src/shared/smack-util.c

/* SPDX-License-Identifier: LGPL-2.1-or-later */
/***
  Copyright © 2013 Intel Corporation

  Author: Auke Kok <auke-jan.h.kok@intel.com>
***/

#include <errno.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/xattr.h>
#include <unistd.h>

#include "alloc-util.h"
#include "errno-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "log.h"
#include "macro.h"
#include "path-util.h"
#include "process-util.h"
#include "smack-util.h"
#include "stdio-util.h"
#include "string-table.h"
#include "xattr-util.h"

#if ENABLE_SMACK
bool mac_smack_use(void) {
        static int cached_use = -1;

        if (cached_use < 0)
                cached_use = access("/sys/fs/smackfs/", F_OK) >= 0;

        return cached_use;
}

static const char* const smack_attr_table[_SMACK_ATTR_MAX] = {
        [SMACK_ATTR_ACCESS]     = "security.SMACK64",
        [SMACK_ATTR_EXEC]       = "security.SMACK64EXEC",
        [SMACK_ATTR_MMAP]       = "security.SMACK64MMAP",
        [SMACK_ATTR_TRANSMUTE]  = "security.SMACK64TRANSMUTE",
        [SMACK_ATTR_IPIN]       = "security.SMACK64IPIN",
        [SMACK_ATTR_IPOUT]      = "security.SMACK64IPOUT",
};

DEFINE_STRING_TABLE_LOOKUP(smack_attr, SmackAttr);

int mac_smack_read(const char *path, SmackAttr attr, char **label) {
        assert(path);
        assert(attr >= 0 && attr < _SMACK_ATTR_MAX);
        assert(label);

        if (!mac_smack_use())
                return 0;

        return getxattr_malloc(path, smack_attr_to_string(attr), label);
}

int mac_smack_read_fd(int fd, SmackAttr attr, char **label) {
        assert(fd >= 0);
        assert(attr >= 0 && attr < _SMACK_ATTR_MAX);
        assert(label);

        if (!mac_smack_use())
                return 0;

        return fgetxattr_malloc(fd, smack_attr_to_string(attr), label);
}

int mac_smack_apply(const char *path, SmackAttr attr, const char *label) {
        int r;

        assert(path);
        assert(attr >= 0 && attr < _SMACK_ATTR_MAX);

        if (!mac_smack_use())
                return 0;

        if (label)
                r = lsetxattr(path, smack_attr_to_string(attr), label, strlen(label), 0);
        else
                r = lremovexattr(path, smack_attr_to_string(attr));
        if (r < 0)
                return -errno;

        return 0;
}

int mac_smack_apply_fd(int fd, SmackAttr attr, const char *label) {
        int r;

        assert(fd >= 0);
        assert(attr >= 0 && attr < _SMACK_ATTR_MAX);

        if (!mac_smack_use())
                return 0;

        if (label)
                r = setxattr(FORMAT_PROC_FD_PATH(fd), smack_attr_to_string(attr), label, strlen(label), 0);
        else
                r = removexattr(FORMAT_PROC_FD_PATH(fd), smack_attr_to_string(attr));
        if (r < 0)
                return -errno;

        return 0;
}

int mac_smack_apply_pid(pid_t pid, const char *label) {
        const char *p;
        int r;

        assert(label);

        if (!mac_smack_use())
                return 0;

        p = procfs_file_alloca(pid, "attr/current");
        r = write_string_file(p, label, WRITE_STRING_FILE_DISABLE_BUFFER);
        if (r < 0)
                return r;

        return r;
}

static int smack_fix_fd(
                int fd,
                const char *label_path,
                LabelFixFlags flags) {

        const char *label;
        struct stat st;
        int r;

        /* The caller should have done the sanity checks. */
        assert(fd >= 0);
        assert(label_path);
        assert(path_is_absolute(label_path));

        /* Path must be in /dev. */
        if (!path_startswith(label_path, "/dev"))
                return 0;

        if (fstat(fd, &st) < 0)
                return -errno;

