2006-04-26 James Antill <james.antill@redhat.com>

	    Ulrich Drepper  <drepper@redhat.com>

	* config.make.in: Add have-libcap.
	* configure.in: Check for libcap.
	* nscd/Makefile (selinux-LIBS): Add -lcap if possible.
	* nscd/connections.c (finish_drop_privileges): When libcap is available
	call preserve_capabilities and install_real_capabilities.
	* nscd/selinux.c: Define preserve_capabilities and
	install_real_capabilities.
	* nscd/selinux.h: Declare preserve_capabilities and
	install_real_capabilities.

4 files changed, 111 insertions, 3 deletions

diff --git a/nscd/Makefile b/nscd/Makefile
index 0b35964e7b..9c98018217 100644
--- a/nscd/Makefile
+++ b/nscd/Makefile
@@ -55,10 +55,13 @@ all-nscd-modules := $(nscd-modules) selinux
 ifeq (yes,$(have-selinux))
 ifeq (yes,$(have-libaudit))
 libaudit = -laudit
+ifeq (yes,$(have-libcap))
+libcap = -lcap
+endif
 endif
 
 nscd-modules += selinux
-selinux-LIBS := -lselinux $(libaudit)
+selinux-LIBS := -lselinux $(libaudit) $(libcap)
 
 # The configure.in check for libselinux and its headers did not use
 # $SYSINCLUDES.  The directory specified by --with-headers usually
diff --git a/nscd/connections.c b/nscd/connections.c
index d975b1818f..b24e7fb527 100644
--- a/nscd/connections.c
+++ b/nscd/connections.c
@@ -1859,6 +1859,11 @@ begin_drop_privileges (void)
 static void
 finish_drop_privileges (void)
 {
+#if defined HAVE_LIBAUDIT && defined HAVE_LIBCAP
+  /* We need to preserve the capabilities to connect to the audit daemon.  */
+  cap_t new_caps = preserve_capabilities ();
+#endif
+
   if (setgroups (server_ngroups, server_groups) == -1)
     {
       dbg_log (_("Failed to run nscd as user '%s'"), server_user);
@@ -1878,4 +1883,9 @@ finish_drop_privileges (void)
       perror ("setuid");
       exit (4);
     }
+
+#if defined HAVE_LIBAUDIT && defined HAVE_LIBCAP
+  /* Remove the temporary capabilities.  */
+  install_real_capabilities (new_caps);
+#endif
 }
diff --git a/nscd/selinux.c b/nscd/selinux.c
index c59251f1b5..f123d68b93 100644
--- a/nscd/selinux.c
+++ b/nscd/selinux.c
@@ -28,12 +28,13 @@
 #include <stdlib.h>
 #include <syslog.h>
 #include <unistd.h>
+#include <sys/prctl.h>
 #include <selinux/av_permissions.h>
 #include <selinux/avc.h>
 #include <selinux/flask.h>
 #include <selinux/selinux.h>
 #ifdef HAVE_LIBAUDIT
-#include <libaudit.h>
+# include <libaudit.h>
 #endif
 
