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NetBSD/lib/libwrap/options.c

622 lines
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C
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/*
* General skeleton for adding options to the access control language. The
* features offered by this module are documented in the hosts_options(5)
* manual page (source file: hosts_options.5, "nroff -man" format).
*
* Notes and warnings for those who want to add features:
*
* In case of errors, abort options processing and deny access. There are too
* many irreversible side effects to make error recovery feasible. For
* example, it makes no sense to continue after we have already changed the
* userid.
*
* In case of errors, do not terminate the process: the routines might be
* called from a long-running daemon that should run forever. Instead, call
* tcpd_jump() which does a non-local goto back into the hosts_access()
* routine.
*
* In case of severe errors, use clean_exit() instead of directly calling
* exit(), or the inetd may loop on an UDP request.
*
* In verification mode (for example, with the "tcpdmatch" command) the
* "dry_run" flag is set. In this mode, an option function should just "say"
* what it is going to do instead of really doing it.
*
* Some option functions do not return (for example, the twist option passes
* control to another program). In verification mode (dry_run flag is set)
* such options should clear the "dry_run" flag to inform the caller of this
* course of action.
*/
#ifndef lint
static char sccsid[] = "@(#) options.c 1.17 96/02/11 17:01:31";
#endif
/* System libraries. */
#include <sys/types.h>
#include <sys/param.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <syslog.h>
#include <pwd.h>
#include <grp.h>
#include <ctype.h>
#include <setjmp.h>
#include <string.h>
#ifndef MAXPATHNAMELEN
#define MAXPATHNAMELEN BUFSIZ
#endif
/* Local stuff. */
#include "tcpd.h"
/* Options runtime support. */
int dry_run = 0; /* flag set in verification mode */
extern jmp_buf tcpd_buf; /* tcpd_jump() support */
/* Options parser support. */
static char whitespace_eq[] = "= \t\r\n";
#define whitespace (whitespace_eq + 1)
static char *get_field(); /* chew :-delimited field off string */
static char *chop_string(); /* strip leading and trailing blanks */
/* List of functions that implement the options. Add yours here. */
static void user_option(); /* execute "user name.group" option */
static void group_option(); /* execute "group name" option */
static void umask_option(); /* execute "umask mask" option */
static void linger_option(); /* execute "linger time" option */
static void keepalive_option(); /* execute "keepalive" option */
static void spawn_option(); /* execute "spawn command" option */
static void twist_option(); /* execute "twist command" option */
static void rfc931_option(); /* execute "rfc931" option */
static void setenv_option(); /* execute "setenv name value" */
static void nice_option(); /* execute "nice" option */
static void severity_option(); /* execute "severity value" */
static void allow_option(); /* execute "allow" option */
static void deny_option(); /* execute "deny" option */
static void banners_option(); /* execute "banners path" option */
/* Structure of the options table. */
struct option {
char *name; /* keyword name, case is ignored */
void (*func) (); /* function that does the real work */
int flags; /* see below... */
};
#define NEED_ARG (1<<1) /* option requires argument */
#define USE_LAST (1<<2) /* option must be last */
#define OPT_ARG (1<<3) /* option has optional argument */
#define EXPAND_ARG (1<<4) /* do %x expansion on argument */
#define need_arg(o) ((o)->flags & NEED_ARG)
#define opt_arg(o) ((o)->flags & OPT_ARG)
#define permit_arg(o) ((o)->flags & (NEED_ARG | OPT_ARG))
#define use_last(o) ((o)->flags & USE_LAST)
#define expand_arg(o) ((o)->flags & EXPAND_ARG)
/* List of known keywords. Add yours here. */
static struct option option_table[] = {
"user", user_option, NEED_ARG,
"group", group_option, NEED_ARG,
"umask", umask_option, NEED_ARG,
"linger", linger_option, NEED_ARG,
"keepalive", keepalive_option, 0,
"spawn", spawn_option, NEED_ARG | EXPAND_ARG,
"twist", twist_option, NEED_ARG | EXPAND_ARG | USE_LAST,
"rfc931", rfc931_option, OPT_ARG,
"setenv", setenv_option, NEED_ARG | EXPAND_ARG,
"nice", nice_option, OPT_ARG,
"severity", severity_option, NEED_ARG,
"allow", allow_option, USE_LAST,
"deny", deny_option, USE_LAST,
"banners", banners_option, NEED_ARG,
0,
};
/* process_options - process access control options */
void process_options(options, request)
char *options;
struct request_info *request;
{
char *key;
char *value;
char *curr_opt;
char *next_opt;
struct option *op;
char bf[BUFSIZ];
for (curr_opt = get_field(options); curr_opt; curr_opt = next_opt) {
next_opt = get_field((char *) 0);
/*
* Separate the option into name and value parts. For backwards
* compatibility we ignore exactly one '=' between name and value.
