glibc/inet/rcmd.c

/*
 * Copyright (C) 1998 WIDE Project.
 * 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 project 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 PROJECT 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 PROJECT 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.
 */
/*
 * 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.
 * 4. 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.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)rcmd.c	8.3 (Berkeley) 3/26/94";
#endif /* LIBC_SCCS and not lint */

#include <sys/param.h>
#include <sys/poll.h>
#include <sys/socket.h>
#include <sys/stat.h>

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

#include <alloca.h>
#include <signal.h>
#include <fcntl.h>
#include <netdb.h>
#include <unistd.h>
#include <pwd.h>
#include <errno.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <ctype.h>
#include <string.h>
#include <libintl.h>
#include <stdlib.h>
#ifdef USE_IN_LIBIO
# include <wchar.h>
#endif


int __ivaliduser (FILE *, u_int32_t, const char *, const char *);
static int __validuser2_sa (FILE *, struct sockaddr *, size_t,
			    const char *, const char *, const char *);
static int ruserok2_sa (struct sockaddr *ra, size_t ralen,
			int superuser, const char *ruser,
			const char *luser, const char *rhost);
static int ruserok_sa (struct sockaddr *ra, size_t ralen,
			int superuser, const char *ruser,
			const char *luser);
int iruserok_af (const void *raddr, int superuser, const char *ruser,
		 const char *luser, sa_family_t af);
int iruserok (u_int32_t raddr, int superuser, const char *ruser,
	      const char *luser);

static char ahostbuf[NI_MAXHOST];

int
rcmd_af(ahost, rport, locuser, remuser, cmd, fd2p, af)
	char **ahost;
	u_short rport;
	const char *locuser, *remuser, *cmd;
	int *fd2p;
	sa_family_t af;
{
	char paddr[INET6_ADDRSTRLEN];
	struct addrinfo hints, *res, *ai;
	struct sockaddr_storage from;
	struct pollfd pfd[2];
	int32_t oldmask;
	pid_t pid;
	int s, lport, timo, error;
	char c;
	int refused;
	char num[8];
	ssize_t n;

	if (af != AF_INET && af != AF_INET6 && af != AF_UNSPEC)
	  {
	    __set_errno (EAFNOSUPPORT);
	    return -1;
	  }

	pid = __getpid();

	memset(&hints, '\0', sizeof(hints));
	hints.ai_flags = AI_CANONNAME;
	hints.ai_family = af;
	hints.ai_socktype = SOCK_STREAM;
	(void)__snprintf(num, sizeof(num), "%d", ntohs(rport));
	error = getaddrinfo(*ahost, num, &hints, &res);
	if (error) {
#ifdef USE_IN_LIBIO
		if (_IO_fwide (stderr, 0) > 0)
			__fwprintf(stderr, L"rcmd: getaddrinfo: %s\n",
				   gai_strerror(error));
		else
#endif
			fprintf(stderr, "rcmd: getaddrinfo: %s\n",
				gai_strerror(error));
                return (-1);
	}

	pfd[0].events = POLLIN;
	pfd[1].events = POLLIN;

	if (res->ai_canonname){
		strncpy(ahostbuf, res->ai_canonname, sizeof(ahostbuf));
		ahostbuf[sizeof(ahostbuf)-1] = '\0';
		*ahost = ahostbuf;
	}
	else
		*ahost = NULL;
	ai = res;
	refused = 0;
	oldmask = __sigblock(sigmask(SIGURG));
	for (timo = 1, lport = IPPORT_RESERVED - 1;;) {
		char errbuf[200];

