added support to password discovery during decryption

added support to decrypted filepath dstfile

added support to password discovery during decryption
added support to decrypted filepath dstfile
Federico Fantini
1 parent 82b49eb6
Showing 3 changed files with 45 additions and 14 deletions
oletools/crypto.py
oletools/msodde.py
oletools/olevba.py
@@ -33,7 +33,7 @@ potentially encrypted files::
             raise crypto.MaxCryptoNestingReached(crypto_nesting, filename)
         decrypted_file = None
         try:
-            decrypted_file = crypto.decrypt(input_file, passwords)
+            decrypted_file, correct_password = crypto.decrypt(input_file, passwords, decrypted_filepath)
             if decrypted_file is None:
                 raise crypto.WrongEncryptionPassword(input_file)
             # might still be encrypted, so call this again recursively
@@ -102,6 +102,7 @@ __version__ = &#39;0.60&#39;
 import sys
 import struct
 import os
+import shutil
 from os.path import splitext, isfile
 from tempfile import mkstemp
 import zipfile
@@ -314,7 +315,7 @@ def check_msoffcrypto():
     return msoffcrypto is not None
  
  
-def decrypt(filename, passwords=None, **temp_file_args):
+def decrypt(filename, passwords=None, decrypted_filepath=None, **temp_file_args):
     """
     Try to decrypt an encrypted file
  
@@ -331,7 +332,10 @@ def decrypt(filename, passwords=None, **temp_file_args):
                            `dirname` or `prefix`. `suffix` will default to
                            suffix of input `filename`, `prefix` defaults to
                            `oletools-decrypt-`; `text` will be ignored
-    :returns: name of the decrypted temporary file (type str) or `None`
+    :param decrypted_filepath: filepath of the decrypted file in case you want to
+                              preserve it
+    :returns: a tuple with the name of the decrypted temporary file (type str) or `None`
+              and the correct password or 'None'
     :raises: :py:class:`ImportError` if :py:mod:`msoffcrypto-tools` not found
     :raises: :py:class:`ValueError` if the given file is not encrypted
     """
@@ -370,6 +374,7 @@ def decrypt(filename, passwords=None, **temp_file_args):
             raise ValueError('Given input file {} is not encrypted!'
                              .format(filename))
  
+        correct_password = None
         for password in passwords:
             log.debug('Trying to decrypt with password {!r}'.format(password))
             write_descriptor = None
@@ -387,6 +392,7 @@ def decrypt(filename, passwords=None, **temp_file_args):
                 # decryption was successfull; clean up and return
                 write_handle.close()
                 write_handle = None
+                correct_password = password
                 break
             except Exception:
                 log.debug('Failed to decrypt', exc_info=True)
@@ -399,6 +405,15 @@ def decrypt(filename, passwords=None, **temp_file_args):
                 if decrypt_file and isfile(decrypt_file):
                     os.unlink(decrypt_file)
                 decrypt_file = None
-    # if we reach this, all passwords were tried without success
-    log.debug('All passwords failed')
-    return decrypt_file
+                correct_password = None
+
+    if decrypt_file and correct_password:
+        log.debug(f'Successfully decrypted the file with password: {correct_password}')
+        if decrypted_filepath:
+            if os.path.isdir(decrypted_filepath) and os.access(decrypted_filepath, os.W_OK):
+                log.info(f"Saving decrypted file in: {decrypted_filepath}")
+                shutil.copy(decrypt_file, decrypted_filepath)
+    else:
+        log.info('All passwords failed')
+
+    return decrypt_file, correct_password
@@ -271,6 +271,9 @@ def process_args(cmd_line_args=None):
     parser.add_argument("-p", "--password", type=str, action='append',
                         help='if encrypted office files are encountered, try '
                              'decryption with this password. May be repeated.')
+    parser.add_argument("--decrypted_filepath", dest='decrypted_filepath', type=str,
+                        default=None,
+                        help='save the decrypted file to this location.')
     filter_group = parser.add_argument_group(
         title='Filter which OpenXML field commands are returned',
         description='Only applies to OpenXML (e.g. docx) and rtf, not to OLE '
@@ -910,7 +913,7 @@ def process_file(filepath, field_filter_mode=None):
 # === MAIN =================================================================
  
