1 files changed, 92 insertions, 0 deletions
diff --git a/shell_cmd.c b/shell_cmd.c
new file mode 100644
index 0000000..62d31bc
--- /dev/null
+++ b/shell_cmd.c
@@ -0,0 +1,92 @@
+ /*
+  * 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
+static char sccsid[] = "@(#) shell_cmd.c 1.5 94/12/28 17:42:44";
+#endif
+
+/* System libraries. */
+
+#include <sys/types.h>
+#include <sys/param.h>
+#include <signal.h>
+#include <stdio.h>
+#include <syslog.h>
+#include <string.h>
+
+extern void exit();
+
+/* Local stuff. */
+
+#include "tcpd.h"
+
+/* Forward declarations. */
+
+static void do_child();
+
+/* shell_cmd - execute shell command */
+
+void    shell_cmd(command)
+char   *command;
+{
+    int     child_pid;
+    int     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", 2) != 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);
+}