/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2013 Gary Mills
 *
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright 2020 Joyent, Inc.
 */

/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*        All Rights Reserved   */

/*
 * University Copyright- Copyright (c) 1982, 1986, 1988
 * The Regents of the University of California
 * All Rights Reserved
 *
 * University Acknowledgment- Portions of this document are derived from
 * software developed by the University of California, Berkeley, and its
 * contributors.
 */

/*
 * This is the new w command which takes advantage of
 * the /proc interface to gain access to the information
 * of all the processes currently on the system.
 *
 * This program also implements 'uptime'.
 *
 * Maintenance note:
 *
 * Much of this code is replicated in whodo.c.  If you're
 * fixing bugs here, then you should probably fix 'em there too.
 */

#include <sys/types.h>
#include <sys/loadavg.h>
#include <sys/queue.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>

#include <ctype.h>
#include <dirent.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <locale.h>
#include <priv_utils.h>
#include <procfs.h>             /* /proc header file */
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <utmpx.h>

/*
 * Use the full lengths from utmpx for user and line.
 */
static struct utmpx dummy;
#define NMAX            (sizeof (dummy.ut_user))
#define LMAX            (sizeof (dummy.ut_line))

/* Print minimum field widths. */
#define LOGIN_WIDTH     8
#define LINE_WIDTH      8

#define DIV60(t)        ((t+30)/60)     /* x/60 rounded */

#define PROCDIR         "/proc"
#define PRINTF(a)       if (printf a < 0) { \
                perror((gettext("%s: printf failed"), prog)); \
                exit(1); }

struct uproc {
        pid_t   p_upid;                 /* process id */
        dev_t   p_ttyd;                 /* controlling tty of process */
        time_t  p_time;                 /* seconds of user & system time */
        time_t  p_ctime;                /* seconds of child user & sys time */
        int     p_igintr;               /* 1 = ignores SIGQUIT and SIGINT */
        char    p_comm[PRARGSZ+1];      /* command */
        char    p_args[PRARGSZ+1];      /* command line arguments */
        STAILQ_ENTRY(uproc) uprocs;
};
STAILQ_HEAD(uprochead, uproc) uphead;

static time_t   findidle(char *);
static void     clnarglist(char *);
static void     prttime(time_t, int);
static void     prtat(time_t *time);

static int      priv_proc_open(const char *, int);
static int      priv_proc_openat(int, const char *, int);
static boolean_t do_proc_read(int, void *, size_t);

static char     *prog;          /* pointer to invocation name */
static int      header = 1;     /* true if -h flag: don't print heading */
static int      lflag = 1;      /* set if -l flag; 0 for -s flag: short form */
static char     *sel_user;      /* login of particular user selected */
static char     firstchar;      /* first char of name of prog invoked as */
static int      login;          /* true if invoked as login shell */
static time_t   now;            /* current time of day */
static time_t   uptime;         /* time of last reboot & elapsed time since */
static int      nusers;         /* number of users logged in now */

/*
 * Basic privs we never need and can drop. This is likely not exhaustive,
 * but should significantly reduce any potential attack surfaces.
 */
static const char *drop_privs[] = {
        PRIV_FILE_WRITE,
        PRIV_NET_ACCESS,
        PRIV_PROC_EXEC,
        PRIV_PROC_FORK,
        PRIV_FILE_LINK_ANY
};

#if SIGQUIT > SIGINT
#define ACTSIZE SIGQUIT
#else
#define ACTSIZE SIGINT
#endif

int
main(int argc, char *argv[])
{
        struct utmpx    *ut;
        struct utmpx    *utmpbegin;
        struct utmpx    *utmpend;
        struct utmpx    *utp;
        struct uproc    *up;
        struct psinfo   info;
        struct sigaction actinfo[ACTSIZE];
        struct pstatus  statinfo;
        struct stat     sbuf;
        DIR             *dirp;
        struct dirent   *dp;
        char            pname[PATH_MAX];
        int             procfd;
        int             dirfd;
        char            *cp;
        int             i;
        int             days, hrs, mins;
        int             entries;
        double          loadavg[3];
        priv_set_t      *pset;

        if (__init_suid_priv(PU_CLEARLIMITSET, PRIV_PROC_OWNER, NULL) != 0) {
                err(EXIT_FAILURE, "failed to enable privilege bracketing");
        }

