/*      $NetBSD: calendar.c,v 1.54 2022/09/19 18:48:30 christos Exp $   */

/*
 * Copyright (c) 1989, 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) 1989, 1993\
 The Regents of the University of California.  All rights reserved.");
#endif /* not lint */

#ifndef lint
#if 0
static char sccsid[] = "@(#)calendar.c  8.4 (Berkeley) 1/7/95";
#endif
__RCSID("$NetBSD: calendar.c,v 1.54 2022/09/19 18:48:30 christos Exp $");
#endif /* not lint */

#include <sys/param.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/uio.h>
#include <sys/wait.h>

#include <assert.h>
#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <pwd.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <tzfile.h>
#include <unistd.h>

#include "pathnames.h"

#define CALENDAR_VERSION        "calendar-20160601"

        /* flags used by calendar file parser */
#define F_ISMONTH       0x01
#define F_ISDAY         0x02
#define F_ISDOW         0x04
#define F_WILDMONTH     0x10
#define F_WILDDAY       0x20

static unsigned short lookahead = 1;
static unsigned short weekend = 2;
static char *fname = NULL;
static char *datestr = NULL;
static const char *defaultnames[] = {"calendar", ".calendar", _PATH_SYSTEM_CALENDAR, NULL};
static struct passwd *pw;
static char path[MAXPATHLEN + 1];
static bool doall = false;
static bool cpp_restricted = false;

/* 1-based month, 0-based days, cumulative */
static const int daytab[][14] = {
        { 0, -1, 30, 58, 89, 119, 150, 180, 211, 242, 272, 303, 333, 364 },
        { 0, -1, 30, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
};
static struct tm *tp;
static const int *cumdays;
static int offset, yrdays;
static char dayname[10];

static struct iovec header[] = {
        { __UNCONST("From: "), 6 },
        { NULL, 0 },
        { __UNCONST(" (Reminder Service)\nTo: "), 24 },
        { NULL, 0 },
        { __UNCONST("\nSubject: "), 10 },
        { NULL, 0 },
        { __UNCONST("'s Calendar\nPrecedence: bulk\n\n"),  30 },
};

static const char *days[] = {
        "sun", "mon", "tue", "wed", "thu", "fri", "sat", NULL,
};

static const char *months[] = {
        "jan", "feb", "mar", "apr", "may", "jun",
        "jul", "aug", "sep", "oct", "nov", "dec", NULL,
};

static void      atodays(int, char *, unsigned short *);
static void      cal(void);
static void      closecal(FILE *);
static void      changeuser(void);
static int       getday(char *);
static int       getfield(char *, char **, int *);
static void      getmmdd(struct tm *, char *);
static int       getmonth(char *);
static bool      isnow(char *);
static FILE     *opencal(FILE **);
static int       tryopen(const char *, int);
static void      settime(void);
static void      usage(void) __dead;

int
main(int argc, char **argv)
{
        int ch;
        const char *caldir;

        (void)setprogname(argv[0]);     /* for portability */

        while ((ch = getopt(argc, argv, "-ad:f:l:vw:x")) != -1) {
                switch (ch) {
                case '-':               /* backward contemptible */
                case 'a':
                        if (getuid()) {
                                errno = EPERM;
                                err(EXIT_FAILURE, NULL);
                        }
                        doall = true;
                        break;
                case 'd':
                        datestr = optarg;
                        break;
                case 'f':
                        fname = optarg;
                        break;
                case 'l':
                        atodays(ch, optarg, &lookahead);
                        break;
                case 'v':
                        printf("%s\n", CALENDAR_VERSION);
                        return 0;
                case 'w':
                        atodays(ch, optarg, &weekend);
                        break;
                case 'x':
                        cpp_restricted = true;
                        break;
                case '?':
                default:
                        usage();
                }
        }
        argc -= optind;
        argv += optind;

        if (argc)
                usage();

