- markus@cvs.openbsd.org 2012/06/30 14:35:09

     [sandbox-systrace.c sshd.c]
     fix a during the load of the sandbox policies (child can still make
     the read-syscall and wait forever for systrace-answers) by replacing
     the read/write synchronisation with SIGSTOP/SIGCONT;
     report and help hshoexer@; ok djm@, dtucker@

diff --git a/ChangeLog b/ChangeLog
index 5608909da8af9b8c3cac78cb30ccbb217523a4f7..66c4ef574ace3f28ce9e87010245273b3e6f67cb 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -4,6 +4,12 @@
      [ssh_config.5 sshd_config.5]
      match the documented MAC order of preference to the actual one;
      ok dtucker@
+   - markus@cvs.openbsd.org 2012/06/30 14:35:09
+     [sandbox-systrace.c sshd.c]
+     fix a during the load of the sandbox policies (child can still make
+     the read-syscall and wait forever for systrace-answers) by replacing
+     the read/write synchronisation with SIGSTOP/SIGCONT;
+     report and help hshoexer@; ok djm@, dtucker@
 
 20120629
  - OpenBSD CVS Sync

diff --git a/sandbox-systrace.c b/sandbox-systrace.c
index 199b69f444633af14b03adb8f1f4eab7782d806a..2d16a627fe379bdb5d5228d934b3b9b1a53ad8fc 100644 (file)
--- a/sandbox-systrace.c
+++ b/sandbox-systrace.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sandbox-systrace.c,v 1.5 2012/06/26 11:02:30 dtucker Exp $ */
+/* $OpenBSD: sandbox-systrace.c,v 1.6 2012/06/30 14:35:09 markus Exp $ */
 /*
  * Copyright (c) 2011 Damien Miller <djm@mindrot.org>
  *
@@ -24,12 +24,14 @@
 #include <sys/ioctl.h>
 #include <sys/syscall.h>
 #include <sys/socket.h>
+#include <sys/wait.h>
 
 #include <dev/systrace.h>
 
 #include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
+#include <signal.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -69,26 +71,21 @@ static const struct sandbox_policy preauth_policy[] = {
 };
 
 struct ssh_sandbox {
-       int child_sock;
-       int parent_sock;
        int systrace_fd;
        pid_t child_pid;
+       void (*osigchld)(int);
 };
 
 struct ssh_sandbox *
 ssh_sandbox_init(void)
 {
        struct ssh_sandbox *box;
-       int s[2];
 
        debug3("%s: preparing systrace sandbox", __func__);
        box = xcalloc(1, sizeof(*box));
-       if (socketpair(AF_UNIX, SOCK_STREAM, 0, s) == -1)
-               fatal("%s: socketpair: %s", __func__, strerror(errno));
-       box->child_sock = s[0];
-       box->parent_sock = s[1];
        box->systrace_fd = -1;
        box->child_pid = 0;
+       box->osigchld = signal(SIGCHLD, SIG_IGN);
 
        return box;
 }
@@ -96,35 +93,38 @@ ssh_sandbox_init(void)
 void
 ssh_sandbox_child(struct ssh_sandbox *box)
 {
-       char whatever = 0;
-
-       close(box->parent_sock);
-       /* Signal parent that we are ready */
        debug3("%s: ready", __func__);
-       if (atomicio(vwrite, box->child_sock, &whatever, 1) != 1)
-               fatal("%s: write: %s", __func__, strerror(errno));
-       /* Wait for parent to signal for us to go */
-       if (atomicio(read, box->child_sock, &whatever, 1) != 1)
-               fatal("%s: read: %s", __func__, strerror(errno));
+       signal(SIGCHLD, box->osigchld);
+       if (kill(getpid(), SIGSTOP) != 0)
+               fatal("%s: kill(%d, SIGSTOP)", __func__, getpid());
        debug3("%s: started", __func__);
-       close(box->child_sock);
 }
 
 static void
 ssh_sandbox_parent(struct ssh_sandbox *box, pid_t child_pid,
     const struct sandbox_policy *allowed_syscalls)
 {
-       int dev_systrace, i, j, found;
-       char whatever = 0;
+       int dev_systrace, i, j, found, status;
+       pid_t pid;
        struct systrace_policy policy;
 
+       /* Wait for the child to send itself a SIGSTOP */
        debug3("%s: wait for child %ld", __func__, (long)child_pid);
+       do {
+               pid = waitpid(child_pid, &status, WUNTRACED);
+       } while (pid == -1 && errno == EINTR);
+       signal(SIGCHLD, box->osigchld);
+       if (!WIFSTOPPED(status)) {
+               if (WIFSIGNALED(status))
+                       fatal("%s: child terminated with signal %d",
+                           __func__, WTERMSIG(status));
+               if (WIFEXITED(status))
+                       fatal("%s: child exited with status %d",
+                           __func__, WEXITSTATUS(status));
+               fatal("%s: child not stopped", __func__);
+       }
+       debug3("%s: child %ld stopped", __func__, (long)child_pid);
        box->child_pid = child_pid;
-       close(box->child_sock);
-       /* Wait for child to signal that it is ready */
-       if (atomicio(read, box->parent_sock, &whatever, 1) != 1)
-               fatal("%s: read: %s", __func__, strerror(errno));
-       debug3("%s: child %ld ready", __func__, (long)child_pid);
 
        /* Set up systracing of child */
        if ((dev_systrace = open("/dev/systrace", O_RDONLY)) == -1)
@@ -175,9 +175,8 @@ ssh_sandbox_parent(struct ssh_sandbox *box, pid_t child_pid,
 
        /* Signal the child to start running */
        debug3("%s: start child %ld", __func__, (long)child_pid);
-       if (atomicio(vwrite, box->parent_sock, &whatever, 1) != 1)
-               fatal("%s: write: %s", __func__, strerror(errno));
-       close(box->parent_sock);
+       if (kill(box->child_pid, SIGCONT) != 0)
+               fatal("%s: kill(%d, SIGCONT)", __func__, box->child_pid);
 }
 
 void

diff --git a/sshd.c b/sshd.c
index 7cc7044bef19ff67e7c19750c667c5974df40cfc..64b846f6ceb94a8339cf12dfb1b9a190269e0b76 100644 (file)
--- a/sshd.c
+++ b/sshd.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshd.c,v 1.391 2012/05/13 01:42:32 dtucker Exp $ */
+/* $OpenBSD: sshd.c,v 1.392 2012/06/30 14:35:09 markus Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -643,9 +643,9 @@ privsep_preauth(Authctxt *authctxt)
        } else if (pid != 0) {
                debug2("Network child is on pid %ld", (long)pid);
 
+               pmonitor->m_pid = pid;
                if (box != NULL)
                        ssh_sandbox_parent_preauth(box, pid);
-               pmonitor->m_pid = pid;
                monitor_child_preauth(authctxt, pmonitor);
 
                /* Sync memory */