From 721aa7e45ba56530c571743de4762605560f90cb Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Pavel=20B=C5=99ezina?= <pbrezina@redhat.com>

Date: Thu, 10 Jan 2019 13:26:49 +0100

Subject: [PATCH] lib: label temporary files with correct selinux context

Resolves:

https://github.com/pbrezina/authselect/issues/128

---

 configure.ac                       |   1 +

 rpm/authselect.spec.in             |   1 +

 src/build_macros.m4                |  13 +++

 src/lib/Makefile.am                |   3 +

 src/lib/util/selinux.c             | 143 +++++++++++++++++++++++++++++

 src/lib/util/{util.h => selinux.h} |  37 +++++---

 src/lib/util/template.c            |  16 +---

 src/lib/util/util.h                |   1 +

 8 files changed, 192 insertions(+), 23 deletions(-)

 create mode 100644 src/lib/util/selinux.c

 copy src/lib/util/{util.h => selinux.h} (50%)

diff --git a/configure.ac b/configure.ac

index 0ddb875439133d10a9ece8b92a2df1719065d349..667d41c1f67264850fd9e175598214d751078a7e 100644

--- a/configure.ac

+++ b/configure.ac

@@ -37,6 +37,7 @@ m4_include(external/po4a.m4)

 dnl Required libraries

 REQUIRE_POPT

 REQUIRE_CMOCKA

+REQUIRE_SELINUX

 dnl Optional build dependencies - man pages generation

 CHECK_ASCIIDOC_TOOLS

diff --git a/rpm/authselect.spec.in b/rpm/authselect.spec.in

index c56ad4e2e0e23c902471fbacdb8bc3742bd8fa2d..f47c77ac3768ccf9c049c9ba512209fad059e418 100644

--- a/rpm/authselect.spec.in

+++ b/rpm/authselect.spec.in

@@ -24,6 +24,7 @@ BuildRequires:  gettext-devel

 BuildRequires:  po4a

 BuildRequires:  %{_bindir}/a2x

 BuildRequires:  libcmocka-devel >= 1.0.0

+BuildRequires:  libselinux-devel

 Requires: authselect-libs%{?_isa} = %{version}-%{release}

 Suggests: sssd

 Suggests: samba-winbind

diff --git a/src/build_macros.m4 b/src/build_macros.m4

index 5da871ec8cadfa200630420b5fe932d8af0473a3..dfedd47fd84c7201cfad30621761a3c1c564bc18 100644

--- a/src/build_macros.m4

+++ b/src/build_macros.m4

@@ -28,3 +28,16 @@ AC_DEFUN([REQUIRE_CMOCKA],

     )

     AM_CONDITIONAL([HAVE_CMOCKA], [test x$have_cmocka = xyes])

 ])

+

+AC_DEFUN([REQUIRE_SELINUX],

+[

+  AC_CHECK_HEADERS(selinux/selinux.h,

+    [AC_CHECK_LIB(selinux, is_selinux_enabled,

+      [SELINUX_LIBS="-lselinux"],

+      [AC_MSG_ERROR([SELinux library is missing])]

+    )],

+    [AC_MSG_ERROR([SELinux headers are missing])]

+  )

+  AC_SUBST(SELINUX_LIBS)

+])

+

diff --git a/src/lib/Makefile.am b/src/lib/Makefile.am

index 2726062c421f7836ebc69fbbc0f5410cf3d19803..6c1191c702efbf52d45c7204311e4e9d1e64de3b 100644

