auth.c

Unix/Linux NAPT协议解析源码

#ifdef HAS_SHADOW
    struct spwd *spwd;
    struct spwd *getspnam();
#endif

    if ((pw = getpwnam(user)) == NULL) {
	return (UPAP_AUTHNAK);
    }

#ifdef HAS_SHADOW
    if ((spwd = getspnam(user)) == NULL) {
        pw->pw_passwd = "";
    } else {
	pw->pw_passwd = spwd->sp_pwdp;
    }
#endif

    /*
     * XXX If no passwd, let them login without one.
     */
    if (pw->pw_passwd == '\0') {
	return (UPAP_AUTHACK);
    }

#ifdef HAS_SHADOW
    if ((pw->pw_passwd && pw->pw_passwd[0] == '@'
	 && pw_auth (pw->pw_passwd+1, pw->pw_name, PW_PPP, NULL))
	|| !valid (passwd, pw)) {
	return (UPAP_AUTHNAK);
    }
#else
    epasswd = crypt(passwd, pw->pw_passwd);
    if (strcmp(epasswd, pw->pw_passwd)) {
	return (UPAP_AUTHNAK);
    }
#endif

    do_syslog(LOG_INFO, "user %s logged in", user);

    /*
     * Write a wtmp entry for this user.
     */
    tty = strrchr(devnam, '/');
    if (tty == NULL)
	tty = devnam;
    else
	tty++;
#ifdef LOGWTMP_WORKED	
    logwtmp(tty, user, "");   /* Add wtmp login entry -- which just returned 1 */
#endif
    logged_in = TRUE;

    return (UPAP_AUTHACK);
}

/*
 * logout - Logout the user.
 */
static void
logout()
{
    char *tty;

    tty = strrchr(devnam, '/');
    if (tty == NULL)
	tty = devnam;
    else
	tty++;
#ifdef LOGWTMP_WORKED
    logwtmp(tty, "", "");	/*	Wipe out wtmp logout entry  */
#endif
    logged_in = FALSE;
}


/*
 * null_login - Check if a username of "" and a password of "" are
 * acceptable, and iff so, set the list of acceptable IP addresses
 * and return 1.
 */
static int
null_login(unit)
    int unit;
{
    char *filename;
    FILE *f;
    int i, ret;
    struct wordlist *addrs;
    char secret[MAXWORDLEN];

    /*
     * Open the file of upap secrets and scan for a suitable secret.
     * We don't accept a wildcard client.
     */
    filename = _PATH_UPAPFILE;
    addrs = NULL;
    f = fopen(filename, "r");
    if (f == NULL)
	return 0;
    check_access(f, filename);

    i = scan_authfile(f, "", our_name, secret, sizeof(secret), &addrs, filename);
    ret = i >= 0 && (i & NONWILD_CLIENT) != 0 && secret[0] == 0;

    if (ret) {
	if (addresses[unit] != NULL)
	    free_wordlist(addresses[unit]);
	addresses[unit] = addrs;
    }

    fclose(f);
    return ret;
}


/*
 * get_upap_passwd - get a password for authenticating ourselves with
 * our peer using PAP.  Returns 1 on success, 0 if no suitable password
 * could be found.
 */
static int
get_upap_passwd()
{
    char *filename;
    FILE *f;
    struct wordlist *addrs;
    char secret[MAXWORDLEN];

    filename = _PATH_UPAPFILE;
    addrs = NULL;
    f = fopen(filename, "r");
    if (f == NULL)
	return 0;
    check_access(f, filename);
    if (scan_authfile(f, user, remote_name, secret, sizeof(secret), NULL, filename) < 0)
	return 0;
    strncpy(passwd, secret, MAXSECRETLEN);
    passwd[MAXSECRETLEN-1] = 0;
    return 1;
}


