/*
 * Copyright (c) 2010-2014, Simon Schubert <2@0x2c.org>.
 * Copyright (c) 2008 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Simon Schubert <2@0x2c.org>.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * This binary is setuid root.  Use extreme caution when touching
 * user-supplied information.  Keep the root window as small as possible.
 */

#include <sys/param.h>
#include <sys/stat.h>

#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <paths.h>
#include <pwd.h>
#include <stdio.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>

#include "dma.h"


static void
logfail(int exitcode, const char *fmt, ...)
{
        int oerrno = errno;
        va_list ap;
        char outs[1024];

        outs[0] = 0;
        if (fmt != NULL) {
                va_start(ap, fmt);
                vsnprintf(outs, sizeof(outs), fmt, ap);
                va_end(ap);
        }

        errno = oerrno;
        if (*outs != 0)
                syslog(LOG_ERR, errno ? "%s: %m" : "%s", outs);
        else
                syslog(LOG_ERR, errno ? "%m" : "unknown error");

        exit(exitcode);
}

/*
 * Create a mbox in /var/mail for a given user, or make sure
 * the permissions are correct for dma.
 */

int
main(int argc, char **argv)
{
        const char *user;
        struct passwd *pw;
        struct group *gr;
        uid_t user_uid;
        gid_t mail_gid;
        int f, maildirfd;

        openlog("dma-mbox-create", 0, LOG_MAIL);

        errno = 0;
        gr = getgrnam(DMA_GROUP);
        if (!gr)
                logfail(EX_CONFIG, "cannot find dma group `%s'", DMA_GROUP);

        mail_gid = gr->gr_gid;

        if (setgid(mail_gid) != 0)
                logfail(EX_NOPERM, "cannot set gid to %d (%s)", mail_gid, DMA_GROUP);
        if (getegid() != mail_gid)
                logfail(EX_NOPERM, "cannot set gid to %d (%s), still at %d", mail_gid, DMA_GROUP, getegid());

        /*
         * We take exactly one argument: the username.
         */
        if (argc != 2) {
                errno = 0;
                logfail(EX_USAGE, "no arguments");
        }
        user = argv[1];

        syslog(LOG_NOTICE, "creating mbox for `%s'", user);

        /* the username may not contain a pathname separator */
        if (strchr(user, '/')) {
                errno = 0;
                logfail(EX_DATAERR, "path separator in username `%s'", user);
                exit(1);
        }

        /* verify the user exists */
        errno = 0;
        pw = getpwnam(user);
        if (!pw)
                logfail(EX_NOUSER, "cannot find user `%s'", user);

        maildirfd = open(_PATH_MAILDIR, O_RDONLY);
        if (maildirfd < 0)
                logfail(EX_NOINPUT, "cannot open maildir %s", _PATH_MAILDIR);

        user_uid = pw->pw_uid;

        f = openat(maildirfd, user, O_RDONLY|O_CREAT|O_NOFOLLOW, 0600);
        if (f < 0)
                logfail(EX_NOINPUT, "cannot open mbox `%s'", user);

        if (fchown(f, user_uid, mail_gid))
                logfail(EX_OSERR, "cannot change owner of mbox `%s'", user);

        if (fchmod(f, 0620))
                logfail(EX_OSERR, "cannot change permissions of mbox `%s'",
                    user);

        /* file should be present with the right owner and permissions */

        syslog(LOG_NOTICE, "successfully created mbox for `%s'", user);

        return (0);
}