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From: xx Z <xxz030811@gmail.com>
Date: Tue, 26 Aug 2025 20:34:59 +0800
Message-ID: <CA+aQVj+bq9iz-zM+s3F9_bDFGA_oZ41T-dHX=f=mMXhAP87K6w@mail.gmail.com>
Subject: Re: How to configure client-side TLS ciphers for streaming replication?
To: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: pgsql-general@lists.postgresql.org
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Thanks for your suggestion.
But I still want to know why we can't set "ssl_ciphers" on the client side.
This is still considered a security issue in some cases, and PostgreSQL has
mature capabilities on the master side to implement this functionality.

Greetings,
Yunfei Zhou

Laurenz Albe <laurenz.albe@cybertec.at>=E4=BA=8E2025=E5=B9=B48=E6=9C=8826=
=E6=97=A5 =E5=91=A8=E4=BA=8C20:17=E5=86=99=E9=81=93=EF=BC=9A

> On Tue, 2025-08-26 at 19:48 +0800, xx Z wrote:
> > Is there a way for a streaming replication standby (client) to restrict
> its list
> > of supported TLS ciphers, similar to how the ssl_ciphers parameter work=
s
> on the
> > primary server?
> > We need this for security compliance but can't find an equivalent
> setting for
> > the client-side connection in primary_conninfo.
>
> I don't think that there is a way to do that on the client side.
> But the streaming replication primary is surely under your control, so it
> should
> be sufficient to set "ssl_siphers" there.
>
> Yours,
> Laurenz Albe
>

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<div dir=3D"auto">Thanks for your suggestion.</div><div dir=3D"auto">But I =
still want to know why we can&#39;t set &quot;ssl_ciphers&quot; on the clie=
nt side.</div><div dir=3D"auto">This is still considered a security issue i=
n some cases, and PostgreSQL has mature capabilities on the master side to =
implement this functionality.</div><div dir=3D"auto"><br></div><div dir=3D"=
auto">Greetings,</div><div dir=3D"auto">Yunfei Zhou</div><div><br><div clas=
s=3D"gmail_quote gmail_quote_container"><div dir=3D"ltr" class=3D"gmail_att=
r">Laurenz Albe &lt;<a href=3D"mailto:laurenz.albe@cybertec.at">laurenz.alb=
e@cybertec.at</a>&gt;=E4=BA=8E2025=E5=B9=B48=E6=9C=8826=E6=97=A5 =E5=91=A8=
=E4=BA=8C20:17=E5=86=99=E9=81=93=EF=BC=9A<br></div><blockquote class=3D"gma=
il_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left-width:1px;border-le=
ft-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)">On Tue,=
 2025-08-26 at 19:48 +0800, xx Z wrote:<br>
&gt; Is there a way for a streaming replication standby (client) to restric=
t its list<br>
&gt; of supported TLS ciphers, similar to how the ssl_ciphers parameter wor=
ks on the<br>
&gt; primary server?<br>
&gt; We need this for security compliance but can&#39;t find an equivalent =
setting for<br>
&gt; the client-side connection in primary_conninfo.<br>
<br>
I don&#39;t think that there is a way to do that on the client side.<br>
But the streaming replication primary is surely under your control, so it s=
hould<br>
be sufficient to set &quot;ssl_siphers&quot; there.<br>
<br>
Yours,<br>
Laurenz Albe<br>
</blockquote></div></div>

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