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ncat_core.c

/***************************************************************************
 * ncat_core.c -- Contains option defintions and miscellaneous functions.  *
 ***********************IMPORTANT NMAP LICENSE TERMS************************
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 * also a registered trademark of Insecure.Com LLC.  This program is free  *
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/* $Id: ncat_core.c 16410 2010-01-06 05:54:55Z david $ */

#include "ncat.h"
#include "util.h"
#include "sys_wrap.h"

#ifndef WIN32
#include <unistd.h>
#include <netdb.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <ctype.h>
#include <time.h>
#include <assert.h>

union sockaddr_u srcaddr;
size_t srcaddrlen;
union sockaddr_u targetss;
size_t targetsslen;

union sockaddr_u httpconnect;
union sockaddr_u socksconnect;

/* Global options structure. */
struct options o;

/* The time the program was started, for exit statistics in connect mode. */
struct timeval start_time;

/* Initializes global options to their default values. */
void options_init(void) {
    o.verbose = 0;
    o.debug = 0;
    o.target = NULL;
    o.af = AF_INET;
    o.broker = 0;
    o.listen = 0;
    o.keepopen = 0;
    o.sendonly = 0;
    o.recvonly = 0;
    o.telnet = 0;
    o.udp = 0;
    o.sctp = 0;
    o.linedelay = 0;
    o.chat = 0;
    o.nodns = 0;
    o.normlogfd = -1;
    o.hexlogfd = -1;
    o.idletimeout = 0;
    o.crlf = 0;
    o.allow = 0;
    o.deny = 0;
    addrset_init(&o.allowset);
    addrset_init(&o.denyset);
    o.httpserver = 0;

    o.numsrcrtes = 0;
    o.srcrteptr = 4;

    o.conn_limit = -1;  /* Unset. */
    o.conntimeout = DEFAULT_CONNECT_TIMEOUT;

    o.cmdexec = NULL;
    o.shellexec = 0;
    o.proxy_auth = NULL;
    o.proxytype = NULL;

#ifdef HAVE_OPENSSL
    o.ssl = 0;
    o.sslcert = NULL;
    o.sslkey = NULL;
    o.sslverify = 0;
    o.ssltrustfile = NULL;
#endif
}

/* Tries to resolve the given name (or literal IP) into a sockaddr structure.
   Pass 0 for the port if you don't care. Returns 0 if hostname cannot be
   resolved. */
int resolve(char *hostname, unsigned short port,
            struct sockaddr_storage *ss, size_t *sslen, int af)
{
  struct addrinfo hints;
  struct addrinfo *result;
  char portbuf[16];
  int rc;

  assert(ss);
  assert(sslen);

  memset(&hints, 0, sizeof(hints));
  hints.ai_family = af;
  hints.ai_socktype = SOCK_DGRAM;
  if (o.nodns)
     hints.ai_flags |= AI_NUMERICHOST;

  /* Make the port number a string to give to getaddrinfo. */
  rc = Snprintf(portbuf, sizeof(portbuf), "%hu", port);
  assert(rc >= 0 && rc < sizeof(portbuf));

  rc = getaddrinfo(hostname, portbuf, &hints, &result);
  if (rc != 0 || result == NULL)
      return 0;
  assert(result->ai_addrlen > 0 && result->ai_addrlen <= (int) sizeof(struct sockaddr_storage));
  *sslen = result->ai_addrlen;
  memcpy(ss, result->ai_addr, *sslen);
  freeaddrinfo(result);
  return 1;
}

/* Read from a client socket into buf, returning the number of bytes read, or -1
   on an error. This takes care of delays, Telnet negotiation, and logging.

   If there is more data pending that won't be noticed by select, a 1 is stored
   in *pending, otherwise 0 is stored there. The caller must loop, processing
   read data until *pending is false. The reason for this is the SSL_read
   function that this function may call, which takes data out of the socket
   buffer (so select may not indicate the socket is readable) and keeps it in
   its own buffer. *pending holds the result of calling SSL_pending. See
   http://www.mail-archive.com/openssl-dev@openssl.org/msg24324.html. */
int ncat_recv(struct fdinfo *fdn, char *buf, size_t size, int *pending)
{
    int n;

    *pending = 0;

#ifdef HAVE_OPENSSL
    if (o.ssl && fdn->ssl)
        n = SSL_read(fdn->ssl, buf, size);
    else
#endif
        n = recv(fdn->fd, buf, size, 0);

    if (n <= 0)
      return n;

    if (o.linedelay)
        ncat_delay_timer(o.linedelay);
    if (o.telnet)
        dotelnet(fdn->fd, (unsigned char *) buf, n);
    ncat_log_recv(buf, n);

