/*      $OpenBSD: vacation.c,v 1.39 2024/08/29 21:04:16 op Exp $        */
/*      $NetBSD: vacation.c,v 1.7 1995/04/29 05:58:27 cgd 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.
 */

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

#include <sys/stat.h>
#include <fcntl.h>
#include <pwd.h>
#include <db.h>
#include <time.h>
#include <syslog.h>
#include <errno.h>
#include <unistd.h>
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#include <paths.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 */
#define VDB     ".vacation.db"          /* dbm's database */
#define VMSG    ".vacation.msg"         /* vacation message */

typedef struct alias {
        struct alias *next;
        char *name;
} ALIAS;
ALIAS *names;

DB *db;
char from[MAXLINE];
char subj[MAXLINE];

int junkmail(void);
int nsearch(char *, char *);
void readheaders(void);
int recent(void);
void sendmessage(char *);
void setinterval(time_t);
void setreply(void);
void usage(void);

#define SECSPERDAY      (24 * 60 * 60)

int
main(int argc, char *argv[])
{
        int ch, iflag, flags;
        struct passwd *pw;
        time_t interval;
        struct stat sb;
        ALIAS *cur;

        opterr = iflag = 0;
        interval = -1;
        while ((ch = getopt(argc, argv, "a:Iir:")) != -1)
                switch ((char)ch) {
                case 'a':                       /* alias */
                        if (!(cur = malloc(sizeof(ALIAS))))
                                break;
                        cur->name = optarg;
                        cur->next = names;
                        names = cur;
                        break;
                case 'I':                       /* backward compatible */
                case 'i':                       /* init the database */
                        iflag = 1;
                        break;
                case 'r':
                        if (isdigit((unsigned char)*optarg)) {
                                interval = atol(optarg) * SECSPERDAY;
                                if (interval < 0)
                                        usage();
                        } else
                                interval = 0;   /* one time only */
                        break;
                default:
                        usage();
                }
        argc -= optind;
        argv += optind;

        if (argc != 1) {
                if (!iflag)
                        usage();
                if (!(pw = getpwuid(getuid()))) {
                        syslog(LOG_ERR,
                            "no such user uid %u.", getuid());
                        exit(1);
                }
        } else if (!(pw = getpwnam(*argv))) {
                syslog(LOG_ERR, "no such user %s.", *argv);
                exit(1);
        }
        if (chdir(pw->pw_dir)) {
                syslog(LOG_NOTICE,
                    "no such directory %s.", pw->pw_dir);
                exit(1);
        }

        /*
         * dbopen(3) can not deal with a zero-length file w/o O_TRUNC.
         */
        if (iflag == 1 || (stat(VDB, &sb) == 0 && sb.st_size == (off_t)0))
                flags = O_CREAT|O_RDWR|O_TRUNC;
        else
                flags = O_CREAT|O_RDWR;

        db = dbopen(VDB, flags, S_IRUSR|S_IWUSR, DB_HASH, NULL);
        if (!db) {
                syslog(LOG_NOTICE, "%s: %m", VDB);
                exit(1);
        }

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

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

        if (!(cur = malloc(sizeof(ALIAS))))
                exit(1);
        cur->name = pw->pw_name;
        cur->next = names;
        names = cur;