        /*
         * After setting up privilege bracketing, we can further reduce the
         * privileges in use. The effective set is set to the basic set minus
         * the privs in drop_privs. The permitted set is the effective set
         * plus PRIV_PROC_OWNER (i.e. the privilege being bracketed).
         */
        pset = priv_allocset();
        if (pset == NULL)
                err(EXIT_FAILURE, "priv_allocset failed");

        priv_basicset(pset);
        for (i = 0; i < ARRAY_SIZE(drop_privs); i++) {
                if (priv_delset(pset, drop_privs[i]) != 0) {
                        err(EXIT_FAILURE,
                            "failed to remove %s privilege from privilege set",
                            drop_privs[i]);
                }
        }

        if (setppriv(PRIV_SET, PRIV_EFFECTIVE, pset) < 0)
                err(EXIT_FAILURE, "failed setting effective privilege set");

        if (priv_addset(pset, PRIV_PROC_OWNER) != 0) {
                err(EXIT_FAILURE,
                    "failed to add PRIV_PROC_OWNER privilege to privilege set");
        }

        if (setppriv(PRIV_SET, PRIV_PERMITTED, pset) < 0)
                err(EXIT_FAILURE, "failed to set permitted privilege set");

        /*
         * Unfortunately, when run as root, privilege bracketing is a no-op,
         * so we have to add PRIV_PROC_OWNER into our effective set for things
         * to work.
         */
        if (getuid() == 0 && setppriv(PRIV_SET, PRIV_EFFECTIVE, pset) < 0) {
                err(EXIT_FAILURE, "failed to set effective privilege set");
        }

        priv_freeset(pset);
        pset = NULL;

        (void) setlocale(LC_ALL, "");
#if !defined(TEXT_DOMAIN)
#define TEXT_DOMAIN "SYS_TEST"
#endif
        (void) textdomain(TEXT_DOMAIN);

        login = (argv[0][0] == '-');
        cp = strrchr(argv[0], '/');
        firstchar = login ? argv[0][1] : (cp == 0) ? argv[0][0] : cp[1];
        prog = argv[0];

        while (argc > 1) {
                if (argv[1][0] == '-') {
                        for (i = 1; argv[1][i]; i++) {
                                switch (argv[1][i]) {

                                case 'h':
                                        header = 0;
                                        break;

                                case 'l':
                                        lflag++;
                                        break;
                                case 's':
                                        lflag = 0;
                                        break;

                                case 'u':
                                case 'w':
                                        firstchar = argv[1][i];
                                        break;

                                default:
                                        (void) fprintf(stderr, gettext(
                                            "%s: bad flag %s\n"),
                                            prog, argv[1]);
                                        exit(1);
                                }
                        }
                } else {
                        if (!isalnum(argv[1][0]) || argc > 2) {
                                (void) fprintf(stderr, gettext(
                                    "usage: %s [ -hlsuw ] [ user ]\n"), prog);
                                exit(1);
                        } else
                                sel_user = argv[1];
                }
                argc--; argv++;
        }

        /*
         * read the UTMPX_FILE (contains information about each logged in user)
         */
        if (stat(UTMPX_FILE, &sbuf) < 0)
                err(EXIT_FAILURE, gettext("stat error of %s"), UTMPX_FILE);

        entries = sbuf.st_size / sizeof (struct futmpx);
        if ((ut = calloc(entries, sizeof (struct utmpx))) == NULL)
                err(EXIT_FAILURE, gettext("calloc error of %s"), UTMPX_FILE);

        (void) utmpxname(UTMPX_FILE);

        utmpbegin = ut;
        utmpend = utmpbegin + entries;

        setutxent();
        while ((ut < utmpend) && ((utp = getutxent()) != NULL))
                (void) memcpy(ut++, utp, sizeof (*ut));
        endutxent();

        (void) time(&now);      /* get current time */

        if (header) {   /* print a header */
                prtat(&now);
                for (ut = utmpbegin; ut < utmpend; ut++) {
                        if (ut->ut_type == USER_PROCESS) {
                                if (!nonuserx(*ut))
                                        nusers++;
                        } else if (ut->ut_type == BOOT_TIME) {
                                uptime = now - ut->ut_xtime;
                                uptime += 30;
                                days = uptime / (60*60*24);
                                uptime %= (60*60*24);
                                hrs = uptime / (60*60);
                                uptime %= (60*60);
                                mins = uptime / 60;

