adapt tag handling in decryption

diff --git a/deltatar/crypto.py b/deltatar/crypto.py
index c6eb711..17466ad 100755 (executable)
--- a/deltatar/crypto.py
+++ b/deltatar/crypto.py
@@ -203,13 +203,14 @@ def hdr_make (hdr):
 
 
 HDR_FMT = "I2n_header { version: %d, paramversion: %d, nacl: %s[%d]," \
-                      " iv: %s[%d], ctsize: %d }"
+                      " iv: %s[%d], ctsize: %d, tag: %s[%d]}"
 
 def hdr_fmt (h):
     return HDR_FMT % (h["version"], h["paramversion"],
                       binascii.hexlify (h["nacl"]), len(h["nacl"]),
                       binascii.hexlify (h["iv"]), len(h["iv"]),
-                      h["ctsize"])
+                      h["ctsize"],
+                      binascii.hexlify (h["tag"]), len(h["tag"]))
 
 
 def hex_spaced_of_bytes (b):
@@ -403,8 +404,8 @@ class Decrypt (Crypto):
         iv = hdr ["iv"]
         self.tag = hdr ["tag"]
         self.aes = Cipher \
-                        ( algorithms.AES (key)
-                        , modes.GCM (hdr["iv"])
+                        ( algorithms.AES (self.key)
+                        , modes.GCM (hdr["iv"], tag=self.tag)
                         , backend = default_backend ()) \
                         . decryptor ()
         # XXX figure out what we want for AAD. Filename (not known to stream)?
@@ -422,8 +423,14 @@ class Decrypt (Crypto):
         return self.next(hdr)
 
 
-    def done (self):
-        return self.aes.finalize_with_tag (self.tag)
+    def done (self, tag=None):
+        try:
+            if tag is None:
+                return True, self.aes.finalize ()
+            else:
+                return self.aes.finalize_with_tag (self.tag)
+        except crypto.cryptography.exceptions.InvalidTag as exn:
+            return False, repr (exn)
 
 
     def process (self, buf):