shell_cmd.c revision 256281
1 /* 2 * shell_cmd() takes a shell command after %<character> substitutions. The 3 * command is executed by a /bin/sh child process, with standard input, 4 * standard output and standard error connected to /dev/null. 5 * 6 * Diagnostics are reported through syslog(3). 7 * 8 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands. 9 */ 10 11#ifndef lint 12static char sccsid[] = "@(#) shell_cmd.c 1.5 94/12/28 17:42:44"; 13#endif 14 15/* System libraries. */ 16 17#include <sys/types.h> 18#include <sys/param.h> 19#include <signal.h> 20#include <stdio.h> 21#include <syslog.h> 22#include <string.h> 23 24extern void exit(); 25 26/* Local stuff. */ 27 28#include "tcpd.h" 29 30/* Forward declarations. */ 31 32static void do_child(); 33 34/* shell_cmd - execute shell command */ 35 36void shell_cmd(command) 37char *command; 38{ 39 int child_pid; 40 int wait_pid; 41 42 /* 43 * Most of the work is done within the child process, to minimize the 44 * risk of damage to the parent. 45 */ 46 47 switch (child_pid = fork()) { 48 case -1: /* error */ 49 tcpd_warn("cannot fork: %m"); 50 break; 51 case 00: /* child */ 52 do_child(command); 53 /* NOTREACHED */ 54 default: /* parent */ 55 while ((wait_pid = wait((int *) 0)) != -1 && wait_pid != child_pid) 56 /* void */ ; 57 } 58} 59 60/* do_child - exec command with { stdin, stdout, stderr } to /dev/null */ 61 62static void do_child(command) 63char *command; 64{ 65 char *error; 66 int tmp_fd; 67 68 /* 69 * Systems with POSIX sessions may send a SIGHUP to grandchildren if the 70 * child exits first. This is sick, sessions were invented for terminals. 71 */ 72 73 signal(SIGHUP, SIG_IGN); 74 75 /* Set up new stdin, stdout, stderr, and exec the shell command. */ 76 77 for (tmp_fd = 0; tmp_fd < 3; tmp_fd++) 78 (void) close(tmp_fd); 79 if (open("/dev/null", 2) != 0) { 80 error = "open /dev/null: %m"; 81 } else if (dup(0) != 1 || dup(0) != 2) { 82 error = "dup: %m"; 83 } else { 84 (void) execl("/bin/sh", "sh", "-c", command, (char *) 0); 85 error = "execl /bin/sh: %m"; 86 } 87 88 /* Something went wrong. We MUST terminate the child process. */ 89 90 tcpd_warn(error); 91 _exit(0); 92} 93