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NetBSD/lib/libwrap/hosts_access.c

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/* $NetBSD: hosts_access.c,v 1.11 2000/01/21 17:08:34 mycroft Exp $ */
/*
* This module implements a simple access control language that is based on
* host (or domain) names, NIS (host) netgroup names, IP addresses (or
* network numbers) and daemon process names. When a match is found the
* search is terminated, and depending on whether PROCESS_OPTIONS is defined,
* a list of options is executed or an optional shell command is executed.
*
* Host and user names are looked up on demand, provided that suitable endpoint
* information is available as sockaddr_in structures or TLI netbufs. As a
* side effect, the pattern matching process may change the contents of
* request structure fields.
*
* Diagnostics are reported through syslog(3).
*
* Compile with -DNETGROUP if your library provides support for netgroups.
*
* Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
*/
#include <sys/cdefs.h>
#ifndef lint
#if 0
static char sccsid[] = "@(#) hosts_access.c 1.21 97/02/12 02:13:22";
#else
__RCSID("$NetBSD: hosts_access.c,v 1.11 2000/01/21 17:08:34 mycroft Exp $");
#endif
#endif
/* System libraries. */
#include <sys/types.h>
#include <sys/param.h>
#ifdef INET6
#include <sys/socket.h>
#endif
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <syslog.h>
#include <ctype.h>
#include <errno.h>
#include <setjmp.h>
#include <string.h>
#include <netdb.h>
#ifdef NETGROUP
#include <netgroup.h>
#include <rpcsvc/ypclnt.h>
#endif
#ifndef INADDR_NONE
#define INADDR_NONE (-1) /* XXX should be 0xffffffff */
#endif
/* Local stuff. */
#include "tcpd.h"
/* Error handling. */
extern jmp_buf tcpd_buf;
/* Delimiters for lists of daemons or clients. */
static char sep[] = ", \t\r\n";
/* Constants to be used in assignments only, not in comparisons... */
#define YES 1
#define NO 0
/*
* These variables are globally visible so that they can be redirected in
* verification mode.
*/
char *hosts_allow_table = HOSTS_ALLOW;
char *hosts_deny_table = HOSTS_DENY;
int hosts_access_verbose = 0;
/*
* In a long-running process, we are not at liberty to just go away.
*/
int resident = (-1); /* -1, 0: unknown; +1: yes */
/* Forward declarations. */
static int table_match __P((char *, struct request_info *));
static int list_match __P((char *, struct request_info *,
int (*)(char *, struct request_info *)));
static int server_match __P((char *, struct request_info *));
static int client_match __P((char *, struct request_info *));
static int host_match __P((char *, struct host_info *));
static int rbl_match __P((char *, char *));
static int string_match __P((char *, char *));
static int masked_match __P((char *, char *, char *));
static int masked_match4 __P((char *, char *, char *));
#ifdef INET6
static int masked_match6 __P((char *, char *, char *));
#endif
/* Size of logical line buffer. */
#define BUFLEN 2048
/* hosts_access - host access control facility */
int hosts_access(request)
struct request_info *request;
{
int verdict;
/*
* If the (daemon, client) pair is matched by an entry in the file
* /etc/hosts.allow, access is granted. Otherwise, if the (daemon,
* client) pair is matched by an entry in the file /etc/hosts.deny,
* access is denied. Otherwise, access is granted. A non-existent
* access-control file is treated as an empty file.
*
* After a rule has been matched, the optional language extensions may
* decide to grant or refuse service anyway. Or, while a rule is being
* processed, a serious error is found, and it seems better to play safe
* and deny service. All this is done by jumping back into the
* hosts_access() routine, bypassing the regular return from the
* table_match() function calls below.
*/
if (resident <= 0)
resident++;
verdict = setjmp(tcpd_buf);
if (verdict != 0)
return (verdict == AC_PERMIT);
if (table_match(hosts_allow_table, request))
return (YES);
if (table_match(hosts_deny_table, request))
return (NO);
return (YES);
}
/* table_match - match table entries with (daemon, client) pair */
static int table_match(table, request)
char *table;
struct request_info *request;
{
FILE *fp;
char sv_list[BUFLEN]; /* becomes list of daemons */
char *cl_list; /* becomes list of clients */
char *sh_cmd = NULL; /* becomes optional shell command */
int match = NO;
struct tcpd_context saved_context;
saved_context = tcpd_context; /* stupid compilers */
/*
* Between the fopen() and fclose() calls, avoid jumps that may cause
* file descriptor leaks.