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

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

        cont = tome = 0;
        while (fgets(buf, sizeof(buf), stdin) && *buf != '\n')
                switch (*buf) {
                case 'A':               /* "Auto-Submitted:" */
                case 'a':
                        cont = 0;
                        if (strncasecmp(buf, "Auto-Submitted:", 15))
                                break;
                        for (p = buf + 15; isspace((unsigned char)*p); ++p)
                                ;
                        /*
                         * RFC 3834 section 2:
                         * Automatic responses SHOULD NOT be issued in response
                         * to any message which contains an Auto-Submitted
                         * header where the field has any value other than "no".
                         */
                        if ((p[0] == 'n' || p[0] == 'N') &&
                            (p[1] == 'o' || p[1] == 'O')) {
                                for (p += 2; isspace((unsigned char)*p); ++p)
                                        ;
                                if (*p == '\0')
                                        break;  /* Auto-Submitted: no */
                        }
                        exit(0);
                case 'F':               /* "From " */
                case 'f':
                        cont = 0;
                        if (!strncasecmp(buf, "From ", 5)) {
                                for (p = buf + 5; *p && *p != ' '; ++p)
                                        ;
                                *p = '\0';
                                (void)strlcpy(from, buf + 5, sizeof(from));
                                from[strcspn(from, "\n")] = '\0';
                                if (junkmail())
                                        exit(0);
                        }
                        break;
                case 'L':               /* "List-Id:" */
                case 'l':
                        cont = 0;
                        /*
                         * If present (with any value), message is coming from a
                         * mailing list, cf. RFC2919.
                         */
                        if (strncasecmp(buf, "List-Id:", 8) == 0)
                                exit(0);
                        break;
                case 'R':               /* "Return-Path:" */
                case 'r':
                        cont = 0;
                        if (strncasecmp(buf, "Return-Path:",
                            sizeof("Return-Path:")-1) ||
                            (buf[12] != ' ' && buf[12] != '\t'))
                                break;
                        for (p = buf + 12; isspace((unsigned char)*p); ++p)
                                ;
                        if (*p == '<') {
                                ++p;
                                p[strcspn(p, ">")] = '\0';
                        }
                        if (strlcpy(from, p, sizeof(from)) >= sizeof(from)) {
                                syslog(LOG_NOTICE,
                                    "Return-Path %s exceeds limits", p);
                                exit(1);
                        }
                        from[strcspn(from, "\n")] = '\0';
                        if (junkmail())
                                exit(0);
                        break;
                case 'P':               /* "Precedence:" */
                case 'p':
                        cont = 0;
                        if (strncasecmp(buf, "Precedence:", 11))
                                break;
                        for (p = buf + 11; isspace((unsigned char)*p); ++p)
                                ;
                        if (!strncasecmp(p, "junk", 4) ||
                            !strncasecmp(p, "bulk", 4) ||
                            !strncasecmp(p, "list", 4))
                                exit(0);
                        break;
                case 'S':               /* Subject: */
                case 's':
                        cont = 0;
                        if (strncasecmp(buf, "Subject:",
                            sizeof("Subject:")-1) ||
                            (buf[8] != ' ' && buf[8] != '\t'))
                                break;
                        for (p = buf + 8; isspace((unsigned char)*p); ++p)
                                ;
                        if (strlcpy(subj, p, sizeof(subj)) >= sizeof(subj)) {
                                syslog(LOG_NOTICE,
                                    "Subject %s exceeds limits", p);
                                exit(1);
                        }
                        subj[strcspn(subj, "\n")] = '\0';
                        break;
                case 'C':               /* "Cc:" */
                case 'c':
                        if (strncasecmp(buf, "Cc:", 3))
                                break;
                        cont = 1;
                        goto findme;
                case 'T':               /* "To:" */
                case 't':
                        if (strncasecmp(buf, "To:", 3))
                                break;
                        cont = 1;
                        goto findme;
                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 (!tome || !*from)
                exit(0);
}

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

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

/*
 * junkmail --
 *      read the header and return if automagic/junk/bulk/list mail
 */
int
junkmail(void)
{
        static struct ignore {
                char    *name;
                int     len;
        } ignore[] = {
                { "-request", 8 },
                { "postmaster", 10 },
                { "uucp", 4 },
                { "mailer-daemon", 13 },
                { "mailer", 6 },
                { "-relay", 6 },
                { NULL, 0 }
        };
        struct ignore *cur;
        int len;
        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(from, '%'))) {
                if (!(p = strchr(from, '@'))) {
                        if ((p = strrchr(from, '!')))
                                ++p;
                        else
                                p = from;
                        for (; *p; ++p)
                                ;
                }
        }
        len = p - from;
        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 bcopy for machines with alignment restrictions
 */
int
recent(void)
{
        time_t then, next;
        DBT key, data;

        /* get interval time */
        key.data = VIT;
        key.size = sizeof(VIT);
        if ((db->get)(db, &key, &data, 0))
                next = SECSPERDAY * 7;
        else
                bcopy(data.data, &next, sizeof(next));

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

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

        key.data = 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.
 */
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
 */
void
sendmessage(char *myname)
{
        char buf[MAXLINE];
        FILE *mfp, *sfp;
        int pvect[2], i;

        mfp = fopen(VMSG, "r");
        if (mfp == NULL) {
                syslog(LOG_NOTICE, "no ~%s/%s file.", myname, VMSG);
                exit(1);
        }
        if (pipe(pvect) == -1) {
                syslog(LOG_ERR, "pipe: %m");
                exit(1);
        }
        i = vfork();
        if (i == -1) {
                syslog(LOG_ERR, "fork: %m");
                exit(1);
        }
        if (i == 0) {
                dup2(pvect[0], 0);
                close(pvect[0]);
                close(pvect[1]);
                close(fileno(mfp));
                execl(_PATH_SENDMAIL, "sendmail", "-f", myname, "--",
                    from, (char *)NULL);
                syslog(LOG_ERR, "can't exec %s: %m", _PATH_SENDMAIL);
                _exit(1);
        }
        close(pvect[0]);
        sfp = fdopen(pvect[1], "w");
        if (sfp == NULL) {
                /* XXX could not fdopen; likely out of memory */
                fclose(mfp);
                close(pvect[1]);
                return;
        }
        fprintf(sfp, "To: %s\n", from);
        fputs("Auto-Submitted: auto-replied\n", sfp);
        while (fgets(buf, sizeof buf, mfp)) {
                char *s = strstr(buf, "$SUBJECT");

                if (s) {
                        *s = 0;
                        fputs(buf, sfp);
                        fputs(subj, sfp);
                        fputs(s+8, sfp);
                } else {
                        fputs(buf, sfp);
                }
        }
        fclose(mfp);
        fclose(sfp);
}

void
usage(void)
{
        syslog(LOG_NOTICE, "uid %u: usage: vacation [-i] [-a alias] login",
            getuid());
        exit(1);
}