from minport - maxport */
  for (count=minport;count<=maxport;count++) {
    printf("\r%6d",count);
    fflush(stdout);
    server.sin_port=count;
    if (!fakeconnect(&server, hostp)) {
      printf("\r   %4d tcp   ",count);
      sp=getservbyport(count,"tcp");
      if (sp==NULL) {
        switch(count) {
          /* Put in known services not in /etc/services here */
          case 2000: printf("(Xnews)");
            break;
          case 6000: printf("(X)");
            break;
          default:
            if (userpc) {
              headp=head;
              while (headp!=NULL) {
                if (headp->pml_map.pm_prot!=IPPROTO_TCP) {
                  headp=headp->pml_next;
                  continue;
                }
                if (count!=headp->pml_map.pm_port) {
                  headp=headp->pml_next;
                  continue;
                }
                rpc = getrpcbynumber(headp->pml_map.pm_prog);
                if (rpc) {
                  printf("%-15s [rpc]", rpc->r_name);
                  break;
                } else {
                  headp=headp->pml_next;
                  continue;
                }
              }
              if (rpc==NULL)
                printf("                [rpc]");
            } else
              printf("???\n");
            break;
        }
      } else
        printf("%-15s",sp->s_name);
      printf("\n");
    }
  }
  printf("\n");
  exit(0);
}

usage(prog)
char *prog;
{
  fprintf(stderr,"Usage: %s [-r] [-m minport] [-M maxport] host\n", prog);
  fprintf(stderr,"Options:\n");
  fprintf(stderr,"-r       Don't use RPC for port info\n");
  fprintf(stderr,"-m port  Specify port number to start at (default 1)\n");
  fprintf(stderr,"-M port  Specify port number to end at   (default 6001)\n");
  return;
}


int scan_return(fd, iph, tcph)
int fd;
struct ip *iph;
struct tcphdr *tcph;

{
  char buf[8*1024], *bp, *bufstop, *cp, abuf[2048];
  int cc, done=0, retval=0;
  struct nit_bufhdr *hdrp;
  struct nit_iftime *ntp;
  struct nit_ifdrops *ndp;
  struct nit_iflen *nlp;
  struct ether_header *ep;
  u_short et;
  register struct ip *ip;
  struct tcphdr *tp;

  while (!done) {
    if ((cc=read(fd, buf, 8*1024)) >= 0) {
      bp=buf;
      bufstop = buf+cc;
      while (bp < bufstop) {
        cp = bp;
        
        /* Get past NIT buffer */
        hdrp = (struct nit_bufhdr *)cp;
        cp += sizeof(*hdrp);
        
        /* get past NIT timer   */
        ntp = (struct nit_iftime *)cp;
        cp += sizeof(*ntp);
        
        /* get past the drops */
        ndp = (struct nit_ifdrops *)cp;
        cp += sizeof(*ndp);

        /* get past packet len  */
        nlp = (struct nit_iflen *)cp;
        cp += sizeof(*nlp);

        /* next snapshot        */
        bp += hdrp->nhb_totlen;

        /* Okay, got the packet, make sure it's a SYN-ACK reply */
        ep = (struct ether_header *)cp;
        et = ntohs(ep->ether_type);
        if ( et >= ETHERTYPE_TRAIL && et < ETHERTYPE_TRAIL+ETHERTYPE_NTRAILER)
          continue;
        cp += sizeof(struct ether_header);
        nlp->nh_pktlen -= sizeof(struct ether_header);
        if (et != ETHERTYPE_IP) continue;
        
        /* It's: ethernet + IP */

        ip=(struct ip *)cp;
        bcopy((char *)ip, (char *)abuf, nlp->nh_pktlen); /* Align */
        ip = (struct ip *)abuf;

        if (ip->ip_p != IPPROTO_TCP)
          continue;

        /* It's ethernet + IP + TCP */
        if (ip->ip_src.s_addr != iph->ip_dst.s_addr)
          continue;
        if (ip->ip_dst.s_addr != iph->ip_src.s_addr)
          continue;

