/*
 *  idmap_autorid: static map between Active Directory/NT RIDs
 *  and RFC 2307 accounts
 *
 *  based on the idmap_rid module, but this module defines the ranges
 *  for the domains by automatically allocating a range for each domain
 *
 *  Copyright (C) Christian Ambach, 2010-2012
 *
 *  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 of the License, 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/>.
 *
 */

#include "includes.h"
#include "system/filesys.h"
#include "winbindd.h"
#include "dbwrap/dbwrap.h"
#include "dbwrap/dbwrap_open.h"
#include "idmap.h"
#include "idmap_rw.h"
#include "../libcli/security/dom_sid.h"
#include "util_tdb.h"
#include "winbindd/idmap_tdb_common.h"

#undef DBGC_CLASS
#define DBGC_CLASS DBGC_IDMAP

#define HWM "NEXT RANGE"
#define ALLOC_HWM_UID "NEXT ALLOC UID"
#define ALLOC_HWM_GID "NEXT ALLOC GID"
#define ALLOC_RANGE "ALLOC"
#define CONFIGKEY "CONFIG"

struct autorid_global_config {
	uint32_t minvalue;
	uint32_t rangesize;
	uint32_t maxranges;
	bool ignore_builtin;
};

struct autorid_domain_config {
	fstring sid;
	uint32_t domainnum;
	struct autorid_global_config *globalcfg;
};

/* handle to the tdb storing domain <-> range assignments */
static struct db_context *autorid_db;

static NTSTATUS idmap_autorid_get_domainrange_action(struct db_context *db,
					      void *private_data)
{
	NTSTATUS ret;
	uint32_t domainnum, hwm;
	char *numstr;
	struct autorid_domain_config *cfg;

	cfg = (struct autorid_domain_config *)private_data;

	ret = dbwrap_fetch_uint32_bystring(db, cfg->sid, &(cfg->domainnum));

	if (NT_STATUS_IS_OK(ret)) {
		/* entry is already present*/
		return ret;
	}

	DEBUG(10, ("Acquiring new range for domain %s\n", cfg->sid));

	/* fetch the current HWM */
	ret = dbwrap_fetch_uint32_bystring(db, HWM, &hwm);
	if (!NT_STATUS_IS_OK(ret)) {
		DEBUG(1, ("Fatal error while fetching current "
			  "HWM value: %s\n", nt_errstr(ret)));
		ret = NT_STATUS_INTERNAL_ERROR;
		goto error;
	}

	/* do we have a range left? */
	if (hwm >= cfg->globalcfg->maxranges) {
		DEBUG(1, ("No more domain ranges available!\n"));
		ret = NT_STATUS_NO_MEMORY;
		goto error;
	}

	/* increase the HWM */
	ret = dbwrap_change_uint32_atomic_bystring(db, HWM, &domainnum, 1);
	if (!NT_STATUS_IS_OK(ret)) {
		DEBUG(1, ("Fatal error while fetching a new "
			  "domain range value!\n"));
		goto error;
	}

	/* store away the new mapping in both directions */
	ret = dbwrap_store_uint32_bystring(db, cfg->sid, domainnum);
	if (!NT_STATUS_IS_OK(ret)) {
		DEBUG(1, ("Fatal error while storing new "
			  "domain->range assignment!\n"));
		goto error;
	}

	numstr = talloc_asprintf(db, "%u", domainnum);
	if (!numstr) {
		ret = NT_STATUS_NO_MEMORY;
		goto error;
	}

	ret = dbwrap_store_bystring(db, numstr,
			string_term_tdb_data(cfg->sid), TDB_INSERT);

	talloc_free(numstr);
	if (!NT_STATUS_IS_OK(ret)) {
		DEBUG(1, ("Fatal error while storing "
			  "new domain->range assignment!\n"));
		goto error;
	}
	DEBUG(5, ("Acquired new range #%d for domain %s\n",
		  domainnum, cfg->sid));

	cfg->domainnum = domainnum;

	return NT_STATUS_OK;

error:
	return ret;

}

static NTSTATUS idmap_autorid_get_domainrange(struct autorid_domain_config *dom,
					      bool read_only)
{
	NTSTATUS ret;

