From cc06e5f0e8724d7e5664b1232f5244334e1fa1fb Mon Sep 17 00:00:00 2001
From: Philipp Gesang <philipp.gesang@intra2net.com>
Date: Fri, 24 Feb 2017 10:50:03 +0100
Subject: [PATCH] make tarfile.py error out on invalid crypto modes and combos
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The tarfile stream ctor will simply gloss over encryption
requested by the caller unless it happens to exactly match the
string (!) “aes”. Furthermore, with non-gzip compression the
encryption will be ignored altogether.

Instead of deceiving the user about the encryption being applied,
have the ctor fail immediately on invalid combinations.
---
 deltatar/tarfile.py |   28 +++++++++++++++++++++++++---
 1 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/deltatar/tarfile.py b/deltatar/tarfile.py
index 07c33f8..8e937b4 100644
--- a/deltatar/tarfile.py
+++ b/deltatar/tarfile.py
@@ -53,7 +53,8 @@ import copy
 import re
 import operator
 
-from . import aescrypto
+#from . import aescrypto
+from . import crypto
 
 try:
     import grp, pwd
@@ -148,6 +149,8 @@ PAX_NUMBER_FIELDS = {
     "size": int
 }
 
+VALID_ENCRYPTION_MODES = [ "aes" ]
+
 #---------------------------------------------------------
 # initialization
 #---------------------------------------------------------
@@ -308,6 +311,9 @@ class InvalidHeaderError(HeaderError):
 class SubsequentHeaderError(HeaderError):
     """Exception for missing and invalid extended headers."""
     pass
+class InvalidEncryptionError(TarError):
+    """Exception for undefined crypto modes and combinations."""
+    pass
 
 #---------------------------
 # internal stream interface
@@ -343,6 +349,7 @@ class _LowLevelFile:
     def tell(self):
         return self.offset
 
+
 class _Stream:
     """Class that serves as an adapter between TarFile and
        a stream-like object.  The stream-like object only
@@ -393,6 +400,9 @@ class _Stream:
         self.bytes_written = 0
 
         try:
+            if enctype != "" and enctype not in VALID_ENCRYPTION_MODES:
+                raise InvalidEncryptionError("unsupported encryption mode %r"
+                                             % enctype)
             if comptype == "gz":
                 try:
                     import zlib
@@ -401,8 +411,8 @@ class _Stream:
                 self.zlib = zlib
                 if mode == "r":
                     if self.enctype == 'aes':
-                        self.encryption = aescrypto.AESCrypt(self.password,
-                                                            key_length=self.key_length)
+                        self.encryption = crypto.AES_GCM_context(self.password,
+                                                                 key_length=self.key_length)
                     self._init_read_gz()
                     self.exception = zlib.error
                 else:
@@ -410,6 +420,10 @@ class _Stream:
                 self.crc = zlib.crc32(b"") & 0xFFFFffff
 
             elif comptype == "bz2":
+                if self.enctype != "":
+                    raise InvalidEncryptionError("encryption mode %r not "
+                                                 "available for compression %s"
+                                                 % (enctype, comptype))
                 try:
                     import bz2
                 except ImportError:
@@ -422,6 +436,10 @@ class _Stream:
                     self.cmp = bz2.BZ2Compressor()
 
             elif comptype == 'xz':
+                if self.enctype != "":
+                    raise InvalidEncryptionError("encryption mode %r not "
+                                                 "available for compression %s"
+                                                 % (enctype, comptype))
                     try:
                         import lzma
                     except ImportError:
@@ -441,6 +459,10 @@ class _Stream:
                     self.__write_to_file(self.encryption.salt_str)
 
             elif comptype != "tar":
+                if self.enctype != "":
+                    raise InvalidEncryptionError("encryption mode %r not "
+                                                 "available for compression %s"
+                                                 % (enctype, comptype))
                 raise CompressionError("unknown compression type %r" % comptype)
 
         except:
-- 
1.7.1