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> 1944743Smarkm#include <signal.h> 2044743Smarkm#include <stdio.h> 2144743Smarkm#include <syslog.h> 2244743Smarkm#include <string.h> 2344743Smarkm 2444743Smarkmextern void exit(); 2544743Smarkm 2644743Smarkm/* Local stuff. */ 2744743Smarkm 2844743Smarkm#include "tcpd.h" 2944743Smarkm 3044743Smarkm/* Forward declarations. */ 3144743Smarkm 3244743Smarkmstatic void do_child(); 3344743Smarkm 3444743Smarkm/* shell_cmd - execute shell command */ 3544743Smarkm 3644743Smarkmvoid shell_cmd(command) 3744743Smarkmchar *command; 3844743Smarkm{ 3944743Smarkm int child_pid; 4044743Smarkm int wait_pid; 4144743Smarkm 4244743Smarkm /* 4344743Smarkm * Most of the work is done within the child process, to minimize the 4444743Smarkm * risk of damage to the parent. 4544743Smarkm */ 4644743Smarkm 4744743Smarkm switch (child_pid = fork()) { 4844743Smarkm case -1: /* error */ 4944743Smarkm tcpd_warn("cannot fork: %m"); 5044743Smarkm break; 5144743Smarkm case 00: /* child */ 5244743Smarkm do_child(command); 5344743Smarkm /* NOTREACHED */ 5444743Smarkm default: /* parent */ 5544743Smarkm while ((wait_pid = wait((int *) 0)) != -1 && wait_pid != child_pid) 5644743Smarkm /* void */ ; 5744743Smarkm } 5844743Smarkm} 5944743Smarkm 6044743Smarkm/* do_child - exec command with { stdin, stdout, stderr } to /dev/null */ 6144743Smarkm 6244743Smarkmstatic void do_child(command) 6344743Smarkmchar *command; 6444743Smarkm{ 6544743Smarkm char *error; 6644743Smarkm int tmp_fd; 6744743Smarkm 6844743Smarkm /* 6944743Smarkm * Systems with POSIX sessions may send a SIGHUP to grandchildren if the 7044743Smarkm * child exits first. This is sick, sessions were invented for terminals. 7144743Smarkm */ 7244743Smarkm 7344743Smarkm signal(SIGHUP, SIG_IGN); 7444743Smarkm 7544743Smarkm /* Set up new stdin, stdout, stderr, and exec the shell command. */ 7644743Smarkm 7744743Smarkm for (tmp_fd = 0; tmp_fd < 3; tmp_fd++) 7844743Smarkm (void) close(tmp_fd); 7944743Smarkm if (open("/dev/null", 2) != 0) { 8044743Smarkm error = "open /dev/null: %m"; 8144743Smarkm } else if (dup(0) != 1 || dup(0) != 2) { 8244743Smarkm error = "dup: %m"; 8344743Smarkm } else { 8444743Smarkm (void) execl("/bin/sh", "sh", "-c", command, (char *) 0); 8544743Smarkm error = "execl /bin/sh: %m"; 8644743Smarkm } 8744743Smarkm 8844743Smarkm /* Something went wrong. We MUST terminate the child process. */ 8944743Smarkm 9044743Smarkm tcpd_warn(error); 9144743Smarkm _exit(0); 9244743Smarkm} 93