auth.c

经典的ppp程序

/*
 * 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.
 */

#define RCSID	"$Id: auth.c,v 1.69 2001/03/12 22:50:01 paulus Exp $"

#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
#include <pwd.h>
#include <grp.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <utmp.h>
#include <fcntl.h>
#if defined(_PATH_LASTLOG) && defined(_linux_)
#include <lastlog.h>
#endif

#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#ifdef USE_PAM
#include <security/pam_appl.h>
#endif

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

#include "pppd.h"
#include "fsm.h"
#include "lcp.h"
#include "ipcp.h"
#include "upap.h"
#include "chap.h"
#ifdef CBCP_SUPPORT
#include "cbcp.h"
#endif
#include "pathnames.h"

static const char rcsid[] = RCSID;

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

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

/* The name by which the peer authenticated itself to us. */
char peer_authname[MAXNAMELEN];

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

/* Set if we have successfully called plogin() */
static int logged_in;

/* List of addresses which the peer may use. */
static struct permitted_ip *addresses[NUM_PPP];

/* Wordlist giving addresses which the peer may use
   without authenticating itself. */
static struct wordlist *noauth_addrs;

/* Extra options to apply, from the secrets file entry for the peer. */
static struct wordlist *extra_options;

/* Number of network protocols which we have opened. */
static int num_np_open;

/* Number of network protocols which have come up. */
static int num_np_up;

/* Set if we got the contents of passwd[] from the pap-secrets file. */
static int passwd_from_file;

/* Set if we require authentication only because we have a default route. */
static bool default_auth;

/* Hook to enable a plugin to control the idle time limit */
int (*idle_time_hook) __P((struct ppp_idle *)) = NULL;

/* Hook for a plugin to say whether we can possibly authenticate any peer */
int (*pap_check_hook) __P((void)) = NULL;

/* Hook for a plugin to check the PAP user and password */
int (*pap_auth_hook) __P((char *user, char *passwd, char **msgp,
			  struct wordlist **paddrs,
			  struct wordlist **popts)) = NULL;

/* Hook for a plugin to know about the PAP user logout */
void (*pap_logout_hook) __P((void)) = NULL;

/* Hook for a plugin to get the PAP password for authenticating us */
int (*pap_passwd_hook) __P((char *user, char *passwd)) = NULL;

/*
 * This is used to ensure that we don't start an auth-up/down
 * script while one is already running.
 */
enum script_state {
    s_down,
    s_up
};

static enum script_state auth_state = s_down;
static enum script_state auth_script_state = s_down;
static pid_t auth_script_pid = 0;

static int used_login;		/* peer authenticated against login database */

/*
 * Option variables.
 */
bool uselogin = 0;		/* Use /etc/passwd for checking PAP */
bool cryptpap = 0;		/* Passwords in pap-secrets are encrypted */
bool refuse_pap = 0;		/* Don't wanna auth. ourselves with PAP */
bool refuse_chap = 0;		/* Don't wanna auth. ourselves with CHAP */
bool usehostname = 0;		/* Use hostname for our_name */
bool auth_required = 0;		/* Always require authentication from peer */
bool allow_any_ip = 0;		/* Allow peer to use any IP address */
bool explicit_remote = 0;	/* User specified explicit remote name */
char remote_name[MAXNAMELEN];	/* Peer's name for authentication */

static char *uafname;		/* name of most recent +ua file */

/* Bits in auth_pending[] */
#define PAP_WITHPEER	1
#define PAP_PEER	2
#define CHAP_WITHPEER	4
#define CHAP_PEER	8

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

/* Prototypes for procedures local to this file. */

static void network_phase __P((int));
static void check_idle __P((void *));
static void connect_time_expired __P((void *));
static int  plogin __P((char *, char *, char **));
static void plogout __P((void));
static int  null_login __P((int));
static int  get_pap_passwd __P((char *));
static int  have_pap_secret __P((int *));
static int  have_chap_secret __P((char *, char *, int, int *));
static int  ip_addr_check __P((u_int32_t, struct permitted_ip *));
static int  scan_authfile __P((FILE *, char *, char *, char *,
			       struct wordlist **, struct wordlist **,
			       char *));
static void free_wordlist __P((struct wordlist *));
static void auth_script __P((char *));
static void auth_script_done __P((void *));
static void set_allowed_addrs __P((int, struct wordlist *, struct wordlist *));
static int  some_ip_ok __P((struct wordlist *));
static int  setupapfile __P((char **));
static int  privgroup __P((char **));
static int  set_noauth_addr __P((char **));
static void check_access __P((FILE *, char *));
static int  wordlist_count __P((struct wordlist *));

