/* Copyright 1988,1990,1993,1994 by Paul Vixie
 * All rights reserved
 *
 * Distribute freely, except: don't remove my name from the source or
 * documentation (don't take credit for my work), mark your changes (don't
 * get me blamed for your possible bugs), don't alter or remove this
 * notice.  May be sold if buildable source is provided to buyer.  No
 * warrantee of any kind, express or implied, is included with this
 * software; use at your own risk, responsibility for damages (if any) to
 * anyone resulting from the use of this software rests entirely with the
 * user.
 *
 * Send bug reports, bug fixes, enhancements, requests, flames, etc., and
 * I'll try to keep a version up to date.  I can be reached as follows:
 * Paul Vixie          <paul@vix.com>          uunet!decwrl!vixie!paul
 *
 * $FreeBSD: src/usr.sbin/cron/cron/do_command.c,v 1.27 2007/06/17 17:25:53 yar Exp $
 */

#include "cron.h"
#include <sys/signal.h>
#if defined(SYSLOG)
# include <syslog.h>
#endif
#if defined(LOGIN_CAP)
# include <login_cap.h>
#endif
#ifdef PAM
# include <security/pam_appl.h>
# include <security/openpam.h>
#endif

static void             child_process(entry *, user *);


void
do_command(entry *e, user *u)
{
        Debug(DPROC, ("[%d] do_command(%s, (%s,%d,%d))\n",
                getpid(), e->cmd, u->name, e->uid, e->gid))

        /* fork to become asynchronous -- parent process is done immediately,
         * and continues to run the normal cron code, which means return to
         * tick().  the child and grandchild don't leave this function, alive.
         *
         * vfork() is unsuitable, since we have much to do, and the parent
         * needs to be able to run off and fork other processes.
         */
        switch (fork()) {
        case -1:
                log_it("CRON",getpid(),"error","can't fork");
                break;
        case 0:
                /* child process */
                acquire_daemonlock(1);
                child_process(e, u);
                Debug(DPROC, ("[%d] child process done, exiting\n", getpid()))
                _exit(OK_EXIT);
                break;
        default:
                /* parent process */
                break;
        }
        Debug(DPROC, ("[%d] main process returning to work\n", getpid()))
}


static void
child_process(entry *e, user *u)
{
        int stdin_pipe[2], stdout_pipe[2];
        int jitter;
        char *input_data;
        char *usernm, *mailto;
        int children = 0;
# if defined(LOGIN_CAP)
        struct passwd *pwd;
        login_cap_t *lc;
# endif

        Debug(DPROC, ("[%d] child_process('%s')\n", getpid(), e->cmd))

        /* mark ourselves as different to PS command watchers by upshifting
         * our program name.  This has no effect on some kernels.
         */
        setproctitle("running job");

        /* discover some useful and important environment settings
         */
        usernm = env_get("LOGNAME", e->envp);
        mailto = env_get("MAILTO", e->envp);

#ifdef PAM
        /* use PAM to see if the user's account is available,
         * i.e., not locked or expired or whatever.  skip this
         * for system tasks from /etc/crontab -- they can run
         * as any user.
         */
        if (strcmp(u->name, SYS_NAME)) {        /* not equal */
                pam_handle_t *pamh = NULL;
                int pam_err;
                struct pam_conv pamc = {
                        .conv = openpam_nullconv,
                        .appdata_ptr = NULL
                };

                Debug(DPROC, ("[%d] checking account with PAM\n", getpid()))

                /* u->name keeps crontab owner name while LOGNAME is the name
                 * of user to run command on behalf of.  they should be the
                 * same for a task from a per-user crontab.
                 */
                if (strcmp(u->name, usernm)) {
                        log_it(usernm, getpid(), "username ambiguity", u->name);
                        exit(ERROR_EXIT);
                }

                pam_err = pam_start("cron", usernm, &pamc, &pamh);
                if (pam_err != PAM_SUCCESS) {
                        log_it("CRON", getpid(), "error", "can't start PAM");
                        exit(ERROR_EXIT);
                }

                pam_err = pam_acct_mgmt(pamh, PAM_SILENT);
                /* Expired password shouldn't prevent the job from running. */
                if (pam_err != PAM_SUCCESS && pam_err != PAM_NEW_AUTHTOK_REQD) {
                        log_it(usernm, getpid(), "USER", "account unavailable");
                        exit(ERROR_EXIT);
                }

