Hi, The attached patch enables SCRAM authentication for dblink connections when using dblink_fdw without requiring a plain-text password on user mapping properties. The implementation is very similar to what was implemented on postgres_fdw [0].
To make it more closer to what was implemented on postgres_fdw a refactor was needed on get connection routines. A connect_pg_server function was created to centralize all the logic to actually open the connection with the foreign server and then replace the duplicated code on dblink_get_conn and dblink_connect to just call this new function. The main reason for this refactor was to centralize the SCRAM logic in a single function, instead of checking if SCRAM is enabled on both functions. A new is_valid_dblink_fdw_option function was also created to check for valid dblink fdw options when creating a server with CREATE SERVER command. The is_valid_dblink_option function only checks for valid libpq options, and the use_scram_passthrough option is only valid on CREATE SERVER options. The documentation was also changed to include a new Foreign Data Wrapper section to describe the SCRAM pass-through feature. Thoughts? [0] https://www.postgresql.org/message-id/27b29a35-9b96-46a9-bc1a-914140869...@gmail.com -- Matheus Alcantara
v1-0002-dblink-Add-SCRAM-pass-through-authentication.patch
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v1-0001-dblink-refactor-get-connection-routines.patch
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