/*      $NetBSD: getusershell.c,v 1.29 2012/03/13 21:13:36 christos Exp $       */

/*-
* Copyright (c) 1999, 2005 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Luke Mewburn.
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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) 1985, 1993
*      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[] = "@(#)getusershell.c      8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: getusershell.c,v 1.29 2012/03/13 21:13:36 christos Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#include "namespace.h"
#include "reentrant.h"

#include <sys/param.h>
#include <sys/file.h>

#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <nsswitch.h>
#include <paths.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#ifdef HESIOD
#include <hesiod.h>
#endif
#ifdef YP
#include <rpc/rpc.h>
#include <rpcsvc/ypclnt.h>
#include <rpcsvc/yp_prot.h>
#endif

#ifdef __weak_alias
__weak_alias(endusershell,_endusershell)
__weak_alias(getusershell,_getusershell)
__weak_alias(setusershell,_setusershell)
#endif

/*
* Local shells should NOT be added here.
* They should be added in /etc/shells.
*/
static const char *const okshells[] = { _PATH_BSHELL, _PATH_CSHELL, NULL };

#ifdef _REENTRANT
static mutex_t __shellmutex = MUTEX_INITIALIZER;
#endif

static char               curshell[MAXPATHLEN + 2];

static const char *const *curokshell = okshells;
static int                shellsfound = 0;

               /*
                *      files methods
                */

       /* state shared between files methods */
struct files_state {
       FILE    *fp;
};

static struct files_state _files_state;


static int
_files_start(struct files_state *state)
{

       _DIAGASSERT(state != NULL);

       if (state->fp == NULL) {
               state->fp = fopen(_PATH_SHELLS, "re");
               if (state->fp == NULL)
                       return NS_UNAVAIL;
       } else {
               rewind(state->fp);
       }
       return NS_SUCCESS;
}

static int
_files_end(struct files_state *state)
{

       _DIAGASSERT(state != NULL);

       if (state->fp) {
               (void) fclose(state->fp);
               state->fp = NULL;
       }
       return NS_SUCCESS;
}

/*ARGSUSED*/
static int
_files_setusershell(void *nsrv, void *nscb, va_list ap)
{

       return _files_start(&_files_state);
}

/*ARGSUSED*/
static int
_files_endusershell(void *nsrv, void *nscb, va_list ap)
{

       return _files_end(&_files_state);
}

/*ARGSUSED*/
static int
_files_getusershell(void *nsrv, void *nscb, va_list ap)
{
       char    **retval = va_arg(ap, char **);

       char    *sp, *cp;
       int      rv;

       _DIAGASSERT(retval != NULL);

       *retval = NULL;
       if (_files_state.fp == NULL) {  /* only start if file not open yet */
               rv = _files_start(&_files_state);
               if (rv != NS_SUCCESS)
                       return rv;
       }

       while (fgets(curshell, (int)sizeof(curshell) - 1, _files_state.fp)
           != NULL) {
               sp = cp = curshell;
               while (*cp != '#' && *cp != '/' && *cp != '\0')
                       cp++;
               if (*cp == '#' || *cp == '\0')
                       continue;
               sp = cp;
               while (!isspace((unsigned char) *cp) && *cp != '#'
                   && *cp != '\0')
                       cp++;
               *cp++ = '\0';
               *retval = sp;
               return NS_SUCCESS;
       }

       return NS_NOTFOUND;
}


#ifdef HESIOD
               /*
                *      dns methods
                */

       /* state shared between dns methods */
struct dns_state {
       void    *context;               /* Hesiod context */
       int      num;                   /* shell index, -1 if no more */
};

static struct dns_state         _dns_state;

static int
_dns_start(struct dns_state *state)
{

       _DIAGASSERT(state != NULL);

       state->num = 0;
       if (state->context == NULL) {                   /* setup Hesiod */
               if (hesiod_init(&state->context) == -1)
                       return NS_UNAVAIL;
       }

       return NS_SUCCESS;
}

static int
_dns_end(struct dns_state *state)
{

       _DIAGASSERT(state != NULL);

       state->num = 0;
       if (state->context) {
               hesiod_end(state->context);
               state->context = NULL;
       }
       return NS_SUCCESS;
}

