/* $OpenBSD: hosts_access.c,v 1.5 2000/02/01 03:23:17 deraadt 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. */ #ifndef lint #if 0 static char sccsid[] = "@(#) hosts_access.c 1.21 97/02/12 02:13:22"; #else static char rcsid[] = "$OpenBSD: hosts_access.c,v 1.5 2000/02/01 03:23:17 deraadt Exp $"; #endif #endif /* System libraries. */ #include #include #include #include #include #include #include #include #include #include #ifdef NETGROUP #include #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(); 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[MAXHOSTNAMELEN]; if (mydomain[0] == '\0') getdomainname(mydomain, sizeof(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; { in_addr_t net; in_addr_t mask; in_addr_t 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 . */ if (!dot_quad_addr_new(string, &addr)) return (NO); if (!dot_quad_addr_new(net_tok, &net) || !dot_quad_addr_new(mask_tok, &mask)) { tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok); return (NO); /* not tcpd_jump() */ } return ((addr & mask) == net); }