upstream: Improve description of KbdInteractiveAuthentication.

[openssh.git] / ssh-keyscan.c

/* $OpenBSD: ssh-keyscan.c,v 1.164 2024/10/18 05:32:51 djm Exp $ */
/*
 * Copyright 1995, 1996 by David Mazieres <dm@lcs.mit.edu>.
 *
 * Modification and redistribution in source and binary forms is
 * permitted provided that due credit is given to the author and the
 * OpenBSD project by leaving this copyright notice intact.
 */

#include "includes.h"
 
#include <sys/types.h>
#include "openbsd-compat/sys-queue.h"
#include <sys/resource.h>
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
#endif

#include <netinet/in.h>
#include <arpa/inet.h>

#ifdef WITH_OPENSSL
#include <openssl/bn.h>
#endif

#include <limits.h>
#include <netdb.h>
#include <errno.h>
#ifdef HAVE_POLL_H
#include <poll.h>
#endif
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>

#include "xmalloc.h"
#include "ssh.h"
#include "sshbuf.h"
#include "sshkey.h"
#include "cipher.h"
#include "digest.h"
#include "kex.h"
#include "compat.h"
#include "myproposal.h"
#include "packet.h"
#include "dispatch.h"
#include "log.h"
#include "atomicio.h"
#include "misc.h"
#include "hostfile.h"
#include "ssherr.h"
#include "ssh_api.h"
#include "dns.h"
#include "addr.h"

/* Flag indicating whether IPv4 or IPv6.  This can be set on the command line.
   Default value is AF_UNSPEC means both IPv4 and IPv6. */
int IPv4or6 = AF_UNSPEC;

int ssh_port = SSH_DEFAULT_PORT;

#define KT_DSA          (1)
#define KT_RSA          (1<<1)
#define KT_ECDSA        (1<<2)
#define KT_ED25519      (1<<3)
#define KT_XMSS         (1<<4)
#define KT_ECDSA_SK     (1<<5)
#define KT_ED25519_SK   (1<<6)

#define KT_MIN          KT_DSA
#define KT_MAX          KT_ED25519_SK

int get_cert = 0;
int get_keytypes = KT_RSA|KT_ECDSA|KT_ED25519|KT_ECDSA_SK|KT_ED25519_SK;

int hash_hosts = 0;             /* Hash hostname on output */

int print_sshfp = 0;            /* Print SSHFP records instead of known_hosts */

int found_one = 0;              /* Successfully found a key */

int hashalg = -1;               /* Hash for SSHFP records or -1 for all */

int quiet = 0;                  /* Don't print key comment lines */

#define MAXMAXFD 256

/* The number of seconds after which to give up on a TCP connection */
int timeout = 5;

int maxfd;
#define MAXCON (maxfd - 10)

extern char *__progname;
struct pollfd *read_wait;
int ncon;

/*
 * Keep a connection structure for each file descriptor.  The state
 * associated with file descriptor n is held in fdcon[n].
 */
typedef struct Connection {
        u_char c_status;        /* State of connection on this file desc. */
#define CS_UNUSED 0             /* File descriptor unused */
#define CS_CON 1                /* Waiting to connect/read greeting */
        int c_fd;               /* Quick lookup: c->c_fd == c - fdcon */
        int c_keytype;          /* Only one of KT_* */
        sig_atomic_t c_done;    /* SSH2 done */
        char *c_namebase;       /* Address to free for c_name and c_namelist */
        char *c_name;           /* Hostname of connection for errors */
        char *c_namelist;       /* Pointer to other possible addresses */
        char *c_output_name;    /* Hostname of connection for output */
        struct ssh *c_ssh;      /* SSH-connection */
        struct timespec c_ts;   /* Time at which connection gets aborted */
        TAILQ_ENTRY(Connection) c_link; /* List of connections in timeout order. */
} con;

