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cronie/src/do_command.c

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/* 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 "config.h"
#include <ctype.h>
#include <errno.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>
#include "externs.h"
#include "funcs.h"
#include "globals.h"
#include "structs.h"
#ifndef isascii
# define isascii(c) ((unsigned)(c)<=0177)
#endif
static int child_process(entry *, char **);
static int safe_p(const char *, const char *);
void do_command(entry * e, user * u) {
pid_t pid = getpid();
int ev;
char **jobenv = 0L;
Debug(DPROC, ("[%ld] do_command(%s, (%s,%ld,%ld))\n",
(long) pid, 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.
*/
switch (fork()) {
case -1:
log_it("CRON", pid, "CAN'T FORK", "do_command", errno);
break;
case 0:
/* child process */
acquire_daemonlock(1);
/* Set up the Red Hat security context for both mail/minder and job processes:
*/
if (cron_set_job_security_context(e, u, &jobenv) != 0) {
_exit(ERROR_EXIT);
}
ev = child_process(e, jobenv);
#ifdef WITH_PAM
cron_close_pam();
#endif
env_free(jobenv);
Debug(DPROC, ("[%ld] child process done, exiting\n", (long) getpid()));
_exit(ev);
break;
default:
/* parent process */
break;
}
Debug(DPROC, ("[%ld] main process returning to work\n", (long) pid));
}
static int child_process(entry * e, char **jobenv) {
int stdin_pipe[2], stdout_pipe[2];
char *input_data, *usernm, *mailto, *mailfrom;
int children = 0;
pid_t pid = getpid();
struct sigaction sa;
/* Ignore SIGPIPE as we will be writing to pipes and do not want to terminate
prematurely */
memset(&sa, 0, sizeof(sa));
sa.sa_handler = SIG_IGN;
sigaction(SIGPIPE, &sa, NULL);
/* 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() explicitly. so we have to reset the signal (which
* was inherited from the parent).
*/
sa.sa_handler = SIG_DFL;
sigaction(SIGCHLD, &sa, NULL);
Debug(DPROC, ("[%ld] child_process('%s')\n", (long) getpid(), e->cmd));
#ifdef CAPITALIZE_FOR_PS
/* mark ourselves as different to PS command watchers by upshifting
* our program name. This has no effect on some kernels.
*/
/*local */ {
char *pch;
for (pch = ProgramName; *pch; pch++)
*pch = (char)MkUpper(*pch);
}
#endif /* CAPITALIZE_FOR_PS */
/* discover some useful and important environment settings
*/
usernm = e->pwd->pw_name;
mailto = env_get("MAILTO", jobenv);
mailfrom = env_get("MAILFROM", e->envp);
/* create some pipes to talk to our future child
*/
if (pipe(stdin_pipe) == -1) { /* child's stdin */
log_it("CRON", pid, "PIPE() FAILED", "stdin_pipe", errno);
return ERROR_EXIT;
}
if (pipe(stdout_pipe) == -1) { /* child's stdout */
log_it("CRON", pid, "PIPE() FAILED", "stdout_pipe", errno);
return ERROR_EXIT;
}
/* 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;
for (input_data = p = e->cmd;
(ch = *input_data) != '\0'; input_data++, p++) {
if (p != input_data)
*p = (char)ch;
if (escaped) {
if (ch == '%')
*--p = (char)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 (fork()) {
case -1:
log_it("CRON", pid, "CAN'T FORK", "child_process", errno);
return ERROR_EXIT;
/*NOTREACHED*/
case 0:
Debug(DPROC, ("[%ld] grandchild process fork()'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((u_char *) e->cmd, strlen(e->cmd));
log_it(usernm, getpid(), "CMD", x, 0);
free(x);
}
if (cron_change_user_permanently(e->pwd, env_get("HOME", jobenv)) < 0)
_exit(ERROR_EXIT);
/* get new pgrp, void tty, etc.
*/
(void) setsid();
/* reset the SIGPIPE back to default so the child will terminate
* if it tries to write to a closed pipe
*/
sa.sa_handler = SIG_DFL;
sigaction(SIGPIPE, &sa, NULL);
/* 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.
*/
if (stdin_pipe[READ_PIPE] != STDIN) {
dup2(stdin_pipe[READ_PIPE], STDIN);
close(stdin_pipe[READ_PIPE]);
}
if (stdout_pipe[WRITE_PIPE] != STDOUT) {
dup2(stdout_pipe[WRITE_PIPE], STDOUT);
close(stdout_pipe[WRITE_PIPE]);
}
dup2(STDOUT, STDERR);
/*
* Exec the command.
*/
{
char *shell = env_get("SHELL", jobenv);
int fd, fdmax = getdtablesize();
/* close all unwanted open file descriptors */
for(fd = STDERR + 1; fd < fdmax; fd++) {
close(fd);
}
#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, (char *) 0, jobenv);
fprintf(stderr, "execl: couldn't exec `%s'\n", shell);
perror("execl");
_exit(ERROR_EXIT);
}
break;
default:
cron_restore_default_security_context();
/* parent process */
break;
}
children++;
/* 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...
*/
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 = 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()));
/* reset the SIGPIPE back to default so the child will terminate
* if it tries to write to a closed pipe
*/
sa.sa_handler = SIG_DFL;
sigaction(SIGPIPE, &sa, NULL);
/* close the pipe we don't use, since we inherited it and
* are part of its reference count now.
