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libdnf/SOURCES/0049-PGP-Set-a-default-creation-SELinux-labels-on-GnuPG-d.patch

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From 8752006f5f9c11bca3f04c99b463fd167caf0ddd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= <ppisar@redhat.com>
Date: Wed, 4 Oct 2023 16:38:12 +0200
Subject: [PATCH] PGP: Set a default creation SELinux labels on GnuPG
directories
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
libdnf used to precreate the directory in /run/user to make sure
a GnuPG agent executed by GPGME library places its socket there.
The directories there are normally created and removed by systemd
(logind PAM session). libdnf created them for a case when a package
manager is invoked out of systemd session, before the super user logs
in. E.g. by a timer job to cache repository metadata.
A problem was when this out-of-session process was a SELinux-confined
process creating files with its own SELinux label different from a DNF
program. Then the directory was created with a SELinux label different
from the one expected by systemd and when logging out a corresponding
user, the mismatching label clashed with systemd.
The same issue was with temporary GnuPG home directories created by
libdnf under /tmp.
This patch fixes both the isseus by restoring a SELinux label of those
directories to the label defined in a default SELinux file context
database.
Obviously the database cannot have a record for a nonspecific
/tmp/tmpdir.XXXXXX (a mkdtemp() template) directory names. Therefore
I changed their names to more specific /tmp/libdnf.XXXXXX. Once
a SELinux policy updates the database, directories under /tmp will get
a correct label.
There is yet another problem with accessing /var/cache/dnf/*/pubring,
but that seems to be pure SELinux policy problem.
This patch adds a new -DENABLE_SELINUX=OFF CMake option to disable the
new dependency on libselinux. A default behavior is to support SELinux.
Implementation details:
I used selabel_lookup() + setfscreatecon() + mkdtemp()
+ setfscreatecon() sequence instead of mkdtemp()
+ selinux_restorecon() sequence because the later polutes stderr if
a SELinux policy does not define the default context. One could
supress stderr messages with selinux_set_callback(), but its effect
cannot be restored.
I also kept the sequence in one function and reused it for creating
/run/user/$PID directories because the code is simpler than spliting
the function into three parts.
https://issues.redhat.com/browse/RHEL-6421
Signed-off-by: Petr Písař <ppisar@redhat.com>
---
CMakeLists.txt | 7 +++
libdnf.spec | 11 +++-
libdnf/CMakeLists.txt | 4 ++
libdnf/repo/Repo.cpp | 121 +++++++++++++++++++++++++++++++++++++-----
4 files changed, 129 insertions(+), 14 deletions(-)
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d895b2bf..e5829e6a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -34,6 +34,7 @@ option(WITH_MAN "Enables hawkey man page generation" ON)
option(WITH_ZCHUNK "Build with zchunk support" ON)
option(ENABLE_RHSM_SUPPORT "Build with Red Hat Subscription Manager support?" OFF)
option(ENABLE_SOLV_URPMREORDER "Build with support for URPM-like solution reordering?" OFF)
+option(ENABLE_SELINUX "Restore SELinux labels on GnuPG directories" ON)
# build options - debugging
@@ -83,6 +84,12 @@ if(ENABLE_RHSM_SUPPORT)
include_directories(${RHSM_INCLUDE_DIRS})
endif()
+if(ENABLE_SELINUX)
+ pkg_check_modules(SELINUX REQUIRED libselinux)
+ include_directories(${SELINUX_INCLUDE_DIRS})
+ add_definitions(-DENABLE_SELINUX=1)
+endif()
+
# glibc: check if fnmatch.h has FNM_CASEFOLD symbol
include(CheckSymbolExists)
diff --git a/libdnf.spec b/libdnf.spec
index aa51dd28..df482f54 100644
--- a/libdnf.spec
+++ b/libdnf.spec
@@ -42,6 +42,8 @@
%bcond_with rhsm
%endif
+%bcond_without selinux
+
%if 0%{?rhel}
%bcond_with zchunk
%else
@@ -84,6 +86,9 @@ BuildRequires: pkgconfig(sqlite3)
BuildRequires: pkgconfig(json-c)
BuildRequires: pkgconfig(cppunit)
BuildRequires: pkgconfig(libcrypto)
+%if %{with selinux}
+BuildRequires: pkgconfig(libselinux)
+%endif
BuildRequires: pkgconfig(modulemd-2.0) >= %{libmodulemd_version}
BuildRequires: pkgconfig(smartcols)
BuildRequires: gettext
@@ -205,7 +210,8 @@ pushd build-py2
%define __builddir build-py2
%endif
%cmake -DPYTHON_DESIRED:FILEPATH=%{__python2} -DWITH_MAN=OFF ../ %{!?with_zchunk:-DWITH_ZCHUNK=OFF} %{!?with_valgrind:-DDISABLE_VALGRIND=1} %{_cmake_opts} -DLIBDNF_MAJOR_VERSION=%{libdnf_major_version} -DLIBDNF_MINOR_VERSION=%{libdnf_minor_version} -DLIBDNF_MICRO_VERSION=%{libdnf_micro_version} \
- -DWITH_SANITIZERS=%{?with_sanitizers:ON}%{!?with_sanitizers:OFF}
+ -DWITH_SANITIZERS=%{?with_sanitizers:ON}%{!?with_sanitizers:OFF} \