		s = rresvport_af(&lport, ai->ai_family);
		if (s < 0) {
			if (errno == EAGAIN) {
#ifdef USE_IN_LIBIO
				if (_IO_fwide (stderr, 0) > 0)
					__fwprintf(stderr, L"%s",
						   _("rcmd: socket: All ports in use\n"));
				else
#endif
					fputs(_("rcmd: socket: All ports in use\n"),
					      stderr);
			} else {
#ifdef USE_IN_LIBIO
				if (_IO_fwide (stderr, 0) > 0)
					__fwprintf(stderr,
						   L"rcmd: socket: %m\n");
				else
#endif
					fprintf(stderr, "rcmd: socket: %m\n");
			}
			__sigsetmask(oldmask);
			freeaddrinfo(res);
			return -1;
		}
		__fcntl(s, F_SETOWN, pid);
		if (__connect(s, ai->ai_addr, ai->ai_addrlen) >= 0)
			break;
		(void)__close(s);
		if (errno == EADDRINUSE) {
			lport--;
			continue;
		}
		if (errno == ECONNREFUSED)
			refused = 1;
		if (ai->ai_next != NULL) {
			int oerrno = errno;
			char *buf = NULL;

			getnameinfo(ai->ai_addr, ai->ai_addrlen,
				    paddr, sizeof(paddr),
				    NULL, 0,
				    NI_NUMERICHOST);

			if (__asprintf (&buf, _("connect to address %s: "),
					paddr) >= 0)
			  {
#ifdef USE_IN_LIBIO
			    if (_IO_fwide (stderr, 0) > 0)
			      __fwprintf(stderr, L"%s", buf);
			    else
#endif
			      fputs (buf, stderr);
			    free (buf);
			  }
			__set_errno (oerrno);
			perror(0);
			ai = ai->ai_next;
			getnameinfo(ai->ai_addr, ai->ai_addrlen,
				    paddr, sizeof(paddr),
				    NULL, 0,
				    NI_NUMERICHOST);
			if (__asprintf (&buf, _("Trying %s...\n"), paddr) >= 0)
			  {
#ifdef USE_IN_LIBIO
			    if (_IO_fwide (stderr, 0) > 0)
			      __fwprintf (stderr, L"%s", buf);
			    else
#endif
			      fputs (buf, stderr);
			    free (buf);
			  }
			continue;
		}
		if (refused && timo <= 16) {
			(void)__sleep(timo);
			timo *= 2;
			ai = res;
			refused = 0;
			continue;
		}
		freeaddrinfo(res);
#ifdef USE_IN_LIBIO
		if (_IO_fwide (stderr, 0) > 0)
			(void)__fwprintf(stderr, L"%s: %s\n", *ahost,
					 __strerror_r(errno,
						      errbuf, sizeof (errbuf)));
		else
#endif
			(void)fprintf(stderr, "%s: %s\n", *ahost,
				      __strerror_r(errno,
						   errbuf, sizeof (errbuf)));
		__sigsetmask(oldmask);
		return -1;
	}
	lport--;
	if (fd2p == 0) {
		__write(s, "", 1);
		lport = 0;
	} else {
		char num[8];
		int s2 = rresvport_af(&lport, ai->ai_family), s3;
		socklen_t len = ai->ai_addrlen;

		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) {
			char *buf = NULL;

			if (__asprintf (&buf, _("\
rcmd: write (setting up stderr): %m\n")) >= 0)
			  {
#ifdef USE_IN_LIBIO
			    if (_IO_fwide (stderr, 0) > 0)
			      __fwprintf(stderr, L"%s", buf);
			    else
#endif
			      fputs (buf, stderr);
			    free (buf);
			  }
			(void)__close(s2);
			goto bad;
		}
		pfd[0].fd = s;
		pfd[1].fd = s2;
		__set_errno (0);
		if (__poll (pfd, 2, -1) < 1 || (pfd[1].revents & POLLIN) == 0){
			char *buf = NULL;

