/*      $NetBSD: mail.local.c,v 1.33 2023/09/06 22:08:38 christos Exp $ */

/*-
 * Copyright (c) 1990, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * 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 University 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 REGENTS 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 REGENTS 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.
 */

#include <sys/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1990, 1993, 1994\
 The Regents of the University of California.  All rights reserved.");
#if 0
static char sccsid[] = "@(#)mail.local.c        8.22 (Berkeley) 6/21/95";
#else
__RCSID("$NetBSD: mail.local.c,v 1.33 2023/09/06 22:08:38 christos Exp $");
#endif
#endif /* not lint */

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

#include <netinet/in.h>

#include <errno.h>
#include <fcntl.h>
#include <pwd.h>
#include <netdb.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <time.h>
#include <unistd.h>
#include <sysexits.h>


#include "pathnames.h"

static int      deliver(int, char *, int);
__dead static void      logerr(int, const char *, ...) __printflike(2, 3);
static void     logwarn(const char *, ...) __printflike(1, 2);
static void     notifybiff(char *);
static int      store(const char *);
__dead static void      usage(void);

int
main(int argc, char *argv[])
{
        struct passwd *pw;
        int ch, fd, eval, lockfile = 0;
        uid_t uid;
        const char *from;

        /* use a reasonable umask */
        (void) umask(0077);

        openlog("mail.local", LOG_PERROR, LOG_MAIL);

        from = NULL;
        while ((ch = getopt(argc, argv, "ldf:r:")) != -1)
                switch (ch) {
                case 'd':               /* backward compatible */
                        break;
                case 'f':
                case 'r':               /* backward compatible */
                        if (from)
                                logerr(EX_USAGE, "multiple -f options");
                        from = optarg;
                        break;
                case 'l':
                        lockfile++;
                        break;
                case '?':
                default:
                        usage();
                }
        argc -= optind;
        argv += optind;

        if (!*argv)
                usage();

        /*
         * If from not specified, use the name from getlogin() if the
         * uid matches, otherwise, use the name from the password file
         * corresponding to the uid.
         */
        uid = getuid();
        if (!from && (!(from = getlogin()) ||
            !(pw = getpwnam(from)) || pw->pw_uid != uid))
                from = (pw = getpwuid(uid)) ? pw->pw_name : "???";

        fd = store(from);
        for (eval = EX_OK; *argv; ++argv) {
                int rval;

                rval = deliver(fd, *argv, lockfile);
                if (eval == EX_OK && rval != EX_OK)
                        eval = rval;
        }
        return eval;
}

static int
store(const char *from)
{
        FILE *fp = NULL;        /* XXX gcc */
        time_t tval;
        int fd, eline;
        char *tn, line[2048];

        tn = strdup(_PATH_LOCTMP);
        if (!tn)
                logerr(EX_OSERR, "not enough memory");
        if ((fd = mkstemp(tn)) == -1 || !(fp = fdopen(fd, "w+")))
                logerr(EX_OSERR, "unable to open temporary file");
        (void)unlink(tn);
        free(tn);

        (void)time(&tval);
        (void)fprintf(fp, "From %s %s", from, ctime(&tval));

        line[0] = '\0';
        for (eline = 1; fgets(line, sizeof(line), stdin);) {
                if (line[0] == '\n')
                        eline = 1;
                else {
                        if (eline && line[0] == 'F' && !memcmp(line, "From ", 5))
                                (void)putc('>', fp);
                        eline = 0;
                }
                (void)fprintf(fp, "%s", line);
                if (ferror(fp))
                        break;
        }

        /* If message not newline terminated, need an extra. */
        if (!index(line, '\n'))
                (void)putc('\n', fp);
        /* Output a newline; note, empty messages are allowed. */
        (void)putc('\n', fp);

        (void)fflush(fp);
        if (ferror(fp))
                logerr(EX_OSERR, "temporary file write error");
        if ((fd = dup(fd)) == -1) 
                logerr(EX_OSERR, "dup failed");
        (void)fclose(fp);
        return fd;
}

static bool
badfile(const char *path, const struct stat *sb)
{
        if (!S_ISREG(sb->st_mode)) {
                logwarn("%s: not a regular file", path);
                return true;
        }

        if (sb->st_nlink != 1) {
                logwarn("%s: linked file", path);
                return true;
        }
        return false;
}

static int
deliver(int fd, char *name, int lockfile)
{
        struct stat sb, nsb;
        struct passwd pwres, *pw;
        char pwbuf[1024];
        int created = 0, mbfd = -1, nr, nw, off, rval = EX_OSERR, lfd = -1;
        char biffmsg[100], buf[8*1024], path[MAXPATHLEN], lpath[MAXPATHLEN];
        off_t curoff;

        /*
         * Disallow delivery to unknown names -- special mailboxes can be
         * handled in the sendmail aliases file.
         */
        if ((getpwnam_r(name, &pwres, pwbuf, sizeof(pwbuf), &pw)) != 0) {
                logwarn("unable to find user %s: %s", name, strerror(errno));
                return EX_TEMPFAIL;
        }
        if (pw == NULL) {
                logwarn("unknown name: %s", name);
                return EX_NOUSER;
        }