#ifdef HAVE_OPENSSL
    /* SSL can buffer our input, so doing another select() won't necessarily
       work for us. Indicate to the caller that this function must be called
       again to get more data. */
    if (o.ssl && fdn->ssl)
        *pending = SSL_pending(fdn->ssl);
#endif

    return n;
}

/* Do a send to a client, without any logging or other side effects. */
static int ncat_send_primitive(struct fdinfo *fdn, const char *buf, size_t size)
{
#ifdef HAVE_OPENSSL
    if (o.ssl && fdn->ssl != NULL)
      return SSL_write(fdn->ssl, buf, size);
#endif
    return send(fdn->fd, buf, size, 0);
}

int ncat_send(struct fdinfo *fdn, const char *buf, size_t size)
{
    int n;

    if (o.recvonly)
        return size;

    n = ncat_send_primitive(fdn, buf, size);
    if (n <= 0)
      return n;

    ncat_log_send(buf, size);

    return n;
}

/* Broadcast a message to all the descriptors in fds. Returns -1 if any of the
   sends failed. */
int ncat_broadcast(fd_set *fds, const fd_list_t *fdlist, const char *msg, size_t size)
{
    struct fdinfo *fdn;
    int i, ret;

    if (o.recvonly)
        return 0;

    ret = 0;
    for (i = 0; i <= fdlist->fdmax; i++) {
        if (!FD_ISSET(i, fds))
            continue;

        fdn = get_fdinfo(fdlist, i);
        if (ncat_send_primitive(fdn, msg, size) <= 0) {
          if (o.debug > 1)
            logdebug("Error sending to fd %d: %s.\n", i, socket_strerror(socket_errno()));
          ret = -1;
        }
    }

    ncat_log_send(msg, size);

    return ret;
}

/* Do telnet WILL/WONT DO/DONT negotiations */
void dotelnet(int s, unsigned char *buf, size_t bufsiz)
{
    unsigned char *end = buf + bufsiz, *p;
    unsigned char tbuf[3];

    for (p = buf; buf < end; p++) {
        if (*p != 255) /* IAC */
            break;

        tbuf[0] = *p++;

        /* Answer DONT for WILL or WONT */
        if (*p == 251 || *p == 252)
            tbuf[1] = 254;

        /* Answer WONT for DO or DONT */
        else if (*p == 253 || *p == 254)
            tbuf[1] = 252;

        tbuf[2] = *++p;

        send(s, (const char *) tbuf, 3, 0);
    }
}

/* Return 1 if user is root, otherwise 0. */
int ncat_checkuid()
{
#ifdef WIN32
    return 1;
#else
    return (getuid() == 0 || geteuid() == 0);
#endif
}

/* sleep(), usleep(), msleep(), Sleep() -- all together now, "portability".
 *
 * There is no upper or lower limit to the delayval, so if you pass in a short
 * length of time <100ms, then you're likely going to get odd results.
 * This is because the Linux timeslice is 10ms-200ms. So don't expect
 * it to return for atleast that long.
 *
 * Block until the specified time has elapsed, then return 1.
 */
int ncat_delay_timer(int delayval)
{
    struct timeval s;

    s.tv_sec = delayval / 1000;
    s.tv_usec = (delayval % 1000) * (long) 1000;

    select(0, NULL, NULL, NULL, &s);
    return 1;
}

/* Open a logfile for writing.
 * Return the open file descriptor. */
int ncat_openlog(char *logfile)
{
    return Open(logfile, O_WRONLY | O_CREAT | O_TRUNC, 0664);
}

static int ncat_hexdump(int logfd, const char *data, int len);

void ncat_log_send(const char *data, size_t len)
{
    if (o.normlogfd != -1)
        Write(o.normlogfd, data, len);

    if (o.hexlogfd != -1)
        ncat_hexdump(o.hexlogfd, data, len);
}

void ncat_log_recv(const char *data, size_t len)
{
    /* Currently the log formats don't distinguish sends and receives. */
    ncat_log_send(data, len);
}

/* Convert session data to a neat hexdump logfile */
static int ncat_hexdump(int logfd, const char *data, int len)
{
    const char *p = data;
    char c;
    int i;
    char bytestr[4] = { 0 };
    char addrstr[10] = { 0 };
    char hexstr[16 * 3 + 5] = { 0 };
    char charstr[16 * 1 + 5] = { 0 };
    char outstr[80] = { 0 };

    /* FIXME: needs to be audited closer */
    for (i = 1; i <= len; i++) {
        if (i % 16 == 1) {
            /* Hex address output */
            Snprintf(addrstr, sizeof(addrstr), "%.4x", (u_int)(p - data));
        }

        c = *p;

        /* If the character isn't printable. Control characters, etc. */
        if (isprint((int) (unsigned char) c) == 0)
            c = '.';

        /* hex for output */
        Snprintf(bytestr, sizeof(bytestr), "%02X ", (unsigned char) *p);
        strncat(hexstr, bytestr, sizeof(hexstr) - strlen(hexstr) - 1);

        /* char for output */
        Snprintf(bytestr, sizeof(bytestr), "%c", c);
        strncat(charstr, bytestr, sizeof(charstr) - strlen(charstr) - 1);

        if (i % 16 == 0) {
            /* neatly formatted output */
            Snprintf(outstr, sizeof(outstr), "[%4.4s]   %-50.50s  %s\n",
                     addrstr, hexstr, charstr);

            Write(logfd, outstr, strlen(outstr));
            zmem(outstr, sizeof(outstr));

            hexstr[0] = 0;
            charstr[0] = 0;
        } else if (i % 8 == 0) {
            /* cat whitespaces where necessary */
            strncat(hexstr, "  ", sizeof(hexstr) - strlen(hexstr) - 1);
            strncat(charstr, " ", sizeof(charstr) - strlen(charstr) - 1);
        }

        /* get the next byte */
        p++;
    }

    /* if there's still data left in the buffer, print it */
    if (strlen(hexstr) > 0) {
        Snprintf(outstr, sizeof(outstr), "[%4.4s]   %-50.50s  %s\n",
                    addrstr, hexstr, charstr);

        Write(logfd, outstr, strlen(outstr));
        zmem(outstr, sizeof(outstr));
    }

    return 1;
}

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