TAILQ_HEAD(conlist, Connection) tq;     /* Timeout Queue */
con *fdcon;

static void keyprint(con *c, struct sshkey *key);

static int
fdlim_get(int hard)
{
#if defined(HAVE_GETRLIMIT) && defined(RLIMIT_NOFILE)
        struct rlimit rlfd;
        rlim_t lim;

        if (getrlimit(RLIMIT_NOFILE, &rlfd) == -1)
                return -1;
        lim = hard ? rlfd.rlim_max : rlfd.rlim_cur;
        if (lim <= 0)
                return -1;
        if (lim == RLIM_INFINITY)
                lim = SSH_SYSFDMAX;
        if (lim >= INT_MAX)
                lim = INT_MAX;
        return lim;
#else
        return (SSH_SYSFDMAX <= 0) ? -1 :
            ((SSH_SYSFDMAX >= INT_MAX) ? INT_MAX : SSH_SYSFDMAX);
#endif
}

static int
fdlim_set(int lim)
{
#if defined(HAVE_SETRLIMIT) && defined(RLIMIT_NOFILE)
        struct rlimit rlfd;
#endif

        if (lim <= 0)
                return (-1);
#if defined(HAVE_SETRLIMIT) && defined(RLIMIT_NOFILE)
        if (getrlimit(RLIMIT_NOFILE, &rlfd) == -1)
                return (-1);
        rlfd.rlim_cur = lim;
        if (setrlimit(RLIMIT_NOFILE, &rlfd) == -1)
                return (-1);
#elif defined (HAVE_SETDTABLESIZE)
        setdtablesize(lim);
#endif
        return (0);
}

/*
 * This is an strsep function that returns a null field for adjacent
 * separators.  This is the same as the 4.4BSD strsep, but different from the
 * one in the GNU libc.
 */
static char *
xstrsep(char **str, const char *delim)
{
        char *s, *e;

        if (!**str)
                return (NULL);

        s = *str;
        e = s + strcspn(s, delim);

        if (*e != '\0')
                *e++ = '\0';
        *str = e;

        return (s);
}

/*
 * Get the next non-null token (like GNU strsep).  Strsep() will return a
 * null token for two adjacent separators, so we may have to loop.
 */
static char *
strnnsep(char **stringp, char *delim)
{
        char *tok;

        do {
                tok = xstrsep(stringp, delim);
        } while (tok && *tok == '\0');
        return (tok);
}


static int
key_print_wrapper(struct sshkey *hostkey, struct ssh *ssh)
{
        con *c;

        if ((c = ssh_get_app_data(ssh)) != NULL)
                keyprint(c, hostkey);
        /* always abort key exchange */
        return -1;
}

static int
ssh2_capable(int remote_major, int remote_minor)
{
        switch (remote_major) {
        case 1:
                if (remote_minor == 99)
                        return 1;
                break;
        case 2:
                return 1;
        default:
                break;
        }
        return 0;
}

static void
keygrab_ssh2(con *c)
{
        char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
        int r;

        switch (c->c_keytype) {
        case KT_DSA:
                myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = get_cert ?
                    "ssh-dss-cert-v01@openssh.com" : "ssh-dss";
                break;
        case KT_RSA:
                myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = get_cert ?
                    "rsa-sha2-512-cert-v01@openssh.com,"
                    "rsa-sha2-256-cert-v01@openssh.com,"
                    "ssh-rsa-cert-v01@openssh.com" :
                    "rsa-sha2-512,"
                    "rsa-sha2-256,"
                    "ssh-rsa";
                break;
        case KT_ED25519:
                myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = get_cert ?
                    "ssh-ed25519-cert-v01@openssh.com" : "ssh-ed25519";
                break;
        case KT_XMSS:
                myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = get_cert ?
                    "ssh-xmss-cert-v01@openssh.com" : "ssh-xmss@openssh.com";
                break;
        case KT_ECDSA:
                myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = get_cert ?
                    "ecdsa-sha2-nistp256-cert-v01@openssh.com,"
                    "ecdsa-sha2-nistp384-cert-v01@openssh.com,"
                    "ecdsa-sha2-nistp521-cert-v01@openssh.com" :
                    "ecdsa-sha2-nistp256,"
                    "ecdsa-sha2-nistp384,"
                    "ecdsa-sha2-nistp521";
                break;
        case KT_ECDSA_SK:
                myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = get_cert ?
                    "sk-ecdsa-sha2-nistp256-cert-v01@openssh.com" :
                    "sk-ecdsa-sha2-nistp256@openssh.com";
                break;
        case KT_ED25519_SK:
                myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = get_cert ?
                    "sk-ssh-ed25519-cert-v01@openssh.com" :
                    "sk-ssh-ed25519@openssh.com";
                break;
        default:
                fatal("unknown key type %d", c->c_keytype);
                break;
        }
        if ((r = kex_setup(c->c_ssh, myproposal)) != 0) {
                free(c->c_ssh);
                fprintf(stderr, "kex_setup: %s\n", ssh_err(r));
                exit(1);
        }
#ifdef WITH_OPENSSL
        c->c_ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client;
        c->c_ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client;
        c->c_ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client;
        c->c_ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client;
        c->c_ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client;
        c->c_ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
        c->c_ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
# ifdef OPENSSL_HAS_ECC
        c->c_ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client;
# endif
#endif
        c->c_ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client;
        c->c_ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_client;
        c->c_ssh->kex->kex[KEX_KEM_MLKEM768X25519_SHA256] = kex_gen_client;
        ssh_set_verify_host_key_callback(c->c_ssh, key_print_wrapper);
        /*
         * do the key-exchange until an error occurs or until
         * the key_print_wrapper() callback sets c_done.
         */
        ssh_dispatch_run(c->c_ssh, DISPATCH_BLOCK, &c->c_done);
}

