/* This file is part of Mailfromd.
   Copyright (C) 2007, 2008 Sergey Poznyakoff

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>. */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <pwd.h>
#include <grp.h>
#include <unistd.h>
#include <mailutils/assoc.h>
#include <mailutils/errno.h>
#include <mailutils/error.h>
#include <mailutils/errno.h>
#include <mailutils/nls.h>
#include <mailutils/list.h>
#include <mailutils/iterator.h>
/* FIXME: */
#include <sysexits.h>
#include "libpies.h"

int
get_user_groups (mu_list_t *pgrouplist, const char *user)
{
  int rc;
  struct group *gr;
  mu_list_t list;

  if (!*pgrouplist)
    {
      rc = mu_list_create (pgrouplist);
      if (rc)
	{
	  mu_error (_("%s: cannot create list: %s"),
		    "get_user_groups", mu_strerror (rc));
	  return rc;
	}
    }
  list = *pgrouplist;
  setgrent ();
  for (rc = 0; rc == 0 && (gr = getgrent ());)
    {
      char **p;
      for (p = gr->gr_mem; *p; p++)
	if (strcmp (*p, user) == 0)
	  {
	    /* FIXME: Avoid duplicating gids */
	    rc = mu_list_append (list, (void *) gr->gr_gid);
	    if (rc)
	      mu_error (_("%s: cannot append to list: %s"),
			"get_user_groups", mu_strerror (rc));
	    break;
	  }
    }
  endgrent ();
  return rc;
}

/* Switch to the given UID/GID */
int
switch_to_privs (uid_t uid, gid_t gid, mu_list_t retain_groups)
{
  int rc = 0;
  gid_t *emptygidset;
  size_t size = 1, j = 1;
  mu_iterator_t itr;

  if (uid == 0)
    {
      mu_error (_("Refusing to run as root"));
      return 1;
    }

  /* Create a list of supplementary groups */
  mu_list_count (retain_groups, &size);
  size++;
  emptygidset = xmalloc (size * sizeof emptygidset[0]);
  emptygidset[0] = gid ? gid : getegid ();

  if (mu_list_get_iterator (retain_groups, &itr) == 0)
    {
      for (mu_iterator_first (itr);
	   !mu_iterator_is_done (itr); mu_iterator_next (itr))
	mu_iterator_current (itr, (void **) (emptygidset + j++));
      mu_iterator_destroy (&itr);
    }

  /* Reset group permissions */
  if (geteuid () == 0 && setgroups (j, emptygidset))
    {
      mu_error (_("setgroups(1, %lu) failed: %s"),
		(unsigned long) emptygidset[0], mu_strerror (errno));
      rc = 1;
    }
  free (emptygidset);

  /* Switch to the user's gid. On some OSes the effective gid must
     be reset first */

#if defined(HAVE_SETEGID)
  if ((rc = setegid (gid)) < 0)
    mu_error (_("setegid(%lu) failed: %s"),
	      (unsigned long) gid, mu_strerror (errno));
#elif defined(HAVE_SETREGID)
  if ((rc = setregid (gid, gid)) < 0)
    mu_error (_("setregid(%lu,%lu) failed: %s"),
	      (unsigned long) gid, (unsigned long) gid, mu_strerror (errno));
#elif defined(HAVE_SETRESGID)
  if ((rc = setresgid (gid, gid, gid)) < 0)
    mu_error (_("setresgid(%lu,%lu,%lu) failed: %s"),
	      (unsigned long) gid,
	      (unsigned long) gid, (unsigned long) gid, mu_strerror (errno));
#endif

  if (rc == 0 && gid != 0)
    {
      if ((rc = setgid (gid)) < 0 && getegid () != gid)
	mu_error (_("setgid(%lu) failed: %s"),
		  (unsigned long) gid, mu_strerror (errno));
      if (rc == 0 && getegid () != gid)
	{
	  mu_error (_("Cannot set effective gid to %lu"),
		    (unsigned long) gid);
	  rc = 1;
	}
    }

  /* Now reset uid */
  if (rc == 0 && uid != 0)
    {
      uid_t euid;

      if (setuid (uid)
	  || geteuid () != uid
	  || (getuid () != uid && (geteuid () == 0 || getuid () == 0)))
	{

#if defined(HAVE_SETREUID)
	  if (geteuid () != uid)
	    {
	      if (setreuid (uid, -1) < 0)
		{
		  mu_error (_("setreuid(%lu,-1) failed: %s"),
			    (unsigned long) uid, mu_strerror (errno));
		  rc = 1;
		}
	      if (setuid (uid) < 0)
		{
		  mu_error (_("second setuid(%lu) failed: %s"),
			    (unsigned long) uid, mu_strerror (errno));
		  rc = 1;
		}
	    }
	  else
#endif
	    {
	      mu_error (_("setuid(%lu) failed: %s"),
			(unsigned long) uid, mu_strerror (errno));
	      rc = 1;
	    }
	}

      euid = geteuid ();
      if (uid != 0 && setuid (0) == 0)
	{
	  mu_error (_("seteuid(0) succeeded when it should not"));
	  rc = 1;
	}
      else if (uid != euid && setuid (euid) == 0)
	{
	  mu_error (_("Cannot drop non-root setuid privileges"));
	  rc = 1;
	}

    }

  return rc;
}


static int
translate_item (void *item, void *data)
{
  mu_list_t dst = data;
  struct group *group = getgrnam (item);
  if (!group)
    {
      mu_error (_("Unknown group: %s"), (char *) item);
      return 1;
    }
  return mu_list_append (dst, (void *) group->gr_gid);
}

static int
grouplist_translate (mu_list_t * pdst, mu_list_t src)
{
  mu_list_t dst;
  int rc;

  if (!src)
    return 0;
  rc = mu_list_create (&dst);
  if (rc)
    {
      mu_error (_("%s: cannot create list: %s"),
		"grouplist_translate", mu_strerror (rc));
      return rc;
    }
  *pdst = dst;
  return mu_list_do (src, translate_item, dst);
}

void
mf_priv_setup (struct mf_privs *privs)
{
  struct passwd *pw;
  mu_list_t grp = NULL;

  if (!privs || !privs->user)
    return;

  pw = getpwnam (privs->user);
  if (!pw)
    {
      mu_error (_("No such user: %s"), privs->user);
      exit (EX_CONFIG);
    }

  grouplist_translate (&grp, privs->groups);
  if (privs->allgroups && get_user_groups (&grp, privs->user))
    exit (EX_CONFIG);
  if (switch_to_privs (pw->pw_uid, pw->pw_gid, grp))
    exit (EX_SOFTWARE);
  mu_list_destroy (&grp);
}


void
mf_epriv_setup (struct mf_privs *privs)
{
  uid_t uid;
  gid_t gid;

  if (privs)
    {
      struct passwd *pw;
      if (!privs->user)
	return;

      pw = getpwnam (privs->user);
      if (!pw)
	{
	  mu_error (_("No such user: %s"), privs->user);
	  exit (EX_CONFIG);
	}
      uid = pw->pw_uid;
      gid = pw->pw_gid;
    }
  else
    {
      uid = 0;
      gid = 0;
    }

  if (setegid (gid))
    {
      mu_error (_("Cannot switch to EGID %lu: %s"),
		(unsigned long) gid, mu_strerror (errno));
      exit (EX_USAGE);
    }
  if (seteuid (uid))
    {
      mu_error (_("Cannot switch to EUID %lu: %s"),
		(unsigned long) uid, mu_strerror (errno));
      exit (EX_USAGE);
    }
}