add support for de-masking database header and reading database password

git-svn-id: https://svn.code.sf.net/p/jackcess/code/jackcess/trunk@486 f203690c-595d-4dc9-a70b-905162fa7fd2

3 files changed, 162 insertions, 8 deletions

diff --git a/src/java/com/healthmarketscience/jackcess/Database.java b/src/java/com/healthmarketscience/jackcess/Database.java
index 215d446..2555a7d 100644
--- a/src/java/com/healthmarketscience/jackcess/Database.java
+++ b/src/java/com/healthmarketscience/jackcess/Database.java
@@ -1024,6 +1024,67 @@ public class Database
   }
 
   /**
+   * @return the current database password, or {@code null} if none set.
+   */
+  public String getDatabasePassword() throws IOException
+  {
+    _pageChannel.readPage(_buffer, 0);
+
+    byte[] pwdBytes = new byte[_format.SIZE_PASSWORD];
+    _buffer.position(_format.OFFSET_PASSWORD);
+    _buffer.get(pwdBytes);
+
+    // de-mask password
+    applyPasswordMask(pwdBytes);
+    
+    boolean hasPassword = false;
+    for(int i = 0; i < pwdBytes.length; ++i) {
+      if(pwdBytes[i] != 0) {
+        hasPassword = true;
+        break;
+      }
+    }
+
+    if(!hasPassword) {
+      return null;
+    }
+
+    String pwd = Column.decodeUncompressedText(pwdBytes, getCharset());
+
+    // remove any trailing null chars
+    int idx = pwd.indexOf('\0');
+    if(idx >= 0) {
+      pwd = pwd.substring(0, idx);
+    }
+
+    return pwd;
+  }
+
+  /**
+   * Applies an extra mask to the password if required for the current
+   * JetFormat.
+   */
+  private void applyPasswordMask(byte[] pwdBytes)
+  {
+    // apply extra password mask if necessary (the extra password mask is
+    // generated from the database creation date stored in the header)
+    int pwdMaskPos = _format.OFFSET_HEADER_DATE;
+    if(pwdMaskPos >= 0) {
+
+      _buffer.position(pwdMaskPos);
+      double dateVal = Double.longBitsToDouble(_buffer.getLong());
+
+      byte[] pwdMask = new byte[4];
+      ByteBuffer.wrap(pwdMask).order(PageChannel.DEFAULT_BYTE_ORDER)
+        .putInt((int)dateVal);
+
+      for(int i = 0; i < pwdBytes.length; ++i) {
+        pwdBytes[i] ^= pwdMask[i % pwdMask.length];
+      }
+    }
+  }
+
+  /**
    * Finds the relationships matching the given from and to tables from the
    * given cursor and adds them to the given list.
    */
diff --git a/src/java/com/healthmarketscience/jackcess/JetFormat.java b/src/java/com/healthmarketscience/jackcess/JetFormat.java
index 8041dbb..4beb69e 100644
--- a/src/java/com/healthmarketscience/jackcess/JetFormat.java
+++ b/src/java/com/healthmarketscience/jackcess/JetFormat.java
@@ -59,6 +59,31 @@ public abstract class JetFormat {
   /** Version code for Jet version 5 */
   private static final byte CODE_VERSION_5 = 0x2;
 
