Fixes #27 - Add option to swap endian

Uses -E in the in cli and checkbox in GUI

Author: helge000

readme.md

@@ -105,6 +105,7 @@ If needed you can use the folowing options to customize the behaviour of *tapeim
 |**Prefix**|Output prefix (default: `file`).|
 |**Extension**|Output file extension (default: `dd`).|
 |**Fill failed blocks**|Fill blocks that give read errors with null bytes. When this option is checked, *tapeimgr* calls *dd* with the flags `conv=noerror,sync`. The use of these flags is often recommended to ensure a forensic image with no missing/offset bytes in case of read errors (source: [*forensicswiki*](https://www.forensicswiki.org/wiki/Dd)), but when used with a block size that is larger than the actual block size it will generate padding bytes that make the extracted data unreadable. Because of this, any user-specified value of  the **Initial Block Size** setting (see above) is ignored when this option is used. **WARNING: this option may result in malformed output if the actual block size is either smaller than 512 bytes, and/or if the block size is not a multiple of 512 bytes! (I have no idea if this is even possible?).**|
+|**Swap little/big endian**|Use this option to swap the endianness of the file by adding `conv=swab` *dd* option. This is needed most commonly if the tape was created on an older [big endian OS](https://geraldonit.com/2017/09/04/big-and-little-endian-operating-systems/).|
 |**Identifier**|Unique identifier. You can either enter an existing identifier yourself, or press the *UUID* button to generate a [Universally unique identifier](https://en.wikipedia.org/wiki/Universally_unique_identifier).|
 |**Description**|A text string that describes the tape (e.g. the title that is written on its inlay card).|
 |**Notes**|Any additional info or notes you want to record with the tape.|
@@ -113,11 +114,12 @@ If needed you can use the folowing options to customize the behaviour of *tapeim
 
 It is also possible to invoke *tapeimgr* with command-line arguments. The general syntax is:
 
-    tapeimgr [-h] [--version] [--fill] [--device DEVICE]
-                [--blocksize SIZE] [--files FILES] [--prefix PREF]
-                [--extension EXT] [--identifier IDENTIFIER]
-                [--description DESCRIPTION] [--notes NOTES]
-                dirOut
+    tapeimgr [-h] [--version] [--fill] [--endianswap]
+             [--device DEVICE] [--blocksize SIZE] [--files FILES]
+             [--prefix PREF] [--extension EXT]
+             [--identifier IDENTIFIER]
+             [--description DESCRIPTION] [--notes NOTES]
+             dirOut
 
 Here `dirOut` is the output directory. So, the command-line equivalent of the first GUI example is:
 
@@ -141,6 +143,7 @@ As with the GUI interface you can customize the default behaviour by using one o
 |`--prefix PREF, -p PREF`|Output prefix (default: `file`).|
 |`--extension EXT, -e EXT`|Output file extension (default: `dd`).|
 |`--fill, -f`|Fill blocks that give read errors with null bytes. When this option is checked, *tapeimgr* calls *dd* with the flags `conv=noerror,sync`. The use of these flags is often recommended to ensure a forensic image with no missing/offset bytes in case of read errors (source: [*forensicswiki*](https://www.forensicswiki.org/wiki/Dd)), but when used with a block size that is larger than the actual block size it will generate padding bytes that make the extracted data unreadable. Because of this, any user-specified value of the `--blocksize`setting (see above) is ignored when this option is used. **WARNING: this option may result in malformed output if the actual block size is either smaller than 512 bytes, and/or if the block size is not a multiple of 512 bytes! (I have no idea if this is even possible?).**|
+|`--endianswap, -E`|Use this option to swap the endianness of the file by adding `conv=swab` *dd* option. This is needed most commonly if the tape was created on an older [big endian OS](https://geraldonit.com/2017/09/04/big-and-little-endian-operating-systems/).|
 |`--identifier IDENTIFIER, -i IDENTIFIER`|Unique identifier. You can either enter an existing identifier yourself, or enter special value `@uuid` to generate a [Universally unique identifier](https://en.wikipedia.org/wiki/Universally_unique_identifier).|
 |`--description DESCRIPTION, -c DESCRIPTION `|A text string that describes the tape (e.g. the title that is written on its inlay card).|
 |`--notes NOTES, -n NOTES`|Any additional info or notes you want to record with the tape.|