*/
curr_opt = chop_string(curr_opt);
if (*(value = curr_opt + strcspn(curr_opt, whitespace_eq))) {
if (*value != '=') {
*value++ = 0;
value += strspn(value, whitespace);
}
if (*value == '=') {
*value++ = 0;
value += strspn(value, whitespace);
}
}
if (*value == 0)
value = 0;
key = curr_opt;
/*
* Disallow missing option names (and empty option fields).
*/
if (*key == 0)
tcpd_jump("missing option name");
/*
* Lookup the option-specific info and do some common error checks.
* Delegate option-specific processing to the specific functions.
*/
for (op = option_table; op->name && STR_NE(op->name, key); op++)
/* VOID */ ;
if (op->name == 0)
tcpd_jump("bad option name: \"%s\"", key);
if (!value && need_arg(op))
tcpd_jump("option \"%s\" requires value", key);
if (value && !permit_arg(op))
tcpd_jump("option \"%s\" requires no value", key);
if (next_opt && use_last(op))
tcpd_jump("option \"%s\" must be at end", key);
if (value && expand_arg(op))
value = chop_string(percent_x(bf, sizeof(bf), value, request));
if (hosts_access_verbose)
syslog(LOG_DEBUG, "option: %s %s", key, value ? value : "");
(*(op->func)) (value, request);
}
}
/* allow_option - grant access */
/* ARGSUSED */
static void allow_option(value, request)
char *value;
struct request_info *request;
{
longjmp(tcpd_buf, AC_PERMIT);
}
/* deny_option - deny access */
/* ARGSUSED */
static void deny_option(value, request)
char *value;
struct request_info *request;
{
longjmp(tcpd_buf, AC_DENY);
}
/* banners_option - expand %<char>, terminate each line with CRLF */
static void banners_option(value, request)
char *value;
struct request_info *request;
{
char path[MAXPATHNAMELEN];
char ibuf[BUFSIZ];
char obuf[2 * BUFSIZ];
struct stat st;
int ch;
FILE *fp;
(void)snprintf(path, sizeof path, "%s/%s", value, eval_daemon(request));
if ((fp = fopen(path, "r")) != 0) {
while ((ch = fgetc(fp)) == 0)
write(request->fd, "", 1);
ungetc(ch, fp);
while (fgets(ibuf, sizeof(ibuf) - 2, fp)) {
if (split_at(ibuf, '\n'))
strcat(ibuf, "\r\n"); /* XXX strcat is safe */
percent_x(obuf, sizeof(obuf), ibuf, request);
write(request->fd, obuf, strlen(obuf));
}
fclose(fp);
} else if (stat(value, &st) < 0) {
tcpd_warn("%s: %m", value);
}
}
/* group_option - switch group id */
/* ARGSUSED */
static void group_option(value, request)
char *value;
struct request_info *request;
{
struct group *grp;
struct group *getgrnam();
if ((grp = getgrnam(value)) == 0)
tcpd_jump("unknown group: \"%s\"", value);
endgrent();
if (dry_run == 0 && setgid(grp->gr_gid))
tcpd_jump("setgid(%s): %m", value);
}
/* user_option - switch user id */
/* ARGSUSED */
static void user_option(value, request)
char *value;
struct request_info *request;
{
struct passwd *pwd;
struct passwd *getpwnam();
char *group;
if ((group = split_at(value, '.')) != 0)
group_option(group, request);
if ((pwd = getpwnam(value)) == 0)
tcpd_jump("unknown user: \"%s\"", value);
endpwent();
if (dry_run == 0 && setuid(pwd->pw_uid))
tcpd_jump("setuid(%s): %m", value);
}
/* umask_option - set file creation mask */
/* ARGSUSED */
static void umask_option(value, request)
char *value;
struct request_info *request;
{
unsigned mask;
char junk;