                pam_end(pamh, pam_err);
        }
#endif

#ifdef USE_SIGCHLD
        /* our parent is watching for our death by catching SIGCHLD.  we
         * do not care to watch for our children's deaths this way -- we
         * use wait() explictly.  so we have to disable the signal (which
         * was inherited from the parent).
         */
        signal(SIGCHLD, SIG_DFL);
#else
        /* on system-V systems, we are ignoring SIGCLD.  we have to stop
         * ignoring it now or the wait() in cron_pclose() won't work.
         * because of this, we have to wait() for our children here, as well.
         */
        signal(SIGCLD, SIG_DFL);
#endif /*BSD*/

        /* create some pipes to talk to our future child
         */
        pipe(stdin_pipe);       /* child's stdin */
        pipe(stdout_pipe);      /* child's stdout */

        /* since we are a forked process, we can diddle the command string
         * we were passed -- nobody else is going to use it again, right?
         *
         * if a % is present in the command, previous characters are the
         * command, and subsequent characters are the additional input to
         * the command.  Subsequent %'s will be transformed into newlines,
         * but that happens later.
         *
         * If there are escaped %'s, remove the escape character.
         */
        /*local*/{
                int escaped = FALSE;
                int ch;
                char *p;

                for (input_data = p = e->cmd; (ch = *input_data);
                     input_data++, p++) {
                        if (p != input_data)
                            *p = ch;
                        if (escaped) {
                                if (ch == '%' || ch == '\\')
                                        *--p = ch;
                                escaped = FALSE;
                                continue;
                        }
                        if (ch == '\\') {
                                escaped = TRUE;
                                continue;
                        }
                        if (ch == '%') {
                                *input_data++ = '\0';
                                break;
                        }
                }
                *p = '\0';
        }

        /* fork again, this time so we can exec the user's command.
         */
        switch (vfork()) {
        case -1:
                log_it("CRON",getpid(),"error","can't vfork");
                exit(ERROR_EXIT);
                /*NOTREACHED*/
        case 0:
                Debug(DPROC, ("[%d] grandchild process Vfork()'ed\n",
                              getpid()))

                jitter = (e->uid == ROOT_UID) ? RootJitter : Jitter;
                if (jitter != 0) {
                        srandom(getpid());
                        sleep(random() % jitter);
                }

                /* write a log message.  we've waited this long to do it
                 * because it was not until now that we knew the PID that
                 * the actual user command shell was going to get and the
                 * PID is part of the log message.
                 */
                /*local*/{
                        char *x = mkprints((u_char *)e->cmd, strlen(e->cmd));

                        log_it(usernm, getpid(), "CMD", x);
                        free(x);
                }

                /* that's the last thing we'll log.  close the log files.
                 */
#ifdef SYSLOG
                closelog();
#endif

                /* get new pgrp, void tty, etc.
                 */
                setsid();

                /* close the pipe ends that we won't use.  this doesn't affect
                 * the parent, who has to read and write them; it keeps the
                 * kernel from recording us as a potential client TWICE --
                 * which would keep it from sending SIGPIPE in otherwise
                 * appropriate circumstances.
                 */
                close(stdin_pipe[WRITE_PIPE]);
                close(stdout_pipe[READ_PIPE]);

                /* grandchild process.  make std{in,out} be the ends of
                 * pipes opened by our daddy; make stderr go to stdout.
                 */
                close(STDIN);   dup2(stdin_pipe[READ_PIPE], STDIN);
                close(STDOUT);  dup2(stdout_pipe[WRITE_PIPE], STDOUT);
                close(STDERR);  dup2(STDOUT, STDERR);

                /* close the pipes we just dup'ed.  The resources will remain.
                 */
                close(stdin_pipe[READ_PIPE]);
                close(stdout_pipe[WRITE_PIPE]);