        settime();
        if (doall) {
                /*
                 * XXX - This ignores the user's CALENDAR_DIR variable.
                 *       Run under user's login shell?
                 */
                if (setgroups(0, NULL) == -1) {
                        err(EXIT_FAILURE, "setgroups");
                }
                while ((pw = getpwent()) != NULL) {
                        if (setegid(pw->pw_gid) == -1) {
                                warn("%s: setegid", pw->pw_name);
                                continue;
                        }
                        if (seteuid(pw->pw_uid) == -1) {
                                warn("%s: seteuid", pw->pw_name);
                                continue;
                        }
                        if (chdir(pw->pw_dir) != -1) {
                                cal();
                        }
                        if (seteuid(0) == -1) {
                                warn("%s: seteuid back to 0", pw->pw_name);
                        }
                }
        } else if ((caldir = getenv("CALENDAR_DIR")) != NULL) {
                if (chdir(caldir) != -1)
                        cal();
        } else if ((pw = getpwuid(geteuid())) != NULL) {
                if (chdir(pw->pw_dir) != -1)
                        cal();
        }
        return 0;
}

static void
cal(void)
{
        bool printing;
        FILE *fp, *in = NULL;
        char *line;

        if ((fp = opencal(&in)) == NULL || in == NULL)
                return;
        printing = false;
        while ((line = fparseln(in,
                    NULL, NULL, NULL, FPARSELN_UNESCCOMM)) != NULL) {
                if (line[0] == '\0')
                        continue;
                if (line[0] != '\t')
                        printing = isnow(line);
                if (printing)
                        (void)fprintf(fp, "%s\n", line);
                free(line);

        }
        closecal(fp);
}

static void
settime(void)
{
        time_t now;

        (void)time(&now);
        tp = localtime(&now);
        if (datestr)
                getmmdd(tp, datestr);

        if (isleap(tp->tm_year + TM_YEAR_BASE)) {
                yrdays = DAYSPERLYEAR;
                cumdays = daytab[1];
        } else {
                yrdays = DAYSPERNYEAR;
                cumdays = daytab[0];
        }
        /* Friday displays Monday's events */
        offset = tp->tm_wday == 5 ? lookahead + weekend : lookahead;
        header[5].iov_base = dayname;
        header[5].iov_len = strftime(dayname, sizeof(dayname), "%A", tp);
}

/*
 * Possible date formats include any combination of:
 *      3-charmonth                     (January, Jan, Jan)
 *      3-charweekday                   (Friday, Monday, mon.)
 *      numeric month or day            (1, 2, 04)
 *
 * Any character may separate them, or they may not be separated.  Any line,
 * following a line that is matched, that starts with "whitespace", is shown
 * along with the matched line.
 */
static bool
isnow(char *endp)
{
        int day;
        int flags;
        int month;
        int v1;
        int v2;

        flags = 0;

        /* didn't recognize anything, skip it */
        if (!(v1 = getfield(endp, &endp, &flags)))
                return false;

        if ((flags & (F_ISDAY|F_ISDOW)) || v1 > 12) {
                /* found a day */
                day = v1;
                /* if no recognizable month, assume wildcard ('*') month */
                if ((month = getfield(endp, &endp, &flags)) == 0) {
                        flags |= F_ISMONTH | F_WILDMONTH;
                        month = tp->tm_mon + 1;
                }
        } else if (flags & F_ISMONTH) {
                month = v1;
                /* if no recognizable day, assume the first */
                if ((day = getfield(endp, &endp, &flags)) == 0)
                        day = 1;
        } else {
                v2 = getfield(endp, &endp, &flags);
                if (flags & F_ISMONTH) {
                        day = v1;
                        month = v2;
                } else {
                        /* F_ISDAY set, v2 > 12, or no way to tell */
                        month = v1;
                        /* if no recognizable day, assume the first */
                        day = v2 ? v2 : 1;
                }
        }
        /* if month is out of range, treat it as '*' */
        if (month < 1 || month > 12) {
                flags |= F_ISMONTH | F_WILDMONTH;
                month = tp->tm_mon + 1;
        }

        if (flags & F_WILDMONTH && flags & F_WILDDAY)
                return true;

        if (flags & F_WILDMONTH && flags & F_ISDAY && day == tp->tm_mday)
                return true;

        if (flags & F_WILDMONTH && flags & F_ISDOW && day == tp->tm_wday + 1)
                return true;

        if (flags & F_ISMONTH && flags & F_WILDDAY && month == tp->tm_mon + 1)
                return true;

        if (flags & F_ISMONTH && flags & F_ISDOW && month == tp->tm_mon + 1 &&
            day == tp->tm_wday + 1)
                return true;

        if (flags & F_ISDOW)
                day = tp->tm_mday + (((day - 1) - tp->tm_wday + 7) % 7);
        day = cumdays[month] + day;