	/*
	 * try to find mapping without locking the database,
	 * if it is not found create a mapping in a transaction unless
	 * read-only mode has been set
	 */
	ret = dbwrap_fetch_uint32_bystring(autorid_db, dom->sid,
					   &(dom->domainnum));

	if (!NT_STATUS_IS_OK(ret)) {
		if (read_only) {
			return NT_STATUS_NOT_FOUND;
		}
		ret = dbwrap_trans_do(autorid_db,
			      idmap_autorid_get_domainrange_action, dom);
	}

	DEBUG(10, ("Using range #%d for domain %s\n", dom->domainnum,
		   dom->sid));

	return ret;
}

static NTSTATUS idmap_autorid_allocate_id(struct idmap_domain *dom,
					  struct unixid *xid) {

	NTSTATUS ret;
	struct idmap_tdb_common_context *commoncfg;
	struct autorid_global_config *globalcfg;
	struct autorid_domain_config domaincfg;

	commoncfg =
	    talloc_get_type_abort(dom->private_data,
				  struct idmap_tdb_common_context);

	globalcfg = talloc_get_type(commoncfg->private_data,
				    struct autorid_global_config);

	if (dom->read_only) {
		DEBUG(3, ("Backend is read-only, refusing "
			  "new allocation request\n"));
		return NT_STATUS_UNSUCCESSFUL;
	}

	/* fetch the range for the allocation pool */

	ZERO_STRUCT(domaincfg);

	domaincfg.globalcfg = globalcfg;
	fstrcpy(domaincfg.sid, ALLOC_RANGE);

	ret = idmap_autorid_get_domainrange(&domaincfg, dom->read_only);

	if (!NT_STATUS_IS_OK(ret)) {
		DEBUG(3, ("Could not determine range for allocation pool, "
			  "check previous messages for reason\n"));
		return ret;
	}

	ret = idmap_tdb_common_get_new_id(dom, xid);

	if (!NT_STATUS_IS_OK(ret)) {
		DEBUG(1, ("Fatal error while allocating new ID!\n"));
		return ret;
	}

	xid->id = globalcfg->minvalue +
		  globalcfg->rangesize * domaincfg.domainnum +
		  xid->id;

	DEBUG(10, ("Returned new %s %d from allocation range\n",
		   (xid->type==ID_TYPE_UID)?"uid":"gid", xid->id));

	return ret;
}

/*
 * map a SID to xid using the idmap_tdb like pool
 */
static NTSTATUS idmap_autorid_map_id_to_sid(struct idmap_domain *dom,
					    struct id_map *map)
{
	NTSTATUS ret;

	/* look out for the mapping */
	ret = idmap_tdb_common_unixid_to_sid(dom, map);

	if (NT_STATUS_IS_OK(ret)) {
		map->status = ID_MAPPED;
		return ret;
	}

	map->status = ID_UNKNOWN;

	DEBUG(10, ("no ID->SID mapping for %d could be found\n", map->xid.id));

	return ret;
}

static NTSTATUS idmap_autorid_id_to_sid(struct autorid_global_config *cfg,
					struct idmap_domain *dom,
					struct id_map *map)
{
	uint32_t range;
	TDB_DATA data = tdb_null;
	char *keystr;
	struct dom_sid sid;
	NTSTATUS status;

	/* can this be one of our ids? */
	if (map->xid.id < cfg->minvalue) {
		DEBUG(10, ("id %d is lower than minimum value, "
			   "ignoring mapping request\n", map->xid.id));
		map->status = ID_UNKNOWN;
		return NT_STATUS_OK;
	}

	if (map->xid.id > (cfg->minvalue + cfg->rangesize * cfg->maxranges)) {
		DEBUG(10, ("id %d is outside of maximum id value, "
			   "ignoring mapping request\n", map->xid.id));
		map->status = ID_UNKNOWN;
		return NT_STATUS_OK;
	}

