/* 
   Unix SMB/CIFS implementation.
   session handling for utmp and PAM

   Copyright (C) tridge@samba.org       2001
   Copyright (C) abartlet@samba.org     2001
   Copyright (C) Gerald (Jerry) Carter  2006   
   
   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/>.
*/

/* a "session" is claimed when we do a SessionSetupX operation
   and is yielded when the corresponding vuid is destroyed.

   sessions are used to populate utmp and PAM session structures
*/

#include "includes.h"

/********************************************************************
********************************************************************/

static struct db_context *session_db_ctx(void)
{
	static struct db_context *ctx;

	if (ctx)
		return ctx;

	ctx = db_open(NULL, lock_path("sessionid.tdb"), 0,
		      TDB_CLEAR_IF_FIRST|TDB_DEFAULT, 
		      O_RDWR | O_CREAT, 0644);
	return ctx;
}

bool session_init(void)
{
	if (session_db_ctx() == NULL) {
		DEBUG(1,("session_init: failed to open sessionid tdb\n"));
		return False;
	}

	return True;
}

/********************************************************************
 called when a session is created
********************************************************************/

bool session_claim(user_struct *vuser)
{
	TDB_DATA key, data;
	int i = 0;
	struct sessionid sessionid;
	struct server_id pid = procid_self();
	fstring keystr;
	const char * hostname;
	struct db_context *ctx;
	struct db_record *rec;
	NTSTATUS status;

	vuser->session_keystr = NULL;

	/* don't register sessions for the guest user - its just too
	   expensive to go through pam session code for browsing etc */
	if (vuser->guest) {
		return True;
	}

	if (!(ctx = session_db_ctx())) {
		return False;
	}

	ZERO_STRUCT(sessionid);

	data.dptr = NULL;
	data.dsize = 0;

	if (lp_utmp()) {

		for (i=1;i<MAX_SESSION_ID;i++) {

			/*
			 * This is very inefficient and needs fixing -- vl
			 */

			struct server_id sess_pid;

			snprintf(keystr, sizeof(keystr), "ID/%d", i);
			key = string_term_tdb_data(keystr);

			rec = ctx->fetch_locked(ctx, NULL, key);

			if (rec == NULL) {
				DEBUG(1, ("Could not lock \"%s\"\n", keystr));
				return False;
			}

			if (rec->value.dsize != sizeof(sessionid)) {
				DEBUG(1, ("Re-using invalid record\n"));
				break;
			}

			sess_pid = ((struct sessionid *)rec->value.dptr)->pid;

			if (!process_exists(sess_pid)) {
				DEBUG(5, ("%s has died -- re-using session\n",
					  procid_str_static(&sess_pid)));
				break;
			}

			TALLOC_FREE(rec);
		}

		if (i == MAX_SESSION_ID) {
			SMB_ASSERT(rec == NULL);
			DEBUG(1,("session_claim: out of session IDs "
				 "(max is %d)\n", MAX_SESSION_ID));
			return False;
		}

		snprintf(sessionid.id_str, sizeof(sessionid.id_str),
			 SESSION_UTMP_TEMPLATE, i);
	} else
	{
		snprintf(keystr, sizeof(keystr), "ID/%s/%u",
			 procid_str_static(&pid), vuser->vuid);
		key = string_term_tdb_data(keystr);

		rec = ctx->fetch_locked(ctx, NULL, key);

		if (rec == NULL) {
			DEBUG(1, ("Could not lock \"%s\"\n", keystr));
			return False;
		}

		snprintf(sessionid.id_str, sizeof(sessionid.id_str),
			 SESSION_TEMPLATE, (long unsigned int)sys_getpid(),
			 vuser->vuid);
	}

	SMB_ASSERT(rec != NULL);

	/* If 'hostname lookup' == yes, then do the DNS lookup.  This is
           needed because utmp and PAM both expect DNS names

	   client_name() handles this case internally.
	*/

	hostname = client_name();
	if (strcmp(hostname, "UNKNOWN") == 0) {
		hostname = client_addr();
	}

	fstrcpy(sessionid.username, vuser->user.unix_name);
	fstrcpy(sessionid.hostname, hostname);
	sessionid.id_num = i;  /* Only valid for utmp sessions */
	sessionid.pid = pid;
	sessionid.uid = vuser->uid;
	sessionid.gid = vuser->gid;
	fstrcpy(sessionid.remote_machine, get_remote_machine_name());
	fstrcpy(sessionid.ip_addr_str, client_addr());
	sessionid.connect_start = time(NULL);

	if (!smb_pam_claim_session(sessionid.username, sessionid.id_str,
				   sessionid.hostname)) {
		DEBUG(1,("pam_session rejected the session for %s [%s]\n",
				sessionid.username, sessionid.id_str));

