libcasper: fix descriptors numbers
    
    Casper services expect that the first 3 descriptors (stdin/stdout/stderr)
    will point to /dev/null. Which Casper will ensure later. The Casper
    services are forked from the original process. If the initial process
    closes one of those descriptors, Casper may reuse one of them for it on
    purpose. If this is the case, then renumarate the descriptors used by
    Casper to higher numbers. This is done already after the fork, so it
    doesn't break the parent process.
    
    Approved by:    so
    Security:       EN-21:12.libcasper
    PR:             255339
    Reported by:    Borja Marcos <borjam (at) sarenet.es>
    Tested by:      jkim@
    
    (cherry picked from commit aa310ebfba3d49a0b6b03a103b969731a8136a73)
    (cherry picked from commit 4e2ae05c3ae8c470829b4c3a78aa8c34a7f0b617)
--- lib/libcasper/libcasper/libcasper_impl.c.orig
+++ lib/libcasper/libcasper/libcasper_impl.c
@@ -32,8 +32,10 @@
  * $FreeBSD$
  */
 
+#include <err.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <paths.h>
 #include <stdlib.h>
 
 #include "libcasper_impl.h"
@@ -44,3 +46,28 @@
 
 	return (fcntl(fd, F_GETFL) != -1 || errno != EBADF);
 }
+
+void
+fd_fix_environment(int *fdp)
+{
+	int nullfd, nfd;
+
+	if (*fdp > STDERR_FILENO)
+		return;
+
+	nullfd = open(_PATH_DEVNULL, O_RDWR);
+	if (nullfd == -1)
+		errx(1, "Unable to open %s", _PATH_DEVNULL);
+
+	while (*fdp <= STDERR_FILENO) {
+		nfd = dup(*fdp);
+		if (nfd == -1)
+			errx(1, "Unable to secure fd");
+		if (dup2(nullfd, *fdp) == -1)
+			errx(1, "Unable to secure fd");
+		*fdp = nfd;
+	}
+
+	close(nullfd);
+}
+
--- lib/libcasper/libcasper/libcasper_impl.h.orig
+++ lib/libcasper/libcasper/libcasper_impl.h
@@ -44,6 +44,7 @@
 struct service_connection;
 
 bool fd_is_valid(int fd);
+void fd_fix_environment(int *fdp);
 
 /* Private service functions. */
 struct service	*service_alloc(const char *name,
--- lib/libcasper/libcasper/service.c.orig
+++ lib/libcasper/libcasper/service.c
@@ -386,24 +386,27 @@
 }
 
 static void
-service_clean(int sock, int procfd, uint64_t flags)
+service_clean(int *sockp, int *procfdp, uint64_t flags)
 {
 	int fd, maxfd, minfd;
 
-	assert(sock > STDERR_FILENO);
-	assert(procfd > STDERR_FILENO);
-	assert(sock != procfd);
+	fd_fix_environment(sockp);
+	fd_fix_environment(procfdp);
+
+	assert(*sockp > STDERR_FILENO);
+	assert(*procfdp > STDERR_FILENO);
+	assert(*sockp != *procfdp);
 
 	if ((flags & CASPER_SERVICE_STDIO) == 0)
 		stdnull();
 
 	if ((flags & CASPER_SERVICE_FD) == 0) {
-		if (procfd > sock) {
-			maxfd = procfd;
-			minfd = sock;
+		if (*procfdp > *sockp) {
+			maxfd = *procfdp;
+			minfd = *sockp;
 		} else {
-			maxfd = sock;
-			minfd = procfd;
+			maxfd = *sockp;
+			minfd = *procfdp;
 		}
 
 		for (fd = STDERR_FILENO + 1; fd < maxfd; fd++) {
@@ -424,7 +427,7 @@
 	assert(service != NULL);
 	assert(service->s_magic == SERVICE_MAGIC);
 	setproctitle("%s", service->s_name);
-	service_clean(sock, procfd, service->s_flags);
+	service_clean(&sock, &procfd, service->s_flags);
 
 	if (service_connection_add(service, sock, NULL) == NULL)
 		_exit(1);
--- lib/libcasper/libcasper/zygote.c.orig
+++ lib/libcasper/libcasper/zygote.c
@@ -52,6 +52,7 @@
 #include <strings.h>
 #include <unistd.h>
 
+#include "libcasper_impl.h"
 #include "zygote.h"
 
 /* Zygote info. */
@@ -104,7 +105,7 @@
  * between sandbox and its owner.
  */
 static void
-zygote_main(int sock)
+zygote_main(int *sockp)
 {
 	int error, procfd;
 	int chanfd[2];
@@ -113,12 +114,14 @@
 	zygote_func_t *func;
 	pid_t pid;
 
-	assert(sock > STDERR_FILENO);
+	fd_fix_environment(sockp);
+
+	assert(*sockp > STDERR_FILENO);
 
 	setproctitle("zygote");
 
 	for (;;) {
-		nvlin = nvlist_recv(sock, 0);
+		nvlin = nvlist_recv(*sockp, 0);
 		if (nvlin == NULL) {
 			if (errno == ENOTCONN) {
 				/* Casper exited. */
@@ -157,7 +160,7 @@
 			break;
 		case 0:
 			/* Child. */
-			close(sock);
+			close(*sockp);
 			close(chanfd[0]);
 			func(chanfd[1]);
 			/* NOTREACHED */
@@ -179,7 +182,7 @@
 			nvlist_move_descriptor(nvlout, "chanfd", chanfd[0]);
 			nvlist_move_descriptor(nvlout, "procfd", procfd);
 		}
-		(void)nvlist_send(sock, nvlout);
+		(void)nvlist_send(*sockp, nvlout);
 		nvlist_destroy(nvlout);
 	}
 	/* NOTREACHED */
@@ -206,7 +209,7 @@
 	case 0:
 		/* Child. */
 		close(sp[0]);
-		zygote_main(sp[1]);
+		zygote_main(&sp[1]);
 		/* NOTREACHED */
 		abort();
 	default: