From c2e5f4d1c16faa84a19906706481cf149769f320 Mon Sep 17 00:00:00 2001
From: Fujii Masao <fujii@postgresql.org>
Date: Thu, 9 Jul 2015 22:30:52 +0900
Subject: [PATCH] Make wal_compression PGC_SUSET rather than PGC_USERSET.
When enabling wal_compression, there is a risk to leak data similarly to
the BREACH and CRIME attacks on SSL where the compression ratio of
a full page image gives a hint of what is the existing data of this page.
This vulnerability is quite cumbersome to exploit in practice, but doable.
So this patch makes wal_compression PGC_SUSET in order to prevent
non-superusers from enabling it and exploiting the vulnerability while
DBA thinks the risk very seriously and disables it in postgresql.conf.
Back-patch to 9.5 where wal_compression was introduced.
---
doc/src/sgml/config.sgml | 1 +
src/backend/utils/misc/guc.c | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 4b7bd8a86e6..b91d6c75d27 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -2303,6 +2303,7 @@ include_dir 'conf.d'
<xref linkend="guc-full-page-writes"> is on or during a base backup.
A compressed page image will be decompressed during WAL replay.
The default value is <literal>off</>.
+ Only superusers can change this setting.
</para>
<para>
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 595a609989d..1bed5250a6c 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -995,7 +995,7 @@ static struct config_bool ConfigureNamesBool[] =
},
{
- {"wal_compression", PGC_USERSET, WAL_SETTINGS,
+ {"wal_compression", PGC_SUSET, WAL_SETTINGS,
gettext_noop("Compresses full-page writes written in WAL file."),
NULL
},
--
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