From c9172f66cfaf4bc83280c1bcfce77380222023b7 Mon Sep 17 00:00:00 2001
From: szaka <szaka>
Date: Sun, 2 Sep 2007 12:38:29 +0000
Subject: [PATCH] add ntfs_security_hash(): hash of a security descriptor
 (Anton Altaparmakov)

---
 include/ntfs-3g/security.h |  3 +++
 libntfs-3g/security.c      | 28 ++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/include/ntfs-3g/security.h b/include/ntfs-3g/security.h
index e903f672..04cc30a9 100644
--- a/include/ntfs-3g/security.h
+++ b/include/ntfs-3g/security.h
@@ -55,4 +55,7 @@ extern char *ntfs_sid_to_mbs(const SID *sid, char *sid_str,
 extern void ntfs_generate_guid(GUID *guid);
 extern int ntfs_sd_add_everyone(ntfs_inode *ni);
 
+extern le32 ntfs_security_hash(const SECURITY_DESCRIPTOR_RELATIVE *sd, 
+			       const u32 len);
+
 #endif /* defined _NTFS_SECURITY_H */
diff --git a/libntfs-3g/security.c b/libntfs-3g/security.c
index 926a1829..2729ae08 100644
--- a/libntfs-3g/security.c
+++ b/libntfs-3g/security.c
@@ -43,6 +43,7 @@
 #include "attrib.h"
 #include "security.h"
 #include "misc.h"
+#include "bitmap.h"
 
 /*
  * The zero GUID.
@@ -338,3 +339,30 @@ int ntfs_sd_add_everyone(ntfs_inode *ni)
 	return ret;
 }
 
+/**
+ * ntfs_security_hash - calculate the hash of a security descriptor
+ * @sd:         self-relative security descriptor whose hash to calculate
+ * @length:     size in bytes of the security descritor @sd
+ *
+ * Calculate the hash of the self-relative security descriptor @sd of length
+ * @length bytes.
+ *
+ * This hash is used in the $Secure system file as the primary key for the $SDH
+ * index and is also stored in the header of each security descriptor in the
+ * $SDS data stream as well as in the index data of both the $SII and $SDH
+ * indexes.  In all three cases it forms part of the SDS_ENTRY_HEADER
+ * structure.
+ *
+ * Return the calculated security hash in little endian.
+ */
+le32 ntfs_security_hash(const SECURITY_DESCRIPTOR_RELATIVE *sd, const u32 len)
+{
+        const le32 *pos = (le32 *)sd;
+        const le32 *end = pos + (len >> 2);
+        u32 hash = 0;
+
+        while (pos < end)
+                hash = le32_to_cpup(pos++) + ntfs_rol32(hash, 3);
+        return cpu_to_le32(hash);
+}
+