Re: How to configure client-side TLS ciphers for streaming replication?

> On 26 Aug 2025, at 22:16, Laurenz Albe <laurenz.albe@cybertec.at> wrote:
> 
> On Tue, 2025-08-26 at 20:34 +0800, xx Z wrote:
>> Thanks for your suggestion.
>> But I still want to know why we can't set "ssl_ciphers" on the client side.
> 
> I'd say because nobody implemented it, perhaps because nobody felt the need.

I think the former is a highly likely suspect here.

>> This is still considered a security issue in some cases, and PostgreSQL has
>> mature capabilities on the master side to implement this functionality.
> 
> That sounds to me like some moderately clueful security auditor is looking
> for a nit to pick.  If you do streaming replication, and you control the
> ciphers on the primary server, what added security benefit do you get by
> controlling the ciphers on the standby server (the client) as well?

I would place this above nitpicking, but I also don't have a clear idea of an
attack (if I did I'd fix it..).  TLS is riddled with weird cases involving
network middleboxes (usually very enterprisy) so insisting on control isn't
necessarily a bad thing.

--
Daniel Gustafsson