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-rw-r--r--contrib/tcp_wrappers/hosts_access.c331
1 files changed, 331 insertions, 0 deletions
diff --git a/contrib/tcp_wrappers/hosts_access.c b/contrib/tcp_wrappers/hosts_access.c
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+++ b/contrib/tcp_wrappers/hosts_access.c
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+ /*
+ * 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.
+ */
+
+#ifndef lint
+static char sccsid[] = "@(#) hosts_access.c 1.21 97/02/12 02:13:22";
+#endif
+
+/* System libraries. */
+
+#include <sys/types.h>
+#include <sys/param.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <stdio.h>
+#include <syslog.h>
+#include <ctype.h>
+#include <errno.h>
+#include <setjmp.h>
+#include <string.h>
+
+extern char *fgets();
+extern int errno;
+
+#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();
+static int list_match();
+static int server_match();
+static int client_match();
+static int host_match();
+static int string_match();
+static int masked_match();
+
+/* 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; /* 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) ();
+{
+ char *tok;
+
+ /*
+ * 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);
+ 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 ((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))));
+ }
+}
+
+/* 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;
+{
+ 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 ((addr = dot_quad_addr(string)) == INADDR_NONE)
+ return (NO);
+ if ((net = dot_quad_addr(net_tok)) == INADDR_NONE
+ || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) {
+ tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok);
+ return (NO); /* not tcpd_jump() */
+ }
+ return ((addr & mask) == net);
+}
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