From 2d2b3b4ae0795594780c0c5a39a554da7aefa4a4 Mon Sep 17 00:00:00 2001
From: Erik Larsson <catacombae@gmail.com>
Date: Fri, 9 Jan 2015 06:56:25 +0100
Subject: [PATCH] Check volume header signature when creating HFSVolume
 derivates.

This sanity check prevents us from accidentally loading the wrong HFS
type. Helps us to catch errors early.
---
 .../hfs/original/HFSOriginalVolume.java         | 11 ++++++++++-
 .../org/catacombae/hfs/plus/HFSPlusVolume.java  | 17 +++++++++++++++--
 src/java/org/catacombae/hfs/x/HFSXVolume.java   |  3 ++-
 3 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/src/java/org/catacombae/hfs/original/HFSOriginalVolume.java b/src/java/org/catacombae/hfs/original/HFSOriginalVolume.java
index f12fc434..75806a00 100644
--- a/src/java/org/catacombae/hfs/original/HFSOriginalVolume.java
+++ b/src/java/org/catacombae/hfs/original/HFSOriginalVolume.java
@@ -63,13 +63,22 @@ public HFSOriginalVolume(ReadableRandomAccessStream hfsFile,
 
         super(hfsFile, cachingEnabled);
 
+        final MasterDirectoryBlock mdb = getHFSMasterDirectoryBlock();
+        if(mdb.getDrSigWord() != MasterDirectoryBlock.SIGNATURE_HFS) {
+            throw new RuntimeException("Invalid volume header signature " +
+                    "(expected: 0x" +
+                    Util.toHexStringBE(MasterDirectoryBlock.SIGNATURE_HFS) +
+                    " actual: 0x" + Util.toHexStringBE(mdb.getDrSigWord()) +
+                    ").");
+        }
+
         this.stringCodec = new MutableStringCodec<CharsetStringCodec>(
                 new CharsetStringCodec(encodingName));
 
         this.allocationFile = createAllocationFile();
     }
 
-    public MasterDirectoryBlock getHFSMasterDirectoryBlock() {
+    public final MasterDirectoryBlock getHFSMasterDirectoryBlock() {
         byte[] currentBlock = new byte[512];
         hfsFile.readFrom(1024, currentBlock);
         return new MasterDirectoryBlock(currentBlock, 0);
diff --git a/src/java/org/catacombae/hfs/plus/HFSPlusVolume.java b/src/java/org/catacombae/hfs/plus/HFSPlusVolume.java
index 1bb4345c..04e0c87a 100644
--- a/src/java/org/catacombae/hfs/plus/HFSPlusVolume.java
+++ b/src/java/org/catacombae/hfs/plus/HFSPlusVolume.java
@@ -65,13 +65,26 @@ public class HFSPlusVolume extends HFSVolume {
 
     public HFSPlusVolume(ReadableRandomAccessStream hfsFile,
             boolean cachingEnabled) {
+        this(hfsFile, cachingEnabled, HFSPlusVolumeHeader.SIGNATURE_HFS_PLUS);
+    }
 
+    protected HFSPlusVolume(ReadableRandomAccessStream hfsFile,
+            boolean cachingEnabled, short volumeHeaderSignature)
+    {
         super(hfsFile, cachingEnabled);
 
+        final HFSPlusVolumeHeader volumeHeader = getHFSPlusVolumeHeader();
+        if(volumeHeader.getSignature() != volumeHeaderSignature) {
+            throw new RuntimeException("Invalid volume header signature " +
+                    "(expected: 0x" +
+                    Util.toHexStringBE(volumeHeaderSignature) + " actual: 0x" +
+                    Util.toHexStringBE(volumeHeader.getSignature()) + ").");
+        }
+
         this.allocationFile = createAllocationFile();
         this.journal = new HFSPlusJournal(this);
 
-        if(getHFSPlusVolumeHeader().getAttributesFile().getExtents().
+        if(volumeHeader.getAttributesFile().getExtents().
                 getExtentDescriptors()[0].getBlockCount() == 0)
         {
             /* TODO: Is this even valid? */
@@ -86,7 +99,7 @@ SynchronizedReadableRandomAccess getBackingStream() {
         return hfsFile;
     }
 
-    public HFSPlusVolumeHeader getHFSPlusVolumeHeader() {
+    public final HFSPlusVolumeHeader getHFSPlusVolumeHeader() {
         //System.err.println("getHFSPlusVolumeHeader()");
 	byte[] currentBlock = new byte[512];
         //System.err.println("  hfsFile.seek(" + (fsOffset + 1024) + ")");
diff --git a/src/java/org/catacombae/hfs/x/HFSXVolume.java b/src/java/org/catacombae/hfs/x/HFSXVolume.java
index 2c9cdfb7..ded80a32 100644
--- a/src/java/org/catacombae/hfs/x/HFSXVolume.java
+++ b/src/java/org/catacombae/hfs/x/HFSXVolume.java
@@ -30,6 +30,7 @@
 import org.catacombae.hfs.types.hfsx.HFSXCatalogKey;
 import org.catacombae.io.ReadableRandomAccessStream;
 import org.catacombae.hfs.plus.HFSPlusVolume;
+import org.catacombae.hfs.types.hfsplus.HFSPlusVolumeHeader;
 
 /**
  * @author <a href="http://www.catacombae.org/" target="_top">Erik Larsson</a>
@@ -40,7 +41,7 @@ public class HFSXVolume extends HFSPlusVolume {
     public HFSXVolume(ReadableRandomAccessStream hfsFile,
             boolean cachingEnabled) {
 
-        super(hfsFile, cachingEnabled);
+        super(hfsFile, cachingEnabled, HFSPlusVolumeHeader.SIGNATURE_HFSX);
 
         CommonBTHeaderRecord.CompareType keyCompareTypeEnum =
                 getCatalogFile().getCatalogHeaderNode().getHeaderRecord().