tapeimgr/cli.py

@@ -58,6 +58,11 @@ def parseCommandLine(self):
                                  dest='fillBlocks',
                                  default=self.tape.fillBlocks,
                                  help='fill blocks that give read errors with null bytes')
+        self.parser.add_argument('--endianswap', '-E',
+                                 action='store_true',
+                                 dest='endianSwap',
+                                 default=self.tape.endianSwap,
+                                 help='swap big/little endian')
         self.parser.add_argument('--device', '-d',
                                  action='store',
                                  type=str,
@@ -110,6 +115,7 @@ def parseCommandLine(self):
         args = self.parser.parse_args()
         self.tape.dirOut = args.dirOut
         self.tape.fillBlocks = args.fillBlocks
+        self.tape.endianSwap = args.endianSwap
         self.tape.tapeDevice = args.device
         self.tape.initBlockSize = args.size
         self.tape.files = args.files

tapeimgr/configure.py

@@ -58,6 +58,7 @@ def writeConfigFile(configRootDir, removeFlag):
     configSettings['prefix'] = 'file'
     configSettings['extension'] = 'dd'
     configSettings['fillBlocks'] = 'False'
+    configSettings['endianSwap'] = 'False'
     configSettings['timeZone'] = 'Europe/Amsterdam'
     configSettings['defaultDir'] = ''
 

tapeimgr/gui.py

@@ -74,6 +74,7 @@ def on_submit(self, event=None):
         self.tape.description = self.description_entry.get().strip()
         self.tape.notes = self.notes_entry.get(1.0, tk.END).strip()
         self.tape.fillBlocks = self.fBlocks.get()
+        self.tape.endianSwap = self.eSwap.get()
 
         # Check if required command line utils are available
         for cmd in shared.REQUIRED_CMDS:
@@ -143,6 +144,7 @@ def on_submit(self, event=None):
                 self.prefix_entry.config(state='disabled')
                 self.extension_entry.config(state='disabled')
                 self.fillblocks_entry.config(state='disabled')
+                self.endianswap_entry.config(state='disabled')
                 self.identifier_entry.config(state='disabled')
                 self.uuidButton.config(state='disabled')
                 self.description_entry.config(state='disabled')
@@ -262,7 +264,14 @@ def build_gui(self):
         self.fillblocks_entry = tk.Checkbutton(self, variable=self.fBlocks)
         self.fillblocks_entry.grid(column=1, row=11, sticky='w')
 
-        ttk.Separator(self, orient='horizontal').grid(column=0, row=12, columnspan=4, sticky='ew')
+        # Swap Endian
+        tk.Label(self, text='Swap little/big endian').grid(column=0, row=12, sticky='w')
+        self.eSwap = tk.BooleanVar()
+        self.eSwap.set(self.tape.endianSwap)
+        self.endianswap_entry = tk.Checkbutton(self, variable=self.eSwap)
+        self.endianswap_entry.grid(column=1, row=12, sticky='w')
+
+        ttk.Separator(self, orient='horizontal').grid(column=0, row=12+1, columnspan=4, sticky='ew')
 
         # Identifier entry field
         tk.Label(self, text='Identifier').grid(column=0, row=13, sticky='w')
@@ -272,45 +281,45 @@ def build_gui(self):
         self.identifier_entry.grid(column=1, row=13, sticky='w')
         self.uuidButton = tk.Button(self, text='UUID', underline=0,
                                     command=self.insertUUID, width=2)
-        self.uuidButton.grid(column=1, row=13, sticky='e')
+        self.uuidButton.grid(column=1, row=13+1, sticky='e')
 
         # Description entry field
         tk.Label(self, text='Description').grid(column=0, row=14, sticky='w')
         self.description_entry = tk.Entry(self, width=35)
         self.description_entry['background'] = 'white'
         self.description_entry.insert(tk.END, self.tape.description)
-        self.description_entry.grid(column=1, row=14, sticky='w', columnspan=1)
+        self.description_entry.grid(column=1, row=14+1, sticky='w', columnspan=1)
 
         # Notes entry field
         tk.Label(self, text='Notes').grid(column=0, row=15, sticky='w')
         self.notes_entry = tk.Text(self, height=6, width=35)
         self.notes_entry['background'] = 'white'
         self.notes_entry.insert(tk.END, self.tape.notes)
-        self.notes_entry.grid(column=1, row=15, sticky='w', columnspan=1)
+        self.notes_entry.grid(column=1, row=15+1, sticky='w', columnspan=1)
 