			if ((errno != 0
			     && __asprintf(&buf, _("\
rcmd: poll (setting up stderr): %m\n")) >= 0)
			    || (errno == 0
				&& __asprintf(&buf, _("\
poll: protocol failure in circuit setup\n")) >= 0))
			  {
#ifdef USE_IN_LIBIO
			    if (_IO_fwide (stderr, 0) > 0)
			      __fwprintf (stderr, L"%s", buf);
			    else
#endif
			      fputs (buf, stderr);
			    free  (buf);
			  }
			(void)__close(s2);
			goto bad;
		}
		s3 = accept(s2, (struct sockaddr *)&from, &len);
		switch (from.ss_family) {
		case AF_INET:
			rport = ntohs(((struct sockaddr_in *)&from)->sin_port);
			break;
		case AF_INET6:
			rport = ntohs(((struct sockaddr_in6 *)&from)->sin6_port);
			break;
		default:
			rport = 0;
			break;
		}
		(void)__close(s2);
		if (s3 < 0) {
#ifdef USE_IN_LIBIO
			if (_IO_fwide (stderr, 0) > 0)
				(void)__fwprintf(stderr,
						 L"rcmd: accept: %m\n");
			else
#endif
				(void)fprintf(stderr,
					      "rcmd: accept: %m\n");
			lport = 0;
			goto bad;
		}
		*fd2p = s3;

		if (rport >= IPPORT_RESERVED || rport < IPPORT_RESERVED / 2){
			char *buf = NULL;

			if (__asprintf(&buf, _("\
socket: protocol failure in circuit setup\n")) >= 0)
			  {
#ifdef USE_IN_LIBIO
			    if (_IO_fwide (stderr, 0) > 0)
			      __fwprintf (stderr, L"%s", buf);
			    else
#endif
			      fputs (buf, stderr);
			    free (buf);
			  }
			goto bad2;
		}
	}
	(void)__write(s, locuser, strlen(locuser)+1);
	(void)__write(s, remuser, strlen(remuser)+1);
	(void)__write(s, cmd, strlen(cmd)+1);
	n = __read(s, &c, 1);
	if (n != 1) {
		char *buf = NULL;

		if ((n == 0
		     && __asprintf(&buf, _("rcmd: %s: short read"),
				   *ahost) >= 0)
		    || (n != 0
			&& __asprintf(&buf, "rcmd: %s: %m\n", *ahost) >= 0))
		  {
#ifdef USE_IN_LIBIO
		    if (_IO_fwide (stderr, 0) > 0)
		      __fwprintf (stderr, L"%s", buf);
		    else
#endif
		      fputs (buf, stderr);
		    free (buf);
		  }
		goto bad2;
	}
	if (c != 0) {
		while (__read(s, &c, 1) == 1) {
			(void)__write(STDERR_FILENO, &c, 1);
			if (c == '\n')
				break;
		}
		goto bad2;
	}
	__sigsetmask(oldmask);
	freeaddrinfo(res);
	return s;
bad2:
	if (lport)
		(void)__close(*fd2p);
bad:
	(void)__close(s);
	__sigsetmask(oldmask);
	freeaddrinfo(res);
	return -1;
}

int
rcmd(ahost, rport, locuser, remuser, cmd, fd2p)
	char **ahost;
	u_short rport;
	const char *locuser, *remuser, *cmd;
	int *fd2p;
{
  return rcmd_af (ahost, rport, locuser, remuser, cmd, fd2p, AF_INET);
}

int
rresvport_af(alport, family)
	int *alport;
	sa_family_t family;
{
	struct sockaddr_storage ss;
	int s;
	size_t len;
	uint16_t *sport;

	switch(family){
	case AF_INET:
		len = sizeof(struct sockaddr_in);
		sport = &((struct sockaddr_in *)&ss)->sin_port;
		break;
	case AF_INET6:
		len = sizeof(struct sockaddr_in6);
		sport = &((struct sockaddr_in6 *)&ss)->sin6_port;
		break;
	default:
		__set_errno (EAFNOSUPPORT);
		return -1;
	}
	s = __socket(family, SOCK_STREAM, 0);
	if (s < 0)
		return -1;

	memset (&ss, '\0', sizeof(ss));
#ifdef SALEN
	ss.__ss_len = len;
#endif
	ss.ss_family = family;

	for (;;) {
		*sport = htons((uint16_t) *alport);
		if (bind(s, (struct sockaddr *)&ss, len) >= 0)
			return s;
		if (errno != EADDRINUSE) {
			(void)__close(s);
			return -1;
		}
		(*alport)--;
		if (*alport == IPPORT_RESERVED/2)
			break;
	}
	(void)__close(s);
	__set_errno (EAGAIN);
	return -1;
}

