/*      $NetBSD: rcmd.c,v 1.73 2024/01/20 14:52:48 christos Exp $       */

/*
 * Copyright (c) 1983, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)rcmd.c      8.3 (Berkeley) 3/26/94";
#else
__RCSID("$NetBSD: rcmd.c,v 1.73 2024/01/20 14:52:48 christos Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#ifdef _LIBC
#include "namespace.h"
#endif
#include <sys/param.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/poll.h>
#include <sys/wait.h>

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

#include <assert.h>
#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <netdb.h>
#include <paths.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>

#include "pathnames.h"

int     orcmd(char **, u_int, const char *, const char *, const char *, int *);
int     orcmd_af(char **, u_int, const char *, const char *, const char *,
    int *, int);
int     __ivaliduser(FILE *, u_int32_t, const char *, const char *);
int     __ivaliduser_sa(FILE *, const struct sockaddr *, socklen_t,
    const char *, const char *);
static  int rshrcmd(int, char **, u_int32_t, const char *,
    const char *, const char *, int *, const char *);
static  int resrcmd(struct addrinfo *, char **, u_int32_t, const char *,
    const char *, const char *, int *);
static  int __icheckhost(const struct sockaddr *, socklen_t,
    const char *);
static  char *__gethostloop(const struct sockaddr *, socklen_t);

int
rcmd(char **ahost, int rport, const char *locuser, const char *remuser,
    const char *cmd, int *fd2p)
{

        return rcmd_af(ahost, rport, locuser, remuser, cmd, fd2p, AF_INET);
}

int
rcmd_af(char **ahost, int rport, const char *locuser, const char *remuser,
    const char *cmd, int *fd2p, int af)
{
        static char hbuf[MAXHOSTNAMELEN];
        char pbuf[NI_MAXSERV];
        struct addrinfo hints, *res;
        int error;
        struct servent *sp;

        _DIAGASSERT(ahost != NULL);
        _DIAGASSERT(locuser != NULL);
        _DIAGASSERT(remuser != NULL);
        _DIAGASSERT(cmd != NULL);
        /* fd2p may be NULL */

        snprintf(pbuf, sizeof(pbuf), "%u", ntohs(rport));
        memset(&hints, 0, sizeof(hints));
        hints.ai_family = af;
        hints.ai_socktype = SOCK_STREAM;
        hints.ai_flags = AI_CANONNAME;
        error = getaddrinfo(*ahost, pbuf, &hints, &res);
        if (error) {
                warnx("%s: %s", *ahost, gai_strerror(error));   /*XXX*/
                return -1;
        }
        if (res->ai_canonname) {
                /*
                 * Canonicalise hostname.
                 * XXX: Should we really do this?
                 */
                strlcpy(hbuf, res->ai_canonname, sizeof(hbuf));
                *ahost = hbuf;
        }

        /*
         * Check if rport is the same as the shell port, and that the fd2p.  If
         * it is not, the program isn't expecting 'rsh' and so we can't use the
         * RCMD_CMD environment.
         */
        sp = getservbyname("shell", "tcp");
        if (sp != NULL && sp->s_port == rport)
                error = rshrcmd(af, ahost, (u_int32_t)rport,
                    locuser, remuser, cmd, fd2p, getenv("RCMD_CMD"));
        else
                error = resrcmd(res, ahost, (u_int32_t)rport,
                    locuser, remuser, cmd, fd2p);
        freeaddrinfo(res);
        return error;
}

/* this is simply a wrapper around hprcmd() that handles ahost first */
int
orcmd(char **ahost, u_int rport, const char *locuser, const char *remuser,
    const char *cmd, int *fd2p)
{
        return orcmd_af(ahost, rport, locuser, remuser, cmd, fd2p, AF_INET);
}

int
orcmd_af(char **ahost, u_int rport, const char *locuser, const char *remuser,
    const char *cmd, int *fd2p, int af)
{
        static char hbuf[MAXHOSTNAMELEN];
        char pbuf[NI_MAXSERV];
        struct addrinfo hints, *res;
        int error;