        /* if today or today + offset days */
        if (day >= tp->tm_yday && day <= tp->tm_yday + offset)
                return true;

        /* if number of days left in this year + days to event in next year */
        if (yrdays - tp->tm_yday + day <= offset)
                return true;

        return false;
}

static int
getfield(char *p, char **endp, int *flags)
{
        int val;
        char *start;
        char savech;

/*
 * note this macro has an arg that isn't used ... it is retained
 * (it is believed) to make the macro call look more "natural"
 * and suggest at the call site what is happening.
 */
#define FLDCHAR(a) (*p != '\0' && !isdigit((unsigned char)*p) && \
    !isalpha((unsigned char)*p) && *p != '*')

        val = 0;
        for (/*EMPTY*/; FLDCHAR(*p); ++p)
                continue;
        if (*p == '*') {                        /* `*' is current month */
                if (!(*flags & F_ISMONTH)) {
                        *flags |= F_ISMONTH | F_WILDMONTH;
                        *endp = p + 1;
                        return tp->tm_mon + 1;
                } else {
                        *flags |= F_ISDAY | F_WILDDAY;
                        *endp = p + 1;
                        return 1;
                }
        }
        if (isdigit((unsigned char)*p)) {
                val = (int)strtol(p, &p, 10);   /* if 0, it's failure */
                for (/*EMPTY*/; FLDCHAR(*p); ++p)
                        continue;
                *endp = p;
                return val;
        }
        for (start = p; *p != '\0' && isalpha((unsigned char)*p); p++)
                continue;

        savech = *p;
        if (p != start) {
                *p = '\0';
                if ((val = getmonth(start)) != 0)
                        *flags |= F_ISMONTH;
                else if ((val = getday(start)) != 0)
                        *flags |= F_ISDOW;
                else {
                        *p = savech;
                        *endp = start;
                        return 0;
                }
        }
        for (*p = savech; FLDCHAR(*p); ++p)
                continue;
        *endp = p;
        return val;
}

static FILE *
opencal(FILE **in)
{
        int fd = -1;
        int pdes[2];

        /* open up calendar file as stdin */
        if (fname == NULL) {
                for (const char **name = defaultnames; *name != NULL; name++) {
                        if ((fd = tryopen(*name, O_RDONLY)) == -1)
                                continue;
                        else
                                break;
                }
                if (fd == -1) {
                        if (doall)
                                return NULL;
                        err(EXIT_FAILURE, "Cannot open calendar file");
                }
        } else if ((fd = tryopen(fname, O_RDONLY)) == -1) {
                if (doall)
                        return NULL;
                err(EXIT_FAILURE, "Cannot open `%s'", fname);
        }

        if (pipe(pdes) == -1) {
                warn("Cannot open pipe");
                return NULL;
        }

        switch (fork()) {
        case -1:
                /* error */
                (void)close(pdes[0]);
                (void)close(pdes[1]);
                return NULL;
        case 0:
                /* child */
                /* set stdin to calendar file */
                if (fd != STDIN_FILENO) {
                        (void)dup2(fd, STDIN_FILENO);
                        (void)close(fd);
                }
                /* set stdout to pipe input */
                if (pdes[1] != STDOUT_FILENO) {
                        (void)dup2(pdes[1], STDOUT_FILENO);
                        (void)close(pdes[1]);
                }
                (void)close(pdes[0]);
                if (doall) {
                        /* become the user properly */
                        changeuser();
                }
                /* tell CPP to only open regular files */
                if(!cpp_restricted && setenv("CPP_RESTRICTED", "", 1) == -1)
                        err(EXIT_FAILURE, "Cannot restrict cpp");
                cpp_restricted = true;

