/*-------------------------------------------------------------------------
 *
 * auth.c--
 *	  Routines to handle network authentication
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/libpq/auth.c,v 1.18 1997/11/17 16:10:06 thomas Exp $
 *
 *-------------------------------------------------------------------------
 */
/*
 * INTERFACE ROUTINES
 *
 *	   backend (postmaster) routines:
 *		be_recvauth				receive authentication information
 *		be_setauthsvc			do/do not permit an authentication service
 *		be_getauthsvc			is an authentication service permitted?
 *
 *	 NOTES
 *		To add a new authentication system:
 *		0. If you can't do your authentication over an existing socket,
 *		   you lose -- get ready to hack around this framework instead of
 *		   using it.  Otherwise, you can assume you have an initialized
 *		   and empty connection to work with.  (Please don't leave leftover
 *		   gunk in the connection after the authentication transactions, or
 *		   the POSTGRES routines that follow will be very unhappy.)
 *		1. Write a set of routines that:
 *				let a client figure out what user/principal name to use
 *				send authentication information (client side)
 *				receive authentication information (server side)
 *		   You can include both routines in this file, using #ifdef FRONTEND
 *		   to separate them.
 *		2. Edit libpq/pqcomm.h and assign a MsgType for your protocol.
 *		3. Edit the static "struct authsvc" array and the generic
 *		   {be,fe}_{get,set}auth{name,svc} routines in this file to reflect
 *		   the new service.  You may have to change the arguments of these
 *		   routines; they basically just reflect what Kerberos v4 needs.
 *		4. Hack on src/{,bin}/Makefile.global and src/{backend,libpq}/Makefile
 *		   to add library and CFLAGS hooks -- basically, grep the Makefile
 *		   hierarchy for KRBVERS to see where you need to add things.
 *
 *		Send mail to post_hackers@postgres.Berkeley.EDU if you have to make
 *		any changes to arguments, etc.	Context diffs would be nice, too.
 *
 *		Someday, this cruft will go away and magically be replaced by a
 *		nice interface based on the GSS API or something.  For now, though,
 *		there's no (stable) UNIX security API to work with...
 *
 */
#include <stdio.h>
#include <string.h>
#include <sys/param.h>			/* for MAXHOSTNAMELEN on most */
#ifndef  MAXHOSTNAMELEN
#include <netdb.h>				/* for MAXHOSTNAMELEN on some */
#endif
#include <pwd.h>
#include <ctype.h>				/* isspace() declaration */

#include <sys/types.h>			/* needed by in.h on Ultrix */
#include <netinet/in.h>
#include <arpa/inet.h>

#include <postgres.h>
#include <miscadmin.h>

#include <libpq/auth.h>
#include <libpq/libpq.h>
#include <libpq/libpq-be.h>
#include <libpq/hba.h>
#include <libpq/password.h>

static int	be_getauthsvc(MsgType msgtype);

/*----------------------------------------------------------------
 * common definitions for generic fe/be routines
 *----------------------------------------------------------------
 */

struct authsvc
{
	char		name[16];		/* service nickname (for command line) */
	MsgType		msgtype;		/* startup packet header type */
	int			allowed;		/* initially allowed (before command line
								 * option parsing)? */
};

/*
 * Command-line parsing routines use this structure to map nicknames
 * onto service types (and the startup packets to use with them).
 *
 * Programs receiving an authentication request use this structure to
 * decide which authentication service types are currently permitted.
 * By default, all authentication systems compiled into the system are
 * allowed.  Unauthenticated connections are disallowed unless there
 * isn't any authentication system.
 */

#if defined(HBA)
static int	useHostBasedAuth = 1;

#else
static int	useHostBasedAuth = 0;

#endif

#if defined(KRB4) || defined(KRB5) || defined(HBA)
#define UNAUTH_ALLOWED 0
#else
#define UNAUTH_ALLOWED 1
#endif

static struct authsvc authsvcs[] = {
	{"unauth", STARTUP_UNAUTH_MSG, UNAUTH_ALLOWED},
	{"hba", STARTUP_HBA_MSG, 1},
	{"krb4", STARTUP_KRB4_MSG, 1},
	{"krb5", STARTUP_KRB5_MSG, 1},
#if defined(KRB5)
	{"kerberos", STARTUP_KRB5_MSG, 1},
#else
	{"kerberos", STARTUP_KRB4_MSG, 1},
#endif
	{"password", STARTUP_PASSWORD_MSG, 1}
};

static n_authsvcs = sizeof(authsvcs) / sizeof(struct authsvc);