        /* It's ethernet + IP + TCP + from target + to us */
        cp+=sizeof(struct ip);
        tp = (struct tcphdr *)cp;
        if (tp->th_sport != tcph->th_dport)
          continue;
        if (tp->th_dport != tcph->th_sport)
          continue;

        /* It's ethernet + IP + TCP + from target + to us + ports right */
        if ((tp->th_flags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) {
          retval=0;
          done=1;
        } else {
          retval=1;
          done=1;
        }
        break;
      } /* While (bp<bufstop) */
    } /* if read */
  } /* while !done */
  return(retval);
}

jmp_buf env_buf;

/* Signal handler for receive timeout */
handle_alarm()
{
  alarm(0); /* Clear the alarm */
  longjmp(env_buf, 1);
}

/*
 * Sends a packet, and waits for the reply
 */
int send_packet(fd, server, servername, localnet, netmask)
int fd;
struct sockaddr_in *server;
char *servername;
u_long localnet;
u_long netmask;

{
  static struct sockaddr sa;
  static struct strbuf ctl, datah;
  static struct ip iph;
  static char buf[2048], pbuf[2048], *oldbp;
  static int computed=0;

  struct ether_header eh;
  struct tcphdr tcph;
  char *bp, *pbp;
  struct ether_addr myaddr, faddr;
  FILE *fp;
  struct hostent *he;
  u_long x;
  int retval;

  if (!computed) {
    /* ARP for the router/host, if possible */
    int s;
    struct arpreq arpreq;
    struct sockaddr_in *s_arp;

    if ((s = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
      perror("Socket");
      exit(1);
    }

    arpreq.arp_pa.sa_family = AF_INET;
    s_arp = (struct sockaddr_in *)&arpreq.arp_pa;
    s_arp->sin_family = AF_INET;
    s_arp->sin_addr.s_addr = server->sin_addr.s_addr;

    /* First, send junk to it to get an ARP entry */
    s_arp->sin_port = 9;
    sendto(s, "blah", 4, 0, (struct sockaddr *)s_arp,
           sizeof(struct sockaddr_in));
    s_arp = (struct sockaddr_in *)&arpreq.arp_ha;
    s_arp->sin_family = AF_UNSPEC;

    if (ioctl(s, SIOCGARP, &arpreq) < 0) {
      perror("ioctl");
      close(s);
      exit(1);
    }

    if (arpreq.arp_flags & ATF_COM) {
      bcopy(arpreq.arp_ha.sa_data, &faddr, 6);
    } else {
      fprintf(stderr, "Can't find destination/router hardware address.\n");
      exit(1);
    }
    /* faddr and myaddr are now computed, create the ether header */
    bcopy(&faddr, &eh.ether_dhost, 6);
    eh.ether_type = htons(ETHERTYPE_IP);
    sa.sa_family = AF_UNSPEC;
    bcopy((char *)&eh, (char *)sa.sa_data, sizeof(struct ether_header));
    ctl.len = sizeof(struct sockaddr);
    ctl.buf = (char *)&sa;
    bp = buf;

    iph.ip_v = IPVERSION;
    iph.ip_hl = 5; /* 20 octets--no options */
    iph.ip_tos = htons(0);   /* No special service */
    iph.ip_len = htons(40);
    iph.ip_id = htons(27); /* "unique" identification */
    iph.ip_off = htons(0);
    iph.ip_ttl = htons(60);
    iph.ip_p = htons(IPPROTO_TCP);
    iph.ip_dst.s_addr = server->sin_addr.s_addr;
    gethostname(buf, 2048);
    he = gethostbyname(buf);
    bcopy((char *)he->h_addr,
          (char *)&iph.ip_src.s_addr,
          sizeof(iph.ip_src.s_addr));
    iph.ip_sum = 0;
    iph.ip_sum = htons(in_cksum_c(&iph, (iph.ip_hl << 2)));
    bcopy((char *)&iph, bp, sizeof(struct ip));
    bp += sizeof(struct ip);
    oldbp = bp;
    computed=1;
  } /* if !computed */
  /* Set up the TCP header */
  bp = oldbp;
  tcph.th_sport = 5894; /* Random number */
  tcph.th_dport = server->sin_port;
  tcph.th_seq = 59595; /* Random number */
  tcph.th_ack = 0;
  tcph.th_off = 5;
  tcph.th_flags = TH_SYN;
  tcph.th_win = 4096;
  tcph.th_sum = 0;
  /* Calculate the TCP checksum on the TCP pseudoheader*/
  pbp=pbuf;
  bcopy((char *)&iph.ip_src.s_addr, pbp, 4);
  pbp+=4;
  bcopy((char *)&iph.ip_dst.s_addr, pbp, 4);
  pbp+=4;
  *pbp=0;
  pbp++;
  *pbp=(char)iph.ip_p;
  pbp++;
  *(u_short *)pbp=(u_short)sizeof(struct tcphdr);
  pbp+=2; /* go past the u_short */
  bcopy((char *)&tcph, pbp, sizeof(struct tcphdr));
  pbp+=sizeof(struct tcphdr);
  if ((pbp-pbuf)%2) {
    *pbp=(char)0;
    pbp++;
  }
  tcph.th_sum = htons(in_cksum_c(pbuf, (int)(pbp-pbuf)));