+ -DENABLE_SELINUX=%{?with_selinux:ON}%{!?with_selinux:OFF}
%make_build
popd
%endif
@@ -219,7 +225,8 @@ pushd build-py3
%define __builddir build-py3
%endif
%cmake -DPYTHON_DESIRED:FILEPATH=%{__python3} -DWITH_GIR=0 -DWITH_MAN=0 -Dgtkdoc=0 ../ %{!?with_zchunk:-DWITH_ZCHUNK=OFF} %{!?with_valgrind:-DDISABLE_VALGRIND=1} %{_cmake_opts} -DLIBDNF_MAJOR_VERSION=%{libdnf_major_version} -DLIBDNF_MINOR_VERSION=%{libdnf_minor_version} -DLIBDNF_MICRO_VERSION=%{libdnf_micro_version} \
- -DWITH_SANITIZERS=%{?with_sanitizers:ON}%{!?with_sanitizers:OFF}
+ -DWITH_SANITIZERS=%{?with_sanitizers:ON}%{!?with_sanitizers:OFF} \
+ -DENABLE_SELINUX=%{?with_selinux:ON}%{!?with_selinux:OFF}
%make_build
popd
%endif
diff --git a/libdnf/CMakeLists.txt b/libdnf/CMakeLists.txt
index 998a6f94..10b15230 100644
--- a/libdnf/CMakeLists.txt
+++ b/libdnf/CMakeLists.txt
@@ -89,6 +89,10 @@ if(ENABLE_RHSM_SUPPORT)
target_link_libraries(libdnf ${RHSM_LIBRARIES})
endif()
+if(ENABLE_SELINUX)
+ target_link_libraries(libdnf ${SELINUX_LIBRARIES})
+endif()
+
set(DNF_SO_VERSION 2)
set_target_properties(libdnf PROPERTIES OUTPUT_NAME "dnf")
set_target_properties(libdnf PROPERTIES SOVERSION ${DNF_SO_VERSION})
diff --git a/libdnf/repo/Repo.cpp b/libdnf/repo/Repo.cpp
index d61a24a5..68b82ccc 100644
--- a/libdnf/repo/Repo.cpp
+++ b/libdnf/repo/Repo.cpp
@@ -51,6 +51,11 @@
#include <gpgme.h>
+#if ENABLE_SELINUX
+#include <selinux/selinux.h>
+#include <selinux/label.h>
+#endif
+
#include <solv/chksum.h>
#include <solv/repo.h>
#include <solv/util.h>
@@ -649,6 +654,78 @@ std::unique_ptr<LrHandle> Repo::Impl::lrHandleInitRemote(const char *destdir)
return h;
}
+/*
+ * @brief Create a temporary directory.
+ *
+ * Creates a temporary directory with 0700 mode attempting to set a proper
+ * SELinux file context. Encountered errors are logged at debug level to
+ * a global logger.
+ *
+ * @param name_template As an input value it is a template according to
+ * mkdtemp(3). As an output value it will contain the created directory name.
+ *
+ * @return 0 if the directory was created, -1 if it wasn't. SELinux failures
+ * are not considered an error.
+ */
+static int create_temporary_directory(char *name_template) {
+ auto logger(Log::getLogger());
+ int retval = 0;
+#if ENABLE_SELINUX
+ char *old_default_context = NULL;
+ char *new_default_context = NULL;
+ int old_default_context_was_retrieved= 0;
+ struct selabel_handle *labeling_handle = NULL;
+
+ /* A purpose of this piece of code is to deal with applications whose
+ * security policy overrides a file context for temporary files but don't
+ * know that libdnf executes GnuPG which expects a default file context. */
+ if (0 == getfscreatecon(&old_default_context)) {
+ old_default_context_was_retrieved = 1;
+ } else {
+ logger->debug(tfm::format("Failed to retrieve a default SELinux context"));
+ }
+
+ labeling_handle = selabel_open(SELABEL_CTX_FILE, NULL, 0);
+ if (NULL == labeling_handle) {
+ logger->debug(tfm::format("Failed to open a SELinux labeling handle: %s",
+ strerror(errno)));
+ } else {
+ if (selabel_lookup(labeling_handle, &new_default_context, name_template, 0700)) {
+ /* Here we could hard-code "system_u:object_r:user_tmp_t:s0", but
+ * that value should be really defined in default file context
+ * SELinux policy. Only log that the policy is incpomplete. */
+ logger->debug(tfm::format("Failed to look up a default SELinux label for \"%s\"",
+ name_template));
+ } else {
+ if (setfscreatecon(new_default_context)) {
+ logger->debug(tfm::format("Failed to set default SELinux context to \"%s\"",
+ new_default_context));
+ }
+ freecon(new_default_context);
+ }
+ selabel_close(labeling_handle);
+ }
+#endif
+
+ /* mkdtemp() assures 0700 mode. */
+ if (NULL == mkdtemp(name_template)) {
+ logger->debug(tfm::format("Failed to create a directory \"%s\": %s",
+ name_template, strerror(errno)));
+ retval = -1;
+ }
+
+#if ENABLE_SELINUX
+ if (old_default_context_was_retrieved) {
+ if (setfscreatecon(old_default_context)) {
+ logger->debug(tfm::format("Failed to restore a default SELinux context"));
+ }
+ }
+ freecon(old_default_context);
+#endif
+
+ return retval;
+}
+
static void gpgImportKey(gpgme_ctx_t context, int keyFd)
{
auto logger(Log::getLogger());
@@ -703,8 +780,8 @@ static std::vector<Key> rawkey2infos(int fd) {
std::unique_ptr<std::remove_pointer<gpgme_ctx_t>::type> context(ctx);
// set GPG home dir
- char tmpdir[] = "/tmp/tmpdir.XXXXXX";
- mkdtemp(tmpdir);
+ char tmpdir[] = "/tmp/libdnf.XXXXXX";
+ create_temporary_directory(tmpdir);
Finalizer tmpDirRemover([&tmpdir](){
dnf_remove_recursive(tmpdir, NULL);
});
@@ -853,6 +930,13 @@ std::vector<Key> Repo::Impl::retrieve(const std::string & url)
* would cause a race condition with calling gpgme_release(), see [2], [3],
* [4].