static void
keyprint_one(const char *host, struct sshkey *key)
{
        char *hostport = NULL, *hashed = NULL;
        const char *known_host;
        int r = 0;

        found_one = 1;

        if (print_sshfp) {
                export_dns_rr(host, key, stdout, 0, hashalg);
                return;
        }

        hostport = put_host_port(host, ssh_port);
        lowercase(hostport);
        if (hash_hosts && (hashed = host_hash(hostport, NULL, 0)) == NULL)
                fatal("host_hash failed");
        known_host = hash_hosts ? hashed : hostport;
        if (!get_cert)
                r = fprintf(stdout, "%s ", known_host);
        if (r >= 0 && sshkey_write(key, stdout) == 0)
                (void)fputs("\n", stdout);
        free(hashed);
        free(hostport);
}

static void
keyprint(con *c, struct sshkey *key)
{
        char *hosts = c->c_output_name ? c->c_output_name : c->c_name;
        char *host, *ohosts;

        if (key == NULL)
                return;
        if (get_cert || (!hash_hosts && ssh_port == SSH_DEFAULT_PORT)) {
                keyprint_one(hosts, key);
                return;
        }
        ohosts = hosts = xstrdup(hosts);
        while ((host = strsep(&hosts, ",")) != NULL)
                keyprint_one(host, key);
        free(ohosts);
}

static int
tcpconnect(char *host)
{
        struct addrinfo hints, *ai, *aitop;
        char strport[NI_MAXSERV];
        int gaierr, s = -1;

        snprintf(strport, sizeof strport, "%d", ssh_port);
        memset(&hints, 0, sizeof(hints));
        hints.ai_family = IPv4or6;
        hints.ai_socktype = SOCK_STREAM;
        if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) {
                error("getaddrinfo %s: %s", host, ssh_gai_strerror(gaierr));
                return -1;
        }
        for (ai = aitop; ai; ai = ai->ai_next) {
                s = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
                if (s == -1) {
                        error("socket: %s", strerror(errno));
                        continue;
                }
                if (set_nonblock(s) == -1)
                        fatal_f("set_nonblock(%d)", s);
                if (connect(s, ai->ai_addr, ai->ai_addrlen) == -1 &&
                    errno != EINPROGRESS)
                        error("connect (`%s'): %s", host, strerror(errno));
                else
                        break;
                close(s);
                s = -1;
        }
        freeaddrinfo(aitop);
        return s;
}

static int
conalloc(const char *iname, const char *oname, int keytype)
{
        char *namebase, *name, *namelist;
        int s;

        namebase = namelist = xstrdup(iname);

        do {
                name = xstrsep(&namelist, ",");
                if (!name) {
                        free(namebase);
                        return (-1);
                }
        } while ((s = tcpconnect(name)) < 0);

        if (s >= maxfd)
                fatal("conalloc: fdno %d too high", s);
        if (fdcon[s].c_status)
                fatal("conalloc: attempt to reuse fdno %d", s);