		TALLOC_FREE(rec);
		return False;
	}

	data.dptr = (uint8 *)&sessionid;
	data.dsize = sizeof(sessionid);

	status = rec->store(rec, data, TDB_REPLACE);

	TALLOC_FREE(rec);

	if (!NT_STATUS_IS_OK(status)) {
		DEBUG(1,("session_claim: unable to create session id "
			 "record: %s\n", nt_errstr(status)));
		return False;
	}

	if (lp_utmp()) {
		sys_utmp_claim(sessionid.username, sessionid.hostname,
			       sessionid.ip_addr_str,
			       sessionid.id_str, sessionid.id_num);
	}

	vuser->session_keystr = talloc_strdup(vuser, keystr);
	if (!vuser->session_keystr) {
		DEBUG(0, ("session_claim:  talloc_strdup() failed for session_keystr\n"));
		return False;
	}
	return True;
}

/********************************************************************
 called when a session is destroyed
********************************************************************/

void session_yield(user_struct *vuser)
{
	TDB_DATA key;
	struct sessionid sessionid;
	struct db_context *ctx;
	struct db_record *rec;

	if (!(ctx = session_db_ctx())) return;

	if (!vuser->session_keystr) {
		return;
	}

	key = string_term_tdb_data(vuser->session_keystr);

	if (!(rec = ctx->fetch_locked(ctx, NULL, key))) {
		return;
	}

	if (rec->value.dsize != sizeof(sessionid))
		return;

	memcpy(&sessionid, rec->value.dptr, sizeof(sessionid));

	if (lp_utmp()) {
		sys_utmp_yield(sessionid.username, sessionid.hostname, 
			       sessionid.ip_addr_str,
			       sessionid.id_str, sessionid.id_num);
	}

	smb_pam_close_session(sessionid.username, sessionid.id_str,
			      sessionid.hostname);

	rec->delete_rec(rec);

	TALLOC_FREE(rec);
}

/********************************************************************
********************************************************************/

static bool session_traverse(int (*fn)(struct db_record *db,
				       void *private_data),
			     void *private_data)
{
	struct db_context *ctx;

	if (!(ctx = session_db_ctx())) {
		DEBUG(3, ("No tdb opened\n"));
		return False;
	}

	ctx->traverse_read(ctx, fn, private_data);
	return True;
}

/********************************************************************
********************************************************************/

struct session_list {
	TALLOC_CTX *mem_ctx;
	int count;
	struct sessionid *sessions;
};

static int gather_sessioninfo(struct db_record *rec, void *state)
{
	struct session_list *sesslist = (struct session_list *) state;
	const struct sessionid *current =
		(const struct sessionid *) rec->value.dptr;

	sesslist->sessions = TALLOC_REALLOC_ARRAY(
		sesslist->mem_ctx, sesslist->sessions, struct sessionid,
		sesslist->count+1);

	if (!sesslist->sessions) {
		sesslist->count = 0;
		return -1;
	}

	memcpy(&sesslist->sessions[sesslist->count], current,
	       sizeof(struct sessionid));

	sesslist->count++;

	DEBUG(7,("gather_sessioninfo session from %s@%s\n", 
		 current->username, current->remote_machine));

	return 0;
}

/********************************************************************
********************************************************************/

int list_sessions(TALLOC_CTX *mem_ctx, struct sessionid **session_list)
{
	struct session_list sesslist;

	sesslist.mem_ctx = mem_ctx;
	sesslist.count = 0;
	sesslist.sessions = NULL;
	
	if (!session_traverse(gather_sessioninfo, (void *) &sesslist)) {
		DEBUG(3, ("Session traverse failed\n"));
		SAFE_FREE(sesslist.sessions);
		*session_list = NULL;
		return 0;
	}

	*session_list = sesslist.sessions;
	return sesslist.count;
}