Fixed extractor bug with --swap enabled

src/binwalk/modules/extractor.py

@@ -532,8 +532,18 @@ class Extractor(Module):
         fname = unique_file_name(bname, extension)
 
         try:
+            # If byte swapping is enabled, we need to start reading at a swap-size
+            # aligned offset, then index in to the read data appropriately.
+            if self.config.swap_size:
+                adjust = offset % self.config.swap_size
+            else:
+                adjust = 0
+
+            offset -= adjust
+
             # Open the target file and seek to the offset
-            fdin = self.config.open_file(file_name, length=size, offset=offset)
+            fdin = self.config.open_file(file_name)
+            fdin.seek(offset)
 
             # Open the output file
             try:
@@ -550,8 +560,9 @@ class Extractor(Module):
                 if not data:
                     break
                 else:
-                    fdout.write(str2bytes(data[:dlen]))
-                    total_size += dlen
+                    fdout.write(str2bytes(data[adjust:dlen]))
+                    total_size += (dlen-adjust)
+                    adjust = 0
 
             # Cleanup
             fdout.close()

src/binwalk/plugins/zlibextract.py

@@ -37,3 +37,4 @@ class ZLIBExtractPlugin(binwalk.core.plugin.Plugin):
             return False
 
         return True
+

src/binwalk/plugins/zlibvalid.py

@@ -14,9 +14,20 @@ class ZlibValidPlugin(binwalk.core.plugin.Plugin):
     def scan(self, result):
         # If this result is a zlib signature match, try to decompress the data
         if result.file and result.description.lower().startswith('zlib'):
+
+            # If byte swapping is enabled, we need to start reading at a swap-size
+            # aligned offset, then index in to the read data appropriately.
+            if self.module.config.swap_size:
+                adjust = result.offset % self.module.config.swap_size
+            else:
+                adjust = 0
+
+            offset = result.offset - adjust
+
             # Seek to and read the suspected zlib data
-            fd = self.module.config.open_file(result.file.name, offset=result.offset, length=self.MAX_DATA_SIZE)
-            data = fd.read(self.MAX_DATA_SIZE)
+            fd = self.module.config.open_file(result.file.name)
+            fd.seek(offset)
+            data = fd.read(self.MAX_DATA_SIZE)[adjust:]
             fd.close()
 
             # Check if this is valid zlib data. It is valid if:
@@ -29,3 +40,4 @@ class ZlibValidPlugin(binwalk.core.plugin.Plugin):
                 # Error -5, incomplete or truncated data input
                 if not str(e).startswith("Error -5"):
                     result.valid = False
+