        _DIAGASSERT(ahost != NULL);
        _DIAGASSERT(locuser != NULL);
        _DIAGASSERT(remuser != NULL);
        _DIAGASSERT(cmd != NULL);
        /* fd2p may be NULL */

        snprintf(pbuf, sizeof(pbuf), "%u", ntohs(rport));
        memset(&hints, 0, sizeof(hints));
        hints.ai_family = af;
        hints.ai_socktype = SOCK_STREAM;
        hints.ai_flags = AI_CANONNAME;
        error = getaddrinfo(*ahost, pbuf, &hints, &res);
        if (error) {
                warnx("%s: %s", *ahost, gai_strerror(error));   /*XXX*/
                return -1;
        }
        if (res->ai_canonname) {
                strlcpy(hbuf, res->ai_canonname, sizeof(hbuf));
                *ahost = hbuf;
        }
        
        error = resrcmd(res, ahost, rport, locuser, remuser, cmd, fd2p);
        freeaddrinfo(res);
        return error;
}

/*ARGSUSED*/
static int
resrcmd(struct addrinfo *res, char **ahost, u_int32_t rport,
    const char *locuser, const char *remuser, const char *cmd, int *fd2p)
{
        struct addrinfo *r;
        struct sockaddr_storage from;
        struct pollfd reads[2];
        sigset_t nmask, omask;
        pid_t pid;
        int s, lport, timo;
        int pollr;
        char c;
        int refused;

        _DIAGASSERT(res != NULL);
        _DIAGASSERT(ahost != NULL);
        _DIAGASSERT(locuser != NULL);
        _DIAGASSERT(remuser != NULL);
        _DIAGASSERT(cmd != NULL);
        /* fd2p may be NULL */

        r = res;
        refused = 0;
        pid = getpid();
        sigemptyset(&nmask);
        sigaddset(&nmask, SIGURG);
        if (sigprocmask(SIG_BLOCK, &nmask, &omask) == -1)
                return -1;
        for (timo = 1, lport = IPPORT_RESERVED - 1;;) {
                s = rresvport_af(&lport, r->ai_family);
                if (s < 0) {
                        if (errno == EAGAIN)
                                warnx("rcmd: socket: All ports in use");
                        else
                                warn("rcmd: socket");
                        if (r->ai_next) {
                                r = r->ai_next;
                                continue;
                        } else {
                                (void)sigprocmask(SIG_SETMASK, &omask, NULL);
                                return -1;
                        }
                }
                fcntl(s, F_SETOWN, pid);
                if (connect(s, r->ai_addr, r->ai_addrlen) >= 0)
                        break;
                (void)close(s);
                if (errno == EADDRINUSE) {
                        lport--;
                        continue;
                } else if (errno == ECONNREFUSED)
                        refused++;
                if (r->ai_next) {
                        int oerrno = errno;
                        char hbuf[NI_MAXHOST];
                        const int niflags = NI_NUMERICHOST;

                        hbuf[0] = '\0';
                        if (getnameinfo(r->ai_addr, r->ai_addrlen,
                            hbuf, (socklen_t)sizeof(hbuf), NULL, 0, niflags) !=
                            0)
                                strlcpy(hbuf, "(invalid)", sizeof(hbuf));
                        errno = oerrno;
                        warn("rcmd: connect to address %s", hbuf);
                        r = r->ai_next;
                        hbuf[0] = '\0';
                        if (getnameinfo(r->ai_addr, r->ai_addrlen,
                            hbuf, (socklen_t)sizeof(hbuf), NULL, 0, niflags) !=
                            0)
                                strlcpy(hbuf, "(invalid)", sizeof(hbuf));
                        (void)fprintf(stderr, "Trying %s...\n", hbuf);
                        continue;
                }
                if (refused && timo <= 16) {
                        (void)sleep((unsigned int)timo);
                        timo *= 2;
                        r = res;
                        refused = 0;
                        continue;
                }
                (void)fprintf(stderr, "%s: %s\n", res->ai_canonname,
                    strerror(errno));
                (void)sigprocmask(SIG_SETMASK, &omask, NULL);
                return -1;
        }
        lport--;
        if (fd2p == 0) {
                write(s, "", 1);
                lport = 0;
        } else {
                char num[8];
                int s2 = rresvport_af(&lport, r->ai_family), s3;
                socklen_t len = sizeof(from);