*
+ * Current solution precreating /run/user/$UID showed problematic when this
+ * library was used out of a systemd-logind session from a programm with an
+ * unexpected SELinux context. Then /run/user/$UID, normally maintained by
+ * systemd, was assigned a SELinux label unexpected by systemd causing errors
+ * on a user logout [5]. We remedy it by restoring the label according to
+ * a file context policy.
+ *
* Since the agent doesn't clean up its sockets properly, by creating this
* directory we make sure they are in a place that is not causing trouble with
* container images.
@@ -861,14 +945,27 @@ std::vector<Key> Repo::Impl::retrieve(const std::string & url)
* [2] https://bugzilla.redhat.com/show_bug.cgi?id=1769831
* [3] https://github.com/rpm-software-management/microdnf/issues/50
* [4] https://bugzilla.redhat.com/show_bug.cgi?id=1781601
+ * [5] https://issues.redhat.com/browse/RHEL-6421
*/
static void ensure_socket_dir_exists() {
auto logger(Log::getLogger());
+ char tmpdir[] = "/run/user/libdnf.XXXXXX";
std::string dirname = "/run/user/" + std::to_string(getuid());
- int res = mkdir(dirname.c_str(), 0700);
- if (res != 0 && errno != EEXIST) {
- logger->debug(tfm::format("Failed to create directory \"%s\": %d - %s",
- dirname, errno, strerror(errno)));
+
+ /* create_temporary_directory() assures 0700 mode and tries its best to
+ * correct a SELinux label. */
+ if (create_temporary_directory(tmpdir)) {
+ return;
+ }
+
+ /* Set the desired name. */
+ if (rename(tmpdir, dirname.c_str())) {
+ if (errno != EEXIST && errno != ENOTEMPTY && errno != EBUSY) {
+ logger->debug(tfm::format("Failed to rename \"%s\" directory to \"%s\": %s",
+ tmpdir, dirname, strerror(errno)));
+ }
+ rmdir(tmpdir);
+ return;
}
}
@@ -1151,8 +1248,8 @@ void Repo::Impl::addCountmeFlag(LrHandle *handle) {
bool Repo::Impl::isMetalinkInSync()
{
auto logger(Log::getLogger());
- char tmpdir[] = "/tmp/tmpdir.XXXXXX";
- mkdtemp(tmpdir);
+ char tmpdir[] = "/tmp/libdnf.XXXXXX";
+ create_temporary_directory(tmpdir);
Finalizer tmpDirRemover([&tmpdir](){
dnf_remove_recursive(tmpdir, NULL);
});
@@ -1221,8 +1318,8 @@ bool Repo::Impl::isRepomdInSync()
{
auto logger(Log::getLogger());
LrYumRepo *yum_repo;
- char tmpdir[] = "/tmp/tmpdir.XXXXXX";
- mkdtemp(tmpdir);
+ char tmpdir[] = "/tmp/libdnf.XXXXXX";
+ create_temporary_directory(tmpdir);
Finalizer tmpDirRemover([&tmpdir](){
dnf_remove_recursive(tmpdir, NULL);
});
@@ -1260,8 +1357,8 @@ void Repo::Impl::fetch(const std::string & destdir, std::unique_ptr<LrHandle> &&
throw RepoError(tfm::format(_("Cannot create repo destination directory \"%s\": %s"),
destdir, errTxt));
}
- auto tmpdir = destdir + "/tmpdir.XXXXXX";
- if (!mkdtemp(&tmpdir.front())) {
+ auto tmpdir = destdir + "/libdnf.XXXXXX";
+ if (create_temporary_directory(&tmpdir.front())) {
const char * errTxt = strerror(errno);
throw RepoError(tfm::format(_("Cannot create repo temporary directory \"%s\": %s"),
tmpdir.c_str(), errTxt));
--
2.41.0
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