/* $NetBSD: do_command.c,v 1.15 2020/04/18 19:32:19 christos Exp $ */
/* Copyright 1988,1990,1993,1994 by Paul Vixie
* All rights reserved
*/
/*
* Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
* Copyright (c) 1997,2000 by Internet Software Consortium, Inc.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
* OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/cdefs.h>
#if !defined(lint) && !defined(LINT)
#if 0
static char rcsid[] = "Id: do_command.c,v 1.9 2004/01/23 18:56:42 vixie Exp";
#else
__RCSID("$NetBSD: do_command.c,v 1.15 2020/04/18 19:32:19 christos Exp $");
#endif
#endif
#include "cron.h"
#include <unistd.h>
static int child_process(entry *);
static int safe_p(const char *, const char *);
pid_t
do_command(entry *e, user *u) {
int retval;
Debug(DPROC, ("[%ld] do_command(%s, (%s,%ld,%ld))\n",
(long)getpid(), e->cmd, u->name,
(long)e->pwd->pw_uid, (long)e->pwd->pw_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.
*/
pid_t jobpid;
switch (jobpid = fork()) {
case -1:
log_it("CRON", getpid(), "error", "can't fork");
break;
case 0:
/* child process */
acquire_daemonlock(1);
retval = child_process(e);
Debug(DPROC, ("[%ld] child process done (rc=%d), exiting\n",
(long)getpid(), retval));
_exit(retval);
break;
default:
/* parent process */
if ((e->flags & SINGLE_JOB) == 0)
jobpid = -1;
break;
}
Debug(DPROC, ("[%ld] main process returning to work\n",(long)getpid()));
/* only return pid if a singleton */
return jobpid;
}
static void
sigchld_handler(int signo) {
for (;;) {
WAIT_T waiter;
PID_T pid = waitpid(-1, &waiter, WNOHANG);
switch (pid) {
case -1:
if (errno == EINTR)
continue;
case 0:
return;
default:
break;
}
}
}
static void
write_data(char *volatile input_data, int *stdin_pipe, int *stdout_pipe)
{
FILE *out = fdopen(stdin_pipe[WRITE_PIPE], "w");
int need_newline = FALSE;
int escaped = FALSE;
int ch;
Debug(DPROC, ("[%ld] child2 sending data to grandchild\n",
(long)getpid()));
#ifdef USE_PAM
cron_pam_child_close();
#else
log_close();
#endif
/* close the pipe we don't use, since we inherited it and
* are part of its reference count now.
*/
(void)close(stdout_pipe[READ_PIPE]);
/* translation:
* \% -> %
* % -> \n
* \x -> \x for all x != %
*/
while ((ch = *input_data++) != '\0') {
if (escaped) {
if (ch != '%')
(void)putc('\\', out);
} else {
if (ch == '%')
ch = '\n';
}
if (!(escaped = (ch == '\\'))) {
(void)putc(ch, out);
need_newline = (ch != '\n');
}
}
if (escaped)
(void)putc('\\', out);
if (need_newline)
(void)putc('\n', out);
/* close the pipe, causing an EOF condition. fclose causes
* stdin_pipe[WRITE_PIPE] to be closed, too.
*/
(void)fclose(out);
Debug(DPROC, ("[%ld] child2 done sending to grandchild\n",
(long)getpid()));
}
static int
read_data(entry *e, const char *mailto, const char *usernm, char **envp,
int *stdout_pipe, pid_t jobpid)
{
FILE *in = fdopen(stdout_pipe[READ_PIPE], "r");
FILE *mail = NULL;
int bytes = 1;
int status = 0;
int ch = getc(in);
int retval = 0;
sig_t oldchld = NULL;
if (ch == EOF)
goto out;
Debug(DPROC|DEXT, ("[%ld] got data (%x:%c) from grandchild\n",
(long)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;
}
/*
* Unsafe, disable mailing.