        (void)snprintf(path, sizeof path, "%s/%s", _PATH_MAILDIR, name);

        if (lockfile) {
                (void)snprintf(lpath, sizeof lpath, "%s/%s.lock",
                    _PATH_MAILDIR, name);

                if((lfd = open(lpath, O_CREAT|O_WRONLY|O_EXCL,
                    S_IRUSR|S_IWUSR)) < 0) {
                        logwarn("%s: can't create: %s", lpath, strerror(errno));
                        return EX_OSERR;
                }
        }

        if (lstat(path, &sb) == -1) {
                if (errno != ENOENT) {
                        logwarn("%s: can't stat: %s", path, strerror(errno));
                        goto bad;
                }
                memset(&sb, 0, sizeof(sb));
                sb.st_dev = NODEV;
        } else if (badfile(path, &sb)) {
                goto bad;
        }
        
        if ((mbfd = open(path, O_APPEND|O_WRONLY|O_EXLOCK|O_NOFOLLOW,
            S_IRUSR|S_IWUSR)) == -1) {
                /* create file */
                if (errno != ENOENT ||
                   (mbfd = open(path, O_APPEND|O_CREAT|O_WRONLY|O_EXLOCK|O_EXCL,
                     S_IRUSR|S_IWUSR)) == -1) {
                        logwarn("%s: can't create: %s", path, strerror(errno));
                        goto bad;
                }
                created = 1;
        } else {
                /* opened existing file, check for TOCTTOU */
                if (fstat(mbfd, &nsb) == -1) {
                        logwarn("%s: can't stat: %s", path, strerror(errno));
                        goto bad;
                }

                if (badfile(path, &nsb)) {
                        goto bad;
                }

                /* file is not what we expected */
                if (nsb.st_ino != sb.st_ino || nsb.st_dev != sb.st_dev) {
                        logwarn("%s: file has changed", path);
                        goto bad;
                }
        }

        if ((curoff = lseek(mbfd, 0, SEEK_END)) == (off_t)-1) {
                logwarn("%s: can't seek: %s", path, strerror(errno));
                goto bad;
        }

        (void)snprintf(biffmsg, sizeof biffmsg, "%s@%lld\n", name,
            (long long)curoff);
        if (lseek(fd, 0, SEEK_SET) == (off_t)-1) {
                logwarn("can't seek: %s", strerror(errno));
                goto bad;
        }

        while ((nr = read(fd, buf, sizeof(buf))) > 0)
                for (off = 0; off < nr;  off += nw)
                        if ((nw = write(mbfd, buf + off, nr - off)) < 0) {
                                logwarn("%s: can't write: %s", path,
                                    strerror(errno));
                                goto trunc;
                        }

        if (nr < 0) {
                logwarn("can't read: %s", strerror(errno));
trunc:          (void)ftruncate(mbfd, curoff);
                goto bad;
        }

        rval = EX_OK;
        /*
         * Set the owner and group.  Historically, binmail repeated this at
         * each mail delivery.  We no longer do this, assuming that if the
         * ownership or permissions were changed there was a reason for doing
         * so.
         */
bad:
        if (lockfile) {
                if (lfd >= 0) {
                        unlink(lpath);
                        close(lfd);
                }
        }

        if (mbfd >= 0) {
                if (created) 
                        (void)fchown(mbfd, pw->pw_uid, pw->pw_gid);

                (void)fsync(mbfd);              /* Don't wait for update. */
                (void)close(mbfd);              /* Implicit unlock. */
        }

        if (rval == EX_OK)
                notifybiff(biffmsg);

        return rval;
}

void
notifybiff(char *msg)
{
        static struct sockaddr_in addr;
        static int f = -1;
        struct hostent *hp;
        struct servent *sp;
        int len;

        if (!addr.sin_family) {
                /* Be silent if biff service not available. */
                if (!(sp = getservbyname("biff", "udp")))
                        return;
                if (!(hp = gethostbyname("localhost"))) {
                        logwarn("localhost: %s", strerror(errno));
                        return;
                }
                addr.sin_len = sizeof(struct sockaddr_in);
                addr.sin_family = hp->h_addrtype;
                addr.sin_port = sp->s_port;
                memcpy(&addr.sin_addr, hp->h_addr, hp->h_length);
        }
        if (f < 0 && (f = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
                logwarn("socket: %s", strerror(errno));
                return;
        }
        len = strlen(msg) + 1;
        if (sendto(f, msg, len, 0, (struct sockaddr *)&addr, sizeof(addr))
            != len)
                logwarn("sendto biff: %s", strerror(errno));
}

static void
usage(void)
{
        logerr(EX_USAGE, "usage: mail.local [-l] [-f from] user ...");
}

static void
logerr(int status, const char *fmt, ...)
{
        va_list ap;

        va_start(ap, fmt);
        vsyslog(LOG_ERR, fmt, ap);
        va_end(ap);

        exit(status);
        /* NOTREACHED */
}

static void
logwarn(const char *fmt, ...)
{
        va_list ap;

        va_start(ap, fmt);
        vsyslog(LOG_ERR, fmt, ap);
        va_end(ap);
        return;
}