#ifdef KRB4
/* This has to be ifdef'd out because krb.h does exist.  This needs
   to be fixed.
*/
/*----------------------------------------------------------------
 * MIT Kerberos authentication system - protocol version 4
 *----------------------------------------------------------------
 */

#include <krb.h>

#ifdef FRONTEND
/* moves to src/libpq/fe-auth.c  */
#else							/* !FRONTEND */

/*
 * pg_krb4_recvauth -- server routine to receive authentication information
 *					   from the client
 *
 * Nothing unusual here, except that we compare the username obtained from
 * the client's setup packet to the authenticated name.  (We have to retain
 * the name in the setup packet since we have to retain the ability to handle
 * unauthenticated connections.)
 */
static int
pg_krb4_recvauth(int sock,
				 struct sockaddr_in * laddr,
				 struct sockaddr_in * raddr,
				 char *username)
{
	long		krbopts = 0;	/* one-way authentication */
	KTEXT_ST	clttkt;
	char		instance[INST_SZ];
	AUTH_DAT	auth_data;
	Key_schedule key_sched;
	char		version[KRB_SENDAUTH_VLEN];
	int			status;

	strcpy(instance, "*");		/* don't care, but arg gets expanded
								 * anyway */
	status = krb_recvauth(krbopts,
						  sock,
						  &clttkt,
						  PG_KRB_SRVNAM,
						  instance,
						  raddr,
						  laddr,
						  &auth_data,
						  PG_KRB_SRVTAB,
						  key_sched,
						  version);
	if (status != KSUCCESS)
	{
		sprintf(PQerrormsg,
				"pg_krb4_recvauth: kerberos error: %s\n",
				krb_err_txt[status]);
		fputs(PQerrormsg, stderr);
		pqdebug("%s", PQerrormsg);
		return (STATUS_ERROR);
	}
	if (strncmp(version, PG_KRB4_VERSION, KRB_SENDAUTH_VLEN))
	{
		sprintf(PQerrormsg,
				"pg_krb4_recvauth: protocol version != \"%s\"\n",
				PG_KRB4_VERSION);
		fputs(PQerrormsg, stderr);
		pqdebug("%s", PQerrormsg);
		return (STATUS_ERROR);
	}
	if (username && *username &&
		strncmp(username, auth_data.pname, NAMEDATALEN))
	{
		sprintf(PQerrormsg,
				"pg_krb4_recvauth: name \"%s\" != \"%s\"\n",
				username,
				auth_data.pname);
		fputs(PQerrormsg, stderr);
		pqdebug("%s", PQerrormsg);
		return (STATUS_ERROR);
	}
	return (STATUS_OK);
}

#endif							/* !FRONTEND */

#else
static int
pg_krb4_recvauth(int sock,
				 struct sockaddr_in * laddr,
				 struct sockaddr_in * raddr,
				 char *username)
{
	sprintf(PQerrormsg,
			"pg_krb4_recvauth: Kerberos not implemented on this "
			"server.\n");
	fputs(PQerrormsg, stderr);
	pqdebug("%s", PQerrormsg);

	return (STATUS_ERROR);
}

#endif							/* KRB4 */


#ifdef KRB5
/* This needs to be ifdef'd out because krb5.h doesn't exist.  This needs
   to be fixed.
*/
/*----------------------------------------------------------------
 * MIT Kerberos authentication system - protocol version 5
 *----------------------------------------------------------------
 */

#include <krb5/krb5.h>

/*
 * pg_an_to_ln -- return the local name corresponding to an authentication
 *				  name
 *
 * XXX Assumes that the first aname component is the user name.  This is NOT
 *	   necessarily so, since an aname can actually be something out of your
 *	   worst X.400 nightmare, like
 *		  ORGANIZATION=U. C. Berkeley/NAME=Paul M. Aoki@CS.BERKELEY.EDU
 *	   Note that the MIT an_to_ln code does the same thing if you don't
 *	   provide an aname mapping database...it may be a better idea to use
 *	   krb5_an_to_ln, except that it punts if multiple components are found,
 *	   and we can't afford to punt.
 */
static char *
pg_an_to_ln(char *aname)
{
	char	   *p;

	if ((p = strchr(aname, '/')) || (p = strchr(aname, '@')))
		*p = '\0';
	return (aname);
}