*/
if ((fp = fopen(table, "r")) != 0) {
tcpd_context.file = table;
tcpd_context.line = 0;
while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) {
if (sv_list[strlen(sv_list) - 1] != '\n') {
tcpd_warn("missing newline or line too long");
continue;
}
if (sv_list[0] == '#' || sv_list[strspn(sv_list, " \t\r\n")] == 0)
continue;
if ((cl_list = split_at(sv_list, ':')) == 0) {
tcpd_warn("missing \":\" separator");
continue;
}
sh_cmd = split_at(cl_list, ':');
match = list_match(sv_list, request, server_match)
&& list_match(cl_list, request, client_match);
}
(void) fclose(fp);
} else if (errno != ENOENT) {
tcpd_warn("cannot open %s: %m", table);
}
if (match) {
if (hosts_access_verbose > 1)
syslog(LOG_DEBUG, "matched: %s line %d",
tcpd_context.file, tcpd_context.line);
if (sh_cmd) {
#ifdef PROCESS_OPTIONS
process_options(sh_cmd, request);
#else
char cmd[BUFSIZ];
shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request));
#endif
}
}
tcpd_context = saved_context;
return (match);
}
/* list_match - match a request against a list of patterns with exceptions */
static int list_match(list, request, match_fn)
char *list;
struct request_info *request;
int (*match_fn) __P((char *, struct request_info *));
{
char *tok;
int l;
/*
* Process tokens one at a time. We have exhausted all possible matches
* when we reach an "EXCEPT" token or the end of the list. If we do find
* a match, look for an "EXCEPT" list and recurse to determine whether
* the match is affected by any exceptions.
*/
for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) {
if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */
return (NO);
l = strlen(tok);
if (*tok == '[' && tok[l - 1] == ']') {
tok[l - 1] = '\0';
tok++;
}
if (match_fn(tok, request)) { /* YES: look for exceptions */
while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT"))
/* VOID */ ;
return (tok == 0 || list_match((char *) 0, request, match_fn) == 0);
}
}
return (NO);
}
/* server_match - match server information */
static int server_match(tok, request)
char *tok;
struct request_info *request;
{
char *host;
if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */
return (string_match(tok, eval_daemon(request)));
} else { /* daemon@host */
return (string_match(tok, eval_daemon(request))
&& host_match(host, request->server));
}
}
/* client_match - match client information */
static int client_match(tok, request)
char *tok;
struct request_info *request;
{
char *host;
if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */
return (host_match(tok, request->client));
} else { /* user@host */
return (host_match(host, request->client)
&& string_match(tok, eval_user(request)));
}
}
/* host_match - match host name and/or address against pattern */
static int host_match(tok, host)
char *tok;
struct host_info *host;
{
char *mask;
/*
* This code looks a little hairy because we want to avoid unnecessary
* hostname lookups.
*
* The KNOWN pattern requires that both address AND name be known; some
* patterns are specific to host names or to host addresses; all other
* patterns are satisfied when either the address OR the name match.
*/
if (tok[0] == '@') { /* netgroup: look it up */
#ifdef NETGROUP
static char *mydomain = 0;
if (mydomain == 0)
yp_get_default_domain(&mydomain);
return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain));
#else
tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */
return (NO);
#endif
} else if (STR_EQ(tok, "KNOWN")) { /* check address and name */
char *name = eval_hostname(host);
return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name));
} else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */
char *name = eval_hostname(host);
return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name));
} else if (strncmp(tok, "{RBL}.", 6) == 0) { /* RBL lookup in domain */
return rbl_match(tok+6, eval_hostaddr(host));
} else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */
return (masked_match(tok, mask, eval_hostaddr(host)));
} else { /* anything else */
return (string_match(tok, eval_hostaddr(host))
|| (NOT_INADDR(tok) && string_match(tok, eval_hostname(host))));
}
}
/* rbl_match() - match host by looking up in RBL domain */
static int rbl_match(rbl_domain, rbl_hostaddr)
