diff options
Diffstat (limited to 'hosts_access.c')
| -rw-r--r-- | hosts_access.c | 331 |
1 files changed, 331 insertions, 0 deletions
diff --git a/hosts_access.c b/hosts_access.c new file mode 100644 index 0000000..9bdc7bc --- /dev/null +++ b/hosts_access.c @@ -0,0 +1,331 @@ + /* + * 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); +} |