	/* determine the range of this uid */
	range = ((map->xid.id - cfg->minvalue) / cfg->rangesize);

	keystr = talloc_asprintf(talloc_tos(), "%u", range);
	if (!keystr) {
		return NT_STATUS_NO_MEMORY;
	}

	status = dbwrap_fetch_bystring(autorid_db, talloc_tos(), keystr, &data);
	TALLOC_FREE(keystr);

	if (!NT_STATUS_IS_OK(status)) {
		DEBUG(4, ("id %d belongs to range %d which does not have "
			  "domain mapping, ignoring mapping request\n",
			  map->xid.id, range));
		TALLOC_FREE(data.dptr);
		map->status = ID_UNKNOWN;
		return NT_STATUS_OK;
	}

	if (strncmp((const char *)data.dptr,
		    ALLOC_RANGE,
		    strlen(ALLOC_RANGE)) == 0) {
		/*
		 * this is from the alloc range, check if there is a mapping
		 */
		DEBUG(5, ("id %d belongs to allocation range, "
			  "checking for mapping\n",
			  map->xid.id));
		TALLOC_FREE(data.dptr);
		return idmap_autorid_map_id_to_sid(dom, map);
	}

	string_to_sid(&sid, (const char *)data.dptr);
	TALLOC_FREE(data.dptr);

	sid_compose(map->sid, &sid,
		    (map->xid.id - cfg->minvalue -
		     range * cfg->rangesize));

	/* We **really** should have some way of validating
	   the SID exists and is the correct type here.  But
	   that is a deficiency in the idmap_rid design. */

	map->status = ID_MAPPED;
	map->xid.type = ID_TYPE_BOTH;

	return NT_STATUS_OK;
}

/**********************************
 Single sid to id lookup function.
**********************************/

static NTSTATUS idmap_autorid_sid_to_id(struct autorid_global_config *global,
					struct autorid_domain_config *domain,
					struct id_map *map)
{
	uint32_t rid;

	sid_peek_rid(map->sid, &rid);

	/* if the rid is higher than the size of the range, we cannot map it */
	if (rid >= global->rangesize) {
		map->status = ID_UNKNOWN;
		DEBUG(2, ("RID %d is larger then size of range (%d), "
			  "user cannot be mapped\n", rid, global->rangesize));
		return NT_STATUS_UNSUCCESSFUL;
	}
	map->xid.id = global->minvalue +
	    (global->rangesize * domain->domainnum)+rid;
	map->xid.type = ID_TYPE_BOTH;

	/* We **really** should have some way of validating
	   the SID exists and is the correct type here.  But
	   that is a deficiency in the idmap_rid design. */

	map->status = ID_MAPPED;

	return NT_STATUS_OK;
}

/**********************************
 lookup a set of unix ids.
**********************************/

static NTSTATUS idmap_autorid_unixids_to_sids(struct idmap_domain *dom,
					      struct id_map **ids)
{
	struct idmap_tdb_common_context *commoncfg;
	struct autorid_global_config *globalcfg;
	NTSTATUS ret;
	int i;
	int num_tomap = 0;
	int num_mapped = 0;

	/* initialize the status to avoid surprise */
	for (i = 0; ids[i]; i++) {
		ids[i]->status = ID_UNKNOWN;
		num_tomap++;
	}

	commoncfg =
	    talloc_get_type_abort(dom->private_data,
				  struct idmap_tdb_common_context);

	globalcfg = talloc_get_type(commoncfg->private_data,
				    struct autorid_global_config);

	for (i = 0; ids[i]; i++) {

		ret = idmap_autorid_id_to_sid(globalcfg, dom, ids[i]);

		if ((!NT_STATUS_IS_OK(ret)) &&
		    (!NT_STATUS_EQUAL(ret, NT_STATUS_NONE_MAPPED))) {
			/* some fatal error occurred, log it */
			DEBUG(3, ("Unexpected error resolving an ID "
				  " (%d)\n", ids[i]->xid.id));
			goto failure;
		}

		if (NT_STATUS_IS_OK(ret) && ids[i]->status == ID_MAPPED) {
			num_mapped++;
		}

	}

	if (num_tomap == num_mapped) {
		return NT_STATUS_OK;
	} else if (num_mapped == 0) {
		return NT_STATUS_NONE_MAPPED;
	}

	return STATUS_SOME_UNMAPPED;


      failure:
	return ret;
}

/*
 * map a SID to xid using the idmap_tdb like pool
 */
static NTSTATUS idmap_autorid_map_sid_to_id(struct idmap_domain *dom,
					    struct id_map *map,
					    struct idmap_tdb_common_context *ctx)
{
	NTSTATUS ret;
	int res;