                if (s2 < 0)
                        goto bad;
                listen(s2, 1);
                (void)snprintf(num, sizeof(num), "%d", lport);
                if (write(s, num, strlen(num) + 1) !=
                    (ssize_t) (strlen(num) + 1)) {
                        warn("rcmd: write (setting up stderr)");
                        (void)close(s2);
                        goto bad;
                }
                reads[0].fd = s;
                reads[0].events = POLLIN;
                reads[1].fd = s2;
                reads[1].events = POLLIN;
                errno = 0;
                pollr = poll(reads, 2, INFTIM);
                if (pollr < 1 || (reads[1].revents & POLLIN) == 0) {
                        if (errno != 0)
                                warn("poll: setting up stderr");
                        else
                                warnx(
                                    "poll: protocol failure in circuit setup");
                        (void)close(s2);
                        goto bad;
                }
                s3 = accept(s2, (struct sockaddr *)(void *)&from, &len);
                (void)close(s2);
                if (s3 < 0) {
                        warn("rcmd: accept");
                        lport = 0;
                        goto bad;
                }
                *fd2p = s3;
                switch (((struct sockaddr *)(void *)&from)->sa_family) {
                case AF_INET:
#ifdef INET6
                case AF_INET6:
#endif
                        if (getnameinfo((struct sockaddr *)(void *)&from, len,
                            NULL, 0, num, (socklen_t)sizeof(num),
                            NI_NUMERICSERV) != 0 ||
                            (atoi(num) >= IPPORT_RESERVED ||
                             atoi(num) < IPPORT_RESERVED / 2)) {
                                warnx(
                                "rcmd: protocol failure in circuit setup.");
                                goto bad2;
                        }
                        break;
                default:
                        break;
                }
        }

        (void)write(s, locuser, strlen(locuser)+1);
        (void)write(s, remuser, strlen(remuser)+1);
        (void)write(s, cmd, strlen(cmd)+1);
        if (read(s, &c, 1) != 1) {
                warn("%s", *ahost);
                goto bad2;
        }
        if (c != 0) {
                while (read(s, &c, 1) == 1) {
                        (void)write(STDERR_FILENO, &c, 1);
                        if (c == '\n')
                                break;
                }
                goto bad2;
        }
        (void)sigprocmask(SIG_SETMASK, &omask, NULL);
        return s;
bad2:
        if (lport)
                (void)close(*fd2p);
bad:
        (void)close(s);
        (void)sigprocmask(SIG_SETMASK, &omask, NULL);
        return -1;
}

/*
 * based on code written by Chris Siebenmann <cks@utcc.utoronto.ca>
 */
/* ARGSUSED */
static int
rshrcmd(int af, char **ahost, u_int32_t rport, const char *locuser,
    const char *remuser, const char *cmd, int *fd2p, const char *rshcmd)
{
        pid_t pid;
        int sp[2], ep[2];
        const char *p;
        struct passwd *pw, pwres;
        char pwbuf[1024];

        _DIAGASSERT(ahost != NULL);
        _DIAGASSERT(locuser != NULL);
        _DIAGASSERT(remuser != NULL);
        _DIAGASSERT(cmd != NULL);
        /* fd2p may be NULL */

        /* What rsh/shell to use. */
        if (rshcmd == NULL)
                rshcmd = _PATH_BIN_RCMD;

