/*      $NetBSD: vacation.c,v 1.38 2023/04/11 10:34:52 hauke Exp $      */

/*
 * Copyright (c) 1983, 1987, 1993
 *      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) 1983, 1987, 1993\
 The Regents of the University of California.  All rights reserved.");
#endif /* not lint */

#ifndef lint
#if 0
static char sccsid[] = "@(#)vacation.c  8.2 (Berkeley) 1/26/94";
#endif
__RCSID("$NetBSD: vacation.c,v 1.38 2023/04/11 10:34:52 hauke Exp $");
#endif /* not lint */

/*
**  Vacation
**  Copyright (c) 1983  Eric P. Allman
**  Berkeley, California
*/

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

#include <ctype.h>
#include <db.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <time.h>
#include <tzfile.h>
#include <unistd.h>

/*
 *  VACATION -- return a message to the sender when on vacation.
 *
 *      This program is invoked as a message receiver.  It returns a
 *      message specified by the user to whomever sent the mail, taking
 *      care not to return a message too often to prevent "I am on
 *      vacation" loops.
 */

#define MAXLINE 1024                    /* max line from mail header */

static const char *dbprefix = ".vacation";      /* dbm's database sans .db */
static const char *msgfile = ".vacation.msg";   /* vacation message */

typedef struct alias {
        struct alias *next;
        const char *name;
} alias_t;
static alias_t *names;

static DB *db;
static char from[MAXLINE];
static char subject[MAXLINE];

static int iflag = 0;           /* Initialize the database */

static int tflag = 0;
#define APPARENTLY_TO           1
#define DELIVERED_TO            2

static int fflag = 0;
#define FROM_FROM               1
#define RETURN_PATH_FROM        2
#define SENDER_FROM             4

static int toanybody = 0;       /* Don't check if we appear in the to or cc */

static int debug = 0;

static void opendb(void);
static int junkmail(const char *);
static int nsearch(const char *, const char *);
static int readheaders(void);
static int recent(void);
static void getfrom(char *);
static void sendmessage(const char *);
static void setinterval(time_t);
static void setreply(void);
static void usage(void) __dead;

int
main(int argc, char **argv)
{
        struct passwd *pw;
        alias_t *cur;
        long interval;
        int ch, rv;
        char *p;

        setprogname(argv[0]);
        opterr = 0;
        interval = -1;
        openlog(getprogname(), 0, LOG_USER);
        while ((ch = getopt(argc, argv, "a:df:F:Iijm:r:s:t:T:")) != -1)
                switch((char)ch) {
                case 'a':                       /* alias */
                        if (!(cur = (alias_t *)malloc((size_t)sizeof(alias_t))))
                                break;
                        cur->name = optarg;
                        cur->next = names;
                        names = cur;
                        break;
                case 'd':
                        debug++;
                        break;
                case 'F':
                        for (p = optarg; *p; p++)
                                switch (*p) {
                                case 'F':
                                        fflag |= FROM_FROM;
                                        break;
                                case 'R':
                                        fflag |= RETURN_PATH_FROM;
                                        break;
                                case 'S':
                                        fflag |= SENDER_FROM;
                                        break;
                                default:
                                        errx(1, "Unknown -f option `%c'", *p);
                                }
                        break;
                case 'f':
                        dbprefix = optarg;
                        break;
                case 'I':                       /* backward compatible */
                case 'i':                       /* init the database */
                        iflag = 1;
                        break;
                case 'j':
                        toanybody = 1;
                        break;
                case 'm':
                        msgfile = optarg;
                        break;
                case 'r':
                case 't':       /* Solaris compatibility */
                        if (!isdigit((unsigned char)*optarg)) {
                                interval = LONG_MAX;
                                break;
                        }
                        if (*optarg == '\0')
                                goto bad;
                        interval = strtol(optarg, &p, 0);
                        if (errno == ERANGE &&
                            (interval == LONG_MAX || interval == LONG_MIN))
                                err(1, "Bad interval `%s'", optarg);
                        switch (*p) {
                        case 's':
                                break;
                        case 'm':
                                interval *= SECSPERMIN;
                                break;
                        case 'h':
                                interval *= SECSPERHOUR;
                                break;
                        case 'd':
                        case '\0':
                                interval *= SECSPERDAY;
                                break;
                        case 'w':
                                interval *= DAYSPERWEEK * SECSPERDAY;
                                break;
                        default:
                        bad:
                                errx(1, "Invalid interval `%s'", optarg);
                        }
                        if (interval < 0 || (*p && p[1]))
                                goto bad;
                        break;
                case 's':
                        (void)strlcpy(from, optarg, sizeof(from));
                        break;
                case 'T':
                        for (p = optarg; *p; p++)
                                switch (*p) {
                                case 'A':
                                        tflag |= APPARENTLY_TO;
                                        break;
                                case 'D':
                                        tflag |= DELIVERED_TO;
                                        break;
                                default:
                                        errx(1, "Unknown -T option `%c'", *p);
                                }
                        break;
                case '?':
                default:
                        usage();
                }
        argc -= optind;
        argv += optind;