        /*
         * Label directories and character devices "*".
         * Label symlinks "_".
         * Don't change anything else.
         */

        if (S_ISDIR(st.st_mode))
                label = SMACK_STAR_LABEL;
        else if (S_ISLNK(st.st_mode))
                label = SMACK_FLOOR_LABEL;
        else if (S_ISCHR(st.st_mode))
                label = SMACK_STAR_LABEL;
        else
                return 0;

        if (setxattr(FORMAT_PROC_FD_PATH(fd), "security.SMACK64", label, strlen(label), 0) < 0) {
                _cleanup_free_ char *old_label = NULL;

                r = -errno;

                /* If the FS doesn't support labels, then exit without warning */
                if (ERRNO_IS_NOT_SUPPORTED(r))
                        return 0;

                /* It the FS is read-only and we were told to ignore failures caused by that, suppress error */
                if (r == -EROFS && (flags & LABEL_IGNORE_EROFS))
                        return 0;

                /* If the old label is identical to the new one, suppress any kind of error */
                if (lgetxattr_malloc(FORMAT_PROC_FD_PATH(fd), "security.SMACK64", &old_label) >= 0 &&
                    streq(old_label, label))
                        return 0;

                return log_debug_errno(r, "Unable to fix SMACK label of %s: %m", label_path);
        }

        return 0;
}

int mac_smack_fix_full(
                int atfd,
                const char *inode_path,
                const char *label_path,
                LabelFixFlags flags) {

        _cleanup_close_ int opened_fd = -EBADF;
        _cleanup_free_ char *p = NULL;
        int r, inode_fd;

        assert(atfd >= 0 || atfd == AT_FDCWD);
        assert(atfd >= 0 || inode_path);

        if (!mac_smack_use())
                return 0;

        if (inode_path) {
                opened_fd = openat(atfd, inode_path, O_NOFOLLOW|O_CLOEXEC|O_PATH);
                if (opened_fd < 0) {
                        if ((flags & LABEL_IGNORE_ENOENT) && errno == ENOENT)
                                return 0;

                        return -errno;
                }
                inode_fd = opened_fd;
        } else
                inode_fd = atfd;

        if (!label_path) {
                if (path_is_absolute(inode_path))
                        label_path = inode_path;
                else {
                        r = fd_get_path(inode_fd, &p);
                        if (r < 0)
                                return r;

                        label_path = p;
                }
        }

        return smack_fix_fd(inode_fd, label_path, flags);
}

int mac_smack_copy(const char *dest, const char *src) {
        int r;
        _cleanup_free_ char *label = NULL;

        assert(dest);
        assert(src);

        r = mac_smack_read(src, SMACK_ATTR_ACCESS, &label);
        if (r < 0)
                return r;

        r = mac_smack_apply(dest, SMACK_ATTR_ACCESS, label);
        if (r < 0)
                return r;

        return r;
}

#else
bool mac_smack_use(void) {
        return false;
}

int mac_smack_read(const char *path, SmackAttr attr, char **label) {
        return -EOPNOTSUPP;
}

int mac_smack_read_fd(int fd, SmackAttr attr, char **label) {
        return -EOPNOTSUPP;
}

int mac_smack_apply(const char *path, SmackAttr attr, const char *label) {
        return 0;
}

int mac_smack_apply_fd(int fd, SmackAttr attr, const char *label) {
        return 0;
}

int mac_smack_apply_pid(pid_t pid, const char *label) {
        return 0;
}

int mac_smack_fix_full(int atfd, const char *inode_path, const char *label_path, LabelFixFlags flags) {
        return 0;
}

int mac_smack_copy(const char *dest, const char *src) {
        return 0;
}
#endif

int rename_and_apply_smack_floor_label(const char *from, const char *to) {

        if (rename(from, to) < 0)
                return -errno;

#if HAVE_SMACK_RUN_LABEL
        return mac_smack_apply(to, SMACK_ATTR_ACCESS, SMACK_FLOOR_LABEL);
#else
        return 0;
#endif
}