95 lines
2.1 KiB
C
95 lines
2.1 KiB
C
/*
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* shell_cmd() takes a shell command after %<character> substitutions. The
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* command is executed by a /bin/sh child process, with standard input,
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* standard output and standard error connected to /dev/null.
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*
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* Diagnostics are reported through syslog(3).
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*
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* Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
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*/
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#ifndef lint
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static char sccsid[] = "@(#) shell_cmd.c 1.5 94/12/28 17:42:44";
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#endif
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/* System libraries. */
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#include <sys/types.h>
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#include <sys/param.h>
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#include <sys/wait.h>
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#include <signal.h>
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#include <stdio.h>
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#include <syslog.h>
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#include <string.h>
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#include <unistd.h>
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#include <fcntl.h>
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extern void exit();
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/* Local stuff. */
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#include "tcpd.h"
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/* Forward declarations. */
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static void do_child(char *command);
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/* shell_cmd - execute shell command */
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void shell_cmd(command)
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char *command;
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{
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int child_pid;
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int wait_pid;
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/*
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* Most of the work is done within the child process, to minimize the
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* risk of damage to the parent.
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*/
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switch (child_pid = fork()) {
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case -1: /* error */
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tcpd_warn("cannot fork: %m");
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break;
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case 00: /* child */
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do_child(command);
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/* NOTREACHED */
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default: /* parent */
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while ((wait_pid = wait((int *) 0)) != -1 && wait_pid != child_pid)
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/* void */ ;
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}
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}
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/* do_child - exec command with { stdin, stdout, stderr } to /dev/null */
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static void do_child(char *command)
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{
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char *error;
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int tmp_fd;
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/*
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* Systems with POSIX sessions may send a SIGHUP to grandchildren if the
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* child exits first. This is sick, sessions were invented for terminals.
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*/
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signal(SIGHUP, SIG_IGN);
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/* Set up new stdin, stdout, stderr, and exec the shell command. */
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for (tmp_fd = 0; tmp_fd < 3; tmp_fd++)
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(void) close(tmp_fd);
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if (open("/dev/null", 2) != 0) {
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error = "open /dev/null: %m";
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} else if (dup(0) != 1 || dup(0) != 2) {
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error = "dup: %m";
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} else {
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(void) execl("/bin/sh", "sh", "-c", command, (char *) 0);
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error = "execl /bin/sh: %m";
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}
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/* Something went wrong. We MUST terminate the child process. */
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tcpd_warn(error);
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_exit(0);
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}
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