        debug3_f("oname %s kt %d", oname, keytype);
        fdcon[s].c_fd = s;
        fdcon[s].c_status = CS_CON;
        fdcon[s].c_namebase = namebase;
        fdcon[s].c_name = name;
        fdcon[s].c_namelist = namelist;
        fdcon[s].c_output_name = xstrdup(oname);
        fdcon[s].c_keytype = keytype;
        monotime_ts(&fdcon[s].c_ts);
        fdcon[s].c_ts.tv_sec += timeout;
        TAILQ_INSERT_TAIL(&tq, &fdcon[s], c_link);
        read_wait[s].fd = s;
        read_wait[s].events = POLLIN;
        ncon++;
        return (s);
}

static void
confree(int s)
{
        if (s >= maxfd || fdcon[s].c_status == CS_UNUSED)
                fatal("confree: attempt to free bad fdno %d", s);
        free(fdcon[s].c_namebase);
        free(fdcon[s].c_output_name);
        fdcon[s].c_status = CS_UNUSED;
        fdcon[s].c_keytype = 0;
        if (fdcon[s].c_ssh) {
                ssh_packet_close(fdcon[s].c_ssh);
                free(fdcon[s].c_ssh);
                fdcon[s].c_ssh = NULL;
        } else
                close(s);
        TAILQ_REMOVE(&tq, &fdcon[s], c_link);
        read_wait[s].fd = -1;
        read_wait[s].events = 0;
        ncon--;
}

static int
conrecycle(int s)
{
        con *c = &fdcon[s];
        int ret;

        ret = conalloc(c->c_namelist, c->c_output_name, c->c_keytype);
        confree(s);
        return (ret);
}

static void
congreet(int s)
{
        int n = 0, remote_major = 0, remote_minor = 0;
        char buf[256], *cp;
        char remote_version[sizeof buf];
        size_t bufsiz;
        con *c = &fdcon[s];

        /* send client banner */
        n = snprintf(buf, sizeof buf, "SSH-%d.%d-OpenSSH-keyscan\r\n",
            PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2);
        if (n < 0 || (size_t)n >= sizeof(buf)) {
                error("snprintf: buffer too small");
                confree(s);
                return;
        }
        if (atomicio(vwrite, s, buf, n) != (size_t)n) {
                error("write (%s): %s", c->c_name, strerror(errno));
                confree(s);
                return;
        }

        /*
         * Read the server banner as per RFC4253 section 4.2.  The "SSH-"
         * protocol identification string may be preceded by an arbitrarily
         * large banner which we must read and ignore.  Loop while reading
         * newline-terminated lines until we have one starting with "SSH-".
         * The ID string cannot be longer than 255 characters although the
         * preceding banner lines may (in which case they'll be discarded
         * in multiple iterations of the outer loop).
         */
        for (;;) {
                memset(buf, '\0', sizeof(buf));
                bufsiz = sizeof(buf);
                cp = buf;
                while (bufsiz-- &&
                    (n = atomicio(read, s, cp, 1)) == 1 && *cp != '\n') {
                        if (*cp == '\r')
                                *cp = '\n';
                        cp++;
                }
                if (n != 1 || strncmp(buf, "SSH-", 4) == 0)
                        break;
        }
        if (n == 0) {
                switch (errno) {
                case EPIPE:
                        error("%s: Connection closed by remote host", c->c_name);
                        break;
                case ECONNREFUSED:
                        break;
                default:
                        error("read (%s): %s", c->c_name, strerror(errno));
                        break;
                }
                conrecycle(s);
                return;
        }
        if (cp >= buf + sizeof(buf)) {
                error("%s: greeting exceeds allowable length", c->c_name);
                confree(s);
                return;
        }
        if (*cp != '\n' && *cp != '\r') {
                error("%s: bad greeting", c->c_name);
                confree(s);
                return;
        }
        *cp = '\0';
        if ((c->c_ssh = ssh_packet_set_connection(NULL, s, s)) == NULL)
                fatal("ssh_packet_set_connection failed");
        ssh_packet_set_timeout(c->c_ssh, timeout, 1);
        ssh_set_app_data(c->c_ssh, c);  /* back link */
        c->c_ssh->compat = 0;
        if (sscanf(buf, "SSH-%d.%d-%[^\n]\n",
            &remote_major, &remote_minor, remote_version) == 3)
                compat_banner(c->c_ssh, remote_version);
        if (!ssh2_capable(remote_major, remote_minor)) {
                debug("%s doesn't support ssh2", c->c_name);
                confree(s);
                return;
        }
        if (!quiet) {
                fprintf(stdout, "%c %s:%d %s\n", print_sshfp ? ';' : '#',
                    c->c_name, ssh_port, chop(buf));
        }
        keygrab_ssh2(c);
        confree(s);
}