        if (argc != 1) {
                if (!iflag)
                        usage();
                if (!(pw = getpwuid(getuid()))) {
                        syslog(LOG_ERR, "%s: no such user uid %u.",
                            getprogname(), getuid());
                        exit(1);
                }
        }
        else if (!(pw = getpwnam(*argv))) {
                syslog(LOG_ERR, "%s: no such user %s.",
                    getprogname(), *argv);
                exit(1);
        }
        if (chdir(pw->pw_dir) == -1 && 
            (dbprefix[0] != '/' || msgfile[0] != '/')) {
                syslog(LOG_ERR, "%s: no such directory %s.",
                    getprogname(), pw->pw_dir);
                exit(1);
        }

        opendb();

        if (interval != -1)
                setinterval((time_t)interval);

        if (iflag) {
                (void)(db->close)(db);
                exit(0);
        }

        if (!(cur = malloc((size_t)sizeof(alias_t)))) {
                syslog(LOG_ERR, "%s: %m", getprogname());
                (void)(db->close)(db);
                exit(1);
        }
        cur->name = pw->pw_name;
        cur->next = names;
        names = cur;

        if ((rv = readheaders()) != -1) {
                (void)(db->close)(db);
                exit(rv);
        }
                
        if (!recent()) {
                setreply();
                (void)(db->close)(db);
                sendmessage(pw->pw_name);
        }
        else
                (void)(db->close)(db);
        exit(0);
        /* NOTREACHED */
}

static void
opendb(void)
{
        char path[MAXPATHLEN];

        (void)snprintf(path, sizeof(path), "%s.db", dbprefix);
        db = dbopen(path, O_CREAT|O_RDWR | (iflag ? O_TRUNC : 0),
            S_IRUSR|S_IWUSR, DB_HASH, NULL);

        if (!db) {
                syslog(LOG_ERR, "%s: %s: %m", getprogname(), path);
                exit(1);
        }
}

/*
 * readheaders --
 *      read mail headers
 */
static int
readheaders(void)
{
        alias_t *cur;
        char *p;
        int tome, cont;
        char buf[MAXLINE];

