/* $OpenBSD: shell_cmd.c,v 1.2 2002/01/02 20:18:33 deraadt Exp $ */ /* * shell_cmd() takes a shell command after %<character> substitutions. The * command is executed by a /bin/sh child process, with standard input, * standard output and standard error connected to /dev/null. * * Diagnostics are reported through syslog(3). * * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands. */ #ifndef lint #if 0 static char sccsid[] = "@(#) shell_cmd.c 1.5 94/12/28 17:42:44"; #else static char rcsid[] = "$OpenBSD: shell_cmd.c,v 1.2 2002/01/02 20:18:33 deraadt Exp $"; #endif #endif /* System libraries. */ #include <sys/types.h> #include <sys/param.h> #include <sys/wait.h> #include <signal.h> #include <stdio.h> #include <syslog.h> #include <string.h> #include <unistd.h> #include <fcntl.h> /* Local stuff. */ #include "tcpd.h" /* Forward declarations. */ static void do_child(); /* shell_cmd - execute shell command */ void shell_cmd(command) char *command; { pid_t child_pid; pid_t wait_pid; /* * Most of the work is done within the child process, to minimize the * risk of damage to the parent. */ switch (child_pid = fork()) { case -1: /* error */ tcpd_warn("cannot fork: %m"); break; case 00: /* child */ do_child(command); /* NOTREACHED */ default: /* parent */ while ((wait_pid = wait((int *) 0)) != -1 && wait_pid != child_pid) /* void */ ; } } /* do_child - exec command with { stdin, stdout, stderr } to /dev/null */ static void do_child(command) char *command; { char *error; int tmp_fd; /* * Systems with POSIX sessions may send a SIGHUP to grandchildren if the * child exits first. This is sick, sessions were invented for terminals. */ signal(SIGHUP, SIG_IGN); /* Set up new stdin, stdout, stderr, and exec the shell command. */ for (tmp_fd = 0; tmp_fd < 3; tmp_fd++) (void) close(tmp_fd); if (open("/dev/null", O_RDWR) != 0) { error = "open /dev/null: %m"; } else if (dup(0) != 1 || dup(0) != 2) { error = "dup: %m"; } else { (void) execl("/bin/sh", "sh", "-c", command, (char *) 0); error = "execl /bin/sh: %m"; } /* Something went wrong. We MUST terminate the child process. */ tcpd_warn(error); _exit(0); }