if (sscanf(value, "%o%c", &mask, &junk) != 1 || (mask & 0777) != mask)
tcpd_jump("bad umask value: \"%s\"", value);
(void) umask(mask);
}
/* spawn_option - spawn a shell command and wait */
/* ARGSUSED */
static void spawn_option(value, request)
char *value;
struct request_info *request;
{
if (dry_run == 0)
shell_cmd(value);
}
/* linger_option - set the socket linger time (Marc Boucher <marc@cam.org>) */
/* ARGSUSED */
static void linger_option(value, request)
char *value;
struct request_info *request;
{
struct linger linger;
char junk;
if (sscanf(value, "%d%c", &linger.l_linger, &junk) != 1
|| linger.l_linger < 0)
tcpd_jump("bad linger value: \"%s\"", value);
if (dry_run == 0) {
linger.l_onoff = (linger.l_linger != 0);
if (setsockopt(request->fd, SOL_SOCKET, SO_LINGER, (char *) &linger,
sizeof(linger)) < 0)
tcpd_warn("setsockopt SO_LINGER %d: %m", linger.l_linger);
}
}
/* keepalive_option - set the socket keepalive option */
/* ARGSUSED */
static void keepalive_option(value, request)
char *value;
struct request_info *request;
{
static int on = 1;
if (dry_run == 0 && setsockopt(request->fd, SOL_SOCKET, SO_KEEPALIVE,
(char *) &on, sizeof(on)) < 0)
tcpd_warn("setsockopt SO_KEEPALIVE: %m");
}
/* nice_option - set nice value */
/* ARGSUSED */
static void nice_option(value, request)
char *value;
struct request_info *request;
{
int niceval = 10;
char junk;
if (value != 0 && sscanf(value, "%d%c", &niceval, &junk) != 1)
tcpd_jump("bad nice value: \"%s\"", value);
if (dry_run == 0 && nice(niceval) < 0)
tcpd_warn("nice(%d): %m", niceval);
}
/* twist_option - replace process by shell command */
static void twist_option(value, request)
char *value;
struct request_info *request;
{
char *error;
if (dry_run != 0) {
dry_run = 0;
} else {
if (resident > 0)
tcpd_jump("twist option in resident process");
syslog(deny_severity, "twist %s to %s", eval_client(request), value);
/* Before switching to the shell, set up stdin, stdout and stderr. */
#define maybe_dup2(from, to) ((from == to) ? to : (close(to), dup(from)))
if (maybe_dup2(request->fd, 0) != 0 ||
maybe_dup2(request->fd, 1) != 1 ||
maybe_dup2(request->fd, 2) != 2) {
error = "twist_option: dup: %m";
} else {
if (request->fd > 2)
close(request->fd);
(void) execl("/bin/sh", "sh", "-c", value, (char *) 0);
error = "twist_option: /bin/sh: %m";
}
/* Something went wrong: we MUST terminate the process. */
tcpd_warn(error);
clean_exit(request);
}
}
/* rfc931_option - look up remote user name */
static void rfc931_option(value, request)
char *value;
struct request_info *request;
{
int timeout;
char junk;
if (value != 0) {
if (sscanf(value, "%d%c", &timeout, &junk) != 1 || timeout <= 0)
tcpd_jump("bad rfc931 timeout: \"%s\"", value);
rfc931_timeout = timeout;
}
(void) eval_user(request);
}
/* setenv_option - set environment variable */
/* ARGSUSED */
static void setenv_option(value, request)
char *value;
struct request_info *request;
{
char *var_value;
if (*(var_value = value + strcspn(value, whitespace)))
*var_value++ = 0;
if (setenv(chop_string(value), chop_string(var_value), 1))
tcpd_jump("memory allocation failure");
}
/*
* The severity option goes last because it comes with a huge amount of ugly
* #ifdefs and tables.
