fe-auth.c

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/*-------------------------------------------------------------------------
 *
 * fe-auth.c
 *	   The front-end (client) authorization routines
 *
 * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * NOTE: the error message strings returned by this module must not
 * exceed INITIAL_EXPBUFFER_SIZE (currently 256 bytes).
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-auth.c,v 1.84.2.3 2003/12/20 18:46:02 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */

/*
 * INTERFACE ROUTINES
 *	   frontend (client) routines:
 *		fe_sendauth				send authentication information
 *		fe_getauthname			get user's name according to the client side
 *								of the authentication system
 *		fe_setauthsvc			set frontend authentication service
 *		fe_getauthsvc			get current frontend authentication service
 *
 *
 *
 */

#include "postgres_fe.h"

#ifdef WIN32
#include "win32.h"
#else
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/param.h>			/* for MAXHOSTNAMELEN on most */
#include <sys/socket.h>
#if defined(HAVE_STRUCT_CMSGCRED) || defined(HAVE_STRUCT_FCRED) || defined(HAVE_STRUCT_SOCKCRED)
#include <sys/uio.h>
#include <sys/ucred.h>
#endif
#ifndef  MAXHOSTNAMELEN
#include <netdb.h>				/* for MAXHOSTNAMELEN on some */
#endif
#include <pwd.h>
#endif

#ifdef HAVE_CRYPT_H
#include <crypt.h>
#endif

#include "libpq-fe.h"
#include "libpq-int.h"
#include "fe-auth.h"
#include "libpq/crypt.h"


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

#define STARTUP_MSG		7		/* Initialise a connection */
#define STARTUP_KRB4_MSG	10	/* krb4 session follows */
#define STARTUP_KRB5_MSG	11	/* krb5 session follows */
#define STARTUP_PASSWORD_MSG	14		/* Password follows */

struct authsvc
{
	const char *name;			/* 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.
 */
static const struct authsvc authsvcs[] = {
#ifdef KRB4
	{"krb4", STARTUP_KRB4_MSG, 1},
	{"kerberos", STARTUP_KRB4_MSG, 1},
#endif   /* KRB4 */
#ifdef KRB5
	{"krb5", STARTUP_KRB5_MSG, 1},
	{"kerberos", STARTUP_KRB5_MSG, 1},
#endif   /* KRB5 */
	{UNAUTHNAME, STARTUP_MSG,
#if defined(KRB4) || defined(KRB5)
		0
#else							/* !(KRB4 || KRB5) */
		1
#endif   /* !(KRB4 || KRB5) */
	},
	{"password", STARTUP_PASSWORD_MSG, 0}
};

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

#ifdef KRB4
/*
 * MIT Kerberos authentication system - protocol version 4
 */

#include "krb.h"

/* for some reason, this is not defined in krb.h ... */
extern char *tkt_string(void);

/*
 * pg_krb4_init -- initialization performed before any Kerberos calls are made
 *
 * For v4, all we need to do is make sure the library routines get the right
 * ticket file if we want them to see a special one.  (They will open the file
 * themselves.)
 */
static void
pg_krb4_init()
{
	char	   *realm;
	static int	init_done = 0;

	if (init_done)
		return;
	init_done = 1;

	/*
	 * If the user set PGREALM, then we use a ticket file with a special
	 * name: <usual-ticket-file-name>@<PGREALM-value>
	 */
	if ((realm = getenv("PGREALM")))
	{
		char		tktbuf[MAXPGPATH];

		(void) snprintf(tktbuf, sizeof(tktbuf), "%s@%s", tkt_string(), realm);
		krb_set_tkt_string(tktbuf);
	}
}

/*
 * pg_krb4_authname -- returns a pointer to static space containing whatever
 *					   name the user has authenticated to the system
 *
 * We obtain this information by digging around in the ticket file.
 */
static char *
pg_krb4_authname(char *PQerrormsg)
{
	char		instance[INST_SZ + 1];
	char		realm[REALM_SZ + 1];
	int			status;
	static char name[SNAME_SZ + 1] = "";

	if (name[0])
		return name;

	pg_krb4_init();

	name[SNAME_SZ] = '\0';
	status = krb_get_tf_fullname(tkt_string(), name, instance, realm);
	if (status != KSUCCESS)
	{
		snprintf(PQerrormsg, PQERRORMSG_LENGTH,
				 "pg_krb4_authname: krb_get_tf_fullname: %s\n",
				 krb_err_txt[status]);
		return (char *) NULL;
	}
	return name;
}