static void
conread(int s)
{
        con *c = &fdcon[s];

        if (c->c_status != CS_CON)
                fatal("conread: invalid status %d", c->c_status);

        congreet(s);
}

static void
conloop(void)
{
        struct timespec seltime, now;
        con *c;
        int i;

        monotime_ts(&now);
        c = TAILQ_FIRST(&tq);

        if (c && timespeccmp(&c->c_ts, &now, >))
                timespecsub(&c->c_ts, &now, &seltime);
        else
                timespecclear(&seltime);

        while (ppoll(read_wait, maxfd, &seltime, NULL) == -1) {
                if (errno == EAGAIN || errno == EINTR || errno == EWOULDBLOCK)
                        continue;
                error("poll error");
        }

        for (i = 0; i < maxfd; i++) {
                if (read_wait[i].revents & (POLLHUP|POLLERR|POLLNVAL))
                        confree(i);
                else if (read_wait[i].revents & (POLLIN))
                        conread(i);
        }

        c = TAILQ_FIRST(&tq);
        while (c && timespeccmp(&c->c_ts, &now, <)) {
                int s = c->c_fd;

                c = TAILQ_NEXT(c, c_link);
                conrecycle(s);
        }
}

static void
do_one_host(char *host)
{
        char *name = strnnsep(&host, " \t\n");
        int j;

        if (name == NULL)
                return;
        for (j = KT_MIN; j <= KT_MAX; j *= 2) {
                if (get_keytypes & j) {
                        while (ncon >= MAXCON)
                                conloop();
                        conalloc(name, *host ? host : name, j);
                }
        }
}

static void
do_host(char *host)
{
        char daddr[128];
        struct xaddr addr, end_addr;
        u_int masklen;

        if (host == NULL)
                return;
        if (addr_pton_cidr(host, &addr, &masklen) != 0) {
                /* Assume argument is a hostname */
                do_one_host(host);
        } else {
                /* Argument is a CIDR range */
                debug("CIDR range %s", host);
                end_addr = addr;
                if (addr_host_to_all1s(&end_addr, masklen) != 0)
                        goto badaddr;
                /*
                 * Note: we deliberately include the all-zero/ones addresses.
                 */
                for (;;) {
                        if (addr_ntop(&addr, daddr, sizeof(daddr)) != 0) {
 badaddr:
                                error("Invalid address %s", host);
                                return;
                        }
                        debug("CIDR expand: address %s", daddr);
                        do_one_host(daddr);
                        if (addr_cmp(&addr, &end_addr) == 0)
                                break;
                        addr_increment(&addr);
                }
        }
}

static void
usage(void)
{
        fprintf(stderr,
            "usage: ssh-keyscan [-46cDHqv] [-f file] [-O option] [-p port] [-T timeout]\n"
            "                   [-t type] [host | addrlist namelist]\n");
        exit(1);
}

int
main(int argc, char **argv)
{
        int debug_flag = 0, log_level = SYSLOG_LEVEL_INFO;
        int opt, fopt_count = 0, j;
        char *tname, *cp, *line = NULL;
        size_t linesize = 0;
        FILE *fp;

        extern int optind;
        extern char *optarg;

        __progname = ssh_get_progname(argv[0]);
        seed_rng();
        TAILQ_INIT(&tq);

        /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
        sanitise_stdfd();

        if (argc <= 1)
                usage();