                                PRINTF((gettext("up")));
                                if (days > 0)
                                        PRINTF((gettext(
                                            " %d day(s),"), days));
                                if (hrs > 0 && mins > 0) {
                                        PRINTF((" %2d:%02d,", hrs, mins));
                                } else {
                                        if (hrs > 0) {
                                                PRINTF((gettext(
                                                    " %d hr(s),"), hrs));
                                        } else { /* mins can be zero */
                                                PRINTF((gettext(
                                                    " %d min(s),"), mins));
                                        }
                                }
                        }
                }

                ut = utmpbegin; /* rewind utmp data */
                PRINTF((((nusers == 1) ?
                    gettext("  %d user") : gettext("  %d users")), nusers));
                /*
                 * Print 1, 5, and 15 minute load averages.
                 */
                (void) getloadavg(loadavg, 3);
                PRINTF((gettext(",  load average: %.2f, %.2f, %.2f\n"),
                    loadavg[LOADAVG_1MIN], loadavg[LOADAVG_5MIN],
                    loadavg[LOADAVG_15MIN]));

                if (firstchar == 'u')   /* uptime command */
                        exit(0);

                if (lflag) {
                        PRINTF((dcgettext(NULL, "User     tty      "
                            "login@         idle    JCPU    PCPU what\n",
                            LC_TIME)));
                } else {
                        PRINTF((dcgettext(NULL,
                            "User     tty         idle what\n",
                            LC_TIME)));
                }

                if (fflush(stdout) == EOF) {
                        err(EXIT_FAILURE, "fflush failed");
                }
        }

        /* Loop through /proc, reading info about each process */
        if ((dirp = opendir(PROCDIR)) == NULL)
                err(EXIT_FAILURE, gettext("could not open %s"), PROCDIR);

        STAILQ_INIT(&uphead);
        while ((dp = readdir(dirp)) != NULL) {
                if (dp->d_name[0] == '.')
                        continue;

                if (snprintf(pname, sizeof (pname), "%s/%s", PROCDIR,
                    dp->d_name) > sizeof (pname))
                        continue;

                dirfd = priv_proc_open(pname, O_RDONLY | O_DIRECTORY);
                if (dirfd < 0)
                        continue;

                procfd = priv_proc_openat(dirfd, "psinfo", O_RDONLY);
                if (procfd < 0) {
                        (void) close(dirfd);
                        continue;
                }
                if (!do_proc_read(procfd, &info, sizeof (info))) {
                        warn(gettext("failed to read %s"), pname);
                        (void) close(dirfd);
                        continue;
                }
                (void) close(procfd);

                /* Not interested in zombies */
                if (info.pr_nlwp == 0)
                        continue;
                /* Not interested in processes without a terminal */
                if (info.pr_ttydev == NODEV)
                        continue;

                procfd = priv_proc_openat(dirfd, "status", O_RDONLY);
                if (procfd < 0) {
                        (void) close(dirfd);
                        continue;
                }
                if (!do_proc_read(procfd, &statinfo, sizeof (statinfo))) {
                        warn(gettext("failed to read %s/status"), pname);
                        (void) close(procfd);
                        (void) close(dirfd);
                        continue;
                }
                (void) close(procfd);

                procfd = priv_proc_openat(dirfd, "sigact", O_RDONLY);
                if (procfd < 0) {
                        (void) close(dirfd);
                        continue;
                }
                if (!do_proc_read(procfd, actinfo, sizeof (actinfo))) {
                        warn(gettext("failed to read %s/sigact"), pname);
                        (void) close(procfd);
                        (void) close(dirfd);
                        continue;
                }
                (void) close(procfd);
                (void) close(dirfd);

                up = calloc(1, sizeof (*up));
                if (up == NULL)
                        err(EXIT_FAILURE, "calloc");
                up->p_upid = info.pr_pid;
                up->p_ttyd = info.pr_ttydev;
                up->p_time =
                    statinfo.pr_utime.tv_sec +
                    statinfo.pr_stime.tv_sec;
                up->p_ctime =
                    statinfo.pr_cutime.tv_sec +
                    statinfo.pr_cstime.tv_sec;
                up->p_igintr =
                    actinfo[SIGINT-1].sa_handler == SIG_IGN &&
                    actinfo[SIGQUIT-1].sa_handler == SIG_IGN;
                (void) strlcpy(up->p_comm, info.pr_fname, sizeof (up->p_comm));
                /* Process args */
                clnarglist(info.pr_psargs);
                (void) strlcpy(up->p_args, info.pr_psargs, sizeof (up->p_args));
                if (up->p_args[0] == 0 || up->p_args[0] == '?' ||
                    (up->p_args[0] == '-' && up->p_args[1] <= ' ')) {
                        (void) strlcat(up->p_args, " (", sizeof (up->p_args));
                        (void) strlcat(up->p_args, up->p_comm,
                            sizeof (up->p_args));
                        (void) strlcat(up->p_args, ")", sizeof (up->p_args));
                }
                STAILQ_INSERT_TAIL(&uphead, up, uprocs);
        }