/*ARGSUSED*/
static int
_dns_setusershell(void *nsrv, void *nscb, va_list ap)
{

       return _dns_start(&_dns_state);
}

/*ARGSUSED*/
static int
_dns_endusershell(void *nsrv, void *nscb, va_list ap)
{

       return _dns_end(&_dns_state);
}

/*ARGSUSED*/
static int
_dns_getusershell(void *nsrv, void *nscb, va_list ap)
{
       char    **retval = va_arg(ap, char **);

       char      shellname[] = "shells-NNNNNNNNNN";
       char    **hp, *ep;
       int       rv;

       _DIAGASSERT(retval != NULL);

       *retval = NULL;

       if (_dns_state.num == -1)                       /* exhausted search */
               return NS_NOTFOUND;

       if (_dns_state.context == NULL) {
                       /* only start if Hesiod not setup */
               rv = _dns_start(&_dns_state);
               if (rv != NS_SUCCESS)
                       return rv;
       }

       hp = NULL;
       rv = NS_NOTFOUND;

                                                       /* find shells-NNN */
       snprintf(shellname, sizeof(shellname), "shells-%d", _dns_state.num);
       _dns_state.num++;

       hp = hesiod_resolve(_dns_state.context, shellname, "shells");
       if (hp == NULL) {
               if (errno == ENOENT)
                       rv = NS_NOTFOUND;
               else
                       rv = NS_UNAVAIL;
       } else {
               if ((ep = strchr(hp[0], '\n')) != NULL)
                       *ep = '\0';                     /* clear trailing \n */
                                               /* only use first result */
               strlcpy(curshell, hp[0], sizeof(curshell));
               *retval = curshell;
               rv = NS_SUCCESS;
       }

       if (hp)
               hesiod_free_list(_dns_state.context, hp);
       if (rv != NS_SUCCESS)
               _dns_state.num = -1;            /* any failure halts search */
       return rv;
}

#endif /* HESIOD */


#ifdef YP
               /*
                *      nis methods
                */
       /* state shared between nis methods */
struct nis_state {
       char            *domain;        /* NIS domain */
       int              done;          /* non-zero if search exhausted */
       char            *current;       /* current first/next match */
       int              currentlen;    /* length of _nis_current */
};

static struct nis_state         _nis_state;

static int
_nis_start(struct nis_state *state)
{

       _DIAGASSERT(state != NULL);

       state->done = 0;
       if (state->current) {
               free(state->current);
               state->current = NULL;
       }
       if (state->domain == NULL) {                    /* setup NIS */
               switch (yp_get_default_domain(&state->domain)) {
               case 0:
                       break;
               case YPERR_RESRC:
                       return NS_TRYAGAIN;
               default:
                       return NS_UNAVAIL;
               }
       }
       return NS_SUCCESS;
}

static int
_nis_end(struct nis_state *state)
{

       _DIAGASSERT(state != NULL);

       if (state->domain)
               state->domain = NULL;
       state->done = 0;
       if (state->current)
               free(state->current);
       state->current = NULL;
       return NS_SUCCESS;
}

/*ARGSUSED*/
static int
_nis_setusershell(void *nsrv, void *nscb, va_list ap)
{

       return _nis_start(&_nis_state);
}

/*ARGSUSED*/
static int
_nis_endusershell(void *nsrv, void *nscb, va_list ap)
{

       return _nis_end(&_nis_state);
}

/*ARGSUSED*/
static int
_nis_getusershell(void *nsrv, void *nscb, va_list ap)
{
       char    **retval = va_arg(ap, char **);

       char    *key, *data;
       int     keylen, datalen, rv, nisr;

       _DIAGASSERT(retval != NULL);

