d9bba27c8b
When using a libpq client linked with OpenSSL 1.0.1 or older to connect to a backend linked with OpenSSL 1.0.2 or newer, the server would send SCRAM-SHA-256-PLUS and SCRAM-SHA-256 as valid mechanisms for the SASL exchange, and the client would choose SCRAM-SHA-256-PLUS even if it does not support channel binding, leading to a confusing error. In this case, what the client ought to do is switch to SCRAM-SHA-256 so as the authentication can move on and succeed. So for a SCRAM authentication over SSL, here are all the cases present and how we deal with them using libpq: 1) Server supports channel binding, it sends SCRAM-SHA-256-PLUS and SCRAM-SHA-256 as allowed mechanisms. 1-1) Client supports channel binding, chooses SCRAM-SHA-256-PLUS. 1-2) Client does not support channel binding, chooses SCRAM-SHA-256. 2) Server does not support channel binding, sends SCRAM-SHA-256 as allowed mechanism. 2-1) Client supports channel binding, still it has no choice but to choose SCRAM-SHA-256. 2-2) Client does not support channel binding, it chooses SCRAM-SHA-256. In all these scenarios the connection should succeed, and the one which was handled incorrectly prior this commit is 1-2), causing the connection attempt to fail because client chose SCRAM-SHA-256-PLUS over SCRAM-SHA-256. Reported-by: Hugh Ranalli Diagnosed-by: Peter Eisentraut Author: Michael Paquier Reviewed-by: Peter Eisentraut Discussion: https://postgr.es/m/CAAhbUMO89SqUk-5mMY+OapgWf-twF2NA5sCucbHEzMfGbvcepA@mail.gmail.com Backpatch-through: 11
PostgreSQL Database Management System ===================================== This directory contains the source code distribution of the PostgreSQL database management system. PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.