  bcopy((char *)&tcph, bp, sizeof(struct tcphdr));
  bp += sizeof(struct tcphdr);

  datah.len = (int)(bp-buf);
  datah.buf = (char *)buf;

  if (putmsg(fd, &ctl, &datah, 0) < 0) {
    perror("putmsg (ctl)");
    switch(errno) {
      case EAGAIN: fprintf(stderr,"EAGAIN\n");break;
      case EBADF: fprintf(stderr,"Bad FD\n");break;
      case EFAULT: fprintf(stderr,"Bad ctlptr or dataptr\n");break;
      case EINTR: fprintf(stderr,"Signal caught\n");break;
      case EINVAL: fprintf(stderr,"undefined flag\n");break;
      case ENOSTR: fprintf(stderr,"No stream\n");break;
      case ENXIO: fprintf(stderr,"hangup downstream\n");break;
      case ERANGE: fprintf(stderr,"data size problem\n");break;
    }
    exit(1);
  }
  /* Now that we've sent the syn, scan all return packets for reply */
  if (!setjmp(env_buf)) {
    signal(SIGALRM, handle_alarm, -1);
    alarm(1);
    retval=scan_return(fd, &iph, &tcph);
    alarm(0);
  } else retval=1;
  return(retval);
}

int fakeconnect(server, servername)
/*
 * Fake the connection, return 1 on failure, 0 on success
 */
struct sockaddr_in *server;
char *servername;
{
  static int if_fd = -1;
  char *device=0;
  u_long localnet;
  u_long netmask;
  int linktype;
  char *lookup_device();
  void lookup_net();

  if (if_fd == -1) {
    if (device==0) {
      device = lookup_device();
      if (device == 0)
        perror("can't find any interfaces");
    }
    if_fd = initdevice(device, &linktype);
    lookup_net(device, &localnet, &netmask);
  }
  return(send_packet(if_fd, server, servername, localnet, netmask));
}


/* ====================== begin nasty NIT stuff ======================= */


/* Not all systems have IFF_LOOPBACK */
#ifdef IFF_LOOPBACK
#define ISLOOPBACK(p) ((p)->ifr_flags & IFF_LOOPBACK)
#else
#define ISLOOPBACK(p) (strcmp((p)->ifr_name, "lo0") == 0)
#endif

char *lookup_device()
{
  struct ifreq ibuf[16], *ifrp, *ifend, *mp;
  struct ifconf ifc;
  int fd;
  int minunit, n;
  char *cp;
  static char device[sizeof(ifrp->ifr_name)];

  fd = socket(AF_INET, SOCK_DGRAM, 0);
  if (fd < 0) {
    perror("newscan: socket");
    exit(1);
  }
  ifc.ifc_len = sizeof(ibuf);
  ifc.ifc_buf = (caddr_t)ibuf;

  if (ioctl(fd, SIOCGIFCONF, (char *)&ifc) < 0 ||
      ifc.ifc_len < sizeof(struct ifreq)) {
    perror("newscan: SIOCGIFCONF: ");
    exit(1);
  }
  ifrp = ibuf;
  ifend = (struct ifreq *)((char *)ibuf + ifc.ifc_len);