        /* locuser must exist on this host. */
        if (getpwnam_r(locuser, &pwres, pwbuf, sizeof(pwbuf), &pw) != 0 ||
            pw == NULL) {
                warnx("%s: unknown user: %s", __func__, locuser);
                return -1;
        }

        /* get a socketpair we'll use for stdin and stdout. */
        if (socketpair(AF_LOCAL, SOCK_STREAM, 0, sp) < 0) {
                warn("%s: socketpair", __func__);
                return -1;
        }
        /* we will use this for the fd2 pointer */
        if (fd2p) {
                if (socketpair(AF_LOCAL, SOCK_STREAM, 0, ep) < 0) {
                        warn("%s: socketpair", __func__);
                        return -1;
                }
                *fd2p = ep[0];
        }
        
        pid = fork();
        if (pid < 0) {
                warn("%s: fork", __func__);
                return -1;
        }
        if (pid == 0) {
                /*
                 * child
                 * - we use sp[1] to be stdin/stdout, and close sp[0]
                 * - with fd2p, we use ep[1] for stderr, and close ep[0]
                 */
                (void)close(sp[0]);
                if (dup2(sp[1], 0) < 0 || dup2(0, 1) < 0) {
                        warn("%s: dup2", __func__);
                        _exit(1);
                }
                (void)close(sp[1]);
                if (fd2p) {
                        if (dup2(ep[1], 2) < 0) {
                                warn("%s: dup2", __func__);
                                _exit(1);
                        }
                        (void)close(ep[0]);
                        (void)close(ep[1]);
                } else if (dup2(0, 2) < 0) {
                        warn("%s: dup2", __func__);
                        _exit(1);
                }
                /* fork again to lose parent. */
                pid = fork();
                if (pid < 0) {
                        warn("%s: second fork", __func__);
                        _exit(1);
                }
                if (pid > 0)
                        _exit(0);

                /* Orphan.  Become local user for rshprog. */
                if (setuid(pw->pw_uid)) {
                        warn("%s: setuid(%lu)", __func__, (u_long)pw->pw_uid);
                        _exit(1);
                }

                /*
                 * If we are rcmd'ing to "localhost" as the same user as we
                 * are, then avoid running remote shell for efficiency.
                 */
                if (strcmp(*ahost, "localhost") == 0 &&
                    strcmp(locuser, remuser) == 0) {
                        if (pw->pw_shell[0] == '\0')
                                rshcmd = _PATH_BSHELL;
                        else
                                rshcmd = pw->pw_shell;
                        p = strrchr(rshcmd, '/');
                        execlp(rshcmd, p ? p + 1 : rshcmd, "-c", cmd, NULL);
                } else {
                        const char *program;
                        program = strrchr(rshcmd, '/');
                        program = program ? program + 1 : rshcmd;
                        if (fd2p)
                                /* ask rcmd to relay signal information */
                                setenv("RCMD_RELAY_SIGNAL", "YES", 1);
                        switch (af) {
                        case AF_INET:
                                execlp(rshcmd, program, "-4", "-l", remuser,
                                    *ahost, cmd, NULL);
                                break;

                        case AF_INET6:
                                execlp(rshcmd, program, "-6", "-l", remuser,
                                    *ahost, cmd, NULL);
                                break;

                        default:
                                /* typically AF_UNSPEC, plus whatever */
                                execlp(rshcmd, program,       "-l", remuser,
                                    *ahost, cmd, NULL);
                                break;
                        }
                }
                warn("%s: exec %s", __func__, rshcmd);
                _exit(1);
        }
        /* Parent */
        (void)close(sp[1]);
        if (fd2p)
                (void)close(ep[1]);