/*
 * have_upap_secret - check whether we have a PAP file with any
 * secrets that we could possibly use for authenticating the peer.
 */
static int
have_upap_secret()
{
    FILE *f;
    int ret;
    char *filename;

    filename = _PATH_UPAPFILE;
    f = fopen(filename, "r");
    if (f == NULL)
	return 0;

    ret = scan_authfile(f, NULL, our_name, NULL, 0, NULL, filename);
    fclose(f);
    if (ret < 0)
	return 0;

    return 1;
}


/*
 * have_chap_secret - check whether we have a CHAP file with a
 * secret that we could possibly use for authenticating `client'
 * on `server'.  Either can be the null string, meaning we don't
 * know the identity yet.
 */
static int
have_chap_secret(client, server)
    char *client;
    char *server;
{
    FILE *f;
    int ret;
    char *filename;

    filename = _PATH_CHAPFILE;
    f = fopen(filename, "r");
    if (f == NULL)
	return 0;

    if (client[0] == 0)
	client = NULL;
    else if (server[0] == 0)
	server = NULL;

    ret = scan_authfile(f, client, server, NULL, 0, NULL, filename);
    fclose(f);
    if (ret < 0)
	return 0;

    return 1;
}


/*
 * get_secret - open the CHAP secret file and return the secret
 * for authenticating the given client on the given server.
 * (We could be either client or server).
 */
int
get_secret(unit, client, server, secret, secret_len, save_addrs)
    int unit;
    char *client;
    char *server;
    char *secret;
    int *secret_len;
    int save_addrs;
{
    FILE *f;
    int ret, len;
    char *filename;
    struct wordlist *addrs;
    char secbuf[MAXWORDLEN];

    filename = _PATH_CHAPFILE;
    addrs = NULL;
    secbuf[0] = 0;

    f = fopen(filename, "r");
    if (f == NULL) {
	do_syslog(LOG_ERR, "Can't open chap secret file %s: %m", filename);
	return 0;
    }
    check_access(f, filename);

    ret = scan_authfile(f, client, server, secbuf, sizeof(secbuf), &addrs, filename);
    fclose(f);
    if (ret < 0)
	return 0;

    if (save_addrs) {
	if (addresses[unit] != NULL)
	    free_wordlist(addresses[unit]);
	addresses[unit] = addrs;
    }

    len = strlen(secbuf);
    if (len > MAXSECRETLEN) {
	do_syslog(LOG_ERR, "Secret for %s on %s is too long", client, server);
	len = MAXSECRETLEN;
    }
    BCOPY(secbuf, secret, len);
    *secret_len = len;

    return 1;
}

/*
 * auth_ip_addr - check whether the peer is authorized to use
 * a given IP address.  Returns 1 if authorized, 0 otherwise.
 */
int
auth_ip_addr(unit, addr)
    int unit;
    u_int32_t addr;
{
    u_int32_t a;
    struct hostent *hp;
    struct wordlist *addrs;

    /* don't allow loopback or multicast address */
    if (bad_ip_adrs(addr))
	return 0;

    if ((addrs = addresses[unit]) == NULL)
	return 1;		/* no restriction */

    for (; addrs != NULL; addrs = addrs->next) {
	/* "-" means no addresses authorized */
	if (strcmp(addrs->word, "-") == 0)
	    break;
	if ((a = inet_addr(addrs->word)) == -1) {
	    if ((hp = gethostbyname(addrs->word)) == NULL) {
		do_syslog(LOG_WARNING, "unknown host %s in auth. address list",
		       addrs->word);
		continue;
	    } else
		a = *(u_int32_t *)hp->h_addr;
	}
	if (addr == a)
	    return 1;
    }
    return 0;			/* not in list => can't have it */
}

/*
 * bad_ip_adrs - return 1 if the IP address is one we don't want
 * to use, such as an address in the loopback net or a multicast address.
 * addr is in network byte order.
 */
int
bad_ip_adrs(addr)
    u_int32_t addr;
{
    addr = ntohl(addr);
    return (addr >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET
	|| IN_MULTICAST(addr) || IN_BADCLASS(addr);
}

/*
 * check_access - complain if a secret file has too-liberal permissions.
 */
void
check_access(f, filename)
    FILE *f;
    char *filename;
{
    struct stat sbuf;

    if (fstat(fileno(f), &sbuf) < 0) {
	do_syslog(LOG_WARNING, "cannot stat secret file %s: %m", filename);
    } else if ((sbuf.st_mode & (S_IRWXG | S_IRWXO)) != 0) {
	do_syslog(LOG_WARNING, "Warning - secret file %s has world and/or group access", filename);
    }
}


