allow systrace to run in the background if possible so that the executed

process gets the terminal correctly and exit status reporting works;
based on a diff from atatat@atatdot.net from netbsd.

3 files changed, 92 insertions, 19 deletions

diff --git a/bin/systrace/intercept.c b/bin/systrace/intercept.c
index c39fc673e01..3580167fe04 100644
--- a/bin/systrace/intercept.c
+++ b/bin/systrace/intercept.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: intercept.c,v 1.11 2002/07/09 15:22:27 provos Exp $	*/
+/*	$OpenBSD: intercept.c,v 1.12 2002/07/09 20:46:18 provos Exp $	*/
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * All rights reserved.
@@ -213,20 +213,65 @@ intercept_register_execcb(void (*cb)(int, pid_t, int, char *, char *, void *), v
 	return (0);
 }
 
+static void
+sigusr1_handler(int signum)
+{                                                                              
+	/* all we need to do is pretend to handle it */
+}
+
 pid_t
-intercept_run(int fd, char *path, char *const argv[])
+intercept_run(int bg, int fd, char *path, char *const argv[])
 {
-	pid_t pid;
-
-	pid = fork();
-	if (pid == -1)
+	sigset_t none, set, oset;
+	sig_t ohandler;
+	pid_t pid, cpid;
+	int status;
+
+	/* Block signals so that timeing on signal delivery does not matter */
+	sigemptyset(&none);
+	sigemptyset(&set);
+	sigaddset(&set, SIGUSR1);
+	if (sigprocmask(SIG_BLOCK, &set, &oset) == -1)
+		err(1, "sigprocmask");
+	ohandler = signal(SIGUSR1, sigusr1_handler);
+	if (ohandler == SIG_ERR)
+		err(1, "signal");
+
+	pid = getpid();
+	cpid = fork();
+	if (cpid == -1)
 		return (-1);
-	if (pid == 0) {
+
+	/*
+	 * If the systrace process should be in the background and we're
+	 * the parent, or vice versa.
+	 */
+	if ((!bg && cpid == 0) || (bg && cpid != 0)) {
 		/* Needs to be closed */
 		close(fd);
 
-		/* Stop myself */
-		raise(SIGSTOP);
+		if (bg) {
+			/* Wait for child to "detach" */
+			cpid = wait(&status);
+			if (cpid == -1)
+				err(1, "wait");
+			if (status != 0)
+				errx(1, "wait: child gave up");
+		}
+
+		/* Sleep */
+		sigsuspend(&none);
+
+		/*
+		 * Woken up, restore signal handling state.
+		 *
+		 * Note that there is either no child or we have no idea
+		 * what pid it might have at this point.  If we fail.
+		 */
+		if (signal(SIGUSR1, ohandler) == SIG_ERR)
+			err(1, "signal");
+		if (sigprocmask(SIG_SETMASK, &oset, NULL) == -1)
+			err(1, "sigprocmask");
 
 		execvp(path, argv);
 
@@ -234,7 +279,25 @@ intercept_run(int fd, char *path, char *const argv[])
 		err(1, "execvp");
 	}
 
-	sleep(1); /* XXX */
+	/* Choose the pid of the systraced process */
+	pid = bg ? pid : cpid;
+
+	/* Setup done, restore signal handling state */
+	if (signal(SIGUSR1, ohandler) == SIG_ERR) {
+		kill(pid, SIGKILL);
+		err(1, "signal");
+	}
+	if (sigprocmask(SIG_SETMASK, &oset, NULL) == -1) {
+		kill(pid, SIGKILL);
+		err(1, "sigprocmask");
+	}
+
+	if (bg) {
+		if (daemon(0, 0) == -1) {
+			kill(pid, SIGKILL);
+			err(1, "daemon");
+		}
+	}
 
 	return (pid);
 }
diff --git a/bin/systrace/intercept.h b/bin/systrace/intercept.h
index d1bd4cc3ab8..029ac2b026f 100644
--- a/bin/systrace/intercept.h
+++ b/bin/systrace/intercept.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: intercept.h,v 1.4 2002/07/09 15:22:27 provos Exp $	*/
+/*	$OpenBSD: intercept.h,v 1.5 2002/07/09 20:46:18 provos Exp $	*/
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * All rights reserved.
@@ -110,7 +110,7 @@ struct intercept_replace {
 TAILQ_HEAD(intercept_tlq, intercept_translate);
 
 int intercept_init(void);
-pid_t intercept_run(int, char *, char * const *);
+pid_t intercept_run(int, int, char *, char * const *);
 int intercept_open(void);
 int intercept_attach(int, pid_t);
 int intercept_attachpid(int, pid_t, char *);
diff --git a/bin/systrace/systrace.c b/bin/systrace/systrace.c
index 1a0d4de8b05..f3224220093 100644
--- a/bin/systrace/systrace.c
+++ b/bin/systrace/systrace.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: systrace.c,v 1.21 2002/07/09 15:22:27 provos Exp $	*/
+/*	$OpenBSD: systrace.c,v 1.22 2002/07/09 20:46:18 provos Exp $	*/
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * All rights reserved.
@@ -512,6 +512,7 @@ main(int argc, char **argv)
 	char *guipath = _PATH_XSYSTRACE;
 	pid_t pidattach = 0;
 	int usex11 = 1;
+	int background;
 
 	while ((c = getopt(argc, argv, "aAituUg:f:p:")) != -1) {
 		switch (c) {
@@ -563,9 +564,6 @@ main(int argc, char **argv)
 	if (getcwd(cwd, sizeof(cwd)) == NULL)
 		err(1, "getcwd");
 
-	if (signal(SIGCHLD, child_handler) == SIG_ERR)
-		err(1, "signal");
-
 	/* Local initalization */
 	systrace_initalias();
 	systrace_initpolicy(filename);
@@ -574,6 +572,9 @@ main(int argc, char **argv)
 	if ((fd = intercept_open()) == -1)
 		exit(1);
 
+	/* See if we can run the systrace process in the background */
+	background = usex11 || automatic || allow;
+
 	if (pidattach == 0) {
 		/* Run a command and attach to it */
 		if ((args = malloc((argc + 1) * sizeof(char *))) == NULL)
@@ -583,22 +584,31 @@ main(int argc, char **argv)
 			args[i] = argv[i];
 		args[i] = NULL;
 
-		pid = intercept_run(fd, args[0], args);
+		pid = intercept_run(background, fd, args[0], args);
 		if (pid == -1)
 			err(1, "fork");
 
 		if (intercept_attach(fd, pid) == -1)
 			err(1, "attach");
 
-		if (kill(pid, SIGCONT) == -1)
+		if (kill(pid, SIGUSR1) == -1)
 			err(1, "kill");
 	} else {
-		/* Attach to a running command */
+		pid_t cpid;
 
+		/* Attach to a running command */
 		if (intercept_attachpid(fd, pidattach, argv[0]) == -1)
 			err(1, "attachpid");
+
+		if (background) {
+			if (daemon(0, 0) == -1)
+				err(1, "daemon");
+		}
 	}
 
+	if (signal(SIGCHLD, child_handler) == SIG_ERR)
+		err(1, "signal");
+
 	/* Start the policy gui if necessary */
 	if (usex11 && !automatic && !allow)
 		requestor_start(guipath);