[PATCH] selinux-h: always use getfilecon wrappers

[Jim Meyering]

This isn't quite ready (ENODATA is one issue, not well tested is
another), but it should give a good idea of what's coming.

With this, the recently-reported chcon abort will be fixed properly,
and I can remove a related hack in ls.c.


>From 321981877c8f31faa724890fd45e2ef967a6befa Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Wed, 7 Oct 2009 19:00:42 +0200
Subject: [PATCH] selinux-h: always use getfilecon wrappers

* lib/getfilecon.c: New file.
* lib/se-selinux.in.h: Use a better inclusion guard symbol name.
[HAVE_SELINUX_SELINUX_H]: Include-next <selinux/selinux.h>.
[!HAVE_SELINUX_SELINUX_H]: Use better parameter names.
(fgetfilecon): Provide a stub.
* m4/selinux-selinux-h.m4 (gl_HEADERS_SELINUX_SELINUX_H): Don't
AC_SUBST SELINUX_SELINUX_H, since now we're generating that
file unconditionally.
When <selinux/selinux.h> is found, arrange to use wrappers.
* modules/selinux-h (Files): Add getfilecon.c.
(Makefile.am): Substitute include-next-related bits
into the now-always-generated selinux/selinux.h file.
---
 ChangeLog               |   16 +++++++++
 lib/getfilecon.c        |   81 +++++++++++++++++++++++++++++++++++++++++++++++
 lib/se-selinux.in.h     |   39 +++++++++++++++-------
 m4/selinux-selinux-h.m4 |   20 +++++++++--
 modules/selinux-h       |   10 +++++-
 5 files changed, 148 insertions(+), 18 deletions(-)
 create mode 100644 lib/getfilecon.c

diff --git a/ChangeLog b/ChangeLog
index 6f9e546..e4e401d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,19 @@
+2009-10-07  Jim Meyering  <address@hidden>
+
+       selinux-h: always use getfilecon wrappers
+       * lib/getfilecon.c: New file.
+       * lib/se-selinux.in.h: Use a better inclusion guard symbol name.
+       [HAVE_SELINUX_SELINUX_H]: Include-next <selinux/selinux.h>.
+       [!HAVE_SELINUX_SELINUX_H]: Use better parameter names.
+       (fgetfilecon): Provide a stub.
+       * m4/selinux-selinux-h.m4 (gl_HEADERS_SELINUX_SELINUX_H): Don't
+       AC_SUBST SELINUX_SELINUX_H, since now we're generating that
+       file unconditionally.
+       When <selinux/selinux.h> is found, arrange to use wrappers.
+       * modules/selinux-h (Files): Add getfilecon.c.
+       (Makefile.am): Substitute include-next-related bits
+       into the now-always-generated selinux/selinux.h file.
+
 2009-10-08  Jim Meyering  <address@hidden>

        unistd: fix comment typo
diff --git a/lib/getfilecon.c b/lib/getfilecon.c
new file mode 100644
index 0000000..65858e9
--- /dev/null
+++ b/lib/getfilecon.c
@@ -0,0 +1,81 @@
+/* wrap getfilecon, lgetfilecon, and fgetfilecon
+   Copyright (C) 2009 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* written by Jim Meyering */
+
+#include <config.h>
+
+#include <selinux/selinux.h>
+
+#include <sys/types.h>
+#include <errno.h>
+#include <string.h>
+
+#undef getfilecon
+#undef lgetfilecon
+#undef fgetfilecon
+int getfilecon (char const *file, security_context_t *con);
+int lgetfilecon (char const *file, security_context_t *con);
+int fgetfilecon (int fd, security_context_t *con);
+
+/* getfilecon, lgetfilecon, and fgetfilecon can all misbehave, be it
+   via an old version of libselinux where these would return 0 and set the
+   result context to NULL, or via a modern kernel+lib operating on a file
+   from a disk whose attributes were set by a kernel from around 2006.
+   In that latter case, the functions return a length of 10 for the
+   "unlabeled" context.  Map both failures to a return value of -1, and
+   set errno to ENOTSUP in the first case, and ENODATA in the latter.  */
+
+static inline int
+map_to_failure (int ret, security_context_t *con)
+{
+  if (ret == 0)
+    {
+      errno = ENOTSUP;
+      return -1;
+    }
+
+  if (ret == 10 && strcmp (*con, "unlabeled") == 0)
+    {
+      freecon (*con);
+      errno = ENODATA;
+      return -1;
+    }
+
+  return ret;
+}
+
+int
+rpl_getfilecon (char const *file, security_context_t *con)
+{
+  int ret = getfilecon (file, con);
+  return map_to_failure (ret, con);
+}
+
+int
+rpl_lgetfilecon (char const *file, security_context_t *con)
+{
+  int ret = lgetfilecon (file, con);
+  return map_to_failure (ret, con);
+}
+
+int
+rpl_fgetfilecon (int fd, security_context_t *con)
+{
+  int ret = fgetfilecon (fd, con);
+  return map_to_failure (ret, con);
+}
diff --git a/lib/se-selinux.in.h b/lib/se-selinux.in.h
index 25cbaae..c09aebd 100644
--- a/lib/se-selinux.in.h
+++ b/lib/se-selinux.in.h
@@ -1,12 +1,22 @@
-#ifndef SELINUX_SELINUX_H
-# define SELINUX_SELINUX_H
+#ifndef _GL_SELINUX_SELINUX_H
+# define _GL_SELINUX_SELINUX_H

-# include <sys/types.h>
-# include <errno.h>
+# if __GNUC__ >= 3
address@hidden@
+# endif
+
+# if HAVE_SELINUX_SELINUX_H
+
address@hidden@ @NEXT_SELINUX_SELINUX_H@
+
+# else
+
+#  include <sys/types.h>
+#  include <errno.h>

 typedef unsigned short security_class_t;
-# define security_context_t char*
-# define is_selinux_enabled() 0
+#  define security_context_t char*
+#  define is_selinux_enabled() 0

 static inline int getcon (security_context_t *con _UNUSED_PARAMETER_)
   { errno = ENOTSUP; return -1; }
@@ -17,20 +27,23 @@ static inline int getfscreatecon (security_context_t *con 
_UNUSED_PARAMETER_)
   { errno = ENOTSUP; return -1; }
 static inline int setfscreatecon (security_context_t con _UNUSED_PARAMETER_)
   { errno = ENOTSUP; return -1; }
-static inline int matchpathcon (char const *s _UNUSED_PARAMETER_,
+static inline int matchpathcon (char const *file _UNUSED_PARAMETER_,
                                mode_t m _UNUSED_PARAMETER_,
                                security_context_t *con _UNUSED_PARAMETER_)
   { errno = ENOTSUP; return -1; }
-static inline int getfilecon (char const *s _UNUSED_PARAMETER_,
+static inline int getfilecon (char const *file _UNUSED_PARAMETER_,
                              security_context_t *con _UNUSED_PARAMETER_)
   { errno = ENOTSUP; return -1; }
-static inline int lgetfilecon (char const *s _UNUSED_PARAMETER_,
+static inline int lgetfilecon (char const *file _UNUSED_PARAMETER_,
                               security_context_t *con _UNUSED_PARAMETER_)
   { errno = ENOTSUP; return -1; }
-static inline int setfilecon (char const *s _UNUSED_PARAMETER_,
+static inline int fgetfilecon (int fd,
+                              security_context_t *con _UNUSED_PARAMETER_)
+  { errno = ENOTSUP; return -1; }
+static inline int setfilecon (char const *file _UNUSED_PARAMETER_,
                              security_context_t con _UNUSED_PARAMETER_)
   { errno = ENOTSUP; return -1; }
-static inline int lsetfilecon (char const *s _UNUSED_PARAMETER_,
+static inline int lsetfilecon (char const *file _UNUSED_PARAMETER_,
                               security_context_t con _UNUSED_PARAMETER_)
   { errno = ENOTSUP; return -1; }
 static inline int fsetfilecon (int fd _UNUSED_PARAMETER_,
@@ -55,4 +68,6 @@ static inline int matchpathcon_init_prefix
     (char const *path _UNUSED_PARAMETER_,
      char const *prefix _UNUSED_PARAMETER_)
   { errno = ENOTSUP; return -1; }
-#endif
+
+# endif
+#endif /* _GL_SELINUX_SELINUX_H */
diff --git a/m4/selinux-selinux-h.m4 b/m4/selinux-selinux-h.m4
index 20dc77c..767c4f7 100644
--- a/m4/selinux-selinux-h.m4
+++ b/m4/selinux-selinux-h.m4
@@ -6,14 +6,26 @@