        /* revert to non-privileged user after opening */
        __priv_relinquish();
        if (getuid() == 0) {
                /*
                 * Since the privilege bracketing functions are effectively
                 * no-ops when running as root, we must explicitly
                 * relinquish PRIV_PROC_OWNER ourselves.
                 */
                pset = priv_allocset();
                if (pset == NULL) {
                        err(EXIT_FAILURE,
                            gettext("failed to allocate privilege set"));
                }

                priv_emptyset(pset);

                if (priv_addset(pset, PRIV_PROC_OWNER) != 0) {
                        err(EXIT_FAILURE, gettext("failed to add "
                            "PRIV_PROC_OWNER to privilege set"));
                }

                if (setppriv(PRIV_OFF, PRIV_PERMITTED, pset) != 0) {
                        err(EXIT_FAILURE,
                            gettext("failed to set permitted privilege set"));
                }

                priv_freeset(pset);
                pset = NULL;
        }

        (void) closedir(dirp);
        (void) time(&now);      /* get current time */

        /*
         * loop through utmpx file, printing process info
         * about each logged in user
         */
        for (ut = utmpbegin; ut < utmpend; ut++) {
                struct uproc *upt;
                char linedev[PATH_MAX];
                char what[1024];
                time_t idle, jobtime, proctime;
                pid_t curpid;

                if (ut->ut_type != USER_PROCESS)
                        continue;
                if (sel_user != NULL &&
                    strncmp(ut->ut_name, sel_user, NMAX) != 0)
                        continue;

                /* print login name of the user */
                PRINTF(("%-*.*s ", LOGIN_WIDTH, NMAX, ut->ut_name));

                /* print tty user is on */
                if (lflag) {
                        PRINTF(("%-*.*s ", LINE_WIDTH, LMAX, ut->ut_line));
                } else {
                        if (strncmp(ut->ut_line, "pts/", strlen("pts/")) == 0) {
                                PRINTF(("%-*.*s ", LINE_WIDTH, LMAX,
                                    &ut->ut_line[4]));
                        } else {
                                PRINTF(("%-*.*s ", LINE_WIDTH, LMAX,
                                    ut->ut_line));
                        }
                }

                /* print when the user logged in */
                if (lflag) {
                        time_t tim = ut->ut_xtime;
                        prtat(&tim);
                }

                /* print idle time */
                idle = findidle(ut->ut_line);
                prttime(idle, 8);

                /*
                 * Go through the list of processes for this terminal,
                 * calculating job/process times, and look for the
                 * "most interesting" process.
                 */
                jobtime = 0;
                proctime = 0;
                curpid = -1;
                (void) strlcpy(what, "-", sizeof (what));

                (void) snprintf(linedev, sizeof (linedev), "/dev/%s",
                    ut->ut_line);
                if (stat(linedev, &sbuf) == -1 ||
                    (sbuf.st_mode & S_IFMT) != S_IFCHR ||
                    sbuf.st_rdev == NODEV)
                        goto skip;

                STAILQ_FOREACH_SAFE(up, &uphead, uprocs, upt) {
                        if (up->p_ttyd != sbuf.st_rdev)
                                continue;
                        jobtime += up->p_time + up->p_ctime;
                        proctime += up->p_time;
                        /*
                         * Check for "most interesting" process, currently
                         * the one having the highest PID.
                         */
                        if (up->p_upid > curpid && !up->p_igintr) {
                                curpid = up->p_upid;
                                if (lflag) {
                                        (void) strlcpy(what, up->p_args,
                                            sizeof (what));
                                } else {
                                        (void) strlcpy(what, up->p_comm,
                                            sizeof (what));
                                }
                        }
                        STAILQ_REMOVE(&uphead, up, uproc, uprocs);
                        free(up);
                }

skip:
                if (lflag) {
                        /* Print CPU time for all processes & children */
                        prttime(jobtime, 8);
                        /* Print cpu time for interesting process */
                        prttime(proctime, 8);
                }
                /* "Most interesting" process */
                PRINTF(("%-.32s\n", what));
        }

        if (fclose(stdout) == EOF)
                err(EXIT_FAILURE, gettext("fclose failed"));

        return (0);
}

#define HR      (60 * 60)
#define DAY     (24 * HR)
#define MON     (30 * DAY)