+  /** mask used to obfuscate the db header */
+  private static final byte[] BASE_HEADER_MASK = new byte[]{
+    (byte)0xB5, (byte)0x6F, (byte)0x03, (byte)0x62, (byte)0x61, (byte)0x08,
+    (byte)0xC2, (byte)0x55, (byte)0xEB, (byte)0xA9, (byte)0x67, (byte)0x72,
+    (byte)0x43, (byte)0x3F, (byte)0x00, (byte)0x9C, (byte)0x7A, (byte)0x9F,
+    (byte)0x90, (byte)0xFF, (byte)0x80, (byte)0x9A, (byte)0x31, (byte)0xC5,
+    (byte)0x79, (byte)0xBA, (byte)0xED, (byte)0x30, (byte)0xBC, (byte)0xDF, 
+    (byte)0xCC, (byte)0x9D, (byte)0x63, (byte)0xD9, (byte)0xE4, (byte)0xC3,
+    (byte)0x7B, (byte)0x42, (byte)0xFB, (byte)0x8A, (byte)0xBC, (byte)0x4E,
+    (byte)0x86, (byte)0xFB, (byte)0xEC, (byte)0x37, (byte)0x5D, (byte)0x44,
+    (byte)0x9C, (byte)0xFA, (byte)0xC6, (byte)0x5E, (byte)0x28, (byte)0xE6, 
+    (byte)0x13, (byte)0xB6, (byte)0x8A, (byte)0x60, (byte)0x54, (byte)0x94,
+    (byte)0x7B, (byte)0x36, (byte)0xF5, (byte)0x72, (byte)0xDF, (byte)0xB1,
+    (byte)0x77, (byte)0xF4, (byte)0x13, (byte)0x43, (byte)0xCF, (byte)0xAF,
+    (byte)0xB1, (byte)0x33, (byte)0x34, (byte)0x61, (byte)0x79, (byte)0x5B,
+    (byte)0x92, (byte)0xB5, (byte)0x7C, (byte)0x2A, (byte)0x05, (byte)0xF1,
+    (byte)0x7C, (byte)0x99, (byte)0x01, (byte)0x1B, (byte)0x98, (byte)0xFD,
+    (byte)0x12, (byte)0x4F, (byte)0x4A, (byte)0x94, (byte)0x6C, (byte)0x3E,
+    (byte)0x60, (byte)0x26, (byte)0x5F, (byte)0x95, (byte)0xF8, (byte)0xD0,
+    (byte)0x89, (byte)0x24, (byte)0x85, (byte)0x67, (byte)0xC6, (byte)0x1F,
+    (byte)0x27, (byte)0x44, (byte)0xD2, (byte)0xEE, (byte)0xCF, (byte)0x65,
+    (byte)0xED, (byte)0xFF, (byte)0x07, (byte)0xC7, (byte)0x46, (byte)0xA1,
+    (byte)0x78, (byte)0x16, (byte)0x0C, (byte)0xED, (byte)0xE9, (byte)0x2D,
+    (byte)0x62, (byte)0xD4};    
+
   /** value of the "AccessVersion" property for access 2000 dbs:
       {@code "08.50"} */
   private static final byte[] ACCESS_VERSION_2000 = new byte[] {
@@ -104,7 +129,12 @@ public abstract class JetFormat {
   
   public final int MAX_ROW_SIZE;
   public final int PAGE_INITIAL_FREE_SPACE;
-  
+
+  public final int OFFSET_MASKED_HEADER;
+  public final byte[] HEADER_MASK;
+  public final int OFFSET_HEADER_DATE;
+  public final int OFFSET_PASSWORD;
+  public final int SIZE_PASSWORD;
   public final int OFFSET_NEXT_TABLE_DEF_PAGE;
   public final int OFFSET_NUM_ROWS;
   public final int OFFSET_NEXT_AUTO_NUMBER;
@@ -221,6 +251,11 @@ public abstract class JetFormat {
     MAX_ROW_SIZE = defineMaxRowSize();
     PAGE_INITIAL_FREE_SPACE = definePageInitialFreeSpace();
     
+    OFFSET_MASKED_HEADER = defineOffsetMaskedHeader();
+    HEADER_MASK = defineHeaderMask();
+    OFFSET_HEADER_DATE = defineOffsetHeaderDate();
+    OFFSET_PASSWORD = defineOffsetPassword();
+    SIZE_PASSWORD = defineSizePassword();
     OFFSET_NEXT_TABLE_DEF_PAGE = defineOffsetNextTableDefPage();
     OFFSET_NUM_ROWS = defineOffsetNumRows();
     OFFSET_NEXT_AUTO_NUMBER = defineOffsetNextAutoNumber();
@@ -306,6 +341,11 @@ public abstract class JetFormat {
   protected abstract int defineMaxRowSize();
   protected abstract int definePageInitialFreeSpace();
   
+  protected abstract int defineOffsetMaskedHeader();
+  protected abstract byte[] defineHeaderMask();
+  protected abstract int defineOffsetHeaderDate();
+  protected abstract int defineOffsetPassword();
+  protected abstract int defineSizePassword();
   protected abstract int defineOffsetNextTableDefPage();
   protected abstract int defineOffsetNumRows();
   protected abstract int defineOffsetNextAutoNumber();
@@ -414,6 +454,20 @@ public abstract class JetFormat {
     protected int definePageInitialFreeSpace() { return PAGE_SIZE - 14; }
 	    
