src/basic/chattr-util.h

/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once

#include <linux/fs.h>
#include <stdbool.h>
#include <stddef.h>

#include "missing_fs.h"

/* The chattr() flags to apply when creating a new file *before* writing to it. In particular, flags such as
 * FS_NOCOW_FL don't work if applied a-posteriori. All other flags are fine (or even necessary, think
 * FS_IMMUTABLE_FL!) to apply after writing to the files. */
#define CHATTR_EARLY_FL                         \
        (FS_NOATIME_FL |                        \
         FS_COMPR_FL   |                        \
         FS_NOCOW_FL   |                        \
         FS_NOCOMP_FL  |                        \
         FS_PROJINHERIT_FL)

#define CHATTR_ALL_FL                           \
        (FS_NOATIME_FL      |                   \
         FS_SYNC_FL         |                   \
         FS_DIRSYNC_FL      |                   \
         FS_APPEND_FL       |                   \
         FS_COMPR_FL        |                   \
         FS_NODUMP_FL       |                   \
         FS_EXTENT_FL       |                   \
         FS_IMMUTABLE_FL    |                   \
         FS_JOURNAL_DATA_FL |                   \
         FS_SECRM_FL        |                   \
         FS_UNRM_FL         |                   \
         FS_NOTAIL_FL       |                   \
         FS_TOPDIR_FL       |                   \
         FS_NOCOW_FL        |                   \
         FS_PROJINHERIT_FL)

typedef enum ChattrApplyFlags {
        CHATTR_FALLBACK_BITWISE       = 1 << 0,
        CHATTR_WARN_UNSUPPORTED_FLAGS = 1 << 1,
} ChattrApplyFlags;

int chattr_full(const char *path, int fd, unsigned value, unsigned mask, unsigned *ret_previous, unsigned *ret_final, ChattrApplyFlags flags);

static inline int chattr_fd(int fd, unsigned value, unsigned mask, unsigned *previous) {
        return chattr_full(NULL, fd, value, mask, previous, NULL, 0);
}
static inline int chattr_path(const char *path, unsigned value, unsigned mask, unsigned *previous) {
        return chattr_full(path, -1, value, mask, previous, NULL, 0);
}

int read_attr_fd(int fd, unsigned *ret);
int read_attr_path(const char *p, unsigned *ret);

/* Combination of chattr flags, that should be appropriate for secrets stored on disk: Secure Remove +
 * Exclusion from Dumping + Synchronous Writing (i.e. not caching in memory) + In-Place Updating (i.e. not
 * spurious copies). */
#define CHATTR_SECRET_FLAGS (FS_SECRM_FL|FS_NODUMP_FL|FS_SYNC_FL|FS_NOCOW_FL)

static inline int chattr_secret(int fd, ChattrApplyFlags flags) {
        return chattr_full(NULL, fd, CHATTR_SECRET_FLAGS, CHATTR_SECRET_FLAGS, NULL, NULL, flags|CHATTR_FALLBACK_BITWISE);
}