int
rresvport(alport)
	int *alport;
{
	return rresvport_af(alport, AF_INET);
}

int	__check_rhosts_file = 1;
char	*__rcmd_errstr;

int
ruserok_af(rhost, superuser, ruser, luser, af)
	const char *rhost, *ruser, *luser;
	int superuser;
	sa_family_t af;
{
	struct addrinfo hints, *res, *res0;
	int gai;
	int ret;

	memset (&hints, '\0', sizeof(hints));
	hints.ai_family = af;
	gai = getaddrinfo(rhost, NULL, &hints, &res0);
	if (gai)
		return -1;
	ret = -1;
	for (res=res0; res; res=res->ai_next)
		if (ruserok2_sa(res->ai_addr, res->ai_addrlen,
				superuser, ruser, luser, rhost) == 0){
			ret = 0;
			break;
		}
	freeaddrinfo(res0);
	return (ret);
}
int
ruserok(rhost, superuser, ruser, luser)
	const char *rhost, *ruser, *luser;
	int superuser;
{
	return ruserok_af(rhost, superuser, ruser, luser, AF_INET);
}

/* Extremely paranoid file open function. */
static FILE *
iruserfopen (const char *file, uid_t okuser)
{
  struct stat64 st;
  char *cp = NULL;
  FILE *res = NULL;

  /* If not a regular file, if owned by someone other than user or
     root, if writeable by anyone but the owner, or if hardlinked
     anywhere, quit.  */
  cp = NULL;
  if (__lxstat64 (_STAT_VER, file, &st))
    cp = _("lstat failed");
  else if (!S_ISREG (st.st_mode))
    cp = _("not regular file");
  else
    {
      res = fopen (file, "r");
      if (!res)
	cp = _("cannot open");
      else if (__fxstat64 (_STAT_VER, fileno (res), &st) < 0)
	cp = _("fstat failed");
      else if (st.st_uid && st.st_uid != okuser)
	cp = _("bad owner");
      else if (st.st_mode & (S_IWGRP|S_IWOTH))
	cp = _("writeable by other than owner");
      else if (st.st_nlink > 1)
	cp = _("hard linked somewhere");
    }

  /* If there were any problems, quit.  */
  if (cp != NULL)
    {
      __rcmd_errstr = cp;
      if (res)
	fclose (res);
      return NULL;
    }

  /* No threads use this stream.  */
  __fsetlocking (res, FSETLOCKING_BYCALLER);

  return res;
}

/*
 * 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.
 */
static int
ruserok2_sa (ra, ralen, superuser, ruser, luser, rhost)
     struct sockaddr *ra;
     size_t ralen;
     int superuser;
     const char *ruser, *luser, *rhost;
{
  FILE *hostf = NULL;
  int isbad = -1;

  if (!superuser)
    hostf = iruserfopen (_PATH_HEQUIV, 0);

  if (hostf)
    {
      isbad = __validuser2_sa (hostf, ra, ralen, luser, ruser, rhost);
      fclose (hostf);

      if (!isbad)
	return 0;
    }

  if (__check_rhosts_file || superuser)
    {
      char *pbuf;
      struct passwd pwdbuf, *pwd;
      size_t dirlen;
      size_t buflen = __sysconf (_SC_GETPW_R_SIZE_MAX);
      char *buffer = __alloca (buflen);
      uid_t uid;

      if (__getpwnam_r (luser, &pwdbuf, buffer, buflen, &pwd) != 0
	  || pwd == NULL)
	return -1;

      dirlen = strlen (pwd->pw_dir);
      pbuf = alloca (dirlen + sizeof "/.rhosts");
      __mempcpy (__mempcpy (pbuf, pwd->pw_dir, dirlen),
		 "/.rhosts", sizeof "/.rhosts");

