auth.c

Unix/Linux NAPT协议解析源码

/*
 * auth.c - PPP authentication and phase control.
 *
 * Copyright (c) 1993 The Australian National University.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the Australian National University.  The name of the University
 * may not be used to endorse or promote products derived from this
 * software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * Copyright (c) 1989 Carnegie Mellon University.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by Carnegie Mellon University.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#ifndef lint
static char rcsid[] = "$Id: auth.c,v 1.15 1995/05/19 03:16:12 paulus Exp $";
#endif

#include <stdio.h>
#include <stddef.h>
/* #include <stdlib.h> */
#include <syslog.h>
#include <pwd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>

#ifdef HAS_SHADOW
#include <shadow.h>
#include <shadow/pwauth.h>
#ifndef PW_PPP
#define PW_PPP PW_LOGIN
#endif
#endif

#include "pppd.h"
#include "fsm.h"
#include "lcp.h"
#include "upap.h"
#include "chap.h"
#include "ipcp.h"
#include "ccp.h"
#include "pathnames.h"

#if defined(sun) && defined(sparc)
#include <alloca.h>
#endif /*sparc*/

extern char *crypt _P((const char *, const char *));

/* Used for storing a sequence of words.  Usually malloced. */
struct wordlist {
    struct wordlist	*next;
    char		word[1];
};

/* Bits in scan_authfile return value */
#define NONWILD_SERVER	1
#define NONWILD_CLIENT	2

#define ISWILD(word)	(word[0] == '*' && word[1] == 0)

#undef FALSE
#define FALSE	0
#undef TRUE
#define TRUE	1

#ifndef IN_LOOPBACKNET
#define IN_LOOPBACKNET 127
#endif

#ifndef IN_MULTICAST
#define IN_MULTICAST(i) (((long)(i) & 0xf0000000) == 0xe0000000)
#endif

#ifndef IN_BADCLASS
#define IN_BADCLASS(i) (((long)(i) & 0xf0000000) == 0xf0000000)
#endif

/* Records which authentication operations haven't completed yet. */
static int auth_pending[NUM_PPP];
static int logged_in;
static struct wordlist *addresses[NUM_PPP];

/* Bits in auth_pending[] */
#define UPAP_WITHPEER	1
#define UPAP_PEER	2
#define CHAP_WITHPEER	4
#define CHAP_PEER	8

/* Prototypes */
void check_access __P((FILE *, char *));

static void network_phase __P((int));
static int  login __P((char *, char *, char **, int *));
static void logout __P((void));
static int  null_login __P((int));
static int  get_upap_passwd __P((void));
static int  have_upap_secret __P((void));
static int  have_chap_secret __P((char *, char *));
static int  scan_authfile __P((FILE *, char *, char *, char *, int, 
				  struct wordlist **, char *));
static void free_wordlist __P((struct wordlist *));

/*
 * An Open on LCP has requested a change from Dead to Establish phase.
 * Do what's necessary to bring the physical layer up.
 */
void
link_required(unit)
    int unit;
{
}

/*
 * LCP has terminated the link; go to the Dead phase and take the
 * physical layer down.
 */
void
link_terminated(unit)
    int unit;
{
    if (phase == PHASE_DEAD)
	return;
    if (logged_in)
	logout();
    phase = PHASE_DEAD;
    do_syslog(LOG_NOTICE, "Connection terminated.");
    if (ppp_exit)
	slirp_exit(0);
}

/*
 * LCP has gone down; it will either die or try to re-establish.
 */
void
link_down(unit)
    int unit;
{
    ipcp_close(0);
    ccp_close(0);
    phase = PHASE_TERMINATE;
}

