Merge branch 'ingela/maint-20/ssl/Bleichenbacher/OTP-14748' into maint-20

* ingela/maint-20/ssl/Bleichenbacher/OTP-14748:
  ssl: Prepare for release
  ssl: Countermeasurements for Bleichenbacher attack

1 files changed, 19 insertions, 2 deletions

diff --git a/lib/ssl/src/ssl_connection.erl b/lib/ssl/src/ssl_connection.erl
index b031d3d47b..b33ce63c32 100644
--- a/lib/ssl/src/ssl_connection.erl
+++ b/lib/ssl/src/ssl_connection.erl
@@ -1367,8 +1367,25 @@ server_certify_and_key_exchange(State0, Connection) ->
     request_client_cert(State2, Connection).
 
 certify_client_key_exchange(#encrypted_premaster_secret{premaster_secret= EncPMS},
-			    #state{private_key = Key} = State, Connection) ->
-    PremasterSecret = ssl_handshake:premaster_secret(EncPMS, Key),
+			    #state{private_key = Key, client_hello_version = {Major, Minor} = Version} = State, Connection) ->
+
+    %% Countermeasure for Bleichenbacher attack always provide some kind of premaster secret
+    %% and fail handshake later.RFC 5246 section 7.4.7.1.
+    PremasterSecret =
+        try ssl_handshake:premaster_secret(EncPMS, Key) of
+            Secret when erlang:byte_size(Secret) == ?NUM_OF_PREMASTERSECRET_BYTES ->
+                case Secret of
+                    <<?BYTE(Major), ?BYTE(Minor), _/binary>> -> %% Correct
+                        Secret;
+                    <<?BYTE(_), ?BYTE(_), Rest/binary>> -> %% Version mismatch
+                        <<?BYTE(Major), ?BYTE(Minor), Rest/binary>>
+                end;
+            _ -> %% erlang:byte_size(Secret) =/= ?NUM_OF_PREMASTERSECRET_BYTES
+                make_premaster_secret(Version, rsa)
+        catch 
+            #alert{description = ?DECRYPT_ERROR} ->
+                make_premaster_secret(Version, rsa)     
+        end,        
     calculate_master_secret(PremasterSecret, State, Connection, certify, cipher);
 
 certify_client_key_exchange(#client_diffie_hellman_public{dh_public = ClientPublicDhKey},