        (void)waitpid(pid, NULL, 0);
        return sp[0];
}

int
rresvport(int *alport)
{

        _DIAGASSERT(alport != NULL);

        return rresvport_af(alport, AF_INET);
}

int
rresvport_af(int *alport, int family)
{
        return rresvport_af_addr(alport, family, NULL);
}

int
rresvport_af_addr(int *alport, int family, void *addr)
{
        struct sockaddr_storage ss;
        struct sockaddr *sa;
        socklen_t salen;
        int s;
        u_int16_t *portp;

        _DIAGASSERT(alport != NULL);

        memset(&ss, 0, sizeof(ss));
        sa = (struct sockaddr *)(void *)&ss;
        switch (family) {
        case AF_INET:
#ifdef BSD4_4
                sa->sa_len =
#endif
                salen = sizeof(struct sockaddr_in);
                if (addr)
                        ((struct sockaddr_in *)(void *)sa)->sin_addr =
                            ((struct sockaddr_in *)addr)->sin_addr;
                portp = &((struct sockaddr_in *)(void *)sa)->sin_port;
                break;
#ifdef INET6
        case AF_INET6:
#ifdef BSD4_4
                sa->sa_len =
#endif
                salen = sizeof(struct sockaddr_in6);
                if (addr)
                        ((struct sockaddr_in6 *)(void *)sa)->sin6_addr =
                            ((struct sockaddr_in6 *)addr)->sin6_addr;
                portp = &((struct sockaddr_in6 *)(void *)sa)->sin6_port;
                break;
#endif
        default:
                errno = EAFNOSUPPORT;
                return -1;
        }
        sa->sa_family = family;
        s = socket(family, SOCK_STREAM, 0);
        if (s < 0)
                return -1;
#ifdef BSD4_4
        switch (family) {
        case AF_INET:
        case AF_INET6:
                *portp = 0;
                if (bindresvport(s, (struct sockaddr_in *)(void *)sa) < 0) {
                        int sverr = errno;

                        (void)close(s);
                        errno = sverr;
                        return -1;
                }
                *alport = (int)ntohs(*portp);
                return s;
        default:
                /* is it necessary to try keep code for other AFs? */
                break;
        }
#endif
        for (;;) {
                *portp = htons((u_short)*alport);
                if (bind(s, sa, salen) >= 0)
                        return s;
                if (errno != EADDRINUSE) {
                        (void)close(s);
                        return -1;
                }
                (*alport)--;
                if (*alport == IPPORT_RESERVED/2) {
                        (void)close(s);
                        errno = EAGAIN;         /* close */
                        return -1;
                }
        }
}

int     __check_rhosts_file = 1;
const char *__rcmd_errstr;

int
ruserok(const char *rhost, int superuser, const char *ruser, const char *luser)
{
        struct addrinfo hints, *res, *r;
        int error;

        _DIAGASSERT(rhost != NULL);
        _DIAGASSERT(ruser != NULL);
        _DIAGASSERT(luser != NULL);

        memset(&hints, 0, sizeof(hints));
        hints.ai_family = PF_UNSPEC;
        hints.ai_socktype = SOCK_DGRAM; /*dummy*/
        error = getaddrinfo(rhost, "0", &hints, &res);
        if (error)
                return -1;

        for (r = res; r; r = r->ai_next) {
                if (iruserok_sa(r->ai_addr, (int)r->ai_addrlen, superuser,
                    ruser, luser) == 0) {
                        freeaddrinfo(res);
                        return 0;
                }
        }
        freeaddrinfo(res);
        return -1;
}

/*
 * New .rhosts strategy: We are passed an ip address. We spin through
 * hosts.equiv and .rhosts looking for a match. When the .rhosts only
 * has ip addresses, we don't have to trust a nameserver.  When it
 * contains hostnames, we spin through the list of addresses the nameserver
 * gives us and look for a match.
 *
 * Returns 0 if ok, -1 if not ok.
 */
int
iruserok(u_int32_t raddr, int superuser, const char *ruser, const char *luser)
{
        struct sockaddr_in irsin;

        memset(&irsin, 0, sizeof(irsin));
        irsin.sin_family = AF_INET;
#ifdef BSD4_4
        irsin.sin_len = sizeof(irsin);
#endif
        memcpy(&irsin.sin_addr, &raddr, sizeof(irsin.sin_addr));
        return iruserok_sa(&irsin, (socklen_t)sizeof(irsin), superuser, ruser,
            luser);
}

