331 lines
9.4 KiB
C
331 lines
9.4 KiB
C
/*
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* This module implements a simple access control language that is based on
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* host (or domain) names, NIS (host) netgroup names, IP addresses (or
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* network numbers) and daemon process names. When a match is found the
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* search is terminated, and depending on whether PROCESS_OPTIONS is defined,
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* a list of options is executed or an optional shell command is executed.
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*
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* Host and user names are looked up on demand, provided that suitable endpoint
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* information is available as sockaddr_in structures or TLI netbufs. As a
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* side effect, the pattern matching process may change the contents of
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* request structure fields.
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*
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* Diagnostics are reported through syslog(3).
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*
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* Compile with -DNETGROUP if your library provides support for netgroups.
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*
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* Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
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*/
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#ifndef lint
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static char sccsid[] = "@(#) hosts_access.c 1.20 96/02/11 17:01:27";
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#endif
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/* System libraries. */
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#include <sys/types.h>
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#include <sys/param.h>
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#include <netinet/in.h>
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#include <arpa/inet.h>
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#include <stdio.h>
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#include <syslog.h>
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#include <ctype.h>
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#include <errno.h>
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#include <setjmp.h>
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#include <string.h>
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extern char *fgets();
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extern int errno;
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#ifndef INADDR_NONE
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#define INADDR_NONE (-1) /* XXX should be 0xffffffff */
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#endif
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/* Local stuff. */
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#include "tcpd.h"
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/* Error handling. */
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extern jmp_buf tcpd_buf;
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/* Delimiters for lists of daemons or clients. */
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static char sep[] = ", \t\r\n";
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/* Constants to be used in assignments only, not in comparisons... */
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#define YES 1
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#define NO 0
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/*
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* These variables are globally visible so that they can be redirected in
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* verification mode.
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*/
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char *hosts_allow_table = HOSTS_ALLOW;
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char *hosts_deny_table = HOSTS_DENY;
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int hosts_access_verbose = 0;
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/*
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* In a long-running process, we are not at liberty to just go away.
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*/
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int resident = (-1); /* -1, 0: unknown; +1: yes */
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/* Forward declarations. */
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static int table_match();
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static int list_match();
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static int server_match();
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static int client_match();
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static int host_match();
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static int string_match();
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static int masked_match();
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/* Size of logical line buffer. */
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#define BUFLEN 2048
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/* hosts_access - host access control facility */
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int hosts_access(request)
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struct request_info *request;
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{
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int verdict;
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/*
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* If the (daemon, client) pair is matched by an entry in the file
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* /etc/hosts.allow, access is granted. Otherwise, if the (daemon,
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* client) pair is matched by an entry in the file /etc/hosts.deny,
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* access is denied. Otherwise, access is granted. A non-existent
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* access-control file is treated as an empty file.
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*
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* After a rule has been matched, the optional language extensions may
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* decide to grant or refuse service anyway. Or, while a rule is being
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* processed, a serious error is found, and it seems better to play safe
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* and deny service. All this is done by jumping back into the
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* hosts_access() routine, bypassing the regular return from the
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* table_match() function calls below.
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*/
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if (resident <= 0)
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resident++;
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if ((verdict = setjmp(tcpd_buf)) != 0)
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return (verdict == AC_PERMIT);
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if (table_match(hosts_allow_table, request))
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return (YES);
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if (table_match(hosts_deny_table, request))
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return (NO);
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return (YES);
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}
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/* table_match - match table entries with (daemon, client) pair */
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static int table_match(table, request)
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char *table;
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struct request_info *request;
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{
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FILE *fp;
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char sv_list[BUFLEN]; /* becomes list of daemons */
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char *cl_list; /* becomes list of clients */
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char *sh_cmd; /* becomes optional shell command */
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int match = NO;
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struct tcpd_context saved_context;
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saved_context = tcpd_context; /* stupid compilers */
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/*
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* Between the fopen() and fclose() calls, avoid jumps that may cause
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* file descriptor leaks.