*/
if (mailto && !safe_p(usernm, mailto))
mailto = NULL;
/* 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 + 1];
(void)gethostname(hostname, MAXHOSTNAMELEN);
if (strlens(MAILFMT, MAILARG, NULL) + 1 >= sizeof mailcmd) {
log_it(usernm, getpid(), "MAIL", "mailcmd too long");
retval = ERROR_EXIT;
goto out;
}
(void)snprintf(mailcmd, sizeof(mailcmd), MAILFMT, MAILARG);
oldchld = signal(SIGCHLD, SIG_DFL);
if (!(mail = cron_popen(mailcmd, "w", e->pwd))) {
log_itx(usernm, getpid(), "MAIL",
"cannot run `%s'", mailcmd);
(void) signal(SIGCHLD, oldchld);
retval = ERROR_EXIT;
goto out;
}
(void)fprintf(mail, "From: root (Cron Daemon)\n");
(void)fprintf(mail, "To: %s\n", mailto);
(void)fprintf(mail, "Subject: Cron <%s@%s> %s\n",
usernm, hostname, e->cmd);
(void)fprintf(mail, "Auto-Submitted: auto-generated\n");
#ifdef MAIL_DATE
(void)fprintf(mail, "Date: %s\n", arpadate(&StartTime));
#endif /*MAIL_DATE*/
for (env = envp; *env; env++)
(void)fprintf(mail, "X-Cron-Env: <%s>\n", *env);
(void)fprintf(mail, "\n");
/* this was the first char from the pipe
*/
(void)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)
(void)putc(ch, mail);
}
/* only close pipe if we opened it -- i.e., we're
* mailing...
*/
if (mailto) {
if (e->flags & MAIL_WHEN_ERR) {
int jstatus = -1;
if (jobpid <= 0)
log_it("CRON", getpid(), "error",
"no job pid");
else {
while (waitpid(jobpid, &jstatus, WNOHANG) == -1)
if (errno != EINTR) {
log_it("CRON", getpid(),
"error", "no job pid");
break;
}
}
/* If everything went well, and -n was set, _and_ we
* have mail, we won't be mailing... so shoot the
* messenger!
*/
if (WIFEXITED(jstatus) && WEXITSTATUS(jstatus) == 0) {
Debug(DPROC, ("[%ld] aborting pipe to mail\n",
(long)getpid()));
status = cron_pabort(mail);
mailto = NULL;
}
}
if (mailto) {
Debug(DPROC, ("[%ld] closing pipe to mail\n",
(long)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);
mail = NULL;
}
(void) signal(SIGCHLD, oldchld);
}
/* 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) {
log_itx(usernm, getpid(), "MAIL",
"mailed %d byte%s of output to `%s' but"
" got status %#04x", bytes,
bytes == 1 ? "" : "s", mailto, status);
}
out:
Debug(DPROC, ("[%ld] got EOF from grandchild\n", (long)getpid()));
(void)fclose(in); /* also closes stdout_pipe[READ_PIPE] */
return retval;
}
extern char **environ;
static int
exec_user_command(entry *e, char **envp, char *usernm, int *stdin_pipe,
int *stdout_pipe, pid_t *jobpid)
{
char *homedir;
char * volatile *ep;
switch (*jobpid = vfork()) {
case -1:
return -1;
case 0:
ep = envp;
Debug(DPROC, ("[%ld] grandchild process vfork()'ed\n",
(long)getpid()));
/* 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.
*/
if ((e->flags & DONT_LOG) == 0) {
char *x = mkprints(e->cmd, strlen(e->cmd));
log_it(usernm, getpid(), "CMD START", x);
free(x);
}
/* that's the last thing we'll log. close the log files.
*/
log_close();
/* get new pgrp, void tty, etc.
*/
if (setsid() == -1)
syslog(LOG_ERR, "setsid() failure: %m");
/* 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.
*/
(void)close(stdin_pipe[WRITE_PIPE]);
(void)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.
*/
if (stdin_pipe[READ_PIPE] != STDIN) {
(void)dup2(stdin_pipe[READ_PIPE], STDIN);
(void)close(stdin_pipe[READ_PIPE]);
}
if (stdout_pipe[WRITE_PIPE] != STDOUT) {
(void)dup2(stdout_pipe[WRITE_PIPE], STDOUT);
(void)close(stdout_pipe[WRITE_PIPE]);
}
(void)dup2(STDOUT, STDERR);
/* set our directory, uid and gid. Set gid first, since once
* we set uid, we've lost root privledges.