       /* Change effective uid while reading .rhosts.  If root and
	  reading an NFS mounted file system, can't read files that
	  are protected read/write owner only.  */
       uid = __geteuid ();
       seteuid (pwd->pw_uid);
       hostf = iruserfopen (pbuf, pwd->pw_uid);

       if (hostf != NULL)
	 {
           isbad = __validuser2_sa (hostf, ra, ralen, luser, ruser, rhost);
           fclose (hostf);
	 }

       seteuid (uid);
       return isbad;
    }
  return -1;
}
/*
 * ruserok_sa() is now discussed on ipng, so
 * currently disabled for external use
 */
static int ruserok_sa(ra, ralen, superuser, ruser, luser)
     struct sockaddr *ra;
     size_t ralen;
     int superuser;
     const char *ruser, *luser;
{
  return ruserok2_sa(ra, ralen, superuser, ruser, luser, "-");
}

/* This is the exported version.  */
int
iruserok_af (raddr, superuser, ruser, luser, af)
     const void *raddr;
     int superuser;
     const char *ruser, *luser;
     sa_family_t af;
{
  struct sockaddr_storage ra;
  size_t ralen;

  memset (&ra, '\0', sizeof(ra));
  switch (af){
  case AF_INET:
    ((struct sockaddr_in *)&ra)->sin_family = AF_INET;
    memcpy (&(((struct sockaddr_in *)&ra)->sin_addr), raddr,
	    sizeof(struct in_addr));
    ralen = sizeof(struct sockaddr_in);
    break;
  case AF_INET6:
    ((struct sockaddr_in6 *)&ra)->sin6_family = AF_INET6;
    memcpy (&(((struct sockaddr_in6 *)&ra)->sin6_addr), raddr,
            sizeof(struct in6_addr));
    ralen = sizeof(struct sockaddr_in6);
    break;
  default:
    return 0;
  }
  return ruserok_sa ((struct sockaddr *)&ra, ralen, superuser, ruser, luser);
}
int
iruserok (raddr, superuser, ruser, luser)
     u_int32_t raddr;
     int superuser;
     const char *ruser, *luser;
{
  return iruserok_af (&raddr, superuser, ruser, luser, AF_INET);
}

/*
 * XXX
 * Don't make static, used by lpd(8).
 *
 * This function is not used anymore. It is only present because lpd(8)
 * calls it (!?!). We simply call __invaliduser2() with an illegal rhost
 * argument. This means that netgroups won't work in .rhost/hosts.equiv
 * files. If you want lpd to work with netgroups, fix lpd to use ruserok()
 * or PAM.
 * Returns 0 if ok, -1 if not ok.
 */
int
__ivaliduser(hostf, raddr, luser, ruser)
	FILE *hostf;
	u_int32_t raddr;
	const char *luser, *ruser;
{
	struct sockaddr_in ra;
	memset(&ra, '\0', sizeof(ra));
	ra.sin_family = AF_INET;
	ra.sin_addr.s_addr = raddr;
	return __validuser2_sa(hostf, (struct sockaddr *)&ra, sizeof(ra),
			       luser, ruser, "-");
}


/* Returns 1 on positive match, 0 on no match, -1 on negative match.  */
static int
internal_function
__checkhost_sa (struct sockaddr *ra, size_t ralen, char *lhost,
		const char *rhost)
{
	struct addrinfo hints, *res0, *res;
	char raddr[INET6_ADDRSTRLEN];
	int match;
	int negate=1;    /* Multiply return with this to get -1 instead of 1 */

	/* Check nis netgroup.  */
	if (strncmp ("+@", lhost, 2) == 0)
		return innetgr (&lhost[2], rhost, NULL, NULL);

	if (strncmp ("-@", lhost, 2) == 0)
		return -innetgr (&lhost[2], rhost, NULL, NULL);

	/* -host */
	if (strncmp ("-", lhost,1) == 0) {
		negate = -1;
		lhost++;
	} else if (strcmp ("+",lhost) == 0) {
		return 1;                    /* asking for trouble, but ok.. */
	}