  
-def process_maybe_encrypted(filepath, passwords=None, crypto_nesting=0,
+def process_maybe_encrypted(filepath, passwords=None, decrypted_filepath=None, crypto_nesting=0,
                             **kwargs):
     """
     Process a file that might be encrypted.
@@ -921,6 +924,8 @@ def process_maybe_encrypted(filepath, passwords=None, crypto_nesting=0,
  
     :param str filepath: path to file on disc.
     :param passwords: list of passwords (str) to try for decryption or None
+    :param decrypted_filepath: filepath of the decrypted file in case you want to
+                               preserve it
     :param int crypto_nesting: How many decryption layers were already used to
                                get the given file.
     :param kwargs: same as :py:func:`process_file`
@@ -949,12 +954,14 @@ def process_maybe_encrypted(filepath, passwords=None, crypto_nesting=0,
         passwords = list(passwords) + crypto.DEFAULT_PASSWORDS
     try:
         logger.debug('Trying to decrypt file')
-        decrypted_file = crypto.decrypt(filepath, passwords)
+        decrypted_file, correct_password = crypto.decrypt(filepath, passwords, decrypted_filepath)
+        if correct_password:
+            logger.info(f"The correct password is: {correct_password}")
         if not decrypted_file:
             logger.error('Decrypt failed, run with debug output to get details')
             raise crypto.WrongEncryptionPassword(filepath)
         logger.info('Analyze decrypted file')
-        result = process_maybe_encrypted(decrypted_file, passwords,
+        result = process_maybe_encrypted(decrypted_file, passwords, decrypted_filepath,
                                          crypto_nesting+1, **kwargs)
     finally:     # clean up
         try:     # (maybe file was not yet created)
@@ -990,7 +997,7 @@ def main(cmd_line_args=None):
     return_code = 1
     try:
         text = process_maybe_encrypted(
-            args.filepath, args.password,
+            args.filepath, args.password, args.decrypted_filepath,
             field_filter_mode=args.field_filter_mode)
         return_code = 0
     except Exception as exc:
@@ -3473,15 +3473,18 @@ class VBA_Parser(object):
             self.is_encrypted = crypto.is_encrypted(self.ole_file)
         return self.is_encrypted
  
-    def decrypt_file(self, passwords_list=None):
+    def decrypt_file(self, passwords_list=None, decrypted_filepath=None):
         decrypted_file = None
+        correct_password = None
         if self.detect_is_encrypted():
             passwords = crypto.DEFAULT_PASSWORDS
             if passwords_list and isinstance(passwords_list, list):
                 passwords.extend(passwords_list)
-            decrypted_file = crypto.decrypt(self.filename, passwords)
+            decrypted_file, correct_password = crypto.decrypt(self.filename, passwords, decrypted_filepath)
+            if correct_password:
+                log.info(f"The correct password is: {correct_password}")
  
-        return decrypted_file
+        return decrypted_file, correct_password
  
     def encode_string(self, unicode_str):
         """
@@ -4370,6 +4373,9 @@ def parse_args(cmd_line_args=None):
                         default=None,
                         help='if the file is a zip archive, open all files '
                              'from it, using the provided password.')
+    parser.add_argument("--decrypted_filepath", dest='decrypted_filepath', type=str,
+                        default=None,
+                        help='save the decrypted file to this location.')
     parser.add_argument("-p", "--password", type=str, action='append',
                         default=[],
                         help='if encrypted office files are encountered, try '
@@ -4551,10 +4557,13 @@ def process_file(filename, data, container, options, crypto_nesting=0):
     try:
         log.debug('Checking encryption passwords {}'.format(options.password))
         passwords = options.password + crypto.DEFAULT_PASSWORDS
-        decrypted_file = crypto.decrypt(filename, passwords)
+        log.debug('Checking decrypted filepath {}'.format(options.decrypted_filepath))
+
+        decrypted_file, correct_password = crypto.decrypt(filename, passwords, options.decrypted_filepath)
         if not decrypted_file:
             log.error('Decrypt failed, run with debug output to get details')
             raise crypto.WrongEncryptionPassword(filename)
+        log.info(f'The correct password is: {correct_password}')
         log.info('Working on decrypted file')
         return process_file(decrypted_file, data, container or filename,
                             options, crypto_nesting+1)