        cont = tome = 0;
#define COMPARE(a, b)           strncmp(a, b, sizeof(b) - 1)
#define CASECOMPARE(a, b)       strncasecmp(a, b, sizeof(b) - 1)
        while (fgets(buf, sizeof(buf), stdin) && *buf != '\n')
                switch(*buf) {
                case 'F':               /* "From " or "From:" */
                        cont = 0;
                        if (COMPARE(buf, "From ") == 0)
                                getfrom(buf + sizeof("From ") - 1);
                        if ((fflag & FROM_FROM) != 0 &&
                            COMPARE(buf, "From:") == 0)
                                getfrom(buf + sizeof("From:") - 1);
                        break;
                case 'P':               /* "Precedence:" rfc 2076 ch 3.9 */
                        cont = 0;
                        if (CASECOMPARE(buf, "Precedence") != 0 ||
                            (buf[10] != ':' && buf[10] != ' ' &&
                            buf[10] != '\t'))
                                break;
                        if ((p = strchr(buf, ':')) == NULL)
                                break;
                        while (*++p && isspace((unsigned char)*p))
                                continue;
                        if (!*p)
                                break;
                        if (CASECOMPARE(p, "junk") == 0 ||
                            CASECOMPARE(p, "bulk") == 0||
                            CASECOMPARE(p, "list") == 0)
                                exit(0);
                        break;
                case 'C':               /* "Cc:" */
                        if (COMPARE(buf, "Cc:"))
                                break;
                        cont = 1;
                        goto findme;
                case 'T':               /* "To:" */
                        if (COMPARE(buf, "To:"))
                                break;
                        cont = 1;
                        goto findme;
                case 'A':
                        /* "Apparently-To:" */
                        if ((tflag & APPARENTLY_TO) != 0 &&
                            COMPARE(buf, "Apparently-To:") == 0) {
                                cont = 1;
                                goto findme;
                        }
                        /* "Auto-Submitted:" rfc 3834 ch 5 */
                        cont = 0;
                        if (CASECOMPARE(buf, "Auto-Submitted") != 0 ||
                            (buf[14] != ':' && buf[14] != ' ' &&
                            buf[14] != '\t'))
                                break;
                        if ((p = strchr(buf, ':')) == NULL)
                                break;
                        while (*++p && isspace((unsigned char)*p))
                                continue;
                        if (CASECOMPARE(p, "no") != 0 )
                                exit(0);
                        break;
                case 'D':               /* "Delivered-To:" */
                        if ((tflag & DELIVERED_TO) == 0 ||
                            COMPARE(buf, "Delivered-To:") != 0)
                                break;
                        cont = 1;
                        goto findme;
                case 'R':               /* "Return-Path:" */
                        cont = 0;
                        if ((fflag & RETURN_PATH_FROM) != 0 &&
                            COMPARE(buf, "Return-Path:") == 0)
                                getfrom(buf + sizeof("Return-Path:") - 1);
                        break;
                case 'S':               /* "Sender:" */
                        cont = 0;
                        if (COMPARE(buf, "Subject:") == 0) {
                                /* trim leading blanks */
                                char *s = NULL;
                                for (p = buf + sizeof("Subject:") - 1; *p; p++)
                                        if (s == NULL &&
                                            !isspace((unsigned char)*p))
                                                s = p;
                                /* trim trailing blanks */
                                if (s) {
                                        for (--p; p != s; p--)
                                                if (!isspace((unsigned char)*p))
                                                        break;
                                        *++p = '\0';
                                }
                                if (s) {
                                        (void)strlcpy(subject, s, sizeof(subject));
                                } else {
                                        subject[0] = '\0';
                                }
                        }
                        if ((fflag & SENDER_FROM) != 0 &&
                            COMPARE(buf, "Sender:") == 0)
                                getfrom(buf + sizeof("Sender:") - 1);
                        break;
                default:
                        if (!isspace((unsigned char)*buf) || !cont || tome) {
                                cont = 0;
                                break;
                        }
findme:                 for (cur = names; !tome && cur; cur = cur->next)
                                tome += nsearch(cur->name, buf);
                }
        if (!toanybody && !tome)
                return 0;
        if (!*from) {
                syslog(LOG_ERR, "%s: no initial \"From\" line.",
                        getprogname());
                return 1;
        }
        return -1;
}

/*
 * nsearch --
 *      do a nice, slow, search of a string for a substring.
 */
static int
nsearch(const char *name, const char *str)
{
        size_t len;

        for (len = strlen(name); *str; ++str)
                if (!strncasecmp(name, str, len))
                        return(1);
        return(0);
}

/*
 * getfrom --
 *      return the first string in the buffer, stripping leading and trailing
 *      blanks and <>.
 */
void
getfrom(char *buf)
{
        char *s, *p;

        if ((s = strchr(buf, '<')) != NULL)
                s++;
        else
                s = buf;

        for (; *s && isspace((unsigned char)*s); s++)
                continue;
        for (p = s; *p && !isspace((unsigned char)*p); p++)
                continue;

        if (*--p == '>')
                *p = '\0';
        else
                *++p = '\0';

        if (junkmail(s))
                exit(0);

        if (!*from)
                (void)strlcpy(from, s, sizeof(from));
}

/*
 * junkmail --
 *      read the header and return if automagic/junk/bulk/list mail
 */
static int
junkmail(const char *addr)
{
        static struct ignore {
                const char *name;
                size_t  len;
        } ignore[] = {
#define INIT(a) { a, sizeof(a) - 1 }
                INIT("-request"),
                INIT("postmaster"),
                INIT("uucp"),
                INIT("mailer-daemon"),
                INIT("mailer"),
                INIT("-relay"),
                {NULL, 0 }
        };
        struct ignore *cur;
        size_t len;
        const char *p;

        /*
         * This is mildly amusing, and I'm not positive it's right; trying
         * to find the "real" name of the sender, assuming that addresses
         * will be some variant of:
         *
         * From site!site!SENDER%site.domain%site.domain@site.domain
         */
        if (!(p = strchr(addr, '%')))
                if (!(p = strchr(addr, '@'))) {
                        if ((p = strrchr(addr, '!')) != NULL)
                                ++p;
                        else
                                p = addr;
                        for (; *p; ++p)
                                continue;
                }
        len = p - addr;
        for (cur = ignore; cur->name; ++cur)
                if (len >= cur->len &&
                    !strncasecmp(cur->name, p - cur->len, cur->len))
                        return(1);
        return(0);
}