/*
 * The link is established.
 * Proceed to the Dead, Authenticate or Network phase as appropriate.
 */
void
link_established(unit)
    int unit;
{
    int auth;
    lcp_options *wo = &lcp_wantoptions[unit];
    lcp_options *go = &lcp_gotoptions[unit];
    lcp_options *ho = &lcp_hisoptions[unit];

    if (auth_required && !(go->neg_chap || go->neg_upap)) {
	/*
	 * We wanted the peer to authenticate itself, and it refused:
	 * treat it as though it authenticated with PAP using a username
	 * of "" and a password of "".  If that's not OK, boot it out.
	 */
	if (!wo->neg_upap || !null_login(unit)) {
	    do_syslog(LOG_WARNING, "peer refused to authenticate");
	    lcp_close(unit);
	    phase = PHASE_TERMINATE;
	    return;
	}
    }

    phase = PHASE_AUTHENTICATE;
    auth = 0;
    if (go->neg_chap) {
	ChapAuthPeer(unit, our_name, go->chap_mdtype);
	auth |= CHAP_PEER;
    } else if (go->neg_upap) {
	upap_authpeer(unit);
	auth |= UPAP_PEER;
    }
    if (ho->neg_chap) {
	ChapAuthWithPeer(unit, our_name, ho->chap_mdtype);
	auth |= CHAP_WITHPEER;
    } else if (ho->neg_upap) {
	upap_authwithpeer(unit, user, passwd);
	auth |= UPAP_WITHPEER;
    }
    auth_pending[unit] = auth;

    if (!auth)
	network_phase(unit);
}

/*
 * Proceed to the network phase.
 */
static void
network_phase(unit)
    int unit;
{
    phase = PHASE_NETWORK;
    ipcp_open(unit);
    ccp_open(unit);
}

/*
 * The peer has failed to authenticate himself using `protocol'.
 */
void
auth_peer_fail(unit, protocol)
    int unit, protocol;
{
    /*
     * Authentication failure: take the link down
     */
    lcp_close(unit);
    phase = PHASE_TERMINATE;
}

/*
 * The peer has been successfully authenticated using `protocol'.
 */
void
auth_peer_success(unit, protocol)
    int unit, protocol;
{
    int bit;

    switch (protocol) {
    case PPP_CHAP:
	bit = CHAP_PEER;
	break;
    case PPP_PAP:
	bit = UPAP_PEER;
	break;
    default:
	do_syslog(LOG_WARNING, "auth_peer_success: unknown protocol %x",
	       protocol);
	return;
    }

    /*
     * If there is no more authentication still to be done,
     * proceed to the network phase.
     */
    if ((auth_pending[unit] &= ~bit) == 0) {
	phase = PHASE_NETWORK;
	ipcp_open(unit);
	ccp_open(unit);
    }
}

/*
 * We have failed to authenticate ourselves to the peer using `protocol'.
 */
void
auth_withpeer_fail(unit, protocol)
    int unit, protocol;
{
    /*
     * We've failed to authenticate ourselves to our peer.
     * He'll probably take the link down, and there's not much
     * we can do except wait for that.
     */
}

/*
 * We have successfully authenticated ourselves with the peer using `protocol'.
 */
void
auth_withpeer_success(unit, protocol)
    int unit, protocol;
{
    int bit;

    switch (protocol) {
    case PPP_CHAP:
	bit = CHAP_WITHPEER;
	break;
    case PPP_PAP:
	bit = UPAP_WITHPEER;
	break;
    default:
	do_syslog(LOG_WARNING, "auth_peer_success: unknown protocol %x",
	       protocol);
	bit = 0;
    }

    /*
     * If there is no more authentication still being done,
     * proceed to the network phase.
     */
    if ((auth_pending[unit] &= ~bit) == 0)
	network_phase(unit);
}


/*
 * check_auth_options - called to check authentication options.
 */
void
check_auth_options()
{
    lcp_options *wo = &lcp_wantoptions[0];
    lcp_options *ao = &lcp_allowoptions[0];

    /* Default our_name to hostname, and user to our_name */
    if (our_name[0] == 0 || usehostname)
	strncpy2(our_name, hostname, sizeof(our_name));
    if (user[0] == 0)
	strncpy2(user, our_name, sizeof(user));

    /* If authentication is required, ask peer for CHAP or PAP. */
    if (auth_required && !wo->neg_chap && !wo->neg_upap) {
	wo->neg_chap = 1;
	wo->neg_upap = 1;
    }