                (void)execl(_PATH_CPP, "tradcpp", "-nostdinc", "-I.",
                    "-I" _PATH_CALENDARS, NULL);
                err(EXIT_FAILURE, "Cannot exec `%s'", _PATH_CPP);
                /*NOTREACHED*/
        default:
                /* parent -- fdopen *in to pipe output */
                *in = fdopen(pdes[0], "r");
                (void)close(pdes[1]);

                /* close calendar file */
                close(fd);

                /* not reading all calendar files, just set output to stdout */
                if (!doall)
                        return stdout;

                /*
                 * Set output to a temporary file, so if no output
                 * don't send mail.
                 */
                (void)snprintf(path, sizeof(path), "%s/_calXXXXXX", _PATH_TMP);
                if ((fd = mkstemp(path)) == -1) {
                        warn("Cannot create temporary file");
                        return NULL;
                }
                return fdopen(fd, "w+");
        }
        /*NOTREACHED*/
}

static int
tryopen(const char *pathname, int flags)
{
        int fd, serrno, zero;
        struct stat st;

        /*
         * XXX: cpp_restricted has inverted sense; it is false by default,
         * and -x sets it to true. CPP_RESTRICTED is set in the environment
         * if cpp_restricted is false... go figure. This should be fixed
         * later.
         */
        if (doall && cpp_restricted == false) {
                /*
                 * We are running with the user's euid, so they can't
                 * cause any mayhem (e.g. opening rewinding tape
                 * devices) that they couldn't do easily enough on
                 * their own. All we really need to worry about is opens
                 * that hang, because that would DoS the calendar run.
                 */
                fd = open(pathname, flags | O_NONBLOCK);
                if (fd == -1) {
                        return -1;
                }
                if (fstat(fd, &st) == -1) {
                        serrno = errno;
                        close(fd);
                        errno = serrno;
                        return -1;
                }
                if (S_ISCHR(st.st_mode) ||
                    S_ISBLK(st.st_mode) ||
                    S_ISFIFO(st.st_mode)) {
                        close(fd);

                        /* Call shenanigans in the daily output */
                        errno = EPERM;
                        warn("%s: %s", pw->pw_name, pathname);

                        errno = EPERM;
                        return -1;
                }
                if (S_ISDIR(st.st_mode)) {
                        /* Don't warn about this */
                        close(fd);
                        errno = EISDIR;
                        return -1;
                }
                if (!S_ISREG(st.st_mode)) {
                        /* There shouldn't be other cases to go here */
                        close(fd);
                        errno = EINVAL;
                        return -1;
                }
                zero = 0;
                if (ioctl(fd, FIONBIO, &zero) == -1) {
                        serrno = errno;
                        warn("%s: %s: FIONBIO", pw->pw_name, pathname);
                        close(fd);
                        errno = serrno;
                        return -1;
                }
                return fd;
        } else {
                return open(pathname, flags);
        }
}

static void
closecal(FILE *fp)
{
        struct stat sbuf;
        ssize_t nread;
        int pdes[2];
        int status;
        char buf[1024];

        if (!doall)
                return;

        (void)rewind(fp);
        if (fstat(fileno(fp), &sbuf) == -1 || sbuf.st_size == 0)
                goto done;
        if (pipe(pdes) == -1)
                goto done;

        switch (fork()) {
        case -1:
                /* error */
                (void)close(pdes[0]);
                (void)close(pdes[1]);
                break;
        case 0:
                /* child -- set stdin to pipe output */
                if (pdes[0] != STDIN_FILENO) {
                        (void)dup2(pdes[0], STDIN_FILENO);
                        (void)close(pdes[0]);
                }
                (void)close(pdes[1]);
                if (doall) {
                        /* become the user properly */
                        changeuser();
                }
                (void)execl(_PATH_SENDMAIL, "sendmail", "-i", "-t", "-F",
                    "\"Reminder Service\"", "-f", "root", NULL);
                err(EXIT_FAILURE, "Cannot exec `%s'", _PATH_SENDMAIL);
                /*NOTREACHED*/
        default:
                /* parent -- write to pipe input */
                (void)close(pdes[0]);