/*
 * Authentication-related options.
 */
option_t auth_options[] = {
    { "auth", o_bool, &auth_required,
      "Require authentication from peer", OPT_PRIO | 1 },
    { "noauth", o_bool, &auth_required,
      "Don't require peer to authenticate", OPT_PRIOSUB | OPT_PRIV,
      &allow_any_ip },
    { "require-pap", o_bool, &lcp_wantoptions[0].neg_upap,
      "Require PAP authentication from peer",
      OPT_PRIOSUB | 1, &auth_required },
    { "+pap", o_bool, &lcp_wantoptions[0].neg_upap,
      "Require PAP authentication from peer",
      OPT_ALIAS | OPT_PRIOSUB | 1, &auth_required },
    { "require-chap", o_bool, &lcp_wantoptions[0].neg_chap,
      "Require CHAP authentication from peer",
      OPT_PRIOSUB | 1, &auth_required },
    { "+chap", o_bool, &lcp_wantoptions[0].neg_chap,
      "Require CHAP authentication from peer",
      OPT_ALIAS | OPT_PRIOSUB | 1, &auth_required },

    { "refuse-pap", o_bool, &refuse_pap,
      "Don't agree to auth to peer with PAP", 1 },
    { "-pap", o_bool, &refuse_pap,
      "Don't allow PAP authentication with peer", OPT_ALIAS | 1 },

    { "refuse-chap", o_bool, &refuse_chap,
      "Don't agree to auth to peer with CHAP", 1 },
    { "-chap", o_bool, &refuse_chap,
      "Don't allow CHAP authentication with peer", OPT_ALIAS | 1 },

    { "name", o_string, our_name,
      "Set local name for authentication",
      OPT_PRIO | OPT_PRIV | OPT_STATIC, NULL, MAXNAMELEN },

    { "+ua", o_special, (void *)setupapfile,
      "Get PAP user and password from file",
      OPT_PRIO | OPT_A2STRVAL, &uafname },

    { "user", o_string, user,
      "Set name for auth with peer", OPT_PRIO | OPT_STATIC, NULL, MAXNAMELEN },

    { "password", o_string, passwd,
      "Password for authenticating us to the peer",
      OPT_PRIO | OPT_STATIC | OPT_HIDE, NULL, MAXSECRETLEN },

    { "usehostname", o_bool, &usehostname,
      "Must use hostname for authentication", 1 },

    { "remotename", o_string, remote_name,
      "Set remote name for authentication", OPT_PRIO | OPT_STATIC,
      &explicit_remote, MAXNAMELEN },

    { "login", o_bool, &uselogin,
      "Use system password database for PAP", 1 },

    { "papcrypt", o_bool, &cryptpap,
      "PAP passwords are encrypted", 1 },

    { "privgroup", o_special, (void *)privgroup,
      "Allow group members to use privileged options", OPT_PRIV | OPT_A2LIST },

    { "allow-ip", o_special, (void *)set_noauth_addr,
      "Set IP address(es) which can be used without authentication",
      OPT_PRIV | OPT_A2LIST },

    { NULL }
};

/*
 * setupapfile - specifies UPAP info for authenticating with peer.
 */
static int
setupapfile(argv)
    char **argv;
{
    FILE *ufile;
    int l;
    char u[MAXNAMELEN], p[MAXSECRETLEN];
    char *fname;

    lcp_allowoptions[0].neg_upap = 1;

    /* open user info file */
    fname = strdup(*argv);
    if (fname == NULL)
	novm("+ua file name");
    seteuid(getuid());
    ufile = fopen(fname, "r");
    seteuid(0);
    if (ufile == NULL) {
	option_error("unable to open user login data file %s", fname);
	return 0;
    }
    check_access(ufile, fname);
    uafname = fname;