# if defined(LOGIN_CAP)
                /* Set user's entire context, but skip the environment
                 * as cron provides a separate interface for this
                 */
                if ((pwd = getpwnam(usernm)) == NULL)
                        pwd = getpwuid(e->uid);
                lc = NULL;
                if (pwd != NULL) {
                        pwd->pw_gid = e->gid;
                        if (e->class != NULL)
                                lc = login_getclass(e->class);
                }
                if (pwd &&
                    setusercontext(lc, pwd, e->uid,
                            LOGIN_SETALL & ~(LOGIN_SETPATH|LOGIN_SETENV)) == 0)
                        endpwent();
                else {
                        /* fall back to the old method */
                        endpwent();
# endif
                        /* set our directory, uid and gid.  Set gid first,
                         * since once we set uid, we've lost root privledges.
                         */
                        setgid(e->gid);
# if defined(BSD)
                        initgroups(usernm, e->gid);
# endif
                        setlogin(usernm);
                        setuid(e->uid);         /* we aren't root after this..*/
#if defined(LOGIN_CAP)
                }
                if (lc != NULL)
                        login_close(lc);
#endif
                chdir(env_get("HOME", e->envp));

                /* exec the command.
                 */
                {
                        char    *shell = env_get("SHELL", e->envp);

# if DEBUGGING
                        if (DebugFlags & DTEST) {
                                fprintf(stderr,
                                "debug DTEST is on, not exec'ing command.\n");
                                fprintf(stderr,
                                "\tcmd='%s' shell='%s'\n", e->cmd, shell);
                                _exit(OK_EXIT);
                        }
# endif /*DEBUGGING*/
                        execle(shell, shell, "-c", e->cmd, NULL, e->envp);
                        warn("execl: couldn't exec `%s'", shell);
                        _exit(ERROR_EXIT);
                }
                break;
        default:
                /* parent process */
                break;
        }

        children++;

        /* middle process, child of original cron, parent of process running
         * the user's command.
         */

        Debug(DPROC, ("[%d] child continues, closing pipes\n", getpid()))

        /* close the ends of the pipe that will only be referenced in the
         * grandchild process...
         */
        close(stdin_pipe[READ_PIPE]);
        close(stdout_pipe[WRITE_PIPE]);

        /*
         * write, to the pipe connected to child's stdin, any input specified
         * after a % in the crontab entry.  while we copy, convert any
         * additional %'s to newlines.  when done, if some characters were
         * written and the last one wasn't a newline, write a newline.
         *
         * Note that if the input data won't fit into one pipe buffer (2K
         * or 4K on most BSD systems), and the child doesn't read its stdin,
         * we would block here.  thus we must fork again.
         */

        if (*input_data && fork() == 0) {
                FILE *out;
                int need_newline = FALSE;
                int escaped = FALSE;
                int ch;

                out = fdopen(stdin_pipe[WRITE_PIPE], "w");
                if (out == NULL) {
                        warn("fdopen failed in child2");
                        _exit(ERROR_EXIT);
                }

                Debug(DPROC, ("[%d] child2 sending data to grandchild\n", getpid()))

                /* close the pipe we don't use, since we inherited it and
                 * are part of its reference count now.
                 */
                close(stdout_pipe[READ_PIPE]);

                /* translation:
                 *      \% -> %
                 *      %  -> \n
                 *      \x -> \x        for all x != %
                 */
                while ((ch = *input_data++)) {
                        if (escaped) {
                                if (ch != '%')
                                        putc('\\', out);
                        } else {
                                if (ch == '%')
                                        ch = '\n';
                        }

                        if (!(escaped = (ch == '\\'))) {
                                putc(ch, out);
                                need_newline = (ch != '\n');
                        }
                }
                if (escaped)
                        putc('\\', out);
                if (need_newline)
                        putc('\n', out);

                /* close the pipe, causing an EOF condition.  fclose causes
                 * stdin_pipe[WRITE_PIPE] to be closed, too.
                 */
                fclose(out);

                Debug(DPROC, ("[%d] child2 done sending to grandchild\n", getpid()))
                exit(0);
        }

        /* close the pipe to the grandkiddie's stdin, since its wicked uncle
         * ernie back there has it open and will close it when he's done.
         */
        close(stdin_pipe[WRITE_PIPE]);

        children++;

        /*
         * read output from the grandchild.  it's stderr has been redirected to
         * it's stdout, which has been redirected to our pipe.  if there is any
         * output, we'll be mailing it to the user whose crontab this is...
         * when the grandchild exits, we'll get EOF.
         */

        Debug(DPROC, ("[%d] child reading output from grandchild\n", getpid()))