-        ttk.Separator(self, orient='horizontal').grid(column=0, row=16, columnspan=4, sticky='ew')
+        ttk.Separator(self, orient='horizontal').grid(column=0, row=16+1, columnspan=4, sticky='ew')
 
         self.start_button = tk.Button(self,
                                       text='Start',
                                       width=10,
                                       underline=0,
                                       command=self.on_submit)
-        self.start_button.grid(column=1, row=17, sticky='w')
+        self.start_button.grid(column=1, row=17+1, sticky='w')
 
         self.quit_button = tk.Button(self,
                                      text='Exit',
                                      width=10,
                                      underline=0,
                                      command=self.on_quit)
-        self.quit_button.grid(column=1, row=17, sticky='e')
+        self.quit_button.grid(column=1, row=17+1, sticky='e')
 
-        ttk.Separator(self, orient='horizontal').grid(column=0, row=18, columnspan=4, sticky='ew')
+        ttk.Separator(self, orient='horizontal').grid(column=0, row=18+1, columnspan=4, sticky='ew')
 
         # Add ScrolledText widget to display logging info
         self.st = ScrolledText.ScrolledText(self, state='disabled', height=15)
         self.st.configure(font='TkFixedFont')
         self.st['background'] = 'white'
-        self.st.grid(column=0, row=19, sticky='ew', columnspan=4)
+        self.st.grid(column=0, row=19+1, sticky='ew', columnspan=4)
 
         # Define bindings for keyboard shortcuts: buttons
         self.root.bind_all('<Control-Key-d>', self.selectOutputDirectory)
@@ -350,6 +359,7 @@ def reset_gui(self, dirOut):
         self.prefix_entry.config(state='normal')
         self.extension_entry.config(state='normal')
         self.fillblocks_entry.config(state='normal')
+        self.endianswap_entry.config(state='normal')
         self.identifier_entry.config(state='normal')
         self.uuidButton.config(state='normal')
         self.description_entry.config(state='normal')
@@ -375,6 +385,7 @@ def reset_gui(self, dirOut):
         self.notes_entry.delete(1.0, tk.END)
         self.notes_entry.insert(tk.END, self.tape.notes)
         self.fBlocks.set(self.tape.fillBlocks)
+        self.eSwap.set(self.tape.endianSwap)
         self.start_button.config(state='normal')
         self.quit_button.config(state='normal')
 

tapeimgr/tape.py

@@ -25,6 +25,7 @@ def __init__(self):
         self.prefix = ''
         self.extension = ''
         self.fillBlocks = ''
+        self.endianSwap = ''
         self.identifier = ''
         self.description = ''
         self.notes = ''
@@ -86,8 +87,10 @@ def getConfiguration(self):
                 self.prefix = configDict['prefix']
                 self.extension = configDict['extension']
                 self.fillBlocks = configDict['fillBlocks']
-                # Convert fillBlocks to Boolean
+                self.endianSwap = configDict['endianSwap']
+                # Convert fillBlocks/endianSwap to Boolean
                 self.fillBlocks = bool(self.fillBlocks == "True")
+                self.endianSwap = bool(self.endianSwap == "True")
                 self.timeZone = configDict['timeZone']
                 self.defaultDir = configDict['defaultDir']
             except KeyError:
@@ -167,6 +170,7 @@ def processTape(self):
         logging.info('prefix: ' + self.prefix)
         logging.info('extension: ' + self.extension)
         logging.info('fill blocks: ' + str(self.fillBlocks))
+        logging.info('endian swap: ' + str(self.endianSwap))
 
         ## Acquisition start date/time
         acquisitionStart = shared.generateDateTime(self.timeZone)
@@ -251,6 +255,7 @@ def processTape(self):
         metadata['prefix'] = self.prefix
         metadata['extension'] = self.extension
         metadata['fillBlocks'] = self.fillBlocks
+        metadata['endianSwap'] = self.endianSwap
         metadata['acquisitionStart'] = acquisitionStart
         metadata['acquisitionEnd'] = acquisitionEnd
         metadata['successFlag'] = self.successFlag
@@ -302,9 +307,17 @@ def processFile(self):
             args.append('of='+ ofName)
             args.append('bs=' + str(self.blockSize))
 
-            if self.fillBlocks:
-                # Add conv=noerror,sync options to argument list
-                args.append('conv=noerror,sync')
+            if self.fillBlocks or self.endianSwap:
+                conversionOpts = []
+                if self.fillBlocks:
+                    # Add conv=noerror,sync options to argument list
+                    conversionOpts.append('noerror')
+                    conversionOpts.append('sync')
+                if self.endianSwap:
+                    # Add conv=swab for endian conversion
+                    conversionOpts.append('swab')
+
+                args.append('conv=' + ','.join(conversionOpts))
 
             ddStatus, ddOut, ddErr = shared.launchSubProcess(args)