    /* get username */
    if (fgets(u, MAXNAMELEN - 1, ufile) == NULL
	|| fgets(p, MAXSECRETLEN - 1, ufile) == NULL){
	option_error("unable to read user login data file %s", fname);
	return 0;
    }
    fclose(ufile);

    /* get rid of newlines */
    l = strlen(u);
    if (l > 0 && u[l-1] == '\n')
	u[l-1] = 0;
    l = strlen(p);
    if (l > 0 && p[l-1] == '\n')
	p[l-1] = 0;

    if (override_value("user", option_priority, fname))
	strlcpy(user, u, sizeof(user));
    if (override_value("passwd", option_priority, fname))
	strlcpy(passwd, p, sizeof(passwd));

    return (1);
}


/*
 * privgroup - allow members of the group to have privileged access.
 */
static int
privgroup(argv)
    char **argv;
{
    struct group *g;
    int i;

    g = getgrnam(*argv);
    if (g == 0) {
	option_error("group %s is unknown", *argv);
	return 0;
    }
    for (i = 0; i < ngroups; ++i) {
	if (groups[i] == g->gr_gid) {
	    privileged = 1;
	    break;
	}
    }
    return 1;
}


/*
 * set_noauth_addr - set address(es) that can be used without authentication.
 * Equivalent to specifying an entry like `"" * "" addr' in pap-secrets.
 */
static int
set_noauth_addr(argv)
    char **argv;
{
    char *addr = *argv;
    int l = strlen(addr) + 1;
    struct wordlist *wp;

    wp = (struct wordlist *) malloc(sizeof(struct wordlist) + l);
    if (wp == NULL)
	novm("allow-ip argument");
    wp->word = (char *) (wp + 1);
    wp->next = noauth_addrs;
    BCOPY(addr, wp->word, l);
    noauth_addrs = wp;
    return 1;
}


/*
 * 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 (pap_logout_hook) {
	pap_logout_hook();
    } else {
	if (logged_in)
	    plogout();
    }
    new_phase(PHASE_DEAD);
    notice("Connection terminated.");
}

/*
 * LCP has gone down; it will either die or try to re-establish.
 */
void
link_down(unit)
    int unit;
{
    int i;
    struct protent *protp;

    auth_state = s_down;
    if (auth_script_state == s_up && auth_script_pid == 0) {
	update_link_stats(unit);
	auth_script_state = s_down;
	auth_script(_PATH_AUTHDOWN);
    }
    for (i = 0; (protp = protocols[i]) != NULL; ++i) {
	if (!protp->enabled_flag)
	    continue;
        if (protp->protocol != PPP_LCP && protp->lowerdown != NULL)
	    (*protp->lowerdown)(unit);
        if (protp->protocol < 0xC000 && protp->close != NULL)
	    (*protp->close)(unit, "LCP down");
    }
    num_np_open = 0;
    num_np_up = 0;
    if (phase != PHASE_DEAD)
	new_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];
    int i;
    struct protent *protp;

    /*
     * Tell higher-level protocols that LCP is up.
     */
    for (i = 0; (protp = protocols[i]) != NULL; ++i)
        if (protp->protocol != PPP_LCP && protp->enabled_flag
	    && protp->lowerup != NULL)
	    (*protp->lowerup)(unit);

    if (auth_required && !(go->neg_chap || go->neg_upap)) {
	/*
	 * We wanted the peer to authenticate itself, and it refused:
	 * if we have some address(es) it can use without auth, fine,
	 * otherwise 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 (noauth_addrs != NULL) {
	    set_allowed_addrs(unit, NULL, NULL);
	} else if (!wo->neg_upap || uselogin || !null_login(unit)) {
	    warn("peer refused to authenticate: terminating link");
	    lcp_close(unit, "peer refused to authenticate");
	    status = EXIT_PEER_AUTH_FAILED;
	    return;
	}
    }

    new_phase(PHASE_AUTHENTICATE);
    used_login = 0;
    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 |= PAP_PEER;
    }
    if (ho->neg_chap) {
	ChapAuthWithPeer(unit, user, ho->chap_mdtype);
	auth |= CHAP_WITHPEER;
    } else if (ho->neg_upap) {
	if (passwd[0] == 0) {
	    passwd_from_file = 1;
	    if (!get_pap_passwd(passwd))
		error("No secret found for PAP login");
	}