#define VIT     "__VACATION__INTERVAL__TIMER__"

/*
 * recent --
 *      find out if user has gotten a vacation message recently.
 *      use memmove for machines with alignment restrictions
 */
static int
recent(void)
{
        DBT key, data;
        time_t then, next;

        /* get interval time */
        key.data = (void *)(intptr_t)VIT;
        key.size = sizeof(VIT);
        if ((db->get)(db, &key, &data, 0))
                next = SECSPERDAY * DAYSPERWEEK;
        else
                (void)memmove(&next, data.data, sizeof(next));

        /* get record for this address */
        key.data = from;
        key.size = strlen(from);
        if (!(db->get)(db, &key, &data, 0)) {
                (void)memmove(&then, data.data, sizeof(then));
                if (next == (time_t)LONG_MAX ||                 /* XXX */
                    then + next > time(NULL))
                        return(1);
        }
        return(0);
}

/*
 * setinterval --
 *      store the reply interval
 */
static void
setinterval(time_t interval)
{
        DBT key, data;

        key.data = (void *)(intptr_t)VIT;
        key.size = sizeof(VIT);
        data.data = &interval;
        data.size = sizeof(interval);
        (void)(db->put)(db, &key, &data, 0);
}

/*
 * setreply --
 *      store that this user knows about the vacation.
 */
static void
setreply(void)
{
        DBT key, data;
        time_t now;

        key.data = from;
        key.size = strlen(from);
        (void)time(&now);
        data.data = &now;
        data.size = sizeof(now);
        (void)(db->put)(db, &key, &data, 0);
}

/*
 * sendmessage --
 *      exec sendmail to send the vacation file to sender
 */
static void
sendmessage(const char *myname)
{
        FILE *mfp, *sfp;
        int i;
        int pvect[2];
        char buf[MAXLINE];

        mfp = fopen(msgfile, "r");
        if (mfp == NULL) {
                syslog(LOG_ERR, "%s: no `%s' file for `%s'.", getprogname(),
                    myname, msgfile);
                exit(1);
        }

        if (debug) {
                sfp = stdout;
        } else {
                if (pipe(pvect) < 0) {
                        syslog(LOG_ERR, "%s: pipe: %m", getprogname());
                        exit(1);
                }
                i = vfork();
                if (i < 0) {
                        syslog(LOG_ERR, "%s: fork: %m", getprogname());
                        exit(1);
                }
                if (i == 0) {
                        (void)dup2(pvect[0], 0);
                        (void)close(pvect[0]);
                        (void)close(pvect[1]);
                        (void)close(fileno(mfp));
                        (void)execl(_PATH_SENDMAIL, "sendmail", "-f", myname,
                            "--", from, NULL);
                        syslog(LOG_ERR, "%s: can't exec %s: %m",
                            getprogname(), _PATH_SENDMAIL);
                        _exit(1);
                }
                (void)close(pvect[0]);
                sfp = fdopen(pvect[1], "w");
                if (sfp == NULL) {
                        syslog(LOG_ERR, "%s: can't fdopen %d: %m",
                            getprogname(), pvect[1]);
                        _exit(1);
                }
        } 
        (void)fprintf(sfp, "To: %s\n", from);
        (void)fputs("Auto-Submitted: auto-replied\n", sfp);
        (void)fputs("Precedence: bulk\n", sfp);
        while (fgets(buf, sizeof buf, mfp) != NULL) {
                char *p;
                if ((p = strstr(buf, "$SUBJECT")) != NULL) {
                        *p = '\0';
                        (void)fputs(buf, sfp);
                        (void)fputs(subject, sfp);
                        p += sizeof("$SUBJECT") - 1;
                        (void)fputs(p, sfp);
                } else
                    (void)fputs(buf, sfp);
        }
        (void)fclose(mfp);
        if (sfp != stdout)
                (void)fclose(sfp);
}

static void
usage(void)
{

        syslog(LOG_ERR, "uid %u: Usage: %s [-dIij] [-a alias] [-f database_file] [-F F|R|S] [-m message_file] [-s sender] [-t interval] [-T A|D]"
            " login", getuid(), getprogname());
        exit(1);
}