/* $NetBSD: hosts_access.c,v 1.16 2002/06/22 11:52:40 itojun 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 #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 1.16 2002/06/22 11:52:40 itojun Exp $"); #endif #endif /* System libraries. */ #include #include #ifdef INET6 #include #endif #include #include #include #include #include #include #include #include #include #include #ifdef NETGROUP #include #include #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, *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(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), NULL, 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 /* * 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) != 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 . */ 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(net_tok, mask_tok, string) 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; int i; char *np, *mp, *ap; int 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