Merge remote-tracking branch 'origin/GP-2052_ryanmkurtz_prelink'

Author: ryanmkurtz

Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/macho/MachHeader.java

@@ -139,11 +139,12 @@ public MachHeader parse() throws IOException, MachException {
 		if (_parsed) {
 			return this;
 		}
+		long currentIndex = _commandIndex;
 		for (int i = 0; i < nCmds; ++i) {
-			_reader.setPointerIndex(_commandIndex);
+			_reader.setPointerIndex(currentIndex);
 			LoadCommand lc = LoadCommandTypes.getLoadCommand(_reader, this);
 			_commands.add(lc);
-			_commandIndex += lc.getCommandSize();
+			currentIndex += lc.getCommandSize();
 		}
 		_parsed = true;
 		return this;
@@ -289,6 +290,15 @@ public boolean isLittleEndian() {//TODO -- if intel it is LE
 		return magic == MachConstants.MH_CIGAM || magic == MachConstants.MH_CIGAM_64;
 	}
 
+	/**
+	 * Gets the size of this {@link MachHeader} in bytes
+	 * 
+	 * @return The size of this {@link MachHeader} in bytes
+	 */
+	public long getSize() {
+		return _commandIndex - _machHeaderStartIndexInProvider;
+	}
+
 	public String getDescription() {//TODO
 		StringBuffer buffer = new StringBuffer();
 		buffer.append("Magic: 0x" + Integer.toHexString(magic));

Ghidra/Features/Base/src/main/java/ghidra/app/util/opinion/MachoPrelinkUtils.java

@@ -22,8 +22,7 @@
 import org.apache.commons.collections4.bidimap.DualHashBidiMap;
 import org.jdom.JDOMException;
 
-import ghidra.app.util.bin.ByteProvider;
-import ghidra.app.util.bin.ByteProviderWrapper;
+import ghidra.app.util.bin.*;
 import ghidra.app.util.bin.format.macho.MachException;
 import ghidra.app.util.bin.format.macho.MachHeader;
 import ghidra.app.util.bin.format.macho.commands.*;
@@ -36,6 +35,42 @@
  */
 public class MachoPrelinkUtils {
 
+	/**
+	 * Check to see if the given {@link ByteProvider} is a Mach-O PRELINK binary
+	 * 
+	 * @param provider The {@link ByteProvider} to check
+	 * @param monitor A monitor
+	 * @return True if the given {@link ByteProvider} is a Mach-O PRELINK binary; otherwise, false
+	 */
+	public static boolean isMachoPrelink(ByteProvider provider, TaskMonitor monitor) {
+		try {
+			MachHeader header = new MachHeader(provider);
+			BinaryReader reader = new BinaryReader(provider, header.isLittleEndian());
+			reader.setPointerIndex(header.getSize());
+
+			// Doing a full header parse is too slow...we really just need to see if a segment
+			// exists that starts with __PRELINK.  Parse the minimal amount to do that check.
+			for (int i = 0; i < header.getNumberOfCommands(); i++) {
+				int type = reader.peekNextInt();
+				if (type == LoadCommandTypes.LC_SEGMENT || type == LoadCommandTypes.LC_SEGMENT_64) {
+					SegmentCommand segment = new SegmentCommand(reader, header.is32bit());
+					if (segment.getSegmentName().startsWith("__PRELINK")) {
+						return true;
+					}
+				}
+				else {
+					type = reader.readNextInt();
+					int size = reader.readNextInt();
+					reader.setPointerIndex(reader.getPointerIndex() + size - 8);
+				}
+			}
+		}
+		catch (MachException | IOException e) {
+			// Assume it's not a Mach-O PRELINK...fall through
+		}
+		return false;
+	}
+
 	/**
 	 * Parses the provider looking for PRELINK XML.
 	 * 

Ghidra/Features/FileFormats/src/main/java/ghidra/file/formats/ios/prelink/PrelinkFileSystem.java

@@ -15,10 +15,9 @@
  */
 package ghidra.file.formats.ios.prelink;
 
-import java.util.*;
-
 import java.io.IOException;
 import java.io.InputStream;
+import java.util.*;
 
 import org.apache.commons.collections4.BidiMap;
 import org.jdom.JDOMException;
@@ -76,18 +75,7 @@ public void close() throws IOException {
 
 	@Override
 	public boolean isValid(TaskMonitor monitor) throws IOException {
-		try {
-			return MachHeader.isMachHeader(provider) &&
-				!MachoPrelinkUtils.parsePrelinkXml(provider, monitor).isEmpty();
-		}
-		catch (JDOMException e) {
-			Msg.warn(this, e.getMessage());
-			return true; // use KModInfo technique to open
-		}
-		catch (IOException e) {
-			Msg.warn(this, e.getMessage());
-			return false;
-		}
+		return MachoPrelinkUtils.isMachoPrelink(provider, monitor);
 	}
 
 	@Override