                header[1].iov_base = header[3].iov_base = (void *)pw->pw_name;
                header[1].iov_len = header[3].iov_len = strlen(pw->pw_name);
                (void)writev(pdes[1], header, 7);
                while ((nread = read(fileno(fp), buf, sizeof(buf))) > 0)
                        (void)write(pdes[1], buf, (size_t)nread);
                (void)close(pdes[1]);
                break;
        }

done:   (void)fclose(fp);
        (void)unlink(path);
        while (wait(&status) != -1)
                continue;
}

static void
changeuser(void)
{
        uid_t uid;
        gid_t gid;

        uid = geteuid();
        gid = getegid();
        assert(uid == pw->pw_uid);
        assert(gid == pw->pw_gid);

        if (seteuid(0) == -1) {
                err(EXIT_FAILURE, "%s: changing user: cannot reassert uid 0",
                    pw->pw_name);
        }
        if (setgid(gid) == -1) {
                err(EXIT_FAILURE, "%s: cannot assume gid %d",
                    pw->pw_name, (int)gid);
        }
        if (initgroups(pw->pw_name, gid) == -1) {
                err(EXIT_FAILURE, "%s: cannot initgroups", pw->pw_name);
        }
        if (setuid(uid) == -1) {
                err(EXIT_FAILURE, "%s: cannot assume uid %d",
                    pw->pw_name, (int)uid);
        }
}

static int
getmonth(char *s)
{
        const char **p;

        for (p = months; *p; ++p)
                if (strncasecmp(s, *p, 3) == 0)
                        return (int)(p - months) + 1;
        return 0;
}

static int
getday(char *s)
{
        const char **p;

        for (p = days; *p; ++p)
                if (strncasecmp(s, *p, 3) == 0)
                        return (int)(p - days) + 1;
        return 0;
}

static void
atodays(int ch, char *arg, unsigned short *rvp)
{
        int u;

        u = atoi(arg);
        if (u < 0 || u > 366)
                warnx("-%c %d out of range 0-366, ignored.", ch, u);
        else
                *rvp = u;
}

#define todigit(x) ((x) - '0')
#define ATOI2(x) (todigit((x)[0]) * 10 + todigit((x)[1]))
#define ISDIG2(x) (isdigit((unsigned char)(x)[0]) && isdigit((unsigned char)(x)[1]))

static void
getmmdd(struct tm *ptm, char *ds)
{
        bool ok = false;
        struct tm ttm;

        ttm = *ptm;
        ttm.tm_isdst = -1;

        if (ISDIG2(ds)) {
                ttm.tm_mon = ATOI2(ds) - 1;
                ds += 2;
        }
        if (ISDIG2(ds)) {
                ttm.tm_mday = ATOI2(ds);
                ds += 2;
                ok = true;
        }
        if (ok) {
                if (ISDIG2(ds) && ISDIG2(ds + 2)) {
                        ttm.tm_year = ATOI2(ds) * 100 - TM_YEAR_BASE;
                        ds += 2;
                        ttm.tm_year += ATOI2(ds);
                } else if (ISDIG2(ds)) {
                        ttm.tm_year = ATOI2(ds);
                        if (ttm.tm_year < 69)
                                ttm.tm_year += 2000 - TM_YEAR_BASE;
                        else
                                ttm.tm_year += 1900 - TM_YEAR_BASE;
                }
        }
        if (ok && mktime(&ttm) == -1)
                ok = false;

        if (ok)
                *ptm = ttm;
        else {
                warnx("Can't convert `%s' to date, ignored.", ds);
                usage();
        }
}

__dead
static void
usage(void)
{
        (void)fprintf(stderr, "usage: %s [-ax] [-d MMDD[[YY]YY]"
            " [-f fname] [-l days] [-w days]\n", getprogname());
        exit(1);
}