--- a/src/lib/Makefile.am

+++ b/src/lib/Makefile.am

@@ -15,6 +15,7 @@ noinst_HEADERS = \

     files/files.h \

     profiles/profiles.h \

     util/file.h \

+    util/selinux.h \

     util/string_array.h \

     util/string.h \

     util/template.h \

@@ -55,6 +56,7 @@ libauthselect_la_SOURCES = \

     profiles/list.c \

     profiles/read.c \

     util/file.c \

+    util/selinux.c \

     util/string_array.c \

     util/string.c \

     util/template.c \

@@ -62,6 +64,7 @@ libauthselect_la_SOURCES = \

     $(NULL)

 libauthselect_la_LIBADD = \

     $(top_builddir)/src/common/libcommon.la \

+    $(SELINUX_LIBS) \

     $(NULL)

 libauthselect_la_CFLAGS = \

     $(AM_CFLAGS) \

diff --git a/src/lib/util/selinux.c b/src/lib/util/selinux.c

new file mode 100644

index 0000000000000000000000000000000000000000..05c8d7b19b13e1eff6086faa58657c3e41a44cc0

--- /dev/null

+++ b/src/lib/util/selinux.c

@@ -0,0 +1,143 @@

+/*

+    Authors:

+        Pavel Březina <pbrezina@redhat.com>

+

+    Copyright (C) 2018 Red Hat

+

+    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 of the License, 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, see <http://www.gnu.org/licenses/>.

+*/

+

+#include <errno.h>

+#include <string.h>

+#include <stdlib.h>

+#include <unistd.h>

+#include <selinux/selinux.h>

+#include <selinux/label.h>

+

+#include "common/common.h"

+

+errno_t

+selinux_get_default_context(const char *path,

+                            char **_context)

+{

+    struct selabel_handle *handle;

+    char *context;

+    errno_t ret;

+

+    handle = selabel_open(SELABEL_CTX_FILE, NULL, 0);

+    if (handle == NULL) {

+        ret = errno;

+        ERROR("Unable to create selable context [%d]: %s", ret, strerror(ret));

+        return ret;

+    }

+

+    ret = selabel_lookup(handle, &context, path, 0);

+    if (ret != 0) {

+        ret = errno;

+        if (ret == ENOENT) {

+            return ENOENT;

+        }

+

+        ERROR("Unable to lookup selinux context [%d]: %s", ret, strerror(ret));

+    } else {

+        *_context = context;

+        ret = EOK;

+    }

+

+    selabel_close(handle);

+

+    return ret;

+}

+

+errno_t

+selinux_mkstemp_of(const char *filepath,

+                   char **_tmpfile)

+{

+    char *original_context = NULL;

+    char *default_context = NULL;

+    char *tmpfile = NULL;

+    errno_t ret;

+    int seret;

+    int fd;

+

+    seret = getfscreatecon(&original_context);

+    if (seret != 0) {

+        ERROR("Unable to get current fscreate selinux context!");

+        return EIO;

+    }

+

+    tmpfile = format("%s.XXXXXX", filepath);

+    if (tmpfile == NULL) {

+        ret = ENOMEM;

+        goto done;

+    }

+

+    ret = selinux_get_default_context(filepath, &default_context);

+    if (ret == ENOENT) {

+        default_context = NULL;

+    } else if (ret != EOK) {

+        ERROR("Unable to get default selinux context for [%s] [%d]: %s!",

+              filepath, ret, strerror(ret));

+        goto done;

+    }

+

+    seret = setfscreatecon(default_context);

+    if (seret != 0) {

+        ERROR("Unable to set fscreate selinux context!");

+        ret = EIO;

+        goto done;

+    }

+

+    fd = mkstemp(tmpfile);

+    if (fd == -1) {

+        ret = errno;

+

+        seret = setfscreatecon(original_context);

+        if (seret != 0) {

+            ERROR("Unable to restore fscreate selinux context!");

+            ret = EIO;

+            goto done;

+        }

+

+        goto done;

+    }

+

+    close(fd);

+

+    seret = setfscreatecon(original_context);

+    if (seret != 0) {

+        ERROR("Unable to restore fscreate selinux context!");

+        ret = EIO;

+        goto done;

+    }

+

+    *_tmpfile = tmpfile;

+

+    ret = EOK;

+

+done:

+    if (original_context != NULL) {

+        freecon(original_context);

