LXR busybox/networking/pscan.c

   1/*
   2 * Pscan is a mini port scanner implementation for busybox
   3 *
   4 * Copyright 2007 Tito Ragusa <farmatito@tiscali.it>
   5 *
   6 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   7 */
   8//config:config PSCAN
   9//config:       bool "pscan (6 kb)"
  10//config:       default y
  11//config:       help
  12//config:       Simple network port scanner.
  13
  14//applet:IF_PSCAN(APPLET(pscan, BB_DIR_USR_BIN, BB_SUID_DROP))
  15
  16//kbuild:lib-$(CONFIG_PSCAN) += pscan.o
  17
  18//usage:#define pscan_trivial_usage
  19//usage:       "[-cb] [-p MIN_PORT] [-P MAX_PORT] [-t TIMEOUT] [-T MIN_RTT] HOST"
  20//usage:#define pscan_full_usage "\n\n"
  21//usage:       "Scan a host, print all open ports\n"
  22//usage:     "\n        -c      Show closed ports too"
  23//usage:     "\n        -b      Show blocked ports too"
  24//usage:     "\n        -p      Scan from this port (default 1)"
  25//usage:     "\n        -P      Scan up to this port (default 1024)"
  26//usage:     "\n        -t      Timeout (default 5000 ms)"
  27//usage:     "\n        -T      Minimum rtt (default 5 ms, increase for congested hosts)"
  28
  29#include "libbb.h"
  30
  31/* debugging */
  32#ifdef DEBUG_PSCAN
  33#define DMSG(...) bb_error_msg(__VA_ARGS__)
  34#define DERR(...) bb_perror_msg(__VA_ARGS__)
  35#else
  36#define DMSG(...) ((void)0)
  37#define DERR(...) ((void)0)
  38#endif
  39
  40static const char *port_name(unsigned port)
  41{
  42        struct servent *server;
  43
  44        server = getservbyport(htons(port), NULL);
  45        if (server)
  46                return server->s_name;
  47        return "unknown";
  48}
  49
  50/* We don't expect to see 1000+ seconds delay, unsigned is enough */
  51#define MONOTONIC_US() ((unsigned)monotonic_us())
  52
  53int pscan_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  54int pscan_main(int argc UNUSED_PARAM, char **argv)
  55{
  56        const char *opt_max_port = "1024";      /* -P: default max port */
  57        const char *opt_min_port = "1";         /* -p: default min port */
  58        const char *opt_timeout = "5000";       /* -t: default timeout in msec */
  59        /* We estimate rtt and wait rtt*4 before concluding that port is
  60         * totally blocked. min rtt of 5 ms may be too low if you are
  61         * scanning an Internet host behind saturated/traffic shaped link.
  62         * Rule of thumb: with min_rtt of N msec, scanning 1000 ports
  63         * will take N seconds at absolute minimum */
  64        const char *opt_min_rtt = "5";          /* -T: default min rtt in msec */
  65        const char *result_str;
  66        len_and_sockaddr *lsap;
  67        int s;
  68        unsigned opt;
  69        unsigned port, max_port, nports;
  70        unsigned closed_ports = 0;
  71        unsigned open_ports = 0;
  72        /* all in usec */
  73        unsigned timeout;
  74        unsigned min_rtt;
  75        unsigned rtt_4;
  76        unsigned start, diff;
  77
  78        opt = getopt32(argv, "^"
  79                "cbp:P:t:T:"
  80                "\0" "=1", /* exactly one non-option */
  81                &opt_min_port, &opt_max_port, &opt_timeout, &opt_min_rtt
  82        );
  83        argv += optind;
  84        max_port = xatou_range(opt_max_port, 1, 65535);
  85        port = xatou_range(opt_min_port, 1, max_port);
  86        nports = max_port - port + 1;
  87        min_rtt = xatou_range(opt_min_rtt, 1, INT_MAX/1000 / 4) * 1000;
  88        timeout = xatou_range(opt_timeout, 1, INT_MAX/1000 / 4) * 1000;
  89        /* Initial rtt is BIG: */
  90        rtt_4 = timeout;
  91
  92        DMSG("min_rtt %u timeout %u", min_rtt, timeout);
  93
  94        lsap = xhost2sockaddr(*argv, port);
  95        printf("Scanning %s ports %u to %u\n Port\tProto\tState\tService\n",
  96                        *argv, port, max_port);
  97
  98        for (; port <= max_port; port++) {