 # From Jim Meyering
 # Provide <selinux/selinux.h>, if necessary.
+# If it is already present, provide wrapper functions to guard against
+# misbehavior from getfilecon, lgetfilecon, and fgetfilecon.

 AC_DEFUN([gl_HEADERS_SELINUX_SELINUX_H],
 [
   AC_REQUIRE([gl_LIBSELINUX])
-  AC_CHECK_HEADERS([selinux/selinux.h],
-                  [SELINUX_SELINUX_H=],
-                  [SELINUX_SELINUX_H=selinux/selinux.h])
-  AC_SUBST([SELINUX_SELINUX_H])
+  AC_CHECK_HEADERS([selinux/selinux.h])
+
+  if test "$ac_cv_header_selinux_selinux_h" = yes; then
+    # We do have <selinux/selinux.h>, so do compile getfilecon.c
+    # and arrange to use its wrappers.
+    AC_LIBOBJ([getfilecon])
+    gl_CHECK_NEXT_HEADERS([selinux/selinux.h])
+    AC_DEFINE([getfilecon], [rpl_getfilecon],
+             [Always use our getfilecon wrapper.])
+    AC_DEFINE([lgetfilecon], [rpl_lgetfilecon],
+             [Always use our lgetfilecon wrapper.])
+    AC_DEFINE([fgetfilecon], [rpl_fgetfilecon],
+             [Always use our fgetfilecon wrapper.])
+  fi

   case "$ac_cv_search_setfilecon:$ac_cv_header_selinux_selinux_h" in
     no:*) # already warned
diff --git a/modules/selinux-h b/modules/selinux-h
index c9a5a04..fd01241 100644
--- a/modules/selinux-h
+++ b/modules/selinux-h
@@ -2,6 +2,7 @@ Description:
 SELinux-related headers for systems that lack them.

 Files:
+lib/getfilecon.c
 lib/se-context.in.h
 lib/se-selinux.in.h
 m4/selinux-context-h.m4
@@ -18,11 +19,16 @@ AC_REQUIRE([AC_C_INLINE])
 Makefile.am:
 lib_SOURCES += se-context.in.h se-selinux.in.h

-BUILT_SOURCES += $(SELINUX_SELINUX_H)
+BUILT_SOURCES += selinux/selinux.h
 selinux/selinux.h: se-selinux.in.h
        $(AM_V_at)$(MKDIR_P) selinux
        $(AM_V_GEN)rm -f address@hidden $@ && \
-       cp $(srcdir)/se-selinux.in.h address@hidden && \
+       { echo '/* DO NOT EDIT! GENERATED AUTOMATICALLY! */' && \
+         sed -e 's|@''INCLUDE_NEXT''@|$(INCLUDE_NEXT)|g' \
+             -e 's|@''PRAGMA_SYSTEM_HEADER''@|@PRAGMA_SYSTEM_HEADER@|g' \
+             -e 's|@''NEXT_SELINUX_SELINUX_H''@|$(NEXT_SELINUX_SELINUX_H)|g' \
+             < $(srcdir)/se-selinux.in.h; \
+       } > address@hidden && \
        chmod a-x address@hidden && \
        mv address@hidden $@
 MOSTLYCLEANFILES += selinux/selinux.h selinux/selinux.h-t
--
1.6.5.rc3.193.gdf7a