Provide Content-MD5 header support for attachments.

Fixes COUCHDB-558.

Thanks to Filipe Manana we now have checks for attachment transfer integrity
using the Content-MD5 header (or trailer). Use of this integrity check is
triggered by specifying a Content-MD5 header in your request with a value that
is a base64 encoded md5. For requests that are using a chunked Transfer-Encoding
it is also possible to use a trailer so that the Content-MD5 doesn't need to be
known before transfer. This works by specifying a header "Trailer:
Content-MD5" and then in the final chunk (the one with a size of zero) you can
specify a Content-MD5 with exactly the same format as in the request headers.

See the ETap test 130-attachments-md5.t for explicit examples of the request
messages.



git-svn-id: https://svn.apache.org/repos/asf/couchdb/trunk@891077 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 24 insertions, 2 deletions

diff --git a/src/couchdb/couch_httpd_db.erl b/src/couchdb/couch_httpd_db.erl
index e1c778a9..8b955c88 100644
--- a/src/couchdb/couch_httpd_db.erl
+++ b/src/couchdb/couch_httpd_db.erl
@@ -1043,8 +1043,9 @@ db_attachment_req(#httpd{method=Method}=Req, Db, DocId, FileNameParts)
                         undefined;
                     Length ->
                         list_to_integer(Length)
-                    end
-                    }]
+                    end,
+                md5 = get_md5_header(Req)
+            }]
     end,
 
     Doc = case extract_header_rev(Req, couch_httpd:qs_value(Req, "rev")) of
@@ -1084,6 +1085,27 @@ db_attachment_req(#httpd{method=Method}=Req, Db, DocId, FileNameParts)
 db_attachment_req(Req, _Db, _DocId, _FileNameParts) ->
     send_method_not_allowed(Req, "DELETE,GET,HEAD,PUT").
 
+
+get_md5_header(Req) ->
+    ContentMD5 = couch_httpd:header_value(Req, "Content-MD5"),
+    Length = couch_httpd:body_length(Req),
+    Trailer = couch_httpd:header_value(Req, "Trailer"),
+    case {ContentMD5, Length, Trailer} of
+        _ when is_list(ContentMD5) orelse is_binary(ContentMD5) ->
+            base64:decode(ContentMD5);
+        {_, chunked, undefined} ->
+            <<>>;
+        {_, chunked, _} ->
+            case re:run(Trailer, "\\bContent-MD5\\b", [caseless]) of
+                {match, _} ->
+                    md5_in_footer;
+                _ ->
+                    <<>>
+            end;
+        _ ->
+            <<>>
+    end.
+
 parse_doc_format(FormatStr) when is_binary(FormatStr) ->
     parse_doc_format(?b2l(FormatStr));
 parse_doc_format(FormatStr) when is_list(FormatStr) ->