/*
 * 2nd and 3rd arguments are typed like this, to avoid dependency between
 * unistd.h and sys/socket.h.  There's no better way.
 */
int
iruserok_sa(const void *raddr, int rlen, int superuser, const char *ruser,
    const char *luser)
{
        const struct sockaddr *sa;
        struct stat sbuf;
        struct passwd *pwd, pwres;
        FILE *hostf;
        uid_t uid;
        gid_t gid;
        int isvaliduser;
        char pbuf[MAXPATHLEN];
        char pwbuf[1024];

        _DIAGASSERT(raddr != NULL);
        _DIAGASSERT(ruser != NULL);
        _DIAGASSERT(luser != NULL);

        sa = raddr;

        __rcmd_errstr = NULL;

        hostf = superuser ? NULL : fopen(_PATH_HEQUIV, "re");

        if (hostf) {
                if (__ivaliduser_sa(hostf, sa, (socklen_t)rlen, luser,
                    ruser) == 0) {
                        (void)fclose(hostf);
                        return 0;
                }
                (void)fclose(hostf);
        }

        isvaliduser = -1;
        if (__check_rhosts_file || superuser) {

                if (getpwnam_r(luser, &pwres, pwbuf, sizeof(pwbuf), &pwd) != 0
                    || pwd == NULL)
                        return -1;
                (void)strlcpy(pbuf, pwd->pw_dir, sizeof(pbuf));
                (void)strlcat(pbuf, "/.rhosts", sizeof(pbuf));

                /*
                 * Change effective uid while opening and reading .rhosts.
                 * If root and reading an NFS mounted file system, can't
                 * read files that are protected read/write owner only.
                 */
                uid = geteuid();
                gid = getegid();
                (void)setegid(pwd->pw_gid);
                (void)initgroups(pwd->pw_name, pwd->pw_gid);
                (void)seteuid(pwd->pw_uid);
                hostf = fopen(pbuf, "re");

                if (hostf != NULL) {
                        /*
                         * If not a regular file, or is owned by someone other
                         * than user or root or if writable by anyone but the
                         * owner, quit.
                         */
                        if (lstat(pbuf, &sbuf) < 0)
                                __rcmd_errstr = ".rhosts lstat failed";
                        else if (!S_ISREG(sbuf.st_mode))
                                __rcmd_errstr = ".rhosts not regular file";
                        else if (fstat(fileno(hostf), &sbuf) < 0)
                                __rcmd_errstr = ".rhosts fstat failed";
                        else if (sbuf.st_uid && sbuf.st_uid != pwd->pw_uid)
                                __rcmd_errstr = "bad .rhosts owner";
                        else if (sbuf.st_mode & (S_IWGRP|S_IWOTH))
                                __rcmd_errstr =
                                        ".rhosts writable by other than owner";
                        else 
                                isvaliduser =
                                    __ivaliduser_sa(hostf, sa, (socklen_t)rlen,
                                                    luser, ruser);

                        (void)fclose(hostf);
                }
                (void)seteuid(uid);
                (void)setegid(gid);

        }
        return isvaliduser;
}

/*
 * XXX
 * Don't make static, used by lpd(8).  We will be able to change the function
 * into static function, when we bump libc major #.
 *
 * Returns 0 if ok, -1 if not ok.
 */
#ifdef notdef   /*_LIBC*/
static
#endif
int
__ivaliduser(FILE *hostf, u_int32_t raddr, const char *luser,
    const char *ruser)
{
        struct sockaddr_in ivusin;

        memset(&ivusin, 0, sizeof(ivusin));
        ivusin.sin_family = AF_INET;
#ifdef BSD4_4
        ivusin.sin_len = sizeof(ivusin);
#endif
        memcpy(&ivusin.sin_addr, &raddr, sizeof(ivusin.sin_addr));
        return __ivaliduser_sa(hostf, (struct sockaddr *)(void *)&ivusin,
            (socklen_t)sizeof(ivusin), luser, ruser);
}

