/* $NetBSD: hosts_access.c,v 1.21 2016/02/17 19:52:20 christos 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 1.21 2016/02/17 19:52:20 christos 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
/* 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.
*/
const char *hosts_allow_table = HOSTS_ALLOW;
const 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(const char *, struct request_info *);
static int list_match(char *, struct request_info *,
int (*)(char *, struct request_info *));
static int server_match(char *, struct request_info *);
static int client_match(char *, struct request_info *);
static int host_match(char *, struct host_info *);
static int hostfile_match(char *, struct host_info *);
static int rbl_match(char *, char *);
static int string_match(char *, char *);
static int masked_match(char *, char *, char *);
static int masked_match4(char *, char *, char *);
#ifdef INET6
static int masked_match6(char *, char *, char *);
#endif
/* Size of logical line buffer. */
#define BUFLEN 2048
/* hosts_access - host access control facility */
int
hosts_access(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(const 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(char *list, struct request_info *request,
int (*match_fn)(char *, struct request_info *))
{
char *tok;
static char *last;
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_r(list, sep, &last); tok != 0;
tok = strtok_r(NULL, sep, &last)) {
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_r(NULL, sep, &last)) && STR_NE(tok, "EXCEPT"))
/* VOID */ ;
return (tok == 0 || list_match(NULL, request, match_fn) == 0);
}
}
return (NO);
}
/* server_match - match server information */
static int
server_match(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(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(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), NULL, mydomain));
#else
tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */
return (NO);
#endif
} else if (tok[0] == '/') { /* /file hack */
return (hostfile_match(tok, host));
} 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))));
}
}
/* hostfile_match - look up host patterns from file */
static int
hostfile_match(char *path, struct host_info *host)
{
char tok[512];
int match = NO;
FILE *fp;
if ((fp = fopen(path, "r")) != 0) {
while (fscanf(fp, "%511s", tok) == 1 && !(match = host_match(tok, host)))
/* void */ ;
fclose(fp);
} else if (errno != ENOENT) {
tcpd_warn("open %s: %m", path);
}
return (match);
}
/* rbl_match() - match host by looking up in RBL domain */
static int
rbl_match(
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);
}
host_address = ntohl(host_address);
/* 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(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(char *net_tok, char *mask_tok, char *string)
{
#ifndef INET6
return masked_match4(net_tok, mask_tok, string);
#else
/*
* masked_match4() is kept just for supporting shortened IPv4 address form.
* If we could get rid of shortened IPv4 form, we could just always use
* masked_match6().
*/
if (dot_quad_addr(net_tok, NULL) != -1 &&
dot_quad_addr(mask_tok, NULL) != -1 &&
dot_quad_addr(string, NULL) != -1) {
return masked_match4(net_tok, mask_tok, string);
} else
return masked_match6(net_tok, mask_tok, string);
#endif
}
static int
masked_match4(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() */
}
if ((net & ~mask) != 0)
tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok);
return ((addr & mask) == net);
}
#ifdef INET6
static int
masked_match6(char *net_tok, char *mask_tok, char *string)
{
union {
struct sockaddr sa;
struct sockaddr_in sin;
struct sockaddr_in6 sin6;
} net, mask, addr;
struct addrinfo hints, *res;
unsigned long masklen;
char *ep;
size_t i;
char *np, *mp, *ap;
size_t alen;
memset(&hints, 0, sizeof(hints));
hints.ai_family = PF_UNSPEC;
hints.ai_socktype = SOCK_DGRAM; /*dummy*/
hints.ai_flags = AI_NUMERICHOST;
if (getaddrinfo(net_tok, "0", &hints, &res) == 0) {
if (res->ai_addrlen > sizeof(net) || res->ai_next) {
freeaddrinfo(res);
return NO;
}
memcpy(&net, res->ai_addr, res->ai_addrlen);
freeaddrinfo(res);
} else
return NO;
memset(&hints, 0, sizeof(hints));
hints.ai_family = net.sa.sa_family;
hints.ai_socktype = SOCK_DGRAM; /*dummy*/
hints.ai_flags = AI_NUMERICHOST;
ep = NULL;
if (getaddrinfo(mask_tok, "0", &hints, &res) == 0) {
if (res->ai_family == AF_INET6 &&
((struct sockaddr_in6 *)res->ai_addr)->sin6_scope_id) {
freeaddrinfo(res);
return NO;
}
if (res->ai_addrlen > sizeof(mask) || res->ai_next) {
freeaddrinfo(res);
return NO;
}
memcpy(&mask, res->ai_addr, res->ai_addrlen);
freeaddrinfo(res);
} else {
ep = NULL;
masklen = strtoul(mask_tok, &ep, 10);
if (ep && !*ep) {
memset(&mask, 0, sizeof(mask));
mask.sa.sa_family = net.sa.sa_family;
mask.sa.sa_len = net.sa.sa_len;
switch (mask.sa.sa_family) {
case AF_INET:
mp = (char *)&mask.sin.sin_addr;
alen = sizeof(mask.sin.sin_addr);
break;
case AF_INET6:
mp = (char *)&mask.sin6.sin6_addr;
alen = sizeof(mask.sin6.sin6_addr);
break;
default:
return NO;
}
if (masklen / 8 > alen)
return NO;
memset(mp, 0xff, masklen / 8);
if (masklen % 8)
mp[masklen / 8] = 0xff00 >> (masklen % 8);
} else
return NO;
}
memset(&hints, 0, sizeof(hints));
hints.ai_family = PF_UNSPEC;
hints.ai_socktype = SOCK_DGRAM; /*dummy*/
hints.ai_flags = AI_NUMERICHOST;
if (getaddrinfo(string, "0", &hints, &res) == 0) {
if (res->ai_addrlen > sizeof(addr) || res->ai_next) {
freeaddrinfo(res);
return NO;
}
/* special case - IPv4 mapped address */
if (net.sa.sa_family == AF_INET && res->ai_family == AF_INET6 &&
IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)res->ai_addr)->sin6_addr)) {
memset(&addr, 0, sizeof(addr));
addr.sa.sa_family = net.sa.sa_family;
addr.sa.sa_len = net.sa.sa_len;
memcpy(&addr.sin.sin_addr,
&((struct sockaddr_in6 *)res->ai_addr)->sin6_addr.s6_addr[12],
sizeof(addr.sin.sin_addr));
} else
memcpy(&addr, res->ai_addr, res->ai_addrlen);
freeaddrinfo(res);
} else
return NO;
if (net.sa.sa_family != mask.sa.sa_family ||
net.sa.sa_family != addr.sa.sa_family) {
return NO;
}
switch (net.sa.sa_family) {
case AF_INET:
np = (char *)&net.sin.sin_addr;
mp = (char *)&mask.sin.sin_addr;
ap = (char *)&addr.sin.sin_addr;
alen = sizeof(net.sin.sin_addr);
break;
case AF_INET6:
np = (char *)&net.sin6.sin6_addr;
mp = (char *)&mask.sin6.sin6_addr;
ap = (char *)&addr.sin6.sin6_addr;
alen = sizeof(net.sin6.sin6_addr);
break;
default:
return NO;
}
for (i = 0; i < alen; i++)
if (np[i] & ~mp[i]) {
tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok);
break;
}
for (i = 0; i < alen; i++)
ap[i] &= mp[i];
if (addr.sa.sa_family == AF_INET6 && addr.sin6.sin6_scope_id &&
addr.sin6.sin6_scope_id != net.sin6.sin6_scope_id)
return NO;
return (memcmp(ap, np, alen) == 0);
}
#endif