/*      $OpenBSD: privsep.c,v 1.16 2006/10/25 20:55:04 moritz Exp $     */

/*
 * Copyright (c) 2003 Can Erkin Acar
 * Copyright (c) 2003 Anil Madhavapeddy <anil@recoil.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/time.h>
#include <sys/socket.h>
#include <sys/ioctl.h>

#include <net/if.h>
#include <net/bpf.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pcap.h>
#include <pcap-int.h>
#include <syslog.h>
#include <unistd.h>
#include "pflogd.h"

enum cmd_types {
        PRIV_SET_SNAPLEN,       /* set the snaplength */
        PRIV_MOVE_LOG,          /* move logfile away */
        PRIV_OPEN_LOG           /* open logfile for appending */
};

static int priv_fd = -1;
static volatile pid_t child_pid = -1;

volatile sig_atomic_t gotsig_chld = 0;

static void sig_pass_to_chld(int);
static void sig_chld(int);
static int  may_read(int, void *, size_t);
static void must_read(int, void *, size_t);
static void must_write(int, void *, size_t);
static int  set_snaplen(int snap);
static int  move_log(const char *name);

extern char *filename;
extern pcap_t *hpcap;

/* based on syslogd privsep */
int
priv_init(void)
{
        int i, fd, socks[2], cmd;
        int snaplen, ret, olderrno;
        struct passwd *pw;

        for (i = 1; i < NSIG; i++)
                signal(i, SIG_DFL);

        /* Create sockets */
        if (socketpair(AF_LOCAL, SOCK_STREAM, PF_UNSPEC, socks) == -1)
                err(1, "socketpair() failed");

        pw = getpwnam("_pflogd");
        if (pw == NULL)
                errx(1, "unknown user _pflogd");
        endpwent();

        child_pid = fork();
        if (child_pid < 0)
                err(1, "fork() failed");

        if (!child_pid) {
                gid_t gidset[1];

                /* Child - drop privileges and return */
                if (chroot(pw->pw_dir) != 0)
                        err(1, "unable to chroot");
                if (chdir("/") != 0)
                        err(1, "unable to chdir");

                gidset[0] = pw->pw_gid;
                if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1)
                        err(1, "setresgid() failed");
                if (setgroups(1, gidset) == -1)
                        err(1, "setgroups() failed");
                if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1)
                        err(1, "setresuid() failed");
                close(socks[0]);
                priv_fd = socks[1];
                return 0;
        }

        /* Father */
        /* Pass ALRM/TERM/HUP/INT/QUIT through to child, and accept CHLD */
        signal(SIGALRM, sig_pass_to_chld);
        signal(SIGTERM, sig_pass_to_chld);
        signal(SIGHUP,  sig_pass_to_chld);
        signal(SIGINT,  sig_pass_to_chld);
        signal(SIGQUIT,  sig_pass_to_chld);
        signal(SIGCHLD, sig_chld);

        setproctitle("[priv]");
        close(socks[1]);

        while (!gotsig_chld) {
                if (may_read(socks[0], &cmd, sizeof(int)))
                        break;
                switch (cmd) {
                case PRIV_SET_SNAPLEN:
                        logmsg(LOG_DEBUG,
                            "[priv]: msg PRIV_SET_SNAPLENGTH received");
                        must_read(socks[0], &snaplen, sizeof(int));

                        ret = set_snaplen(snaplen);
                        if (ret) {
                                logmsg(LOG_NOTICE,
                                   "[priv]: set_snaplen failed for snaplen %d",
                                   snaplen);
                        }

                        must_write(socks[0], &ret, sizeof(int));
                        break;

                case PRIV_OPEN_LOG:
                        logmsg(LOG_DEBUG,
                            "[priv]: msg PRIV_OPEN_LOG received");
                        /* create or append logs but do not follow symlinks */
                        fd = open(filename,
                            O_RDWR|O_CREAT|O_APPEND|O_NONBLOCK|O_NOFOLLOW,
                            0600);
                        olderrno = errno;
                        send_fd(socks[0], fd);
                        if (fd < 0)
                                logmsg(LOG_NOTICE,
                                    "[priv]: failed to open %s: %s",
                                    filename, strerror(olderrno));
                        else
                                close(fd);
                        break;

                case PRIV_MOVE_LOG:
                        logmsg(LOG_DEBUG,
                            "[priv]: msg PRIV_MOVE_LOG received");
                        ret = move_log(filename);
                        must_write(socks[0], &ret, sizeof(int));
                        break;

                default:
                        logmsg(LOG_ERR, "[priv]: unknown command %d", cmd);
                        _exit(1);
                        /* NOTREACHED */
                }
        }