*/
struct syslog_names {
char *name;
int value;
};
static struct syslog_names log_fac[] = {
#ifdef LOG_KERN
"kern", LOG_KERN,
#endif
#ifdef LOG_USER
"user", LOG_USER,
#endif
#ifdef LOG_MAIL
"mail", LOG_MAIL,
#endif
#ifdef LOG_DAEMON
"daemon", LOG_DAEMON,
#endif
#ifdef LOG_AUTH
"auth", LOG_AUTH,
#endif
#ifdef LOG_LPR
"lpr", LOG_LPR,
#endif
#ifdef LOG_NEWS
"news", LOG_NEWS,
#endif
#ifdef LOG_UUCP
"uucp", LOG_UUCP,
#endif
#ifdef LOG_CRON
"cron", LOG_CRON,
#endif
#ifdef LOG_LOCAL0
"local0", LOG_LOCAL0,
#endif
#ifdef LOG_LOCAL1
"local1", LOG_LOCAL1,
#endif
#ifdef LOG_LOCAL2
"local2", LOG_LOCAL2,
#endif
#ifdef LOG_LOCAL3
"local3", LOG_LOCAL3,
#endif
#ifdef LOG_LOCAL4
"local4", LOG_LOCAL4,
#endif
#ifdef LOG_LOCAL5
"local5", LOG_LOCAL5,
#endif
#ifdef LOG_LOCAL6
"local6", LOG_LOCAL6,
#endif
#ifdef LOG_LOCAL7
"local7", LOG_LOCAL7,
#endif
0,
};
static struct syslog_names log_sev[] = {
#ifdef LOG_EMERG
"emerg", LOG_EMERG,
#endif
#ifdef LOG_ALERT
"alert", LOG_ALERT,
#endif
#ifdef LOG_CRIT
"crit", LOG_CRIT,
#endif
#ifdef LOG_ERR
"err", LOG_ERR,
#endif
#ifdef LOG_WARNING
"warning", LOG_WARNING,
#endif
#ifdef LOG_NOTICE
"notice", LOG_NOTICE,
#endif
#ifdef LOG_INFO
"info", LOG_INFO,
#endif
#ifdef LOG_DEBUG
"debug", LOG_DEBUG,
#endif
0,
};
/* severity_map - lookup facility or severity value */
static int severity_map(table, name)
struct syslog_names *table;
char *name;
{
struct syslog_names *t;
for (t = table; t->name; t++)
if (STR_EQ(t->name, name))
return (t->value);
tcpd_jump("bad syslog facility or severity: \"%s\"", name);
/* NOTREACHED */
}
/* severity_option - change logging severity for this event (Dave Mitchell) */
/* ARGSUSED */
static void severity_option(value, request)
char *value;
struct request_info *request;
{
char *level = split_at(value, '.');
allow_severity = deny_severity = level ?
severity_map(log_fac, value) | severity_map(log_sev, level) :
severity_map(log_sev, value);
}
/* get_field - return pointer to next field in string */
static char *get_field(string)
char *string;
{
static char *last = "";
char *src;
char *dst;
char *ret;
int ch;
/*
* This function returns pointers to successive fields within a given
* string. ":" is the field separator; warn if the rule ends in one. It
* replaces a "\:" sequence by ":", without treating the result of
* substitution as field terminator. A null argument means resume search
* where the previous call terminated. This function destroys its
* argument.
*
* Work from explicit source or from memory. While processing \: we
* overwrite the input. This way we do not have to maintain buffers for
* copies of input fields.
*/
src = dst = ret = (string ? string : last);
if (src[0] == 0)
return (0);
while (ch = *src) {
if (ch == ':') {
if (*++src == 0)
tcpd_warn("rule ends in \":\"");
break;
}
if (ch == '\\' && src[1] == ':')
src++;
*dst++ = *src++;
}
last = src;
*dst = 0;
return (ret);
}
/* chop_string - strip leading and trailing blanks from string */
static char *chop_string(string)
register char *string;
{
char *start = 0;
char *end;
char *cp;
for (cp = string; *cp; cp++) {
if (!isspace(*cp)) {
if (start == 0)
start = cp;
end = cp;
}
}
return (start ? (end[1] = 0, start) : cp);
}
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