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/* $OpenBSD: ntp_dns.c,v 1.28 2023/04/19 12:58:16 jsg Exp $ */
/*
* Copyright (c) 2003-2008 Henning Brauer <henning@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/types.h>
#include <sys/resource.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>
#include <err.h>
#include <errno.h>
#include <poll.h>
#include <fcntl.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include "ntpd.h"
volatile sig_atomic_t quit_dns = 0;
static struct imsgbuf *ibuf_dns;
extern int non_numeric;
void sighdlr_dns(int);
int dns_dispatch_imsg(struct ntpd_conf *);
int probe_root_ns(void);
void probe_root(void);
void
sighdlr_dns(int sig)
{
switch (sig) {
case SIGTERM:
case SIGINT:
quit_dns = 1;
break;
}
}
void
ntp_dns(struct ntpd_conf *nconf, struct passwd *pw)
{
struct pollfd pfd[1];
int nfds, nullfd;
res_init();
if (setpriority(PRIO_PROCESS, 0, 0) == -1)
log_warn("could not set priority");
log_init(nconf->debug ? LOG_TO_STDERR : LOG_TO_SYSLOG, nconf->verbose,
LOG_DAEMON);
if (!nconf->debug && setsid() == -1)
fatal("setsid");
log_procinit("dns");
if ((nullfd = open("/dev/null", O_RDWR)) == -1)
fatal(NULL);
if (!nconf->debug) {
dup2(nullfd, STDIN_FILENO);
dup2(nullfd, STDOUT_FILENO);
dup2(nullfd, STDERR_FILENO);
}
close(nullfd);
setproctitle("dns engine");
if (setgroups(1, &pw->pw_gid) ||
setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) ||
setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid))
fatal("can't drop privileges");
signal(SIGTERM, sighdlr_dns);
signal(SIGINT, sighdlr_dns);
signal(SIGHUP, SIG_IGN);
if ((ibuf_dns = malloc(sizeof(struct imsgbuf))) == NULL)
fatal(NULL);
imsg_init(ibuf_dns, PARENT_SOCK_FILENO);
if (pledge("stdio dns", NULL) == -1)
err(1, "pledge");
if (non_numeric)
probe_root();
else
log_debug("all addresses numeric, no dns probe");
while (quit_dns == 0) {
pfd[0].fd = ibuf_dns->fd;
pfd[0].events = POLLIN;
if (ibuf_dns->w.queued)
pfd[0].events |= POLLOUT;
if ((nfds = poll(pfd, 1, INFTIM)) == -1)
if (errno != EINTR) {
log_warn("poll error");
quit_dns = 1;
}
if (nfds > 0 && (pfd[0].revents & POLLOUT))
if (msgbuf_write(&ibuf_dns->w) <= 0 &&
errno != EAGAIN) {
log_warn("pipe write error (to ntp engine)");
quit_dns = 1;
}
if (nfds > 0 && pfd[0].revents & POLLIN) {
nfds--;
if (dns_dispatch_imsg(nconf) == -1)
quit_dns = 1;
}
}
msgbuf_clear(&ibuf_dns->w);
free(ibuf_dns);
exit(0);
}
int
dns_dispatch_imsg(struct ntpd_conf *nconf)
{
struct imsg imsg;
int n, cnt;
char *name;
struct ntp_addr *h, *hn;
struct ibuf *buf;
const char *str;
size_t len;
if (((n = imsg_read(ibuf_dns)) == -1 && errno != EAGAIN) || n == 0)
return (-1);
for (;;) {
if ((n = imsg_get(ibuf_dns, &imsg)) == -1)
return (-1);
if (n == 0)
break;
switch (imsg.hdr.type) {
case IMSG_HOST_DNS:
case IMSG_CONSTRAINT_DNS:
if (imsg.hdr.type == IMSG_HOST_DNS)
str = "IMSG_HOST_DNS";
else
str = "IMSG_CONSTRAINT_DNS";
name = imsg.data;
if (imsg.hdr.len < 1 + IMSG_HEADER_SIZE)
fatalx("invalid %s received", str);
len = imsg.hdr.len - 1 - IMSG_HEADER_SIZE;
if (name[len] != '\0' ||
strlen(name) != len)
fatalx("invalid %s received", str);
if ((cnt = host_dns(name, nconf->status.synced,
&hn)) == -1)
break;
buf = imsg_create(ibuf_dns, imsg.hdr.type,
imsg.hdr.peerid, 0,
cnt * (sizeof(struct sockaddr_storage) + sizeof(int)));
if (cnt > 0) {
if (buf) {
for (h = hn; h != NULL; h = h->next) {
if (imsg_add(buf, &h->ss,
sizeof(h->ss)) == -1) {
buf = NULL;
break;
}
if (imsg_add(buf, &h->notauth,
sizeof(int)) == -1) {
buf = NULL;
break;
}
}
}
host_dns_free(hn);
hn = NULL;
}
if (buf)
imsg_close(ibuf_dns, buf);
break;
case IMSG_SYNCED:
nconf->status.synced = 1;
break;
case IMSG_UNSYNCED:
nconf->status.synced = 0;
break;
default:
break;
}
imsg_free(&imsg);
}
return (0);
}
int
probe_root_ns(void)
{
int ret;
int old_retrans, old_retry, old_options;
unsigned char buf[4096];
old_retrans = _res.retrans;
old_retry = _res.retry;
old_options = _res.options;
_res.retrans = 1;
_res.retry = 1;
_res.options |= RES_USE_CD;
ret = res_query(".", C_IN, T_NS, buf, sizeof(buf));
_res.retrans = old_retrans;
_res.retry = old_retry;
_res.options = old_options;
return ret;
}
void
probe_root(void)
{
int n;
n = probe_root_ns();
if (n < 0) {
/* give programs like unwind a second chance */
sleep(1);
n = probe_root_ns();
}
if (imsg_compose(ibuf_dns, IMSG_PROBE_ROOT, 0, 0, -1, &n,
sizeof(int)) == -1)
fatalx("probe_root");
}
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