/*      $OpenBSD: ypldap_dns.c,v 1.8 2015/01/16 06:40:22 deraadt 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 MIND, 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/param.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/tree.h>
#include <sys/queue.h>

#include <netinet/in.h>
#include <arpa/nameser.h>

#include <netdb.h>
#include <pwd.h>
#include <errno.h>
#include <event.h>
#include <resolv.h>
#include <poll.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>

#include "ypldap.h"

volatile sig_atomic_t    quit_dns = 0;
struct imsgev           *iev_dns;

void    dns_dispatch_imsg(int, short, void *);
void    dns_sig_handler(int, short, void *);
void    dns_shutdown(void);
int     host_dns(const char *, struct ypldap_addr_list *);

void
dns_sig_handler(int sig, short event, void *p)
{
        switch (sig) {
        case SIGINT:
        case SIGTERM:
                dns_shutdown();
                break;
        default:
                fatalx("unexpected signal");
        }
}

void
dns_shutdown(void)
{
        log_info("dns engine exiting");
        _exit(0);
}

pid_t
ypldap_dns(int pipe_ntp[2], struct passwd *pw)
{
        pid_t                    pid;
        struct event     ev_sigint;
        struct event     ev_sigterm;
        struct event     ev_sighup;
        struct env       env;

        switch (pid = fork()) {
        case -1:
                fatal("cannot fork");
                break;
        case 0:
                break;
        default:
                return (pid);
        }

        setproctitle("dns engine");
        close(pipe_ntp[0]);

        if (setgroups(0, NULL) ||
            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");
        endservent();

        event_init();
        signal_set(&ev_sigint, SIGINT, dns_sig_handler, NULL);
        signal_set(&ev_sigterm, SIGTERM, dns_sig_handler, NULL);
        signal_set(&ev_sighup, SIGHUP, dns_sig_handler, NULL);
        signal_add(&ev_sigint, NULL);
        signal_add(&ev_sigterm, NULL);
        signal_add(&ev_sighup, NULL);

        if ((env.sc_iev = calloc(1, sizeof(*env.sc_iev))) == NULL)
                fatal(NULL);

        env.sc_iev->events = EV_READ;
        env.sc_iev->data = &env;
        imsg_init(&env.sc_iev->ibuf, pipe_ntp[1]);
        env.sc_iev->handler = dns_dispatch_imsg;
        event_set(&env.sc_iev->ev, env.sc_iev->ibuf.fd, env.sc_iev->events,
            env.sc_iev->handler, &env);
        event_add(&env.sc_iev->ev, NULL);

        event_dispatch();
        dns_shutdown();

        return (0);
}

void
dns_dispatch_imsg(int fd, short events, void *p)
{
        struct imsg              imsg;
        int                      n, cnt;
        char                    *name;
        struct ypldap_addr_list hn = TAILQ_HEAD_INITIALIZER(hn);
        struct ypldap_addr      *h;
        struct ibuf             *buf;
        struct env              *env = p;
        struct imsgev           *iev = env->sc_iev;
        struct imsgbuf          *ibuf = &iev->ibuf;
        int                      shut = 0;

        if ((events & (EV_READ | EV_WRITE)) == 0)
                fatalx("unknown event");

        if (events & EV_READ) {
                if ((n = imsg_read(ibuf)) == -1 && errno != EAGAIN)
                        fatal("imsg_read error");
                if (n == 0)
                        shut = 1;
        }
        if (events & EV_WRITE) {
                if ((n = msgbuf_write(&ibuf->w)) == -1 && errno != EAGAIN)
                        fatal("msgbuf_write");
                if (n == 0)
                        shut = 1;
                goto done;
        }

        for (;;) {
                if ((n = imsg_get(ibuf, &imsg)) == -1)
                        fatal("client_dispatch_imsg: imsg_get error");
                if (n == 0)
                        break;

                switch (imsg.hdr.type) {
                case IMSG_HOST_DNS:
                        name = imsg.data;
                        if (imsg.hdr.len < 1 + IMSG_HEADER_SIZE)
                                fatalx("invalid IMSG_HOST_DNS received");
                        imsg.hdr.len -= 1 + IMSG_HEADER_SIZE;
                        if (name[imsg.hdr.len] != '\0' ||
                            strlen(name) != imsg.hdr.len)
                                fatalx("invalid IMSG_HOST_DNS received");
                        if ((cnt = host_dns(name, &hn)) == -1)
                                break;
                        buf = imsg_create(ibuf, IMSG_HOST_DNS,
                            imsg.hdr.peerid, 0,
                            cnt * sizeof(struct sockaddr_storage));
                        if (buf == NULL)
                                break;
                        if (cnt > 0) {
                                while(!TAILQ_EMPTY(&hn)) {
                                        h = TAILQ_FIRST(&hn);
                                        TAILQ_REMOVE(&hn, h, next);
                                        imsg_add(buf, &h->ss, sizeof(h->ss));
                                        free(h);
                                }
                        }

                        imsg_close(ibuf, buf);
                        break;
                default:
                        break;
                }
                imsg_free(&imsg);
        }

done:
        if (!shut)
                imsg_event_add(iev);
        else {
                /* this pipe is dead, so remove the event handler */
                event_del(&iev->ev);
                event_loopexit(NULL);
        }
}

int
host_dns(const char *s, struct ypldap_addr_list *hn)
{
        struct addrinfo          hints, *res0, *res;
        int                      error, cnt = 0;
        struct sockaddr_in      *sa_in;
        struct sockaddr_in6     *sa_in6;
        struct ypldap_addr      *h;

        memset(&hints, 0, sizeof(hints));
        hints.ai_family = PF_UNSPEC;
        hints.ai_socktype = SOCK_DGRAM; /* DUMMY */
        error = getaddrinfo(s, NULL, &hints, &res0);
        if (error == EAI_AGAIN || error == EAI_NONAME)
                        return (0);
        if (error) {
                log_warnx("could not parse \"%s\": %s", s,
                    gai_strerror(error));
                return (-1);
        }

        for (res = res0; res && cnt < MAX_SERVERS_DNS; res = res->ai_next) {
                if (res->ai_family != AF_INET &&
                    res->ai_family != AF_INET6)
                        continue;
                if ((h = calloc(1, sizeof(struct ypldap_addr))) == NULL)
                        fatal(NULL);
                h->ss.ss_family = res->ai_family;
                if (res->ai_family == AF_INET) {
                        sa_in = (struct sockaddr_in *)&h->ss;
                        sa_in->sin_len = sizeof(struct sockaddr_in);
                        sa_in->sin_addr.s_addr = ((struct sockaddr_in *)
                            res->ai_addr)->sin_addr.s_addr;
                } else {
                        sa_in6 = (struct sockaddr_in6 *)&h->ss;
                        sa_in6->sin6_len = sizeof(struct sockaddr_in6);
                        memcpy(&sa_in6->sin6_addr, &((struct sockaddr_in6 *)
                            res->ai_addr)->sin6_addr, sizeof(struct in6_addr));
                }

                TAILQ_INSERT_HEAD(hn, h, next);
                cnt++;
        }
        freeaddrinfo(res0);
        return (cnt);
}