*/
close(stdout_pipe[READ_PIPE]);
if (cron_change_user_permanently(e->pwd, env_get("HOME", jobenv)) < 0)
_exit(ERROR_EXIT);
/* translation:
* \% -> %
* % -> \n
* \x -> \x for all x != %
*/
while ((ch = *input_data++) != '\0') {
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, ("[%ld] child2 done sending to grandchild\n",
(long) 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, ("[%ld] child reading output from grandchild\n",
(long) getpid()));
/*local */ {
FILE *in = fdopen(stdout_pipe[READ_PIPE], "r");
int ch = getc(in);
if (ch != EOF) {
FILE *mail = NULL;
int bytes = 1;
int status = 0;
#if defined(SYSLOG)
char logbuf[1024];
int bufidx = 0;
if (SyslogOutput) {
if (ch != '\n')
logbuf[bufidx++] = (char)ch;
}
#endif
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;
}
/* get sender address. this is MAILFROM if set (and safe),
* the user account name otherwise.
*/
if (!mailfrom || !*mailfrom || !safe_p(usernm, mailfrom)) {
mailfrom = e->pwd->pw_name;
}
/* 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...
*/
/* Also skip it if MailCmd is set to "off" */
if (mailto && safe_p(usernm, mailto)
&& strncmp(MailCmd,"off",3) && !SyslogOutput) {
char **env;
char mailcmd[MAX_COMMAND+1]; /* +1 for terminator */
char hostname[MAXHOSTNAMELEN];
char *content_type = env_get("CONTENT_TYPE", jobenv),
*content_transfer_encoding =
env_get("CONTENT_TRANSFER_ENCODING", jobenv);
gethostname(hostname, MAXHOSTNAMELEN);
if (MailCmd[0] == '\0') {
if (snprintf(mailcmd, sizeof mailcmd, MAILFMT, MAILARG, mailfrom)
>= sizeof mailcmd) {
fprintf(stderr, "mailcmd too long\n");
(void) _exit(ERROR_EXIT);
}
}
else {
strncpy(mailcmd, MailCmd, MAX_COMMAND+1);
}
if (!(mail = cron_popen(mailcmd, "w", e->pwd, jobenv))) {
perror(mailcmd);
(void) _exit(ERROR_EXIT);
}
fprintf(mail, "From: \"(Cron Daemon)\" <%s>\n", mailfrom);
fprintf(mail, "To: %s\n", mailto);
fprintf(mail, "Subject: Cron <%s@%s> %s\n",
usernm, first_word(hostname, "."), e->cmd);
#ifdef MAIL_DATE
fprintf(mail, "Date: %s\n", arpadate(&StartTime));
#endif /*MAIL_DATE */
fprintf(mail, "MIME-Version: 1.0\n");
if (content_type == 0L) {
fprintf(mail, "Content-Type: text/plain; charset=%s\n",
cron_default_mail_charset);
}
else { /* user specified Content-Type header.
* disallow new-lines for security reasons
* (else users could specify arbitrary mail headers!)
*/
char *nl = content_type;
size_t ctlen = strlen(content_type);
while ((*nl != '\0')
&& ((nl = strchr(nl, '\n')) != 0L)
&& (nl < (content_type + ctlen))
)
*nl = ' ';
fprintf(mail, "Content-Type: %s\n", content_type);
}
if (content_transfer_encoding != 0L) {
char *nl = content_transfer_encoding;
size_t ctlen = strlen(content_transfer_encoding);
while ((*nl != '\0')
&& ((nl = strchr(nl, '\n')) != 0L)
&& (nl < (content_transfer_encoding + ctlen))
)
*nl = ' ';
fprintf(mail, "Content-Transfer-Encoding: %s\n",
content_transfer_encoding);
}
/* The Auto-Submitted header is
* defined (and suggested by) RFC3834.
*/
fprintf(mail, "Auto-Submitted: auto-generated\n");
fprintf(mail, "Precedence: bulk\n");
for (env = jobenv; *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 (mail)
putc(ch, mail);
#if defined(SYSLOG)
if (SyslogOutput) {
logbuf[bufidx++] = (char)ch;
if ((ch == '\n') || (bufidx == sizeof(logbuf)-1)) {
if (ch == '\n')
logbuf[bufidx-1] = '\0';
else
logbuf[bufidx] = '\0';
log_it(usernm, getpid(), "CMDOUT", logbuf, 0);
bufidx = 0;
}
}
#endif
}
/* only close pipe if we opened it -- i.e., we're
* mailing...
*/
if (mail) {
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);
}
#if defined(SYSLOG)
if (SyslogOutput) {
if (bufidx) {
logbuf[bufidx] = '\0';
log_it(usernm, getpid(), "CMDOUT", logbuf, 0);
}
}
#endif
/* 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 (mail && status && !SyslogOutput) {
char buf[MAX_TEMPSTR];
sprintf(buf,
"mailed %d byte%s of output but got status 0x%04x\n",
bytes, (bytes == 1) ? "" : "s", status);
log_it(usernm, getpid(), "MAIL", buf, 0);
}
} /*if data from grandchild */
Debug(DPROC, ("[%ld] got EOF from grandchild\n", (long) getpid()));
fclose(in); /* also closes stdout_pipe[READ_PIPE] */
}
/* wait for children to die.
*/
for (; children > 0; children--) {
WAIT_T waiter;
PID_T child;
Debug(DPROC, ("[%ld] waiting for grandchild #%d to finish\n",
(long) getpid(), children));
while ((child = wait(&waiter)) < OK && errno == EINTR) ;
if (child < OK) {
Debug(DPROC,
("[%ld] no more grandchildren--mail written?\n",
(long) getpid()));
break;
}
Debug(DPROC, ("[%ld] grandchild #%ld finished, status=%04x",
(long) getpid(), (long) child, WEXITSTATUS(waiter)));
if (WIFSIGNALED(waiter) && WCOREDUMP(waiter))
Debug(DPROC, (", dumped core"));
Debug(DPROC, ("\n"));
}
return OK_EXIT;
}
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, 0);
return (FALSE);
}
return (TRUE);
}
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