144743Smarkm /* 244743Smarkm * shell_cmd() takes a shell command after %<character> substitutions. The 344743Smarkm * command is executed by a /bin/sh child process, with standard input, 444743Smarkm * standard output and standard error connected to /dev/null. 544743Smarkm * 644743Smarkm * Diagnostics are reported through syslog(3). 744743Smarkm * 844743Smarkm * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands. 944743Smarkm */ 1044743Smarkm 1144743Smarkm#ifndef lint 1244743Smarkmstatic char sccsid[] = "@(#) shell_cmd.c 1.5 94/12/28 17:42:44"; 1344743Smarkm#endif 1444743Smarkm 1544743Smarkm/* System libraries. */ 1644743Smarkm 1744743Smarkm#include <sys/types.h> 1844743Smarkm#include <sys/param.h> 19257398Ssbruno#include <sys/wait.h> 2044743Smarkm#include <signal.h> 2144743Smarkm#include <stdio.h> 2244743Smarkm#include <syslog.h> 2344743Smarkm#include <string.h> 24257398Ssbruno#include <unistd.h> 25257398Ssbruno#include <fcntl.h> 2644743Smarkm 2744743Smarkmextern void exit(); 2844743Smarkm 2944743Smarkm/* Local stuff. */ 3044743Smarkm 3144743Smarkm#include "tcpd.h" 3244743Smarkm 3344743Smarkm/* Forward declarations. */ 3444743Smarkm 35350345Sbrooksstatic void do_child(char *command); 3644743Smarkm 3744743Smarkm/* shell_cmd - execute shell command */ 3844743Smarkm 3944743Smarkmvoid shell_cmd(command) 4044743Smarkmchar *command; 4144743Smarkm{ 4244743Smarkm int child_pid; 4344743Smarkm int wait_pid; 4444743Smarkm 4544743Smarkm /* 4644743Smarkm * Most of the work is done within the child process, to minimize the 4744743Smarkm * risk of damage to the parent. 4844743Smarkm */ 4944743Smarkm 5044743Smarkm switch (child_pid = fork()) { 5144743Smarkm case -1: /* error */ 5244743Smarkm tcpd_warn("cannot fork: %m"); 5344743Smarkm break; 5444743Smarkm case 00: /* child */ 5544743Smarkm do_child(command); 5644743Smarkm /* NOTREACHED */ 5744743Smarkm default: /* parent */ 5844743Smarkm while ((wait_pid = wait((int *) 0)) != -1 && wait_pid != child_pid) 5944743Smarkm /* void */ ; 6044743Smarkm } 6144743Smarkm} 6244743Smarkm 6344743Smarkm/* do_child - exec command with { stdin, stdout, stderr } to /dev/null */ 6444743Smarkm 65350345Sbrooksstatic void do_child(char *command) 6644743Smarkm{ 6744743Smarkm char *error; 6844743Smarkm int tmp_fd; 6944743Smarkm 7044743Smarkm /* 7144743Smarkm * Systems with POSIX sessions may send a SIGHUP to grandchildren if the 7244743Smarkm * child exits first. This is sick, sessions were invented for terminals. 7344743Smarkm */ 7444743Smarkm 7544743Smarkm signal(SIGHUP, SIG_IGN); 7644743Smarkm 7744743Smarkm /* Set up new stdin, stdout, stderr, and exec the shell command. */ 7844743Smarkm 7944743Smarkm for (tmp_fd = 0; tmp_fd < 3; tmp_fd++) 8044743Smarkm (void) close(tmp_fd); 8144743Smarkm if (open("/dev/null", 2) != 0) { 8244743Smarkm error = "open /dev/null: %m"; 8344743Smarkm } else if (dup(0) != 1 || dup(0) != 2) { 8444743Smarkm error = "dup: %m"; 8544743Smarkm } else { 8644743Smarkm (void) execl("/bin/sh", "sh", "-c", command, (char *) 0); 8744743Smarkm error = "execl /bin/sh: %m"; 8844743Smarkm } 8944743Smarkm 9044743Smarkm /* Something went wrong. We MUST terminate the child process. */ 9144743Smarkm 9244743Smarkm tcpd_warn(error); 9344743Smarkm _exit(0); 9444743Smarkm} 95