        /*local*/{
                FILE *in;
                int ch;

                in = fdopen(stdout_pipe[READ_PIPE], "r");
                if (in == NULL) {
                        warn("fdopen failed in child");
                        _exit(ERROR_EXIT);
                }

                ch = getc(in);
                if (ch != EOF) {
                        FILE *mail;
                        int bytes = 1;
                        int status = 0;

                        Debug(DPROC|DEXT,
                                ("[%d] got data (%x:%c) from grandchild\n",
                                        getpid(), ch, ch))

                        /* get name of recipient.  this is MAILTO if set to a
                         * valid local username; USER otherwise.
                         */
                        if (mailto) {
                                /* MAILTO was present in the environment
                                 */
                                if (!*mailto) {
                                        /* ... but it's empty. set to NULL
                                         */
                                        mailto = NULL;
                                }
                        } else {
                                /* MAILTO not present, set to USER.
                                 */
                                mailto = usernm;
                        }

                        /* if we are supposed to be mailing, MAILTO will
                         * be non-NULL.  only in this case should we set
                         * up the mail command and subjects and stuff...
                         */

                        if (mailto) {
                                char **env;
                                char mailcmd[MAX_COMMAND];
                                char hostname[MAXHOSTNAMELEN];

                                gethostname(hostname, MAXHOSTNAMELEN);
                                snprintf(mailcmd, sizeof(mailcmd),
                                         MAILARGS, MAILCMD);
                                if (!(mail = cron_popen(mailcmd, "w", e))) {
                                        warn("%s", MAILCMD);
                                        _exit(ERROR_EXIT);
                                }
                                fprintf(mail, "From: %s (Cron Daemon)\n", usernm);
                                fprintf(mail, "To: %s\n", mailto);
                                fprintf(mail, "Subject: Cron <%s@%s> %s\n",
                                        usernm, first_word(hostname, "."),
                                        e->cmd);
# if defined(MAIL_DATE)
                                fprintf(mail, "Date: %s\n",
                                        arpadate(&TargetTime));
# endif /* MAIL_DATE */
                                for (env = e->envp;  *env;  env++)
                                        fprintf(mail, "X-Cron-Env: <%s>\n",
                                                *env);
                                fprintf(mail, "\n");

                                /* this was the first char from the pipe
                                 */
                                putc(ch, mail);
                        }

                        /* we have to read the input pipe no matter whether
                         * we mail or not, but obviously we only write to
                         * mail pipe if we ARE mailing.
                         */

                        while (EOF != (ch = getc(in))) {
                                bytes++;
                                if (mailto)
                                        putc(ch, mail);
                        }

                        /* only close pipe if we opened it -- i.e., we're
                         * mailing...
                         */

                        if (mailto) {
                                Debug(DPROC, ("[%d] closing pipe to mail\n",
                                        getpid()))
                                /* Note: the pclose will probably see
                                 * the termination of the grandchild
                                 * in addition to the mail process, since
                                 * it (the grandchild) is likely to exit
                                 * after closing its stdout.
                                 */
                                status = cron_pclose(mail);
                        }

                        /* if there was output and we could not mail it,
                         * log the facts so the poor user can figure out
                         * what's going on.
                         */
                        if (mailto && status) {
                                char buf[MAX_TEMPSTR];

                                snprintf(buf, sizeof(buf),
                        "mailed %d byte%s of output but got status 0x%04x\n",
                                        bytes, (bytes==1)?"":"s",
                                        status);
                                log_it(usernm, getpid(), "MAIL", buf);
                        }

                } /*if data from grandchild*/

                Debug(DPROC, ("[%d] got EOF from grandchild\n", getpid()))

                fclose(in);     /* also closes stdout_pipe[READ_PIPE] */
        }

        /* wait for children to die.
         */
        for (;  children > 0;  children--)
        {
                WAIT_T          waiter;
                PID_T           pid;

                Debug(DPROC, ("[%d] waiting for grandchild #%d to finish\n",
                        getpid(), children))
                pid = wait(&waiter);
                if (pid < OK) {
                        Debug(DPROC, ("[%d] no more grandchildren--mail written?\n",
                                getpid()))
                        break;
                }
                Debug(DPROC, ("[%d] grandchild #%d finished, status=%04x",
                        getpid(), pid, WEXITSTATUS(waiter)))
                if (WIFSIGNALED(waiter) && WCOREDUMP(waiter))
                        Debug(DPROC, (", dumped core"))
                Debug(DPROC, ("\n"))
        }
}