+    }

+

+    if (default_context != NULL) {

+        freecon(default_context);

+    }

+

+    if (ret != EOK) {

+        free(tmpfile);

+    }

+

+    return ret;

+}

diff --git a/src/lib/util/util.h b/src/lib/util/selinux.h

similarity index 50%

copy from src/lib/util/util.h

copy to src/lib/util/selinux.h

index b81990722d62ccf466c0687454c82ea3ee171436..26f2374140562dd085145845ed3092a0ddcf924e 100644

--- a/src/lib/util/util.h

+++ b/src/lib/util/selinux.h

@@ -18,20 +18,33 @@

     along with this program.  If not, see <http://www.gnu.org/licenses/>.

 */

-#ifndef _UTIL_H_

-#define _UTIL_H_

+#ifndef _SELINUX_H_

+#define _SELINUX_H_

+

+#include "common/errno_t.h"

 /**

- * Many of the utility functions are not as effective as they can be but

- * this is OK since authselect works only with small configuration files

- * therefore we can prefer clean and simple code over performance.

+ * Get default security context for @path.

+ *

+ * @param path Path to the file.

+ *

+ * @return EOK on success, ENOENT if context was not found, other errno code

+ *         is returned on failure.

  */

+errno_t

+selinux_get_default_context(const char *path);

-#include "common/common.h"

-#include "lib/util/file.h"

-#include "lib/util/string.h"

-#include "lib/util/string_array.h"

-#include "lib/util/template.h"

-#include "lib/util/textfile.h"

+/**

+ * Create temporary file created on @filepath.XXXXXX with security context

+ * set to default security context of @filepath.

+ *

+ * @param filepath File for which a temporary file should be created.

+ * @param _tmpfile Create temporary file.

+ *

+ * @return EOK on success, other errno code on failure.

+ */

+errno_t

+selinux_mkstemp_of(const char *filepath,

+                   char **_tmpfile);

-#endif /* _UTIL_H_ */

+#endif /* _SELINUX_H_ */

diff --git a/src/lib/util/template.c b/src/lib/util/template.c

index 0eedd2b04146f201a5c37f45c1d08f01c079d61f..9773dcbf1ecbde4fe2408f1b816dce129747806f 100644

--- a/src/lib/util/template.c

+++ b/src/lib/util/template.c

@@ -27,6 +27,7 @@

 #include "common/common.h"

 #include "lib/util/template.h"

 #include "lib/util/textfile.h"

+#include "lib/util/selinux.h"

 #include "lib/util/string.h"

 #include "lib/util/string_array.h"

@@ -594,23 +595,16 @@ template_write_temporary(const char *filepath,

     mode_t oldmask;

     char *tmpfile;

     errno_t ret;

-    int fd;

-

-    tmpfile = format("%s.XXXXXX", filepath);

-    if (tmpfile == NULL) {

-        return ENOMEM;

-    }

     oldmask = umask(mode);

-    fd = mkstemp(tmpfile);;

-    if (fd == -1) {

-        ret = errno;

+    ret = selinux_mkstemp_of(filepath, &tmpfile);

+    if (ret != EOK) {

+        ERROR("Unable to create temporary file for [%s] [%d]: %s",

+              filepath, ret, strerror(ret));

         goto done;

     }

-    close(fd);

-

     ret = template_write(tmpfile, content, mode);

     if (ret != EOK) {

         goto done;

diff --git a/src/lib/util/util.h b/src/lib/util/util.h

index b81990722d62ccf466c0687454c82ea3ee171436..e75afaef316fc8f8fd4d2aabbab7be1aa24e9ac7 100644

--- a/src/lib/util/util.h

+++ b/src/lib/util/util.h

@@ -29,6 +29,7 @@

 #include "common/common.h"

 #include "lib/util/file.h"

+#include "lib/util/selinux.h"

 #include "lib/util/string.h"

 #include "lib/util/string_array.h"

 #include "lib/util/template.h"

-- 

2.17.2