#ifdef FRONTEND
/* moves to src/libpq/fe-auth.c  */
#else							/* !FRONTEND */

/*
 * pg_krb5_recvauth -- server routine to receive authentication information
 *					   from the client
 *
 * We still need to compare the username obtained from the client's setup
 * packet to the authenticated name, as described in pg_krb4_recvauth.	This
 * is a bit more problematic in v5, as described above in pg_an_to_ln.
 *
 * In addition, as described above in pg_krb5_sendauth, we still need to
 * canonicalize the server name v4-style before constructing a principal
 * from it.  Again, this is kind of iffy.
 *
 * Finally, we need to tangle with the fact that v5 doesn't let you explicitly
 * set server keytab file names -- you have to feed lower-level routines a
 * function to retrieve the contents of a keytab, along with a single argument
 * that allows them to open the keytab.  We assume that a server keytab is
 * always a real file so we can allow people to specify their own filenames.
 * (This is important because the POSTGRES keytab needs to be readable by
 * non-root users/groups; the v4 tools used to force you do dump a whole
 * host's worth of keys into a file, effectively forcing you to use one file,
 * but kdb5_edit allows you to select which principals to dump.  Yay!)
 */
static int
pg_krb5_recvauth(int sock,
				 struct sockaddr_in * laddr,
				 struct sockaddr_in * raddr,
				 char *username)
{
	char		servbuf[MAXHOSTNAMELEN + 1 +
									sizeof(PG_KRB_SRVNAM)];
	char	   *hostp,
			   *kusername = (char *) NULL;
	krb5_error_code code;
	krb5_principal client,
				server;
	krb5_address sender_addr;
	krb5_rdreq_key_proc keyproc = (krb5_rdreq_key_proc) NULL;
	krb5_pointer keyprocarg = (krb5_pointer) NULL;

	/*
	 * Set up server side -- since we have no ticket file to make this
	 * easy, we construct our own name and parse it.  See note on
	 * canonicalization above.
	 */
	strcpy(servbuf, PG_KRB_SRVNAM);
	*(hostp = servbuf + (sizeof(PG_KRB_SRVNAM) - 1)) = '/';
	if (gethostname(++hostp, MAXHOSTNAMELEN) < 0)
		strcpy(hostp, "localhost");
	if (hostp = strchr(hostp, '.'))
		*hostp = '\0';
	if (code = krb5_parse_name(servbuf, &server))
	{
		sprintf(PQerrormsg,
			  "pg_krb5_recvauth: Kerberos error %d in krb5_parse_name\n",
				code);
		com_err("pg_krb5_recvauth", code, "in krb5_parse_name");
		return (STATUS_ERROR);
	}

	/*
	 * krb5_sendauth needs this to verify the address in the client
	 * authenticator.
	 */
	sender_addr.addrtype = raddr->sin_family;
	sender_addr.length = sizeof(raddr->sin_addr);
	sender_addr.contents = (krb5_octet *) & (raddr->sin_addr);

	if (strcmp(PG_KRB_SRVTAB, ""))
	{
		keyproc = krb5_kt_read_service_key;
		keyprocarg = PG_KRB_SRVTAB;
	}

	if (code = krb5_recvauth((krb5_pointer) & sock,
							 PG_KRB5_VERSION,
							 server,
							 &sender_addr,
							 (krb5_pointer) NULL,
							 keyproc,
							 keyprocarg,
							 (char *) NULL,
							 (krb5_int32 *) NULL,
							 &client,
							 (krb5_ticket **) NULL,
							 (krb5_authenticator **) NULL))
	{
		sprintf(PQerrormsg,
				"pg_krb5_recvauth: Kerberos error %d in krb5_recvauth\n",
				code);
		com_err("pg_krb5_recvauth", code, "in krb5_recvauth");
		krb5_free_principal(server);
		return (STATUS_ERROR);
	}
	krb5_free_principal(server);

