From 963d0db414ae2fbd11476bd638e7c62fb9e38d43 Mon Sep 17 00:00:00 2001
From: Philipp Gesang <philipp.gesang@intra2net.com>
Date: Tue, 28 Mar 2017 14:28:06 +0200
Subject: [PATCH] return collected fixed iv parts from .close() when encrypting

Provisional implementation for dumping the IVs in the info file
that will be superseded once the crypto context can be provided
to tarfile by the user.
---
 deltatar/crypto.py  |    2 +-
 deltatar/tarfile.py |   41 ++++++++++++++++++++++++-----------------
 2 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/deltatar/crypto.py b/deltatar/crypto.py
index 8c826b3..fa8a2cf 100755
--- a/deltatar/crypto.py
+++ b/deltatar/crypto.py
@@ -466,7 +466,7 @@ class Encrypt (Crypto):
                                    self.ctsize, self.enc.tag)
         if ok is False:
             raise Exception ("XXX error constructing header: %r" % hdr) ## we need to converge on a sensible error handling strategy
-        return data, hdr
+        return data, hdr, self.pfx
 
 
     def process (self, buf):
diff --git a/deltatar/tarfile.py b/deltatar/tarfile.py
index 1d84365..0431d5f 100644
--- a/deltatar/tarfile.py
+++ b/deltatar/tarfile.py
@@ -117,8 +117,9 @@ GNU_FORMAT = 1                  # GNU tar format
 PAX_FORMAT = 2                  # POSIX.1-2001 (pax) format
 DEFAULT_FORMAT = GNU_FORMAT
 
-DELTATAR_HEADER_VERSION    = 1
-DELTATAR_PARAMETER_VERSION = 1
+DELTATAR_HEADER_VERSION     = 1
+DELTATAR_PARAMETER_VERSION  = 1
+DELTATAR_PDTCRYPT_EXTENSION = "pdtcrypt"
 
 GZ_FMT_HEADER        = b"<BBBBLBB"
 GZ_MAGIC             = (0x1f, 0x8b) # 0o37, 0o213
@@ -163,8 +164,6 @@ PAX_NUMBER_FIELDS = {
     "size": int
 }
 
-VALID_ENCRYPTION_MODES = [ "aes" ]
-
 #---------------------------------------------------------
 # initialization
 #---------------------------------------------------------
@@ -603,7 +602,10 @@ class _Stream:
         Seek back to header position, read dummy bytes, finalize crypto
         obtaining the actual header, write header, seek back to current
         position.
+
+        Returns the list of IV fixed parts as used during encryption.
         """
+        fixed = None
         if      self.encryption is not None \
             and self.lasthdr    is not None :
             self.__sync ()
@@ -614,10 +616,11 @@ class _Stream:
             dpos = pos1 - self.lasthdr
             assert dpos == crypto.I2N_HDR_SIZE
             self.fileobj.seek_set (pos0)
-            data, hdr = self.encryption.done (dummy)
+            data, hdr, fixed = self.encryption.done (dummy)
             self.__write_to_file(hdr, pos=self.lasthdr)
             self.__write_to_file(data) # append remainder of data
             self.lasthdr = -1
+        return fixed
 
 
     def _finalize_write_gz (self):
@@ -759,27 +762,31 @@ class _Stream:
         """Close the _Stream object. No operation should be
            done on it afterwards.
         """
+        fixed = None
+
         if self.closed:
             return
 
         if self.mode == "w":
             self._finalize_write_gz ()
             self.__enc_write(self.buf)
-            self._finalize_write_encrypt ()
-
-        if close_fileobj and not self._extfileobj:
-            self.fileobj.close()
-
-        # read the zlib crc and length and check them
-        if not close_fileobj and self.mode == "r" and self.comptype == "gz":
-            read_crc = self.__read(4)
-            read_length = self.__read(4)
-            calculated_crc = self.crc
-            if struct.unpack("<L", read_crc)[0] != calculated_crc:
-                raise CompressionError("bad gzip crc")
+            fixed = self._finalize_write_encrypt ()
 
+        if close_fileobj is True:
+            if not self._extfileobj:
+                self.fileobj.close()
+        else:
+            # read the zlib crc and length and check them
+            if self.mode == "r" and self.comptype == "gz":
+                read_crc = self.__read(4)
+                read_length = self.__read(4)
+                calculated_crc = self.crc
+                if struct.unpack("<L", read_crc)[0] != calculated_crc:
+                    raise CompressionError("bad gzip crc")
         self.closed = True
 
+        return fixed
+
     def _init_read_gz(self):
         """Initialize for reading a gzip compressed fileobj.
         """
-- 
1.7.1