*/
#ifdef LOGIN_CAP
{
#ifdef BSD_AUTH
auth_session_t *as;
#endif
login_cap_t *lc;
char *p;
if ((lc = login_getclass(e->pwd->pw_class)) == NULL) {
warnx("unable to get login class for `%s'",
e->pwd->pw_name);
_exit(ERROR_EXIT);
}
if (setusercontext(lc, e->pwd, e->pwd->pw_uid, LOGIN_SETALL) < 0) {
warnx("setusercontext failed for `%s'",
e->pwd->pw_name);
_exit(ERROR_EXIT);
}
#ifdef BSD_AUTH
as = auth_open();
if (as == NULL || auth_setpwd(as, e->pwd) != 0) {
warn("can't malloc");
_exit(ERROR_EXIT);
}
if (auth_approval(as, lc, usernm, "cron") <= 0) {
warnx("approval failed for `%s'",
e->pwd->pw_name);
_exit(ERROR_EXIT);
}
auth_close(as);
#endif /* BSD_AUTH */
login_close(lc);
/* If no PATH specified in crontab file but
* we just added one via login.conf, add it to
* the crontab environment.
*/
if (env_get("PATH", envp) == NULL && environ != NULL) {
if ((p = getenv("PATH")) != NULL)
ep = env_set(envp, p);
}
}
#else
if (setgid(e->pwd->pw_gid) != 0) {
syslog(LOG_ERR, "setgid(%d) failed for %s: %m",
e->pwd->pw_gid, e->pwd->pw_name);
_exit(ERROR_EXIT);
}
if (initgroups(usernm, e->pwd->pw_gid) != 0) {
syslog(LOG_ERR, "initgroups(%s, %d) failed for %s: %m",
usernm, e->pwd->pw_gid, e->pwd->pw_name);
_exit(ERROR_EXIT);
}
#if (defined(BSD)) && (BSD >= 199103)
if (setlogin(usernm) < 0) {
syslog(LOG_ERR, "setlogin(%s) failure for %s: %m",
usernm, e->pwd->pw_name);
_exit(ERROR_EXIT);
}
#endif /* BSD */
#ifdef USE_PAM
if (!cron_pam_setcred())
_exit(ERROR_EXIT);
cron_pam_child_close();
#endif
if (setuid(e->pwd->pw_uid) != 0) {
syslog(LOG_ERR, "setuid(%d) failed for %s: %m",
e->pwd->pw_uid, e->pwd->pw_name);
_exit(ERROR_EXIT);
}
/* we aren't root after this... */
#endif /* LOGIN_CAP */
homedir = env_get("HOME", __UNVOLATILE(ep));
if (chdir(homedir) != 0) {
syslog(LOG_ERR, "chdir(%s) $HOME failed for %s: %m",
homedir, e->pwd->pw_name);
_exit(ERROR_EXIT);
}
#ifdef USE_SIGCHLD
/* our grandparent is watching for our death by catching
* SIGCHLD. the parent is ignoring SIGCHLD's; we want
* to restore default behaviour.
*/
(void) signal(SIGCHLD, SIG_DFL);
#endif
(void) signal(SIGPIPE, SIG_DFL);
(void) signal(SIGUSR1, SIG_DFL);
(void) signal(SIGHUP, SIG_DFL);
/*
* Exec the command.
