src/core/apparmor-setup.c

/* SPDX-License-Identifier: LGPL-2.1+ */

#include <errno.h>
#if HAVE_APPARMOR
#  include <sys/apparmor.h>
#endif
#include <unistd.h>

#include "apparmor-setup.h"
#include "apparmor-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "log.h"
#include "macro.h"
#include "string-util.h"
#include "strv.h"

#if HAVE_APPARMOR
DEFINE_TRIVIAL_CLEANUP_FUNC(aa_policy_cache *, aa_policy_cache_unref);
DEFINE_TRIVIAL_CLEANUP_FUNC(aa_features *, aa_features_unref);
#endif

int mac_apparmor_setup(void) {
#if HAVE_APPARMOR
        int r;
        _cleanup_(aa_policy_cache_unrefp) aa_policy_cache *policy_cache = NULL;
        _cleanup_(aa_features_unrefp) aa_features *features = NULL;
        const char *current_file;
        _cleanup_free_ char *current_profile = NULL, *cache_dir_path = NULL;

        if (!mac_apparmor_use()) {
                log_debug("AppArmor either not supported by the kernel or disabled.");
                return 0;
        }

        /* To enable LSM stacking a patch to the kernel is proposed to create a
         * per-LSM subdirectory to distinguish between the LSMs. Therefore, we
         * read the file from the LSM specific directory first and only if that
         * fails the one from the generic directory.
         */
        FOREACH_STRING(current_file, "/proc/self/attr/apparmor/current", "/proc/self/attr/current") {
                r = read_one_line_file(current_file, &current_profile);
                if (r == -ENOENT)
                        continue;
                else if (r < 0)
                        log_warning_errno(r, "Failed to read current AppArmor profile from file %s, ignoring: %m", current_file);
                else
                        break;
        }
        if (!current_profile) {
                log_warning("Failed to get the current AppArmor profile of systemd from /proc/self/attr/apparmor/current or /proc/self/attr/current, ignoring.");
                return 0;
        }
        if (!streq(current_profile, "unconfined")) {
                log_debug("We are already confined in an AppArmor profile.");
                return 0;
        }

        r = aa_features_new_from_kernel(&features);
        if (r < 0) {
                log_warning_errno(errno, "Failed to get the AppArmor feature set from the kernel, ignoring: %m");
                return 0;
        }
        cache_dir_path = aa_policy_cache_dir_path_preview(features, AT_FDCWD, "/etc/apparmor/earlypolicy");
        if (!cache_dir_path) {
                log_debug_errno(errno, "Failed to get the path of the early AppArmor policy cache directory.");
                return 0;
        }

        /* aa_policy_cache_new will internally use the same path as aa_policy_cache_dir_path_preview has returned. */
        r = aa_policy_cache_new(&policy_cache, features, AT_FDCWD, "/etc/apparmor/earlypolicy", 0);
        if (r < 0) {
                if (errno == ENOENT) {
                        log_debug_errno(errno, "The early AppArmor policy cache directory %s does not exist.", cache_dir_path);
                        return 0;
                }
                log_warning_errno(errno, "Failed to create a new AppArmor policy cache, ignoring: %m");
                return 0;
        }
        r = aa_policy_cache_replace_all(policy_cache, NULL);
        if (r < 0) {
                log_warning_errno(errno, "Failed to load the profiles from the early AppArmor policy cache directory %s, ignoring: %m", cache_dir_path);
                return 0;
        }

        log_info("Successfully loaded all binary profiles from AppArmor early policy cache at %s.", cache_dir_path);

        r = aa_change_profile("systemd");
        if (r < 0) {
                if (errno == ENOENT)
                        log_debug_errno(errno, "Failed to change to AppArmor profile 'systemd'. Please ensure that one of the binary profile files in policy cache directory %s contains a profile with that name.", cache_dir_path);
                else
                        log_error_errno(errno, "Failed to change to AppArmor profile 'systemd': %m");
                return 0;
        }

        log_info("Changed to AppArmor profile systemd.");
#endif
        return 0;
}