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*/
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if ((fp = fopen(table, "r")) != 0) {
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tcpd_context.file = table;
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tcpd_context.line = 0;
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while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) {
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if (sv_list[strlen(sv_list) - 1] != '\n') {
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tcpd_warn("missing newline or line too long");
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continue;
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}
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if (sv_list[0] == '#' || sv_list[strspn(sv_list, " \t\r\n")] == 0)
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continue;
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if ((cl_list = split_at(sv_list, ':')) == 0) {
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tcpd_warn("missing \":\" separator");
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continue;
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}
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sh_cmd = split_at(cl_list, ':');
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match = list_match(sv_list, request, server_match)
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&& list_match(cl_list, request, client_match);
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}
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(void) fclose(fp);
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} else if (errno != ENOENT) {
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tcpd_warn("cannot open %s: %m", table);
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}
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if (match) {
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if (hosts_access_verbose > 1)
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syslog(LOG_DEBUG, "matched: %s line %d",
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tcpd_context.file, tcpd_context.line);
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if (sh_cmd) {
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#ifdef PROCESS_OPTIONS
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process_options(sh_cmd, request);
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#else
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char cmd[BUFSIZ];
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shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request));
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#endif
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}
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}
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tcpd_context = saved_context;
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return (match);
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}
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/* list_match - match a request against a list of patterns with exceptions */
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static int list_match(list, request, match_fn)
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char *list;
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struct request_info *request;
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int (*match_fn) ();
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{
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char *tok;
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/*
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* Process tokens one at a time. We have exhausted all possible matches
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* when we reach an "EXCEPT" token or the end of the list. If we do find
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* a match, look for an "EXCEPT" list and recurse to determine whether
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* the match is affected by any exceptions.
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*/
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for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) {
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if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */
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return (NO);
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if (match_fn(tok, request)) { /* YES: look for exceptions */
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while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT"))
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/* VOID */ ;
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return (tok == 0 || list_match((char *) 0, request, match_fn) == 0);
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}
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}
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return (NO);
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}
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/* server_match - match server information */
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static int server_match(tok, request)
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char *tok;
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struct request_info *request;
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{
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char *host;
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if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */
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return (string_match(tok, eval_daemon(request)));
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} else { /* daemon@host */
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return (string_match(tok, eval_daemon(request))
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&& host_match(host, request->server));
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}
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}
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/* client_match - match client information */
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static int client_match(tok, request)
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char *tok;
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struct request_info *request;
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{
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char *host;
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if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */
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return (host_match(tok, request->client));
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} else { /* user@host */
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return (host_match(host, request->client)
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&& string_match(tok, eval_user(request)));
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}
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}
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/* host_match - match host name and/or address against pattern */
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static int host_match(tok, host)
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char *tok;
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struct host_info *host;
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{
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char *mask;
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/*
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* This code looks a little hairy because we want to avoid unnecessary
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* hostname lookups.
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*
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* The KNOWN pattern requires that both address AND name be known; some
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* patterns are specific to host names or to host addresses; all other
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* patterns are satisfied when either the address OR the name match.
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*/
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if (tok[0] == '@') { /* netgroup: look it up */
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#ifdef NETGROUP
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static char *mydomain = 0;
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if (mydomain == 0)
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yp_get_default_domain(&mydomain);
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return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain));
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#else
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tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */
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return (NO);
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#endif
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} else if (STR_EQ(tok, "KNOWN")) { /* check address and name */
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char *name = eval_hostname(host);
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return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name));
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} else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */
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char *name = eval_hostname(host);
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return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name));
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} else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */
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return (masked_match(tok, mask, eval_hostaddr(host)));
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} else { /* anything else */
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return (string_match(tok, eval_hostaddr(host))
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|| (NOT_INADDR(tok) && string_match(tok, eval_hostname(host))));
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}
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}
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/* string_match - match string against pattern */
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static int string_match(tok, string)
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char *tok;
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char *string;
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{
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int n;
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if (tok[0] == '.') { /* suffix */
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n = strlen(string) - strlen(tok);
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return (n > 0 && STR_EQ(tok, string + n));
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} else if (STR_EQ(tok, "ALL")) { /* all: match any */
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return (YES);
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} else if (STR_EQ(tok, "KNOWN")) { /* not unknown */
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return (STR_NE(string, unknown));
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} else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */
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return (STRN_EQ(tok, string, n));
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} else { /* exact match */
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return (STR_EQ(tok, string));
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}
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}
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/* masked_match - match address against netnumber/netmask */
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static int masked_match(net_tok, mask_tok, string)
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char *net_tok;
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char *mask_tok;
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char *string;
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{
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unsigned long net;
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unsigned long mask;
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unsigned long addr;
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/*
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* Disallow forms other than dotted quad: the treatment that inet_addr()
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* gives to forms with less than four components is inconsistent with the
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* access control language. John P. Rouillard <rouilj@cs.umb.edu>.
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*/
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if ((addr = dot_quad_addr(string)) == INADDR_NONE)
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return (NO);
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if ((net = dot_quad_addr(net_tok)) == INADDR_NONE
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|| (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) {
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tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok);
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return (NO); /* not tcpd_jump() */
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}
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return ((addr & mask) == net);
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}
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