       *retval = NULL;

       if (_nis_state.done)                            /* exhausted search */
               return NS_NOTFOUND;
       if (_nis_state.domain == NULL) {
                                       /* only start if NIS not setup */
               rv = _nis_start(&_nis_state);
               if (rv != NS_SUCCESS)
                       return rv;
       }

       key = NULL;
       data = NULL;
       rv = NS_NOTFOUND;

       if (_nis_state.current) {                       /* already searching */
               nisr = yp_next(_nis_state.domain, "shells",
                   _nis_state.current, _nis_state.currentlen,
                   &key, &keylen, &data, &datalen);
               free(_nis_state.current);
               _nis_state.current = NULL;
               switch (nisr) {
               case 0:
                       _nis_state.current = key;
                       _nis_state.currentlen = keylen;
                       key = NULL;
                       break;
               case YPERR_NOMORE:
                       rv = NS_NOTFOUND;
                       goto nisent_out;
               default:
                       rv = NS_UNAVAIL;
                       goto nisent_out;
               }
       } else {                                        /* new search */
               if (yp_first(_nis_state.domain, "shells",
                   &_nis_state.current, &_nis_state.currentlen,
                   &data, &datalen)) {
                       rv = NS_UNAVAIL;
                       goto nisent_out;
               }
       }

       data[datalen] = '\0';                           /* clear trailing \n */
       strlcpy(curshell, data, sizeof(curshell));
       *retval = curshell;
       rv = NS_SUCCESS;

nisent_out:
       if (key)
               free(key);
       if (data)
               free(data);
       if (rv != NS_SUCCESS)                   /* any failure halts search */
               _nis_state.done = 1;
       return rv;
}

#endif /* YP */


               /*
                *      public functions
                */

void
endusershell(void)
{
       static const ns_dtab dtab[] = {
               NS_FILES_CB(_files_endusershell, NULL)
               NS_DNS_CB(_dns_endusershell, NULL)
               NS_NIS_CB(_nis_endusershell, NULL)
               NS_NULL_CB
       };

       mutex_lock(&__shellmutex);

       curokshell = okshells;          /* reset okshells fallback state */
       shellsfound = 0;

                                       /* force all endusershell() methods */
       (void) nsdispatch(NULL, dtab, NSDB_SHELLS, "endusershell",
           __nsdefaultfiles_forceall);
       mutex_unlock(&__shellmutex);
}

__aconst char *
getusershell(void)
{
       int              rv;
       __aconst char   *retval;

       static const ns_dtab dtab[] = {
               NS_FILES_CB(_files_getusershell, NULL)
               NS_DNS_CB(_dns_getusershell, NULL)
               NS_NIS_CB(_nis_getusershell, NULL)
               NS_NULL_CB
       };

       mutex_lock(&__shellmutex);

       retval = NULL;
       do {
               rv = nsdispatch(NULL, dtab, NSDB_SHELLS, "getusershell",
                   __nsdefaultsrc, &retval);
                               /* loop until failure or non-blank result */
       } while (rv == NS_SUCCESS && retval[0] == '\0');

       if (rv == NS_SUCCESS) {
               shellsfound++;
       } else if (shellsfound == 0) {  /* no shells; fall back to okshells */
               if (curokshell != NULL) {
                       retval = __UNCONST(*curokshell);
                       curokshell++;
                       rv = NS_SUCCESS;
               }
       }

       mutex_unlock(&__shellmutex);
       return (rv == NS_SUCCESS) ? retval : NULL;
}

void
setusershell(void)
{
       static const ns_dtab dtab[] = {
               NS_FILES_CB(_files_setusershell, NULL)
               NS_DNS_CB(_dns_setusershell, NULL)
               NS_NIS_CB(_nis_setusershell, NULL)
               NS_NULL_CB
       };

       mutex_lock(&__shellmutex);

       curokshell = okshells;          /* reset okshells fallback state */
       shellsfound = 0;

                                       /* force all setusershell() methods */
       (void) nsdispatch(NULL, dtab, NSDB_SHELLS, "setusershell",
           __nsdefaultfiles_forceall);
       mutex_unlock(&__shellmutex);
}

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