1 files changed, 64 insertions, 0 deletions
diff --git a/src/basic/chattr-util.h b/src/basic/chattr-util.h
new file mode 100644
index 0000000..c1ee63b
--- /dev/null
+++ b/src/basic/chattr-util.h
@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <fcntl.h>
+#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(int dir_fd, const char *path, unsigned value, unsigned mask, unsigned *ret_previous, unsigned *ret_final, ChattrApplyFlags flags);
+static inline int chattr_at(int dir_fd, const char *path, unsigned value, unsigned mask, unsigned *previous) {
+        return chattr_full(dir_fd, path, value, mask, previous, NULL, 0);
+}
+static inline int chattr_fd(int fd, unsigned value, unsigned mask, unsigned *previous) {
+        return chattr_full(fd, NULL, value, mask, previous, NULL, 0);
+}
+static inline int chattr_path(const char *path, unsigned value, unsigned mask, unsigned *previous) {
+        return chattr_full(AT_FDCWD, path, 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(fd, NULL, CHATTR_SECRET_FLAGS, CHATTR_SECRET_FLAGS, NULL, NULL, flags|CHATTR_FALLBACK_BITWISE);
+}