	/*
	 * The "client" structure comes out of the ticket and is therefore
	 * authenticated.  Use it to check the username obtained from the
	 * postmaster startup packet.
	 */
	if ((code = krb5_unparse_name(client, &kusername)))
	{
		sprintf(PQerrormsg,
			"pg_krb5_recvauth: Kerberos error %d in krb5_unparse_name\n",
				code);
		com_err("pg_krb5_recvauth", code, "in krb5_unparse_name");
		krb5_free_principal(client);
		return (STATUS_ERROR);
	}
	krb5_free_principal(client);
	if (!kusername)
	{
		sprintf(PQerrormsg,
				"pg_krb5_recvauth: could not decode username\n");
		fputs(PQerrormsg, stderr);
		pqdebug("%s", PQerrormsg);
		return (STATUS_ERROR);
	}
	kusername = pg_an_to_ln(kusername);
	if (username && strncmp(username, kusername, NAMEDATALEN))
	{
		sprintf(PQerrormsg,
				"pg_krb5_recvauth: name \"%s\" != \"%s\"\n",
				username, kusername);
		fputs(PQerrormsg, stderr);
		pqdebug("%s", PQerrormsg);
		free(kusername);
		return (STATUS_ERROR);
	}
	free(kusername);
	return (STATUS_OK);
}

#endif							/* !FRONTEND */


#else
static int
pg_krb5_recvauth(int sock,
				 struct sockaddr_in * laddr,
				 struct sockaddr_in * raddr,
				 char *username)
{
	sprintf(PQerrormsg,
			"pg_krb5_recvauth: Kerberos not implemented on this "
			"server.\n");
	fputs(PQerrormsg, stderr);
	pqdebug("%s", PQerrormsg);

	return (STATUS_ERROR);
}

#endif							/* KRB5 */

static int
pg_password_recvauth(Port *port, char *database, char *DataDir)
{
	PacketBuf	buf;
	char	   *user,
			   *password;

	if (PacketReceive(port, &buf, BLOCKING) != STATUS_OK)
	{
		sprintf(PQerrormsg,
				"pg_password_recvauth: failed to receive authentication packet.\n");
		fputs(PQerrormsg, stderr);
		pqdebug("%s", PQerrormsg);
		return STATUS_ERROR;
	}

	user = buf.data;
	password = buf.data + strlen(user) + 1;

	return verify_password(user, password, port, database, DataDir);
}

/*
 * be_recvauth -- server demux routine for incoming authentication information
 */
int
be_recvauth(MsgType msgtype_arg, Port *port, char *username, StartupInfo *sp)
{
	MsgType		msgtype;

	/*
	 * A message type of STARTUP_MSG (which once upon a time was the only
	 * startup message type) means user wants us to choose.  "unauth" is
	 * what used to be the only choice, but installation may choose "hba"
	 * instead.
	 */
	if (msgtype_arg == STARTUP_MSG)
	{
		if (useHostBasedAuth)
			msgtype = STARTUP_HBA_MSG;
		else
			msgtype = STARTUP_UNAUTH_MSG;
	}
	else
		msgtype = msgtype_arg;


	if (!username)
	{
		sprintf(PQerrormsg,
				"be_recvauth: no user name passed\n");
		fputs(PQerrormsg, stderr);
		pqdebug("%s", PQerrormsg);
		return (STATUS_ERROR);
	}
	if (!port)
	{
		sprintf(PQerrormsg,
				"be_recvauth: no port structure passed\n");
		fputs(PQerrormsg, stderr);
		pqdebug("%s", PQerrormsg);
		return (STATUS_ERROR);
	}