    /*
     * Check whether we have appropriate secrets to use
     * to authenticate ourselves and/or the peer.
     */
    if (ao->neg_upap && passwd[0] == 0 && !get_upap_passwd())
	ao->neg_upap = 0;
    if (wo->neg_upap && !uselogin && !have_upap_secret())
	wo->neg_upap = 0;
    if (ao->neg_chap && !have_chap_secret(our_name, remote_name))
	ao->neg_chap = 0;
    if (wo->neg_chap && !have_chap_secret(remote_name, our_name))
	wo->neg_chap = 0;

    if (auth_required && !wo->neg_chap && !wo->neg_upap) {
	fprintf(stderr, "\
pppd: peer authentication required but no authentication files accessible\n");
	exit(1);
    }

}


/*
 * check_passwd - Check the user name and passwd against the PAP secrets
 * file.  If requested, also check against the system password database,
 * and login the user if OK.
 *
 * returns:
 *	UPAP_AUTHNAK: Authentication failed.
 *	UPAP_AUTHACK: Authentication succeeded.
 * In either case, msg points to an appropriate message.
 */
int
check_passwd(unit, auser, userlen, apasswd, passwdlen, msg, msglen)
    int unit;
    char *auser;
    int userlen;
    char *apasswd;
    int passwdlen;
    char **msg;
    int *msglen;
{
    int ret;
    char *filename;
    FILE *f;
    struct wordlist *addrs;
    char passwd[256], user[256];
    char secret[MAXWORDLEN];
    static int attempts = 0;

    /*
     * Make copies of apasswd and auser, then null-terminate them.
     */
    BCOPY(apasswd, passwd, passwdlen);
    passwd[passwdlen] = '\0';
    BCOPY(auser, user, userlen);
    user[userlen] = '\0';

    /*
     * Open the file of upap secrets and scan for a suitable secret
     * for authenticating this user.
     */
    filename = _PATH_UPAPFILE;
    addrs = NULL;
    ret = UPAP_AUTHACK;
    f = fopen(filename, "r");
    if (f == NULL) {
	if (!uselogin) {
	    do_syslog(LOG_ERR, "Can't open upap password file %s: %m", filename);
	    ret = UPAP_AUTHNAK;
	}

    } else {
	check_access(f, filename);
	if (scan_authfile(f, user, our_name, secret, sizeof(secret), &addrs, filename) < 0
	    || (secret[0] != 0 && (cryptpap || strcmp(passwd, secret) != 0)
		&& strcmp(crypt(passwd, secret), secret) != 0)) {
	    do_syslog(LOG_WARNING, "upap authentication failure for %s", user);
	    ret = UPAP_AUTHNAK;
	}
	fclose(f);
    }

    if (uselogin && ret == UPAP_AUTHACK) {
	ret = login(user, passwd, msg, msglen);
	if (ret == UPAP_AUTHNAK) {
	    do_syslog(LOG_WARNING, "upap login failure for %s", user);
	}
    }

    if (ret == UPAP_AUTHNAK) {
	*msg = "Login incorrect";
	*msglen = strlen(*msg);
	/*
	 * Frustrate passwd stealer programs.
	 * Allow 10 tries, but start backing off after 3 (stolen from login).
	 * On 10'th, drop the connection.
	 */
	if (attempts++ >= 10) {
	    do_syslog(LOG_WARNING, "%d LOGIN FAILURES ON %s, %s",
		   attempts, devnam, user);
	    quit();
	}
	if (attempts > 3)
	    sleep((u_int) (attempts - 3) * 5);
	if (addrs != NULL)
	    free_wordlist(addrs);

    } else {
	attempts = 0;			/* Reset count */
	*msg = "Login ok";
	*msglen = strlen(*msg);
	if (addresses[unit] != NULL)
	    free_wordlist(addresses[unit]);
	addresses[unit] = addrs;
    }

    return ret;
}


/*
 * login - Check the user name and password against the system
 * password database, and login the user if OK.
 *
 * returns:
 *	UPAP_AUTHNAK: Login failed.
 *	UPAP_AUTHACK: Login succeeded.
 * In either case, msg points to an appropriate message.
 */
static int
login(user, passwd, msg, msglen)
    char *user;
    char *passwd;
    char **msg;
    int *msglen;
{
    struct passwd *pw;
    char *epasswd;
    char *tty;