	/* see if we already have a mapping */
	ret = idmap_tdb_common_sid_to_unixid(dom, map);

	if (NT_STATUS_IS_OK(ret)) {
		map->status = ID_MAPPED;
		return ret;
	}

	/* bad things happened */
	if (!NT_STATUS_EQUAL(ret, NT_STATUS_NONE_MAPPED)) {
		DEBUG(1, ("Looking up SID->ID mapping for %s failed\n",
			  sid_string_dbg(map->sid)));
		return ret;
	}

	if (dom->read_only) {
		DEBUG(3, ("Not allocating new mapping for %s, because backend "
			  "is read-only\n", sid_string_dbg(map->sid)));
		return NT_STATUS_NONE_MAPPED;
	}

	DEBUG(10, ("Creating new mapping in pool for %s\n",
		   sid_string_dbg(map->sid)));

	/* create new mapping */
	res = dbwrap_transaction_start(ctx->db);
	if (res != 0) {
		DEBUG(2, ("transaction_start failed\n"));
		return NT_STATUS_INTERNAL_DB_CORRUPTION;
	}

	ret = idmap_tdb_common_new_mapping(dom, map);

	map->status = (NT_STATUS_IS_OK(ret))?ID_MAPPED:ID_UNMAPPED;

	if (!NT_STATUS_IS_OK(ret)) {
		if (dbwrap_transaction_cancel(ctx->db) != 0) {
			smb_panic("Cancelling transaction failed");
		}
		return ret;
	}

	res = dbwrap_transaction_commit(ctx->db);
	if (res == 0) {
		return ret;
	}

	DEBUG(2, ("transaction_commit failed\n"));
	return NT_STATUS_INTERNAL_DB_CORRUPTION;

}

/**********************************
 lookup a set of sids.
**********************************/

static NTSTATUS idmap_autorid_sids_to_unixids(struct idmap_domain *dom,
					      struct id_map **ids)
{
	struct idmap_tdb_common_context *commoncfg;
	struct autorid_global_config *global;
	NTSTATUS ret;
	int i;
	int num_tomap = 0;
	int num_mapped = 0;

	/* initialize the status to avoid surprise */
	for (i = 0; ids[i]; i++) {
		ids[i]->status = ID_UNKNOWN;
		num_tomap++;
	}

	commoncfg =
	    talloc_get_type_abort(dom->private_data,
				  struct idmap_tdb_common_context);

	global = talloc_get_type(commoncfg->private_data,
				 struct autorid_global_config);

	for (i = 0; ids[i]; i++) {
		struct winbindd_tdc_domain *domain;
		struct autorid_domain_config domaincfg;
		uint32_t rid;
		struct dom_sid domainsid;

		ZERO_STRUCT(domaincfg);

		DEBUG(10, ("Trying to map %s\n", sid_string_dbg(ids[i]->sid)));

		sid_copy(&domainsid, ids[i]->sid);
		if (!sid_split_rid(&domainsid, &rid)) {
			DEBUG(4, ("Could not determine domain SID from %s, "
				  "ignoring mapping request\n",
				  sid_string_dbg(ids[i]->sid)));
			continue;
		}

		/* is this a well-known SID? */

		if (sid_check_is_wellknown_domain(&domainsid, NULL)) {

			DEBUG(10, ("SID %s is well-known, using pool\n",
				   sid_string_dbg(ids[i]->sid)));

			ret = idmap_autorid_map_sid_to_id(dom, ids[i],
							  commoncfg);

			if (!NT_STATUS_IS_OK(ret) &&
			    !NT_STATUS_EQUAL(ret, NT_STATUS_NONE_MAPPED)) {
				DEBUG(3, ("Unexpected error resolving "
					  "SID (%s)\n",
					  sid_string_dbg(ids[i]->sid)));
				goto failure;
			}

			if (ids[i]->status == ID_MAPPED) {
				num_mapped++;
			}

			continue;
		}

		/* BUILTIN is passdb's job */
		if (dom_sid_equal(&domainsid, &global_sid_Builtin) &&
		    global->ignore_builtin) {
			DEBUG(10, ("Ignoring request for BUILTIN domain\n"));
			continue;
		}

		/*
		 * Check if the domain is around
		 */
		domain = wcache_tdc_fetch_domainbysid(talloc_tos(),
						      &domainsid);
		if (domain == NULL) {
			DEBUG(10, ("Ignoring unknown domain sid %s\n",
				   sid_string_dbg(&domainsid)));
			continue;
		}
		TALLOC_FREE(domain);

		domaincfg.globalcfg = global;
		sid_to_fstring(domaincfg.sid, &domainsid);

		ret = idmap_autorid_get_domainrange(&domaincfg, dom->read_only);