  mp = 0;
  minunit = 666;
  while (ifrp < ifend) {
    struct ifreq ifr;
    /*
     * Need a template to preserve address info that is
     * used below to locate the next entry.  (Otherwise,
     * SIOCGIFFLAGS stomps over it because the requests
     * are returned in a union.)
     */
    bcopy(ifrp->ifr_name, ifr.ifr_name, sizeof(ifr.ifr_name));
    if (ioctl(fd, SIOCGIFFLAGS, (char *)&ifr) < 0) {
      fprintf(stderr, "newscan: SIOCGIFFLAGS: ");
      perror(ifrp->ifr_name);
      exit(1);
    }
    if ((ifr.ifr_flags & IFF_UP) && !ISLOOPBACK(&ifr)) {
      for (cp = ifrp->ifr_name; !isdigit(*cp); ++cp)
        ;
      n = atoi(cp);
      if (n < minunit) {
        minunit = n;
        mp = ifrp;
      }
    }
#if BSD >= 199006
    n = ifrp->ifr_addr.sa_len + sizeof(ifrp->ifr_name);
    if (n < sizeof(*ifrp))
      ++ifrp;
    else
      ifrp = (struct ifreq *)((char *)ifrp + n);
#else
    ++ifrp;
#endif
  }
  close(fd);
  if (mp == 0)
    return (0);

  (void)strcpy(device, mp->ifr_name);
  return (device);
}

/*
 * Get the netmask of an IP address.  This routine is used if
 * SIOCGIFNETMASK doesn't work.
 */
static u_long
ipaddrtonetmask(addr)
u_long addr;
{
  char str[80];

  if (IN_CLASSA(addr))
    return (IN_CLASSA_NET);
  if (IN_CLASSB(addr))
    return (IN_CLASSB_NET);
  if (IN_CLASSC(addr))
    return (IN_CLASSC_NET);
  sprintf(str,"unknown IP address class: %08X", addr);
  perror(str);
  /* NOTREACHED */
}

void
lookup_net(device, netp, maskp)
char *device;
u_long *netp;
u_long *maskp;
{
  int fd;
  struct ifreq ifr;
  struct sockaddr_in *sin = (struct sockaddr_in *)&ifr.ifr_addr;

  /* Use data gram socket to get IP address. */
  if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
    perror("newscan: socket");
    exit(1);
  }
  (void)strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
  if (ioctl(fd, SIOCGIFADDR, (char *)&ifr) < 0) {
    /*
     * This will fail if an IP address hasn't been assigned.
     */
    *netp = 0;
    *maskp = 0;
    return;
  }
  *netp = sin->sin_addr.s_addr;
  if (ioctl(fd, SIOCGIFNETMASK, (char *)&ifr) < 0)
    *maskp = 0;
  else
    *maskp = sin->sin_addr.s_addr;
  if (*maskp == 0)
    *maskp = ipaddrtonetmask(*netp);
  *netp &= *maskp;
  (void)close(fd);
}

u_long snaplen = 0;

int
initdevice(device,linktype)
char *device;
int *linktype;
{
  struct strioctl si;             /* struct for ioctl() */
  struct timeval timeout;         /* timeout for ioctl() */
  struct ifreq ifr;               /* interface request struct */
  u_long if_flags;                /* modes for interface             */
  int  ret;
  /*  int chunksize = (8*1024); */
  int chunksize = 0;
  int if_fd;
  char *dev = "/dev/nit";
  int nonblock;

  struct ether_header eh;
  struct ip iptest;
  struct packetfilt pf;
  register u_short *fwp = pf.Pf_Filter;
  u_short ethoffset;
  u_short ipoffset;
  u_short masker = 255;

  si.ic_timout = INFTIM;

