diff --git a/lib/ansible/parsing/vault/__init__.py b/lib/ansible/parsing/vault/__init__.py index d8cf66feca..1d4eeef465 100644 --- a/lib/ansible/parsing/vault/__init__.py +++ b/lib/ansible/parsing/vault/__init__.py @@ -22,6 +22,7 @@ import shlex import shutil import sys import tempfile +import random from io import BytesIO from subprocess import call from ansible.errors import AnsibleError @@ -219,22 +220,90 @@ class VaultEditor: def __init__(self, password): self.vault = VaultLib(password) + + def _shred_file_custom(self, tmp_path): + """"Destroy a file, when shred (core-utils) is not available + + Unix `shred' destroys files "so that they can be recovered only with great difficulty with + specialised hardware, if at all". It is based on the method from the paper + "Secure Deletion of Data from Magnetic and Solid-State Memory", + Proceedings of the Sixth USENIX Security Symposium (San Jose, California, July 22-25, 1996). + + We do not go to that length to re-implement shred in Python; instead, overwriting with a block + of random data should suffice. + + See https://github.com/ansible/ansible/pull/13700 . + """ + + file_len = os.path.getsize(tmp_path) + max_chunk_len = min(1024*1024*2, file_len) + + passes = 3 + with open(tmp_path, "wb") as fh: + for _ in range(passes): + fh.seek(0, 0) + # get a random chunk of data, each pass with other length + chunk_len = random.randint(max_chunk_len/2, max_chunk_len) + data = os.urandom(chunk_len) + + for _ in range(0, file_len // chunk_len): + fh.write(data) + fh.write(data[:file_len % chunk_len]) + + assert(fh.tell() == file_len) # FIXME remove this assert once we have unittests to check its accuracy + os.fsync(fh) + + + def _shred_file(self, tmp_path): + """Securely destroy a decrypted file + Note standard limitations of GNU shred apply (For flash, overwriting would have no effect + due to wear leveling; for other storage systems, the async kernel->filesystem->disk calls never + guarantee data hits the disk; etc). Furthermore, if your tmp dirs is on tmpfs (ramdisks), + it is a non-issue. + + Nevertheless, some form of overwriting the data (instead of just removing the fs index entry) is + a good idea. If shred is not available (e.g. on windows, or no core-utils installed), fall back on + a custom shredding method. + """ + + if not os.path.isfile(tmp_path): + # file is already gone + return + + try: + r = call(['shred', tmp_path]) + except OSError as e: + # shred is not available on this system, or some other error occured. + r = 1 + + if r != 0: + # we could not successfully execute unix shred; therefore, do custom shred. + self._shred_file_custom(tmp_path) + + os.remove(tmp_path) + def _edit_file_helper(self, filename, existing_data=None, force_save=False): # Create a tempfile _, tmp_path = tempfile.mkstemp() if existing_data: - self.write_data(existing_data, tmp_path) + self.write_data(existing_data, tmp_path, shred=False) # drop the user into an editor on the tmp file - call(self._editor_shell_command(tmp_path)) + try: + call(self._editor_shell_command(tmp_path)) + except: + # whatever happens, destroy the decrypted file + self._shred_file(tmp_path) + raise + tmpdata = self.read_data(tmp_path) # Do nothing if the content has not changed if existing_data == tmpdata and not force_save: - os.remove(tmp_path) + self._shred_file(tmp_path) return # encrypt new data and write out to tmp @@ -258,7 +327,7 @@ class VaultEditor: ciphertext = self.read_data(filename) plaintext = self.vault.decrypt(ciphertext) - self.write_data(plaintext, output_file or filename) + self.write_data(plaintext, output_file or filename, shred=False) def create_file(self, filename): """ create a new encrypted file """ @@ -323,13 +392,21 @@ class VaultEditor: return data - def write_data(self, data, filename): + def write_data(self, data, filename, shred=True): + """write data to given path + + if shred==True, make sure that the original data is first shredded so + that is cannot be recovered + """ bytes = to_bytes(data, errors='strict') if filename == '-': sys.stdout.write(bytes) else: if os.path.isfile(filename): - os.remove(filename) + if shred: + self._shred_file(filename) + else: + os.remove(filename) with open(filename, "wb") as fh: fh.write(bytes) @@ -338,6 +415,7 @@ class VaultEditor: # overwrite dest with src if os.path.isfile(dest): prev = os.stat(dest) + # old file 'dest' was encrypted, no need to _shred_file os.remove(dest) shutil.move(src, dest)