		/* read-only mode and a new domain range would be required? */
		if (NT_STATUS_EQUAL(ret, NT_STATUS_NOT_FOUND) &&
		    dom->read_only) {
			DEBUG(10, ("read-only is enabled, did not allocate "
				   "new range for domain %s\n",
				   sid_string_dbg(&domainsid)));
			continue;
		}

		if (!NT_STATUS_IS_OK(ret)) {
			DEBUG(3, ("Could not determine range for domain, "
				  "check previous messages for reason\n"));
			goto failure;
		}

		ret = idmap_autorid_sid_to_id(global, &domaincfg, ids[i]);

		if ((!NT_STATUS_IS_OK(ret)) &&
		    (!NT_STATUS_EQUAL(ret, NT_STATUS_NONE_MAPPED))) {
			/* some fatal error occurred, log it */
			DEBUG(3, ("Unexpected error resolving a SID (%s)\n",
				  sid_string_dbg(ids[i]->sid)));
			goto failure;
		}

		if (NT_STATUS_IS_OK(ret)) {
			num_mapped++;
		}
	}

	if (num_tomap == num_mapped) {
		return NT_STATUS_OK;
	} else if (num_mapped == 0) {
		return NT_STATUS_NONE_MAPPED;
	}

	return STATUS_SOME_UNMAPPED;

      failure:
	return ret;

}

/* initialize the given HWM to 0 if it does not exist yet */
static NTSTATUS idmap_autorid_init_hwm(const char *hwm) {

	NTSTATUS status;
	uint32_t hwmval;

	status = dbwrap_fetch_uint32_bystring(autorid_db, hwm, &hwmval);
	if (NT_STATUS_EQUAL(status, NT_STATUS_NOT_FOUND))  {
		status = dbwrap_trans_store_int32_bystring(autorid_db, hwm, 0);
		if (!NT_STATUS_IS_OK(status)) {
			DEBUG(0,
			      ("Unable to initialise HWM (%s) in autorid "
			       "database: %s\n", hwm, nt_errstr(status)));
			return NT_STATUS_INTERNAL_DB_ERROR;
		}
	} else if (!NT_STATUS_IS_OK(status)) {
		DEBUG(0, ("unable to fetch HWM (%s) from autorid "
			  "database: %s\n", hwm,  nt_errstr(status)));
		return status;
	}

	return NT_STATUS_OK;
}

/*
 * open and initialize the database which stores the ranges for the domains
 */
static NTSTATUS idmap_autorid_db_init(void)
{
	NTSTATUS status;

	if (autorid_db) {
		/* its already open */
		return NT_STATUS_OK;
	}

	/* Open idmap repository */
	autorid_db = db_open(NULL, state_path("autorid.tdb"), 0,
			     TDB_DEFAULT, O_RDWR | O_CREAT, 0644,
			     DBWRAP_LOCK_ORDER_1);

	if (!autorid_db) {
		DEBUG(0, ("Unable to open idmap_autorid database '%s'\n",
			  state_path("autorid.tdb")));
		return NT_STATUS_UNSUCCESSFUL;
	}

	/* Initialize high water mark for the currently used range to 0 */

	status = idmap_autorid_init_hwm(HWM);
	NT_STATUS_NOT_OK_RETURN(status);

	status = idmap_autorid_init_hwm(ALLOC_HWM_UID);
	NT_STATUS_NOT_OK_RETURN(status);

	status = idmap_autorid_init_hwm(ALLOC_HWM_GID);

	return status;
}

static struct autorid_global_config *idmap_autorid_loadconfig(TALLOC_CTX * ctx)
{

	TDB_DATA data;
	struct autorid_global_config *cfg;
	unsigned long minvalue, rangesize, maxranges;
	NTSTATUS status;

	status = dbwrap_fetch_bystring(autorid_db, ctx, CONFIGKEY, &data);

	if (!NT_STATUS_IS_OK(status)) {
		DEBUG(10, ("No saved config found\n"));
		return NULL;
	}

	cfg = talloc_zero(ctx, struct autorid_global_config);
	if (!cfg) {
		return NULL;
	}

	if (sscanf((char *)data.dptr,
		   "minvalue:%lu rangesize:%lu maxranges:%lu",
		   &minvalue, &rangesize, &maxranges) != 3) {
		DEBUG(1,
		      ("Found invalid configuration data"
		       "creating new config\n"));
		return NULL;
	}

	cfg->minvalue = minvalue;
	cfg->rangesize = rangesize;
	cfg->maxranges = maxranges;