	/* Try for raw ip address first. */
	/* XXX */
	if (getnameinfo(ra, ralen,
			raddr, sizeof(raddr), NULL, 0,
			NI_NUMERICHOST) == 0
	    && strcmp(raddr, lhost) == 0)
		return negate;

	/* Better be a hostname. */
	match = 0;
	memset(&hints, '\0', sizeof(hints));
	hints.ai_family = ra->sa_family;
	if (getaddrinfo(lhost, NULL, &hints, &res0) == 0){
		/* Spin through ip addresses. */
		for (res = res0; res; res = res->ai_next)
		  {
		    if (res->ai_family == ra->sa_family
			&& !memcmp(res->ai_addr, ra, res->ai_addrlen))
		      {
			match = 1;
			break;
		      }
		  }
		freeaddrinfo (res0);
	}
	return negate * match;
}

/* Returns 1 on positive match, 0 on no match, -1 on negative match.  */
static int
internal_function
__icheckuser (const char *luser, const char *ruser)
{
    /*
      luser is user entry from .rhosts/hosts.equiv file
      ruser is user id on remote host
      */

    /* [-+]@netgroup */
    if (strncmp ("+@", luser, 2) == 0)
	return innetgr (&luser[2], NULL, ruser, NULL);

    if (strncmp ("-@", luser,2) == 0)
	return -innetgr (&luser[2], NULL, ruser, NULL);

    /* -user */
    if (strncmp ("-", luser, 1) == 0)
	return -(strcmp (&luser[1], ruser) == 0);

    /* + */
    if (strcmp ("+", luser) == 0)
	return 1;

    /* simple string match */
    return strcmp (ruser, luser) == 0;
}

/*
 * Returns 1 for blank lines (or only comment lines) and 0 otherwise
 */
static int
__isempty (char *p)
{
    while (*p && isspace (*p)) {
	++p;
    }

    return (*p == '\0' || *p == '#') ? 1 : 0 ;
}

/*
 * Returns 0 if positive match, -1 if _not_ ok.
 */
static int
__validuser2_sa(hostf, ra, ralen, luser, ruser, rhost)
	FILE *hostf;
	struct sockaddr *ra;
	size_t ralen;
	const char *luser, *ruser, *rhost;
{
    register const char *user;
    register char *p;
    int hcheck, ucheck;
    char *buf = NULL;
    size_t bufsize = 0;
    int retval = -1;

    while (__getline (&buf, &bufsize, hostf) > 0) {
	buf[bufsize - 1] = '\0'; /* Make sure it's terminated.  */
        p = buf;

	/* Skip empty or comment lines */
	if (__isempty (p)) {
	    continue;
	}

	/* Skip lines that are too long. */
	if (strchr (p, '\n') == NULL) {
	    int ch = getc_unlocked (hostf);

	    while (ch != '\n' && ch != EOF)
		ch = getc_unlocked (hostf);
	    continue;
	}

	for (;*p && !isspace(*p); ++p) {
	    *p = _tolower (*p);
	}

	/* Next we want to find the permitted name for the remote user.  */
	if (*p == ' ' || *p == '\t') {
	    /* <nul> terminate hostname and skip spaces */
	    for (*p++='\0'; *p && isspace (*p); ++p);

	    user = p;                   /* this is the user's name */
	    while (*p && !isspace (*p))
		++p;                    /* find end of user's name */
	} else
	    user = p;

	*p = '\0';              /* <nul> terminate username (+host?) */

	/* buf -> host(?) ; user -> username(?) */

	/* First check host part */
	hcheck = __checkhost_sa (ra, ralen, buf, rhost);

	if (hcheck < 0)
	    break;

	if (hcheck) {
	    /* Then check user part */
	    if (! (*user))
		user = luser;

	    ucheck = __icheckuser (user, ruser);

	    /* Positive 'host user' match? */
	    if (ucheck > 0) {
		retval = 0;
		break;
	    }

	    /* Negative 'host -user' match? */
	    if (ucheck < 0)
		break;

	    /* Neither, go on looking for match */
	}
    }

    if (buf != NULL)
      free (buf);

    return retval;
}