Add basic infrastructure for storing xattr items

[wimlib] / include / wimlib / xattr.h

diff --git a/include/wimlib/xattr.h b/include/wimlib/xattr.h
new file mode 100644 (file)
index 0000000..56f7ab8
--- /dev/null
+++ b/include/wimlib/xattr.h
@@ -0,0 +1,124 @@
+#ifndef _WIMLIB_XATTR_H
+#define _WIMLIB_XATTR_H
+
+#include <string.h>
+
+#include "wimlib/endianness.h"
+#include "wimlib/tagged_items.h"
+#include "wimlib/util.h"
+
+#undef HAVE_XATTR_SUPPORT
+#if defined(HAVE_SYS_XATTR_H) && \
+       defined(HAVE_LLISTXATTR) && defined(HAVE_LGETXATTR) && \
+       defined(HAVE_FSETXATTR) && defined(HAVE_LSETXATTR)
+#  define HAVE_XATTR_SUPPORT 1
+#endif
+
+/*
+ * On-disk format of an entry in an extended attributes tagged item (wimlib
+ * extension).  An xattr item consists of a series of variable-length xattr
+ * name/value pairs, each of which begins with this header.
+ *
+ * Currently this is only used for Linux-style xattrs, but in the future we may
+ * use this for Windows-style xattrs too.
+ */
+struct wimlib_xattr_entry {
+
+       /* length of xattr name in bytes */
+       le16 name_len;
+
+       /* reserved, must be 0 */
+       le16 reserved;
+
+       /* length of xattr value in bytes */
+       le32 value_len;
+
+       /* followed by the xattr name with no terminating null */
+       char name[0];
+
+       /* followed by the xattr value with no terminating null */
+       /* u8 value[0]; */
+
+       /* then zero-padded to a 4-byte boundary */
+} _aligned_attribute(4);
+
+static inline size_t
+xattr_entry_size(const struct wimlib_xattr_entry *entry)
+{
+       return ALIGN(sizeof(*entry) + le16_to_cpu(entry->name_len) +
+                    le32_to_cpu(entry->value_len), 4);
+}
+
+static inline struct wimlib_xattr_entry *
+xattr_entry_next(const struct wimlib_xattr_entry *entry)
+{
+       return (void *)entry + xattr_entry_size(entry);
+}
+
+/* Currently we use the Linux limits when validating xattr names and values */
+#define XATTR_NAME_MAX 255
+#define XATTR_SIZE_MAX 65536
+
+static inline bool
+valid_xattr_entry(const struct wimlib_xattr_entry *entry, size_t avail)
+{
+       if (avail < sizeof(*entry))
+               return false;
+
+       if (entry->name_len == 0 ||
+           le16_to_cpu(entry->name_len) > XATTR_NAME_MAX)
+               return false;
+
+       if (entry->reserved != 0)
+               return false;
+
+       if (le32_to_cpu(entry->value_len) > XATTR_SIZE_MAX)
+               return false;
+
+       if (avail < xattr_entry_size(entry))
+               return false;
+
+       if (memchr(entry->name, '\0', le16_to_cpu(entry->name_len)))
+               return false;
+
+       return true;
+}
+
+/* Is the xattr of the specified name security-related? */
+static inline bool
+is_security_xattr(const char *name)
+{
+#define XATTR_SECURITY_PREFIX "security."
+#define XATTR_SYSTEM_PREFIX "system."
+#define XATTR_POSIX_ACL_ACCESS  "posix_acl_access"
+#define XATTR_NAME_POSIX_ACL_ACCESS XATTR_SYSTEM_PREFIX XATTR_POSIX_ACL_ACCESS
+#define XATTR_POSIX_ACL_DEFAULT  "posix_acl_default"
+#define XATTR_NAME_POSIX_ACL_DEFAULT XATTR_SYSTEM_PREFIX XATTR_POSIX_ACL_DEFAULT
+
+       return !strncmp(name, XATTR_SECURITY_PREFIX,
+                       sizeof(XATTR_SECURITY_PREFIX) - 1) ||
+              !strcmp(name, XATTR_NAME_POSIX_ACL_ACCESS) ||
+              !strcmp(name, XATTR_NAME_POSIX_ACL_DEFAULT);
+}
+
+static inline const void *
+inode_get_linux_xattrs(const struct wim_inode *inode, u32 *len_ret)
+{
+       return inode_get_tagged_item(inode, TAG_WIMLIB_LINUX_XATTRS, 0,
+                                    len_ret);
+}
+
+static inline bool
+inode_has_linux_xattrs(const struct wim_inode *inode)
+{
+       return inode_get_linux_xattrs(inode, NULL) != NULL;
+}
+
+static inline bool
+inode_set_linux_xattrs(struct wim_inode *inode, const void *entries, u32 len)
+{
+       return inode_set_tagged_data(inode, TAG_WIMLIB_LINUX_XATTRS,
+                                    entries, len);
+}
+
+#endif /* _WIMLIB_XATTR_H  */