  /* Set up the Packet Filter */
  ethoffset=((u_int)&eh.ether_type-(u_int)&eh.ether_dhost)/(sizeof(u_short));
  ipoffset = 11;
  *fwp++ = ENF_PUSHZERO;
  *fwp++ = ENF_PUSHWORD + ethoffset;
  *fwp++ = ENF_PUSHLIT;
  *fwp++ = htons(ETHERTYPE_IP);
  *fwp++ = ENF_COR;
  *fwp++ = ENF_PUSHWORD + ipoffset;
  *fwp++ = ENF_PUSHLIT;
  *fwp++ = (u_short)255;
  *fwp++ = ENF_AND;
  *fwp++ = ENF_PUSHLIT;
  *fwp++ = (u_short)6;
  *fwp++ = ENF_COR;
  *fwp++ = ENF_PUSHLIT;
  *fwp++ = (u_short)1;

  /* open /dev/nit Read/write */
  if ((if_fd = open(dev, O_RDWR)) < 0) {
    (void) fprintf(stderr, "newscan: open: ");
    perror(dev);
    exit(-1);
  }

  /* arrange to get discrete messages from the STREAM and use NIT_BUF */
  ioctl(if_fd, I_SRDOPT, (char*)RMSGD);

  /* it is important to have this stuff in the stream BEFORE! the nbuf */
  si.ic_cmd = NIOCSETF;
  si.ic_len = sizeof(struct packetfilt);
  si.ic_dp = (char*)&pf;
  pf.Pf_FilterLen = fwp - &pf.Pf_Filter[0];
  if (ioctl(if_fd, I_PUSH, "pf")<0) {
    perror("I_PUSH pf");
    fprintf(stderr,"No pf being used\n");
  } else {
    if ((ioctl(if_fd, I_STR, (char*)&si)) < 0) {
      perror("newscan: NIOCSETF");
      /* exit(-1); */
      fprintf(stderr,"No pf being used (or one already applied)\n");
    }
  }

  ioctl(if_fd, I_PUSH, "nbuf");

  /* set the timeout */
  timeout.tv_sec = 1;
  timeout.tv_usec = 0;
  si.ic_cmd = NIOCSTIME;
  si.ic_len = sizeof(timeout);
  si.ic_dp = (char*)&timeout;
  if ((ret = ioctl(if_fd, I_STR, (char*)&si)) < 0) {
    perror("newscan: NIOCSTIME");
    exit(-1);
  }

  /* set the chunksize */
  si.ic_cmd = NIOCSCHUNK;
  si.ic_len = sizeof(chunksize);
  si.ic_dp = (char*)&chunksize;
  if ((ret = ioctl(if_fd, I_STR, (char*)&si)) < 0) {
    perror("newscan: NIOCSCHUNK");
    exit(-1);
  }

  /* Set up the NIT device (bind it,set snapshot length etc) */
  /* bind the interface */
  strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
  ifr.ifr_name[sizeof(ifr.ifr_name) - 1] = ' ';
  si.ic_cmd = NIOCBIND;
  si.ic_len = sizeof(ifr);
  si.ic_dp = (char*)&ifr;
  if ((ret = ioctl(if_fd, I_STR, (char*)&si)) < 0) {
    (void) fprintf(stderr, "newscan: NIOCBIND");
    perror(ifr.ifr_name);
    exit(1);
  }

  /* set the snapshot length */
  si.ic_cmd = NIOCSSNAP;
  si.ic_len = sizeof(snaplen);
  si.ic_dp = (char*)&snaplen;
  if ((ret = ioctl(if_fd, I_STR, (char*)&si)) < 0) {
    perror("newscan: NIOCSSNAP");
    exit(1);
  }

  /* set the interface flags */
  si.ic_cmd = NIOCSFLAGS;
  if_flags = NI_TIMESTAMP | NI_LEN | NI_DROPS;
  if_flags |= NI_PROMISC;
  si.ic_len = sizeof(if_flags);
  si.ic_dp = (char*)&if_flags;
  if ((ioctl(if_fd, I_STR, (char*)&si)) < 0) {
    perror("newscan: NIOCSFLAGS");
    exit(1);
  }

  nonblock = 1;
  ioctl(if_fd, FIONBIO,&nonblock);

  ioctl(if_fd, I_FLUSH, (char*)FLUSHR);
  /*
   * NIT supports only ethernets.
   */
  *linktype = 1;

  return if_fd;
}