#ifdef notdef   /*_LIBC*/
static
#endif
int
__ivaliduser_sa(FILE *hostf, const struct sockaddr *raddr, socklen_t salen,
    const char *luser, const char *ruser)
{
        char *user, *p;
        int ch;
        char buf[MAXHOSTNAMELEN + 128];         /* host + login */
        const char *auser, *ahost;
        int hostok, userok;
        char *rhost = NULL;
        int firsttime = 1;
        char domain[MAXHOSTNAMELEN];

        getdomainname(domain, sizeof(domain));

        _DIAGASSERT(hostf != NULL);
        _DIAGASSERT(luser != NULL);
        _DIAGASSERT(ruser != NULL);

        while (fgets(buf, (int)sizeof(buf), hostf)) {
                p = buf;
                /* Skip lines that are too long. */
                if (strchr(p, '\n') == NULL) {
                        while ((ch = getc(hostf)) != '\n' && ch != EOF)
                                ;
                        continue;
                }
                while (*p != '\n' && *p != ' ' && *p != '\t' && *p != '\0') {
                        *p = isupper((unsigned char)*p) ?
                            tolower((unsigned char)*p) : *p;
                        p++;
                }
                if (*p == ' ' || *p == '\t') {
                        *p++ = '\0';
                        while (*p == ' ' || *p == '\t')
                                p++;
                        user = p;
                        while (*p != '\n' && *p != ' ' &&
                            *p != '\t' && *p != '\0')
                                p++;
                } else
                        user = p;
                *p = '\0';

                if (p == buf)
                        continue;

                auser = *user ? user : luser;
                ahost = buf;

                if (ahost[0] == '+')
                        switch (ahost[1]) {
                        case '\0':
                                hostok = 1;
                                break;

                        case '@':
                                if (firsttime) {
                                        rhost = __gethostloop(raddr, salen);
                                        firsttime = 0;
                                }
                                if (rhost)
                                        hostok = innetgr(&ahost[2], rhost,
                                            NULL, domain);
                                else
                                        hostok = 0;
                                break;

                        default:
                                hostok = __icheckhost(raddr, salen, &ahost[1]);
                                break;
                        }
                else if (ahost[0] == '-')
                        switch (ahost[1]) {
                        case '\0':
                                hostok = -1;
                                break;

                        case '@':
                                if (firsttime) {
                                        rhost = __gethostloop(raddr, salen);
                                        firsttime = 0;
                                }
                                if (rhost)
                                        hostok = -innetgr(&ahost[2], rhost,
                                            NULL, domain);
                                else
                                        hostok = 0;
                                break;

                        default:
                                hostok =
                                    -__icheckhost(raddr, salen, &ahost[1]);
                                break;
                        }
                else
                        hostok = __icheckhost(raddr, salen, ahost);


                if (auser[0] == '+')
                        switch (auser[1]) {
                        case '\0':
                                userok = 1;
                                break;

                        case '@':
                                userok = innetgr(&auser[2], NULL, ruser,
                                    domain);
                                break;

                        default:
                                userok = strcmp(ruser, &auser[1]) == 0;
                                break;
                        }
                else if (auser[0] == '-')
                        switch (auser[1]) {
                        case '\0':
                                userok = -1;
                                break;

                        case '@':
                                userok = -innetgr(&auser[2], NULL, ruser,
                                    domain);
                                break;

                        default:
                                userok =
                                    -(strcmp(ruser, &auser[1]) == 0 ? 1 : 0);
                                break;
                        }
                else
                        userok = strcmp(ruser, auser) == 0;