	DEBUG(10, ("Loaded previously stored configuration "
		   "minvalue:%d rangesize:%d\n",
		   cfg->minvalue, cfg->rangesize));

	return cfg;

}

static NTSTATUS idmap_autorid_saveconfig(struct autorid_global_config *cfg)
{

	NTSTATUS status;
	TDB_DATA data;
	char *cfgstr;

	cfgstr =
	    talloc_asprintf(talloc_tos(),
			    "minvalue:%u rangesize:%u maxranges:%u",
			    cfg->minvalue, cfg->rangesize, cfg->maxranges);

	if (!cfgstr) {
		return NT_STATUS_NO_MEMORY;
	}

	data = string_tdb_data(cfgstr);

	status = dbwrap_trans_store_bystring(autorid_db, CONFIGKEY,
					     data, TDB_REPLACE);

	talloc_free(cfgstr);

	return status;
}

static NTSTATUS idmap_autorid_preallocate_wellknown(struct idmap_domain *dom)
{
	const char *groups[] = { "S-1-1-0", "S-1-2-0", "S-1-2-1",
		"S-1-3-0", "S-1-3-1", "S-1-3-2", "S-1-3-3", "S-1-3-4",
		"S-1-5-1", "S-1-5-2", "S-1-5-3", "S-1-5-4", "S-1-5-6",
		"S-1-5-7", "S-1-5-8", "S-1-5-9", "S-1-5-10", "S-1-5-11",
		"S-1-5-12", "S-1-5-13", "S-1-5-14", "S-1-5-15",
		"S-1-5-17", "S-1-5-18", "S-1-5-19", "S-1-5-20"
	};

	struct id_map **maps;
	int i, num;
	NTSTATUS status;

	if (dom->read_only) {
		return NT_STATUS_OK;
	}

	num = sizeof(groups)/sizeof(char*);

	maps = talloc_zero_array(talloc_tos(), struct id_map*, num+1);
	if (!maps) {
		return NT_STATUS_NO_MEMORY;
	}

	for (i = 0; i < num; i++) {
		maps[i] = talloc(maps, struct id_map);
		maps[i]->xid.type = ID_TYPE_GID;
		maps[i]->sid = dom_sid_parse_talloc(maps, groups[i]);
	}

	maps[num] = NULL;

	status = idmap_autorid_sids_to_unixids(dom, maps);

	DEBUG(10,("Preallocation run finished with status %s\n",
		  nt_errstr(status)));

	talloc_free(maps);

	return NT_STATUS_IS_OK(status)?NT_STATUS_OK:NT_STATUS_UNSUCCESSFUL;
}

static NTSTATUS idmap_autorid_initialize(struct idmap_domain *dom)
{
	struct idmap_tdb_common_context *commonconfig;
	struct autorid_global_config *config;
	struct autorid_global_config *storedconfig = NULL;
	NTSTATUS status;
	uint32_t hwm;

	if (!strequal(dom->name, "*")) {
		DEBUG(0, ("idmap_autorid_initialize: Error: autorid configured "
			  "for domain '%s'. But autorid can only be used for "
			  "the default idmap configuration.\n", dom->name));
		return NT_STATUS_INVALID_PARAMETER;
	}

	commonconfig = talloc_zero(dom, struct idmap_tdb_common_context);
	if (!commonconfig) {
		DEBUG(0, ("Out of memory!\n"));
		return NT_STATUS_NO_MEMORY;
	}

	commonconfig->rw_ops = talloc_zero(commonconfig, struct idmap_rw_ops);
	if (commonconfig->rw_ops == NULL) {
		DEBUG(0, ("Out of memory!\n"));
		return NT_STATUS_NO_MEMORY;
	}

	config = talloc_zero(commonconfig, struct autorid_global_config);
	if (!config) {
		DEBUG(0, ("Out of memory!\n"));
		return NT_STATUS_NO_MEMORY;
	}