char *rbl_domain; /* RBL domain */
char *rbl_hostaddr; /* hostaddr */
{
char *rbl_name;
unsigned long host_address;
int ret = NO;
size_t len = strlen(rbl_domain) + (4 * 4) + 2;
if (dot_quad_addr(rbl_hostaddr, &host_address) != 0) {
tcpd_warn("unable to convert %s to address", rbl_hostaddr);
return (NO);
}
/* construct the rbl name to look up */
if ((rbl_name = malloc(len)) == NULL) {
tcpd_jump("not enough memory to build RBL name for %s in %s", rbl_hostaddr, rbl_domain);
/* NOTREACHED */
}
snprintf(rbl_name, len, "%u.%u.%u.%u.%s",
(unsigned int) ((host_address) & 0xff),
(unsigned int) ((host_address >> 8) & 0xff),
(unsigned int) ((host_address >> 16) & 0xff),
(unsigned int) ((host_address >> 24) & 0xff),
rbl_domain);
/* look it up */
if (gethostbyname(rbl_name) != NULL) {
/* successful lookup - they're on the RBL list */
ret = YES;
}
free(rbl_name);
return ret;
}
/* string_match - match string against pattern */
static int string_match(tok, string)
char *tok;
char *string;
{
int n;
if (tok[0] == '.') { /* suffix */
n = strlen(string) - strlen(tok);
return (n > 0 && STR_EQ(tok, string + n));
} else if (STR_EQ(tok, "ALL")) { /* all: match any */
return (YES);
} else if (STR_EQ(tok, "KNOWN")) { /* not unknown */
return (STR_NE(string, unknown));
} else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */
return (STRN_EQ(tok, string, n));
} else { /* exact match */
return (STR_EQ(tok, string));
}
}
/* masked_match - match address against netnumber/netmask */
static int masked_match(net_tok, mask_tok, string)
char *net_tok;
char *mask_tok;
char *string;
{
#ifndef INET6
return masked_match4(net_tok, mask_tok, string);
#else
if (dot_quad_addr(net_tok, NULL) != INADDR_NONE
&& dot_quad_addr(mask_tok, NULL) != INADDR_NONE
&& dot_quad_addr(string, NULL) != INADDR_NONE) {
return masked_match4(net_tok, mask_tok, string);
} else
return masked_match6(net_tok, mask_tok, string);
#endif
}
static int masked_match4(net_tok, mask_tok, string)
char *net_tok;
char *mask_tok;
char *string;
{
unsigned long net;
unsigned long mask;
unsigned long addr;
/*
* Disallow forms other than dotted quad: the treatment that inet_addr()
* gives to forms with less than four components is inconsistent with the
* access control language. John P. Rouillard <rouilj@cs.umb.edu>.
*/
if (dot_quad_addr(string, &addr) != 0)
return (NO);
if (dot_quad_addr(net_tok, &net) != 0
|| dot_quad_addr(mask_tok, &mask) != 0) {
tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok);
return (NO); /* not tcpd_jump() */
}
return ((addr & mask) == net);
}
#ifdef INET6
/* Ugly because it covers IPv4 mapped address. I hate mapped addresses. */
static int masked_match6(net_tok, mask_tok, string)
char *net_tok;
char *mask_tok;
char *string;
{
struct in6_addr net;
struct in6_addr mask;
struct in6_addr addr;
int masklen;
int fail;
int i;
int maskoff;
int netaf;
const int sizoff64 = sizeof(struct in6_addr) - sizeof(struct in_addr);
memset(&addr, 0, sizeof(addr));
if (inet_pton(AF_INET6, string, &addr) == 1)
; /* okay */
else if (inet_pton(AF_INET, string, &addr.s6_addr[sizoff64]) == 1)
addr.s6_addr[10] = addr.s6_addr[11] = 0xff;
else
return NO;
memset(&net, 0, sizeof(net));
if (inet_pton(AF_INET6, net_tok, &net) == 1) {
netaf = AF_INET6;
maskoff = 0;
} else if (inet_pton(AF_INET, net_tok, &net.s6_addr[sizoff64]) == 1) {
netaf = AF_INET;
maskoff = sizoff64;
net.s6_addr[10] = net.s6_addr[11] = 0xff;
} else
return NO;
fail = 0;
if (mask_tok[strspn(mask_tok, "0123456789")] == '\0') {
masklen = atoi(mask_tok) + maskoff * 8;
if (0 <= masklen && masklen <= 128) {
memset(&mask, 0, sizeof(mask));
memset(&mask, 0xff, masklen / 8);
if (masklen % 8) {
((u_char *)&mask)[masklen / 8] =
(0xff00 >> (masklen % 8)) & 0xff;
}
} else
fail++;
} else if (netaf == AF_INET6 && inet_pton(AF_INET6, mask_tok, &mask) == 1)
; /* okay */
else if (netaf == AF_INET
&& inet_pton(AF_INET, mask_tok, &mask.s6_addr[12]) == 1) {
memset(&mask, 0xff, sizoff64);
} else
fail++;
if (fail) {
tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok);
return (NO); /* not tcpd_jump() */
}
for (i = 0; i < sizeof(addr); i++)
addr.s6_addr[i] &= mask.s6_addr[i];
return (memcmp(&addr, &net, sizeof(addr)) == 0);
}
#endif
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