	switch (msgtype)
	{
		case STARTUP_KRB4_MSG:
			if (!be_getauthsvc(msgtype))
			{
				sprintf(PQerrormsg,
						"be_recvauth: krb4 authentication disallowed\n");
				fputs(PQerrormsg, stderr);
				pqdebug("%s", PQerrormsg);
				return (STATUS_ERROR);
			}
			if (pg_krb4_recvauth(port->sock, (struct sockaddr_in *) &port->laddr,
								 (struct sockaddr_in *) &port->raddr,
								 username) != STATUS_OK)
			{
				sprintf(PQerrormsg,
						"be_recvauth: krb4 authentication failed\n");
				fputs(PQerrormsg, stderr);
				pqdebug("%s", PQerrormsg);
				return (STATUS_ERROR);
			}
			break;
		case STARTUP_KRB5_MSG:
			if (!be_getauthsvc(msgtype))
			{
				sprintf(PQerrormsg,
						"be_recvauth: krb5 authentication disallowed\n");
				fputs(PQerrormsg, stderr);
				pqdebug("%s", PQerrormsg);
				return (STATUS_ERROR);
			}
			if (pg_krb5_recvauth(port->sock, (struct sockaddr_in *) &port->laddr,
								 (struct sockaddr_in *) &port->raddr,
								 username) != STATUS_OK)
			{
				sprintf(PQerrormsg,
						"be_recvauth: krb5 authentication failed\n");
				fputs(PQerrormsg, stderr);
				pqdebug("%s", PQerrormsg);
				return (STATUS_ERROR);
			}
			break;
		case STARTUP_UNAUTH_MSG:
			if (!be_getauthsvc(msgtype))
			{
				sprintf(PQerrormsg,
						"be_recvauth: "
						"unauthenticated connections disallowed\n");
				fputs(PQerrormsg, stderr);
				pqdebug("%s", PQerrormsg);
				return (STATUS_ERROR);
			}
			break;
		case STARTUP_HBA_MSG:
			if (hba_recvauth(port, sp->database, sp->user, DataDir) != STATUS_OK)
			{
				sprintf(PQerrormsg,
					  "be_recvauth: host-based authentication failed\n");
				fputs(PQerrormsg, stderr);
				pqdebug("%s", PQerrormsg);
				return (STATUS_ERROR);
			}
			break;
		case STARTUP_PASSWORD_MSG:
			if (!be_getauthsvc(msgtype))
			{
				sprintf(PQerrormsg,
						"be_recvauth: "
						"plaintext password authentication disallowed\n");
				fputs(PQerrormsg, stderr);
				pqdebug("%s", PQerrormsg);
				return (STATUS_ERROR);
			}
			if (pg_password_recvauth(port, sp->database, DataDir) != STATUS_OK)
			{

				/*
				 * pg_password_recvauth or lower-level routines have
				 * already set
				 */
				/* the error message											 */
				return (STATUS_ERROR);
			}
			break;
		default:
			sprintf(PQerrormsg,
					"be_recvauth: unrecognized message type: %d\n",
					msgtype);
			fputs(PQerrormsg, stderr);
			pqdebug("%s", PQerrormsg);
			return (STATUS_ERROR);
	}
	return (STATUS_OK);
}

/*
 * be_setauthsvc -- enable/disable the authentication services currently
 *					selected for use by the backend
 * be_getauthsvc -- returns whether a particular authentication system
 *					(indicated by its message type) is permitted by the
 *					current selections
 *
 * be_setauthsvc encodes the command-line syntax that
 *		-a "<service-name>"
 * enables a service, whereas
 *		-a "no<service-name>"
 * disables it.
 */
void
be_setauthsvc(char *name)
{
	int			i,
				j;
	int			turnon = 1;

	if (!name)
		return;
	if (!strncmp("no", name, 2))
	{
		turnon = 0;
		name += 2;
	}
	if (name[0] == '\0')
		return;
	for (i = 0; i < n_authsvcs; ++i)
		if (!strcmp(name, authsvcs[i].name))
		{
			for (j = 0; j < n_authsvcs; ++j)
				if (authsvcs[j].msgtype == authsvcs[i].msgtype)
					authsvcs[j].allowed = turnon;
			break;
		}
	if (i == n_authsvcs)
	{
		sprintf(PQerrormsg,
				"be_setauthsvc: invalid name %s, ignoring...\n",
				name);
		fputs(PQerrormsg, stderr);
		pqdebug("%s", PQerrormsg);
	}
	return;
}

static int
be_getauthsvc(MsgType msgtype)
{
	int			i;

	for (i = 0; i < n_authsvcs; ++i)
		if (msgtype == authsvcs[i].msgtype)
			return (authsvcs[i].allowed);
	return (0);
}