  99                DMSG("rtt %u", rtt_4);
 100
 101                /* The SOCK_STREAM socket type is implemented on the TCP/IP protocol. */
 102                set_nport(&lsap->u.sa, htons(port));
 103                s = xsocket(lsap->u.sa.sa_family, SOCK_STREAM, 0);
 104                /* We need unblocking socket so we don't need to wait for ETIMEOUT. */
 105                /* Nonblocking connect typically "fails" with errno == EINPROGRESS */
 106                ndelay_on(s);
 107
 108                DMSG("connect to port %u", port);
 109                result_str = NULL;
 110                start = MONOTONIC_US();
 111                if (connect(s, &lsap->u.sa, lsap->len) == 0) {
 112                        /* Unlikely, for me even localhost fails :) */
 113                        DMSG("connect succeeded");
 114                        goto open;
 115                }
 116                /* Check for untypical errors... */
 117                if (errno != EAGAIN && errno != EINPROGRESS
 118                 && errno != ECONNREFUSED
 119                ) {
 120                        bb_perror_nomsg_and_die();
 121                }
 122
 123                diff = 0;
 124                while (1) {
 125                        if (errno == ECONNREFUSED) {
 126                                if (opt & 1) /* -c: show closed too */
 127                                        result_str = "closed";
 128                                closed_ports++;
 129                                break;
 130                        }
 131                        DERR("port %u errno %d @%u", port, errno, diff);
 132
 133                        if (diff > rtt_4) {
 134                                if (opt & 2) /* -b: show blocked too */
 135                                        result_str = "blocked";
 136                                break;
 137                        }
 138                        /* Can sleep (much) longer than specified delay.
 139                         * We check rtt BEFORE we usleep, otherwise
 140                         * on localhost we'll have no writes done (!)
 141                         * before we exceed (rather small) rtt */
 142                        usleep(rtt_4/8);
 143 open:
 144                        diff = MONOTONIC_US() - start;
 145                        DMSG("write to port %u @%u", port, diff - start);
 146                        if (write(s, " ", 1) >= 0) { /* We were able to write to the socket */
 147                                open_ports++;
 148                                result_str = "open";
 149                                break;
 150                        }
 151                }
 152                DMSG("out of loop @%u", diff);
 153                if (result_str)
 154                        printf("%5u" "\t" "tcp" "\t" "%s" "\t" "%s" "\n",
 155                                        port, result_str, port_name(port));
 156
 157                /* Estimate new rtt - we don't want to wait entire timeout
 158                 * for each port. *4 allows for rise in net delay.
 159                 * We increase rtt quickly (rtt_4*4), decrease slowly
 160                 * (diff is at least rtt_4/8, *4 == rtt_4/2)
 161                 * because we don't want to accidentally miss ports. */
 162                rtt_4 = diff * 4;
 163                if (rtt_4 < min_rtt)
 164                        rtt_4 = min_rtt;
 165                if (rtt_4 > timeout)
 166                        rtt_4 = timeout;
 167                /* Clean up */
 168                close(s);
 169        }
 170        if (ENABLE_FEATURE_CLEAN_UP) free(lsap);
 171
 172        printf("%u closed, %u open, %u timed out (or blocked) ports\n",
 173                                        closed_ports,
 174                                        open_ports,
 175                                        nports - (closed_ports + open_ports));
 176        return EXIT_SUCCESS;
 177}
 178