     @Override
+    protected int defineOffsetMaskedHeader() { return 24; }
+    @Override
+    protected byte[] defineHeaderMask() { 
+      byte[] mask = new byte[BASE_HEADER_MASK.length - 2];
+      System.arraycopy(BASE_HEADER_MASK, 0, mask, 0, mask.length);
+      return mask; 
+    }
+    @Override
+    protected int defineOffsetHeaderDate() { return -1; }
+    @Override
+    protected int defineOffsetPassword() { return 66; }
+    @Override
+    protected int defineSizePassword() { return 20; }
+    @Override
     protected int defineOffsetNextTableDefPage() { return 4; }
     @Override
     protected int defineOffsetNumRows() { return 12; }
@@ -590,6 +644,16 @@ public abstract class JetFormat {
     protected int definePageInitialFreeSpace() { return PAGE_SIZE - 14; }
     
     @Override
+    protected int defineOffsetMaskedHeader() { return 24; }
+    @Override
+    protected byte[] defineHeaderMask() { return BASE_HEADER_MASK; }
+    @Override
+    protected int defineOffsetHeaderDate() { return 114; }
+    @Override
+    protected int defineOffsetPassword() { return 66; }
+    @Override
+    protected int defineSizePassword() { return 40; }
+    @Override
     protected int defineOffsetNextTableDefPage() { return 4; }
     @Override
     protected int defineOffsetNumRows() { return 16; }
diff --git a/src/java/com/healthmarketscience/jackcess/PageChannel.java b/src/java/com/healthmarketscience/jackcess/PageChannel.java
index e72bcd7..92c573c 100644
--- a/src/java/com/healthmarketscience/jackcess/PageChannel.java
+++ b/src/java/com/healthmarketscience/jackcess/PageChannel.java
@@ -161,6 +161,11 @@ public class PageChannel implements Channel, Flushable {
                             getFormat().PAGE_SIZE + " bytes from page " +
                             pageNumber + ", only read " + bytesRead);
     }
+
+    if(pageNumber == 0) {
+      // de-mask header
+      applyHeaderMask(buffer);
+    }
   }
   
   /**
@@ -192,10 +197,21 @@ public class PageChannel implements Channel, Flushable {
           "Page buffer is too large, size " + (page.remaining() - pageOffset));
     }
     
-    page.position(pageOffset);
-    _channel.write(page, (getPageOffset(pageNumber) + pageOffset));
-    if(_autoSync) {
-      flush();
+    if(pageNumber == 0) {
+      // re-mask header
+      applyHeaderMask(page);
+    }
+    try {
+      page.position(pageOffset);
+      _channel.write(page, (getPageOffset(pageNumber) + pageOffset));
+      if(_autoSync) {
+        flush();
+      }
+    } finally {
+      if(pageNumber == 0) {
+        // de-mask header
+        applyHeaderMask(page);
+      }
     }
   }
   
@@ -265,11 +281,11 @@ public class PageChannel implements Channel, Flushable {
   }
 
   /**
-   * @return A newly-allocated buffer of the given size and LITTLE_ENDIAN byte
-   *         order
+   * @return A newly-allocated buffer of the given size and DEFAULT_BYTE_ORDER
+   *         byte order
    */
   public ByteBuffer createBuffer(int size) {
-    return createBuffer(size, ByteOrder.LITTLE_ENDIAN);
+    return createBuffer(size, DEFAULT_BYTE_ORDER);
   }
   
   /**
@@ -295,6 +311,19 @@ public class PageChannel implements Channel, Flushable {
   }
 
   /**
+   * Applies the XOR mask to the database header in the given buffer.
+   */
+  private void applyHeaderMask(ByteBuffer buffer) {
+      // de/re-obfuscate the header
+      byte[] headerMask = _format.HEADER_MASK;
+      for(int idx = 0; idx < headerMask.length; ++idx) {
+        int pos = idx + _format.OFFSET_MASKED_HEADER;
+        byte b = (byte)(buffer.get(pos) ^ headerMask[idx]);
+        buffer.put(pos, b);
+      }
+  }
+
+  /**
    * @return a duplicate of the current buffer narrowed to the given position
    *         and limit.  mark will be set at the current position.
    */