	status = idmap_autorid_db_init();
	if (!NT_STATUS_IS_OK(status)) {
		goto error;
	}

	config->minvalue = dom->low_id;
	config->rangesize = lp_parm_int(-1, "idmap config *",
					"rangesize", 100000);

	if (config->rangesize < 2000) {
		DEBUG(1, ("autorid rangesize must be at least 2000\n"));
		status = NT_STATUS_INVALID_PARAMETER;
		goto error;
	}

	config->maxranges = (dom->high_id - dom->low_id + 1) /
	    config->rangesize;

	if (config->maxranges == 0) {
		DEBUG(1, ("allowed uid range is smaller then rangesize, "
			  "increase uid range or decrease rangesize\n"));
		status = NT_STATUS_INVALID_PARAMETER;
		goto error;
	}

	/* check if the high-low limit is a multiple of the rangesize */
	if ((dom->high_id - dom->low_id + 1) % config->rangesize != 0) {
		DEBUG(5, ("High uid-low uid difference of %d "
			  "is not a multiple of the rangesize %d, "
			  "limiting ranges to lower boundary number of %d\n",
			  (dom->high_id - dom->low_id + 1), config->rangesize,
			  config->maxranges));
	}

	DEBUG(10, ("Current configuration in config is "
		   "minvalue:%d rangesize:%d maxranges:%d\n",
		   config->minvalue, config->rangesize, config->maxranges));

	/* read previously stored config and current HWM */
	storedconfig = idmap_autorid_loadconfig(talloc_tos());

	status = dbwrap_fetch_uint32_bystring(autorid_db, HWM, &hwm);
	if (!NT_STATUS_IS_OK(status)) {
		DEBUG(1, ("Fatal error while fetching current "
			  "HWM value: %s\n", nt_errstr(status)));
		status = NT_STATUS_INTERNAL_ERROR;
		goto error;
	}

	/* did the minimum value or rangesize change? */
	if (storedconfig &&
	    ((storedconfig->minvalue != config->minvalue) ||
	     (storedconfig->rangesize != config->rangesize))) {
		DEBUG(1, ("New configuration values for rangesize or "
			  "minimum uid value conflict with previously "
			  "used values! Aborting initialization\n"));
		status = NT_STATUS_INVALID_PARAMETER;
		goto error;
	}

	/*
	 * has the highest uid value been reduced to setting that is not
	 * sufficient any more for already existing ranges?
	 */
	if (hwm > config->maxranges) {
		DEBUG(1, ("New upper uid limit is too low to cover "
			  "existing mappings! Aborting initialization\n"));
		status = NT_STATUS_INVALID_PARAMETER;
		goto error;
	}

	status = idmap_autorid_saveconfig(config);

	if (!NT_STATUS_IS_OK(status)) {
		DEBUG(1, ("Failed to store configuration data!\n"));
		goto error;
	}

	DEBUG(5, ("%d domain ranges with a size of %d are available\n",
		  config->maxranges, config->rangesize));

	config->ignore_builtin = lp_parm_bool(-1, "idmap config *",
					      "ignore builtin", false);

	/* fill the TDB common configuration */
	commonconfig->private_data = config;

	commonconfig->db = autorid_db;
	commonconfig->max_id = config->rangesize -1;
	commonconfig->hwmkey_uid = ALLOC_HWM_UID;
	commonconfig->hwmkey_gid = ALLOC_HWM_GID;
	commonconfig->rw_ops->get_new_id = idmap_autorid_allocate_id;
	commonconfig->rw_ops->set_mapping = idmap_tdb_common_set_mapping;

	dom->private_data = commonconfig;

	/* preallocate well-known SIDs in the pool */
	status = idmap_autorid_preallocate_wellknown(dom);

	goto done;

error:
	talloc_free(config);

done:
	talloc_free(storedconfig);

	return status;
}

/*
  Close the idmap tdb instance
*/
static struct idmap_methods autorid_methods = {
	.init = idmap_autorid_initialize,
	.unixids_to_sids = idmap_autorid_unixids_to_sids,
	.sids_to_unixids = idmap_autorid_sids_to_unixids,
	.allocate_id	 = idmap_autorid_allocate_id
};

NTSTATUS samba_init_module(void)
{
	return smb_register_idmap(SMB_IDMAP_INTERFACE_VERSION,
				  "autorid", &autorid_methods);
}