 #include "dbg_log.h"
@@ -149,6 +150,90 @@ audit_init (void)
       && errno != EINVAL && errno != EPROTONOSUPPORT && errno != EAFNOSUPPORT)
     dbg_log (_("Failed opening connection to the audit subsystem: %m"));
 }
+
+
+# ifdef HAVE_LIBCAP
+static const cap_value_t new_cap_list[] =
+  { CAP_AUDIT_WRITE };
+#  define nnew_cap_list (sizeof (new_cap_list) / sizeof (new_cap_list[0]))
+static const cap_value_t tmp_cap_list[] =
+  { CAP_AUDIT_WRITE, CAP_SETUID, CAP_SETGID };
+#  define ntmp_cap_list (sizeof (tmp_cap_list) / sizeof (tmp_cap_list[0]))
+
+cap_t
+preserve_capabilities (void)
+{
+  if (getuid () != 0)
+    /* Not root, then we cannot preserve anything.  */
+    return NULL;
+
+  if (prctl (PR_SET_KEEPCAPS, 1) == -1)
+    {
+      dbg_log (_("Failed to set keep-capabilities"));
+      error (EXIT_FAILURE, errno, _("prctl(KEEPCAPS) failed"));
+      /* NOTREACHED */
+    }
+
+  cap_t tmp_caps = cap_init ();
+  cap_t new_caps;
+  if (tmp_caps != NULL)
+    new_caps = cap_init ();
+
+  if (tmp_caps == NULL || new_caps == NULL)
+    {
+      if (tmp_caps != NULL)
+	free_caps (tmp_caps);
+
+      dbg_log (_("Failed to initialize drop of capabilities"));
+      error (EXIT_FAILURE, 0, _("cap_init failed"));
+    }
+
+  /* There is no reason why these should not work.  */
+  cap_set_flag (new_caps, CAP_PERMITTED, nnew_cap_list, new_cap_list, CAP_SET);
+  cap_set_flag (new_caps, CAP_EFFECTIVE, nnew_cap_list, new_cap_list, CAP_SET);
+
+  cap_set_flag (tmp_caps, CAP_PERMITTED, ntmp_cap_list, tmp_cap_list, CAP_SET);
+  cap_set_flag (tmp_caps, CAP_EFFECTIVE, ntmp_cap_list, tmp_cap_list, CAP_SET);
+
+  int res = cap_set_proc (tmp_caps);
+
+  cap_free (tmp_caps);
+
+  if (__builtin_expect (res != 0, 0))
+    {
+      cap_free (new_caps);
+      dbg_log (_("Failed to drop capabilities\n"));
+      error (EXIT_FAILURE, 0, _("cap_set_proc failed"));
+    }
+
+  return new_caps;
+}
+
+void
+install_real_capabilities (cap_t new_caps)
+{
+  /* If we have no capabilities there is nothing to do here.  */
+  if (new_caps == NULL)
+    return;
+
+  if (cap_set_proc (new_caps))
+    {
+      cap_free (new_caps);
+      dbg_log (_("Failed to drop capabilities"));
+      error (EXIT_FAILURE, 0, _("cap_set_proc failed"));
+      /* NOTREACHED */
+    }
+
+  cap_free (new_caps);
+
+  if (prctl (PR_SET_KEEPCAPS, 0) == -1)
+    {
+      dbg_log (_("Failed to unset keep-capabilities"));
+      error (EXIT_FAILURE, errno, _("prctl(KEEPCAPS) failed"));
+      /* NOTREACHED */
+    }
+}
+# endif /* HAVE_LIBCAP */
 #endif /* HAVE_LIBAUDIT */
 
 /* Determine if we are running on an SELinux kernel. Set selinux_enabled
diff --git a/nscd/selinux.h b/nscd/selinux.h
index b9eb053aa0..9ce0628486 100644
--- a/nscd/selinux.h
+++ b/nscd/selinux.h
@@ -1,5 +1,5 @@
 /* Header for nscd SELinux access controls.
-   Copyright (C) 2004 Free Software Foundation, Inc.
+   Copyright (C) 2004, 2006 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Matthew Rickard <mjricka@epoch.ncsc.mil>, 2004.
 
@@ -22,6 +22,9 @@
 #define _SELINUX_H 1
 
 #include "nscd.h"
+#ifdef HAVE_LIBCAP
+# include <sys/capabilities.h>
+#endif
 
 #ifdef HAVE_SELINUX
 /* Global variable to tell if the kernel has SELinux support.  */
@@ -42,6 +45,13 @@ extern int nscd_request_avc_has_perm (int fd, request_type req);
 extern void nscd_avc_cache_stats (struct avc_cache_stats *cstats);
 /* Display statistics on AVC usage.  */
 extern void nscd_avc_print_stats (struct avc_cache_stats *cstats);
+
+# ifdef HAVE_LIBCAP
+/* Preserve capabilities to connect to connnect to the audit daemon.  */
+extern cap_t preserve_capabilities (void);
+/* Install final capabilities.  */
+extern void install_real_capabilities (cap_t new_caps);
+# endif
 #else
 # define selinux_enabled 0
 # define nscd_avc_init() (void) 0