/*
 * scan_authfile - Scan an authorization file for a secret suitable
 * for authenticating `client' on `server'.  The return value is -1
 * if no secret is found, otherwise >= 0.  The return value has
 * NONWILD_CLIENT set if the secret didn't have "*" for the client, and
 * NONWILD_SERVER set if the secret didn't have "*" for the server.
 * Any following words on the line (i.e. address authorization
 * info) are placed in a wordlist and returned in *addrs.  
 */
static int
scan_authfile(f, client, server, secret, max_secret, addrs, filename)
    FILE *f;
    char *client;
    char *server;
    char *secret;
    int max_secret;
    struct wordlist **addrs;
    char *filename;
{
    int newline, xxx;
    int got_flag, best_flag;
    FILE *sf;
    struct wordlist *ap, *addr_list, *addr_last;
    char word[MAXWORDLEN];
    char atfile[MAXWORDLEN];

    if (addrs != NULL)
	*addrs = NULL;
    addr_list = NULL;
    if (!getword(f, word, &newline, filename))
	return -1;		/* file is empty??? */
    newline = 1;
    best_flag = -1;
    for (;;) {
	/*
	 * Skip until we find a word at the start of a line.
	 */
	while (!newline && getword(f, word, &newline, filename))
	    ;
	if (!newline)
	    break;		/* got to end of file */

	/*
	 * Got a client - check if it's a match or a wildcard.
	 */
	got_flag = 0;
	if (client != NULL && strcmp(word, client) != 0 && !ISWILD(word)) {
	    newline = 0;
	    continue;
	}
	if (!ISWILD(word))
	    got_flag = NONWILD_CLIENT;

	/*
	 * Now get a server and check if it matches.
	 */
	if (!getword(f, word, &newline, filename))
	    break;
	if (newline)
	    continue;
	if (server != NULL && strcmp(word, server) != 0 && !ISWILD(word))
	    continue;
	if (!ISWILD(word))
	    got_flag |= NONWILD_SERVER;

	/*
	 * Got some sort of a match - see if it's better than what
	 * we have already.
	 */
	if (got_flag <= best_flag)
	    continue;

	/*
	 * Get the secret.
	 */
	if (!getword(f, word, &newline, filename))
	    break;
	if (newline)
	    continue;

	/*
	 * Special syntax: @filename means read secret from file.
	 */
	if (word[0] == '@') {
	    strncpy2(atfile, word+1, sizeof(atfile));
	    if ((sf = fopen(atfile, "r")) == NULL) {
		do_syslog(LOG_WARNING, "can't open indirect secret file %s",
		       atfile);
		continue;
	    }
	    check_access(sf, atfile);
	    if (!getword(sf, word, &xxx, atfile)) {
		do_syslog(LOG_WARNING, "no secret in indirect secret file %s",
		       atfile);
		fclose(sf);
		continue;
	    }
	    fclose(sf);
	}

	if (secret != NULL)
	    strncpy2(secret, word, max_secret);

	best_flag = got_flag;

	/*
	 * Now read address authorization info and make a wordlist.
	 */
	if (addr_list)
	    free_wordlist(addr_list);
	addr_list = addr_last = NULL;
	for (;;) {
	    if (!getword(f, word, &newline, filename) || newline)
		break;
	    ap = (struct wordlist *) malloc(sizeof(struct wordlist)
					    + strlen(word));
	    if (ap == NULL)
		novm("authorized addresses");
	    ap->next = NULL;
            /* TODO: check lengths should be ok, alloced correctly above.*/
	    strcpy(ap->word, word);
	    if (addr_list == NULL)
		addr_list = ap;
	    else
		addr_last->next = ap;
	    addr_last = ap;
	}
	if (!newline)
	    break;
    }

    if (addrs != NULL)
	*addrs = addr_list;
    else if (addr_list != NULL)
	free_wordlist(addr_list);

    return best_flag;
}

/*
 * free_wordlist - release memory allocated for a wordlist.
 */
static void
free_wordlist(wp)
    struct wordlist *wp;
{
    struct wordlist *next;

    while (wp != NULL) {
	next = wp->next;
	free(wp);
	wp = next;
    }
}