*/
{
char *shell = env_get("SHELL", __UNVOLATILE(ep));
# if DEBUGGING
if (DebugFlags & DTEST) {
(void)fprintf(stderr,
"debug DTEST is on, not exec'ing command.\n");
(void)fprintf(stderr,
"\tcmd='%s' shell='%s'\n", e->cmd, shell);
_exit(OK_EXIT);
}
# endif /*DEBUGGING*/
(void)execle(shell, shell, "-c", e->cmd, NULL, envp);
warn("execl: couldn't exec `%s'", shell);
_exit(ERROR_EXIT);
}
return 0;
default:
/* parent process */
return 0;
}
}
static int
child_process(entry *e) {
int stdin_pipe[2], stdout_pipe[2];
char * volatile input_data;
char *usernm, * volatile mailto;
struct sigaction sact;
char **envp = e->envp;
int retval = OK_EXIT;
pid_t jobpid = 0;
Debug(DPROC, ("[%ld] child_process('%s')\n", (long)getpid(), e->cmd));
setproctitle("running job");
/* discover some useful and important environment settings
*/
usernm = e->pwd->pw_name;
mailto = env_get("MAILTO", envp);
memset(&sact, 0, sizeof(sact));
sigemptyset(&sact.sa_mask);
sact.sa_flags = 0;
#ifdef SA_RESTART
sact.sa_flags |= SA_RESTART;
#endif
sact.sa_handler = sigchld_handler;
(void) sigaction(SIGCHLD, &sact, NULL);
/* create some pipes to talk to our future child
*/
if (pipe(stdin_pipe) == -1) /* child's stdin */
log_it("CRON", getpid(), "error", "create child stdin pipe");
if (pipe(stdout_pipe) == -1) /* child's stdout */
log_it("CRON", getpid(), "error", "create child stdout pipe");
/* 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. An escaped % will have the escape character stripped
* from it. Subsequent %'s will be transformed into newlines,
* but that happens later.
*/
/*local*/{
int escaped = FALSE;
int ch;
char *p;
/* translation:
* \% -> %
* % -> end of command, following is command input.
* \x -> \x for all x != %
*/
input_data = p = e->cmd;
while ((ch = *input_data++) != '\0') {
if (escaped) {
if (ch != '%')
*p++ = '\\';
} else {
if (ch == '%') {
break;
}
}
if (!(escaped = (ch == '\\'))) {
*p++ = (char)ch;
}
}
if (ch == '\0') {
/* move pointer back, so that code below
* won't think we encountered % sequence */
input_data--;
}
if (escaped)
*p++ = '\\';
*p = '\0';
}
#ifdef USE_PAM
if (!cron_pam_start(usernm))
return ERROR_EXIT;
if (!(envp = cron_pam_getenvlist(envp))) {
retval = ERROR_EXIT;
goto child_process_end;
}
#endif
/* fork again, this time so we can exec the user's command.
*/
if (exec_user_command(e, envp, usernm, stdin_pipe, stdout_pipe,
&jobpid) == -1) {
retval = ERROR_EXIT;
goto child_process_end;
}
/* middle process, child of original cron, parent of process running
* the user's command.
*/
Debug(DPROC, ("[%ld] child continues, closing pipes\n",(long)getpid()));
/* close the ends of the pipe that will only be referenced in the
* grandchild process...
*/
(void)close(stdin_pipe[READ_PIPE]);
(void)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) {
switch (fork()) {
case 0:
write_data(input_data, stdin_pipe, stdout_pipe);
exit(EXIT_SUCCESS);
case -1:
retval = ERROR_EXIT;
goto child_process_end;
default:
break;
}
}
/* 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.
*/
(void)close(stdin_pipe[WRITE_PIPE]);
/*
* 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, ("[%ld] child reading output from grandchild\n",
(long)getpid()));
retval = read_data(e, mailto, usernm, envp, stdout_pipe, jobpid);
if (retval)
goto child_process_end;
/* wait for children to die.
*/
sigchld_handler(0);
/* Log the time when we finished deadling with the job */
/*local*/{
char *x = mkprints(e->cmd, strlen(e->cmd));
log_it(usernm, getpid(), "CMD FINISH", x);
free(x);
}
child_process_end:
#ifdef USE_PAM
cron_pam_finish();
#endif
return retval;
}
static int
safe_p(const char *usernm, const char *s) {
static const char safe_delim[] = "@!:%-.,"; /* conservative! */
const char *t;
int ch, first;
for (t = s, first = 1; (ch = *t++) != '\0'; first = 0) {
if (isascii(ch) && isprint(ch) &&
(isalnum(ch) || (!first && strchr(safe_delim, ch))))
continue;
log_it(usernm, getpid(), "UNSAFE", s);
return (FALSE);
}
return (TRUE);
}