        while ((opt = getopt(argc, argv, "cDHqv46O:p:T:t:f:")) != -1) {
                switch (opt) {
                case 'H':
                        hash_hosts = 1;
                        break;
                case 'c':
                        get_cert = 1;
                        break;
                case 'D':
                        print_sshfp = 1;
                        break;
                case 'p':
                        ssh_port = a2port(optarg);
                        if (ssh_port <= 0) {
                                fprintf(stderr, "Bad port '%s'\n", optarg);
                                exit(1);
                        }
                        break;
                case 'T':
                        timeout = convtime(optarg);
                        if (timeout == -1 || timeout == 0) {
                                fprintf(stderr, "Bad timeout '%s'\n", optarg);
                                usage();
                        }
                        break;
                case 'v':
                        if (!debug_flag) {
                                debug_flag = 1;
                                log_level = SYSLOG_LEVEL_DEBUG1;
                        }
                        else if (log_level < SYSLOG_LEVEL_DEBUG3)
                                log_level++;
                        else
                                fatal("Too high debugging level.");
                        break;
                case 'q':
                        quiet = 1;
                        break;
                case 'f':
                        if (strcmp(optarg, "-") == 0)
                                optarg = NULL;
                        argv[fopt_count++] = optarg;
                        break;
                case 'O':
                        /* Maybe other misc options in the future too */
                        if (strncmp(optarg, "hashalg=", 8) != 0)
                                fatal("Unsupported -O option");
                        if ((hashalg = ssh_digest_alg_by_name(
                            optarg + 8)) == -1)
                                fatal("Unsupported hash algorithm");
                        break;
                case 't':
                        get_keytypes = 0;
                        tname = strtok(optarg, ",");
                        while (tname) {
                                int type = sshkey_type_from_shortname(tname);

                                switch (type) {
#ifdef WITH_DSA
                                case KEY_DSA:
                                        get_keytypes |= KT_DSA;
                                        break;
#endif
                                case KEY_ECDSA:
                                        get_keytypes |= KT_ECDSA;
                                        break;
                                case KEY_RSA:
                                        get_keytypes |= KT_RSA;
                                        break;
                                case KEY_ED25519:
                                        get_keytypes |= KT_ED25519;
                                        break;
                                case KEY_XMSS:
                                        get_keytypes |= KT_XMSS;
                                        break;
                                case KEY_ED25519_SK:
                                        get_keytypes |= KT_ED25519_SK;
                                        break;
                                case KEY_ECDSA_SK:
                                        get_keytypes |= KT_ECDSA_SK;
                                        break;
                                case KEY_UNSPEC:
                                default:
                                        fatal("Unknown key type \"%s\"", tname);
                                }
                                tname = strtok(NULL, ",");
                        }
                        break;
                case '4':
                        IPv4or6 = AF_INET;
                        break;
                case '6':
                        IPv4or6 = AF_INET6;
                        break;
                default:
                        usage();
                }
        }
        if (optind == argc && !fopt_count)
                usage();

        log_init("ssh-keyscan", log_level, SYSLOG_FACILITY_USER, 1);

        maxfd = fdlim_get(1);
        if (maxfd < 0)
                fatal("%s: fdlim_get: bad value", __progname);
        if (maxfd > MAXMAXFD)
                maxfd = MAXMAXFD;
        if (MAXCON <= 0)
                fatal("%s: not enough file descriptors", __progname);
        if (maxfd > fdlim_get(0))
                fdlim_set(maxfd);
        fdcon = xcalloc(maxfd, sizeof(con));
        read_wait = xcalloc(maxfd, sizeof(struct pollfd));
        for (j = 0; j < maxfd; j++)
                read_wait[j].fd = -1;

        for (j = 0; j < fopt_count; j++) {
                if (argv[j] == NULL)
                        fp = stdin;
                else if ((fp = fopen(argv[j], "r")) == NULL)
                        fatal("%s: %s: %s", __progname,
                            fp == stdin ? "<stdin>" : argv[j], strerror(errno));

                while (getline(&line, &linesize, fp) != -1) {
                        /* Chomp off trailing whitespace and comments */
                        if ((cp = strchr(line, '#')) == NULL)
                                cp = line + strlen(line) - 1;
                        while (cp >= line) {
                                if (*cp == ' ' || *cp == '\t' ||
                                    *cp == '\n' || *cp == '#')
                                        *cp-- = '\0';
                                else
                                        break;
                        }

                        /* Skip empty lines */
                        if (*line == '\0')
                                continue;

                        do_host(line);
                }

                if (ferror(fp))
                        fatal("%s: %s: %s", __progname,
                            fp == stdin ? "<stdin>" : argv[j], strerror(errno));

                if (fp != stdin)
                        fclose(fp);
        }
        free(line);

        while (optind < argc)
                do_host(argv[optind++]);

        while (ncon > 0)
                conloop();

        return found_one ? 0 : 1;
}