From 3ae9343ebe4f3b7ddcdafcee22c987e49dead451 Mon Sep 17 00:00:00 2001
From: Victor Shyba <victor1984@riseup.net>
Date: Wed, 15 Mar 2017 20:28:23 -0300
Subject: [feature] send tag header from server

---
 client/src/leap/soledad/client/_blobs.py |  7 ++++++-
 server/src/leap/soledad/server/_blobs.py | 16 ++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/client/src/leap/soledad/client/_blobs.py b/client/src/leap/soledad/client/_blobs.py
index 2cc06146..97d4c39c 100644
--- a/client/src/leap/soledad/client/_blobs.py
+++ b/client/src/leap/soledad/client/_blobs.py
@@ -198,12 +198,17 @@ class BlobManager(object):
         logger.info("Staring download of blob: %s" % blob_id)
         # TODO this needs to be connected in a tube
         uri = self.remote + self.user + '/' + blob_id
-        buf = DecrypterBuffer(doc_id, rev, self.secret)
         data = yield treq.get(uri)
 
         if data.code == 404:
             logger.warn("Blob not found in server: %s" % blob_id)
             defer.returnValue(None)
+        elif not data.headers.hasHeader('Tag'):
+            logger.error("Server didn't send a tag header for: %s" % blob_id)
+            defer.returnValue(None)
+        tag = data.headers.getRawHeaders('Tag')[0]
+        tag = base64.urlsafe_b64decode(tag)
+        buf = DecrypterBuffer(doc_id, rev, self.secret, tag)
 
         # incrementally collect the body of the response
         yield treq.collect(data, buf.write)
diff --git a/server/src/leap/soledad/server/_blobs.py b/server/src/leap/soledad/server/_blobs.py
index 3b840391..454ff5fe 100644
--- a/server/src/leap/soledad/server/_blobs.py
+++ b/server/src/leap/soledad/server/_blobs.py
@@ -26,6 +26,7 @@ environments.
 """
 import commands
 import os
+import base64
 
 from twisted.web import static
 from twisted.web import resource
@@ -66,6 +67,14 @@ class IBlobsBackend(Interface):
         :returns: a deferred that fires upon finishing.
         """
 
+    def tag_header(user, blob_id, request):
+        """
+        Adds a header 'Tag' with the last 20 bytes of the encoded file,
+        which contains the tag.
+
+        :returns: a deferred that fires upon finishing.
+        """
+
     def write_blob(user, blob_id, request):
         """
         Write blob to the storage, reading it from the passed request.
@@ -91,6 +100,12 @@ class FilesystemBlobsBackend(object):
     path = '/tmp/blobs/'
     quota = 200 * 1024  # in KB
 
+    def tag_header(self, user, blob_id, request):
+        with open(self._get_path(user, blob_id)) as doc_file:
+                doc_file.seek(-16, 2)
+                tag = base64.urlsafe_b64encode(doc_file.read())
+                request.responseHeaders.setRawHeaders('Tag', [tag])
+
     def read_blob(self, user, blob_id, request):
         print "USER", user
         print "BLOB_ID", blob_id
@@ -168,6 +183,7 @@ class BlobsResource(resource.Resource):
     def render_GET(self, request):
         print "GETTING", request.path
         user, blob_id = self._split_path(request.path)
+        self._handler.tag_header(user, blob_id, request)
         return self._handler.read_blob(user, blob_id, request)
 
     def render_PUT(self, request):
-- 
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