        _exit(1);
}

/* this is called from parent */
static int
set_snaplen(int snap)
{
        if (hpcap == NULL)
                return (1);

        hpcap->snapshot = snap;
        set_pcap_filter();

        return 0;
}

static int
move_log(const char *name)
{
        char ren[PATH_MAX];
        u_int32_t len;

        for (;;) {
                int fd;

                len = snprintf(ren, sizeof(ren), "%s.bad.%08x",
                    name, arc4random());
                if (len >= sizeof(ren)) {
                        logmsg(LOG_ERR, "[priv] new name too long");
                        return (1);
                }

                /* lock destinanion */
                fd = open(ren, O_CREAT|O_EXCL, 0);
                if (fd >= 0) {
                        close(fd);
                        break;
                }
                /* if file exists, try another name */
                if (errno != EEXIST && errno != EINTR) {
                        logmsg(LOG_ERR, "[priv] failed to create new name: %s",
                            strerror(errno));
                        return (1);                     
                }
        }

        if (rename(name, ren)) {
                logmsg(LOG_ERR, "[priv] failed to rename %s to %s: %s",
                    name, ren, strerror(errno));
                return (1);
        }

        logmsg(LOG_NOTICE,
               "[priv]: log file %s moved to %s", name, ren);

        return (0);
}

/*
 * send the snaplength to privileged process
 */
int
priv_set_snaplen(int snaplen)
{
        int cmd, ret;

        if (priv_fd < 0)
                errx(1, "%s: called from privileged portion", __func__);

        cmd = PRIV_SET_SNAPLEN;

        must_write(priv_fd, &cmd, sizeof(int));
        must_write(priv_fd, &snaplen, sizeof(int));

        must_read(priv_fd, &ret, sizeof(int));

        /* also set hpcap->snapshot in child */
        if (ret == 0)
                hpcap->snapshot = snaplen;

        return (ret);
}

/* Open log-file */
int
priv_open_log(void)
{
        int cmd, fd;

        if (priv_fd < 0)
                errx(1, "%s: called from privileged portion", __func__);

        cmd = PRIV_OPEN_LOG;
        must_write(priv_fd, &cmd, sizeof(int));
        fd = receive_fd(priv_fd);

        return (fd);
}
/* Move-away and reopen log-file */
int
priv_move_log(void)
{
        int cmd, ret;

        if (priv_fd < 0)
                errx(1, "%s: called from privileged portion\n", __func__);

        cmd = PRIV_MOVE_LOG;
        must_write(priv_fd, &cmd, sizeof(int));
        must_read(priv_fd, &ret, sizeof(int));

        return (ret);
}

/* If priv parent gets a TERM or HUP, pass it through to child instead */
static void
sig_pass_to_chld(int sig)
{
        int oerrno = errno;

        if (child_pid != -1)
                kill(child_pid, sig);
        errno = oerrno;
}

/* if parent gets a SIGCHLD, it will exit */
static void
sig_chld(int sig __unused)
{
        gotsig_chld = 1;
}

/* Read all data or return 1 for error.  */
static int
may_read(int fd, void *buf, size_t n)
{
        char *s = buf;
        ssize_t res;
        size_t pos = 0;

        while (n > pos) {
                res = read(fd, s + pos, n - pos);
                switch (res) {
                case -1:
                        if (errno == EINTR || errno == EAGAIN)
                                continue;
                        /* FALLTHROUGH */
                case 0:
                        return (1);
                default:
                        pos += res;
                }
        }
        return (0);
}

/* Read data with the assertion that it all must come through, or
 * else abort the process.  Based on atomicio() from openssh. */
static void
must_read(int fd, void *buf, size_t n)
{
        char *s = buf;
        ssize_t res;
        size_t pos = 0;

        while (n > pos) {
                res = read(fd, s + pos, n - pos);
                switch (res) {
                case -1:
                        if (errno == EINTR || errno == EAGAIN)
                                continue;
                        /* FALLTHROUGH */
                case 0:
                        _exit(0);
                default:
                        pos += res;
                }
        }
}

/* Write data with the assertion that it all has to be written, or
 * else abort the process.  Based on atomicio() from openssh. */
static void
must_write(int fd, void *buf, size_t n)
{
        char *s = buf;
        ssize_t res;
        size_t pos = 0;

        while (n > pos) {
                res = write(fd, s + pos, n - pos);
                switch (res) {
                case -1:
                        if (errno == EINTR || errno == EAGAIN)
                                continue;
                        /* FALLTHROUGH */
                case 0:
                        _exit(0);
                default:
                        pos += res;
                }
        }
}