/*
 * pg_krb4_sendauth -- client routine to send authentication information to
 *					   the server
 *
 * This routine does not do mutual authentication, nor does it return enough
 * information to do encrypted connections.  But then, if we want to do
 * encrypted connections, we'll have to redesign the whole RPC mechanism
 * anyway.
 *
 * If the user is too lazy to feed us a hostname, we try to come up with
 * something other than "localhost" since the hostname is used as an
 * instance and instance names in v4 databases are usually actual hostnames
 * (canonicalized to omit all domain suffixes).
 */
static int
pg_krb4_sendauth(char *PQerrormsg, int sock,
				 struct sockaddr_in * laddr,
				 struct sockaddr_in * raddr,
				 const char *hostname)
{
	long		krbopts = 0;	/* one-way authentication */
	KTEXT_ST	clttkt;
	int			status;
	char		hostbuf[MAXHOSTNAMELEN];
	const char *realm = getenv("PGREALM");		/* NULL == current realm */

	if (!hostname || !(*hostname))
	{
		if (gethostname(hostbuf, MAXHOSTNAMELEN) < 0)
			strcpy(hostbuf, "localhost");
		hostname = hostbuf;
	}

	pg_krb4_init();

	status = krb_sendauth(krbopts,
						  sock,
						  &clttkt,
						  PG_KRB_SRVNAM,
						  hostname,
						  realm,
						  (u_long) 0,
						  (MSG_DAT *) NULL,
						  (CREDENTIALS *) NULL,
						  NULL,
						  laddr,
						  raddr,
						  PG_KRB4_VERSION);
	if (status != KSUCCESS)
	{
		snprintf(PQerrormsg, PQERRORMSG_LENGTH,
				 libpq_gettext("Kerberos 4 error: %s\n"),
				 krb_err_txt[status]);
		return STATUS_ERROR;
	}
	return STATUS_OK;
}
#endif   /* KRB4 */

#ifdef KRB5
/*
 * MIT Kerberos authentication system - protocol version 5
 */

#include <krb5.h>
#include <com_err.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. [e-mail]
 *	   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;
}


/*
 * Various krb5 state which is not connection specific, and a flag to
 * indicate whether we have initialised it yet.
 */
static int	pg_krb5_initialised;
static krb5_context pg_krb5_context;
static krb5_ccache pg_krb5_ccache;
static krb5_principal pg_krb5_client;
static char *pg_krb5_name;


static int
pg_krb5_init(char *PQerrormsg)
{
	krb5_error_code retval;

	if (pg_krb5_initialised)
		return STATUS_OK;

	retval = krb5_init_context(&pg_krb5_context);
	if (retval)
	{
		snprintf(PQerrormsg, PQERRORMSG_LENGTH,
				 "pg_krb5_init: krb5_init_context: %s\n",
				 error_message(retval));
		return STATUS_ERROR;
	}

	retval = krb5_cc_default(pg_krb5_context, &pg_krb5_ccache);
	if (retval)
	{
		snprintf(PQerrormsg, PQERRORMSG_LENGTH,
				 "pg_krb5_init: krb5_cc_default: %s\n",
				 error_message(retval));
		krb5_free_context(pg_krb5_context);
		return STATUS_ERROR;
	}

	retval = krb5_cc_get_principal(pg_krb5_context, pg_krb5_ccache,
								   &pg_krb5_client);
	if (retval)
	{
		snprintf(PQerrormsg, PQERRORMSG_LENGTH,
				 "pg_krb5_init: krb5_cc_get_principal: %s\n",
				 error_message(retval));
		krb5_cc_close(pg_krb5_context, pg_krb5_ccache);
		krb5_free_context(pg_krb5_context);
		return STATUS_ERROR;
	}

	retval = krb5_unparse_name(pg_krb5_context, pg_krb5_client, &pg_krb5_name);
	if (retval)
	{
		snprintf(PQerrormsg, PQERRORMSG_LENGTH,
				 "pg_krb5_init: krb5_unparse_name: %s\n",
				 error_message(retval));
		krb5_free_principal(pg_krb5_context, pg_krb5_client);
		krb5_cc_close(pg_krb5_context, pg_krb5_ccache);
		krb5_free_context(pg_krb5_context);
		return STATUS_ERROR;
	}

	pg_krb5_name = pg_an_to_ln(pg_krb5_name);

	pg_krb5_initialised = 1;
	return STATUS_OK;
}


/*
 * pg_krb5_authname -- returns a pointer to static space containing whatever
 *					   name the user has authenticated to the system
  */
static const char *
pg_krb5_authname(char *PQerrormsg)
{
	if (pg_krb5_init(PQerrormsg) != STATUS_OK)
		return NULL;

	return pg_krb5_name;
}


/*
 * pg_krb5_sendauth -- client routine to send authentication information to
 *					   the server
 */
static int
pg_krb5_sendauth(char *PQerrormsg, int sock, const char *hostname)
{
	krb5_error_code retval;
	int			ret;
	krb5_principal server;
	krb5_auth_context auth_context = NULL;
	krb5_error *err_ret = NULL;
	int			flags;

	ret = pg_krb5_init(PQerrormsg);
	if (ret != STATUS_OK)
		return ret;

	retval = krb5_sname_to_principal(pg_krb5_context, hostname, PG_KRB_SRVNAM,
									 KRB5_NT_SRV_HST, &server);
	if (retval)
	{
		snprintf(PQerrormsg, PQERRORMSG_LENGTH,
				 "pg_krb5_sendauth: krb5_sname_to_principal: %s\n",
				 error_message(retval));
		return STATUS_ERROR;
	}