                /* Check if one component did not match */
                if (hostok == 0 || userok == 0)
                        continue;

                /* Check if we got a forbidden pair */
                if (userok == -1 || hostok == -1)
                        return -1;

                /* Check if we got a valid pair */
                if (hostok == 1 && userok == 1)
                        return 0;
        }
        return -1;
}

/*
 * Returns "true" if match, 0 if no match.
 */
static int
__icheckhost(const struct sockaddr *raddr, socklen_t salen, const char *lhost)
{
        struct addrinfo hints, *res, *r;
        char h1[NI_MAXHOST], h2[NI_MAXHOST];
        int error;
        const int niflags = NI_NUMERICHOST;

        _DIAGASSERT(raddr != NULL);
        _DIAGASSERT(lhost != NULL);

        h1[0] = '\0';
        if (getnameinfo(raddr, salen, h1, (socklen_t)sizeof(h1), NULL, 0,
            niflags) != 0)
                return 0;

        /* Resolve laddr into sockaddr */
        memset(&hints, 0, sizeof(hints));
        hints.ai_family = raddr->sa_family;
        hints.ai_socktype = SOCK_DGRAM; /*dummy*/
        res = NULL;
        error = getaddrinfo(lhost, "0", &hints, &res);
        if (error)
                return 0;

        /*
         * Try string comparisons between raddr and laddr.
         */
        for (r = res; r; r = r->ai_next) {
                h2[0] = '\0';
                if (getnameinfo(r->ai_addr, r->ai_addrlen, h2,
                    (socklen_t)sizeof(h2), NULL, 0, niflags) != 0)
                        continue;
                if (strcmp(h1, h2) == 0) {
                        freeaddrinfo(res);
                        return 1;
                }
        }

        /* No match. */
        freeaddrinfo(res);
        return 0;
}

/*
 * Return the hostname associated with the supplied address.
 * Do a reverse lookup as well for security. If a loop cannot
 * be found, pack the numeric IP address into the string.
 */
static char *
__gethostloop(const struct sockaddr *raddr, socklen_t salen)
{
        static char remotehost[NI_MAXHOST];
        char h1[NI_MAXHOST], h2[NI_MAXHOST];
        struct addrinfo hints, *res, *r;
        int error;
        const int niflags = NI_NUMERICHOST;

        _DIAGASSERT(raddr != NULL);

        h1[0] = remotehost[0] = '\0';
        if (getnameinfo(raddr, salen, remotehost, (socklen_t)sizeof(remotehost),
            NULL, 0, NI_NAMEREQD) != 0)
                return NULL;
        if (getnameinfo(raddr, salen, h1, (socklen_t)sizeof(h1), NULL, 0,
            niflags) != 0)
                return NULL;

        /*
         * Look up the name and check that the supplied
         * address is in the list
         */
        memset(&hints, 0, sizeof(hints));
        hints.ai_family = raddr->sa_family;
        hints.ai_socktype = SOCK_DGRAM; /*dummy*/
        hints.ai_flags = AI_CANONNAME;
        res = NULL;
        error = getaddrinfo(remotehost, "0", &hints, &res);
        if (error)
                return NULL;

        for (r = res; r; r = r->ai_next) {
                h2[0] = '\0';
                if (getnameinfo(r->ai_addr, r->ai_addrlen, h2,
                    (socklen_t)sizeof(h2), NULL, 0, niflags) != 0)
                        continue;
                if (strcmp(h1, h2) == 0) {
                        freeaddrinfo(res);
                        return remotehost;
                }
        }

        /*
         * either the DNS administrator has made a configuration
         * mistake, or someone has attempted to spoof us
         */
        syslog(LOG_NOTICE, "rcmd: address %s not listed for host %s",
            h1, res->ai_canonname ? res->ai_canonname : remotehost);
        freeaddrinfo(res);
        return NULL;
}