/*
 * Prttime prints an elapsed time in hours, minutes, or seconds,
 * right-justified with the rightmost column always blank.
 * The second argument is the minimum field width.
 */
static void
prttime(time_t tim, int width)
{
        char value[36];

        if (tim >= 36 * 60) {
                (void) snprintf(value, sizeof (value), "%d:%02d:%02d",
                    (int)tim / HR, (int)(tim % HR) / 60, (int)tim % 60);
        } else if (tim >= 60) {
                (void) snprintf(value, sizeof (value), "%d:%02d",
                    (int)tim / 60, (int)tim % 60);
        } else if (tim > 0) {
                (void) snprintf(value, sizeof (value), "%d", (int)tim);
        } else {
                (void) strlcpy(value, "0", sizeof (value));
        }
        width = (width > 2) ? width - 1 : 1;
        PRINTF(("%*s ", width, value));
}

/*
 * Prints the ISO date or time given a pointer to a time of day,
 * left-justfied in a 12-character expanding field with the
 * rightmost column always blank.
 * Includes a dcgettext() override in case a message catalog is needed.
 */
static void
prtat(time_t *time)
{
        struct tm       *p;

        p = localtime(time);
        if (now - *time <= 18 * HR) {
                char timestr[50];

                (void) strftime(timestr, sizeof (timestr),
                    dcgettext(NULL, "%T", LC_TIME), p);
                PRINTF(("%-11s ", timestr));
        } else if (now - *time <= 7 * DAY) {
                char weekdaytime[20];

                (void) strftime(weekdaytime, sizeof (weekdaytime),
                    dcgettext(NULL, "%a %H:%M", LC_TIME), p);
                PRINTF(("%-11s ", weekdaytime));
        } else {
                char monthtime[20];

                (void) strftime(monthtime, sizeof (monthtime),
                    dcgettext(NULL, "%F", LC_TIME), p);
                PRINTF(("%-11s ", monthtime));
        }
}

/*
 * find & return number of minutes current tty has been idle
 */
static time_t
findidle(char *devname)
{
        struct stat stbuf;
        time_t lastaction, diff;
        char ttyname[64];

        (void) strlcpy(ttyname, "/dev/", sizeof (ttyname));
        (void) strlcat(ttyname, devname, sizeof (ttyname));
        if (stat(ttyname, &stbuf) != -1) {
                lastaction = stbuf.st_atime;
                diff = now - lastaction;
                diff = DIV60(diff);
                if (diff < 0)
                        diff = 0;
        } else
                diff = 0;
        return (diff);
}

/*
 * given a pointer to the argument string get rid of unsavory characters.
 */
static void
clnarglist(char *arglist)
{
        char    *c;
        int     err = 0;

        /* get rid of unsavory characters */
        for (c = arglist; *c != '\0'; c++) {
                if ((*c < ' ') || (*c > 0176)) {
                        if (err++ > 5) {
                                *arglist = '\0';
                                break;
                        }
                        *c = '?';
                }
        }
}

static int
priv_proc_open(const char *path, int oflag)
{
        int fd, errsave = 0;

        if (__priv_bracket(PRIV_ON) != 0)
                err(EXIT_FAILURE, gettext("privilege bracketing failed"));

        do {
                fd = open(path, oflag);
                if (fd < 0)
                        errsave = errno;
        } while (fd < 0 && errno == EAGAIN);

        if (__priv_bracket(PRIV_OFF) != 0)
                err(EXIT_FAILURE, gettext("privilege bracketing failed"));

        if (fd < 0)
                errno = errsave;

        return (fd);
}

static int
priv_proc_openat(int dfd, const char *path, int mode)
{
        int fd, errsave = 0;

        if (__priv_bracket(PRIV_ON) != 0)
                err(EXIT_FAILURE, gettext("privilege bracketing failed"));

        do {
                fd = openat(dfd, path, mode);
                if (fd < 0)
                        errsave = errno;
        } while (fd < 0 && errno == EAGAIN);

        if (__priv_bracket(PRIV_OFF) != 0)
                err(EXIT_FAILURE, gettext("privilege bracketing failed"));

        if (fd < 0)
                errno = errsave;

        return (fd);
}

static boolean_t
do_proc_read(int fd, void *buf, size_t bufsize)
{
        ssize_t n;

        do {
                n = pread(fd, buf, bufsize, 0);
                if (n == bufsize)
                        return (B_TRUE);
                /*
                 * Retry on a partial read or EAGAIN, otherwise fail
                 */
        } while (n >= 0 || errno == EAGAIN);

        return (B_FALSE);
}