postgres.git / summary / log / commit / refs
commit 99f205407e85e1e54b1a89c0453c64ec3df3ed2d
Author: Jacob Champion <jchampion@postgresql.org>
Commit: Noah Misch <noah@leadboat.com>
Date: Mon Aug 10 13:38:30 2026 +0000
Add an output_plugin_libraries GUC to bless trusted output plugins
REPLICATION users were not previously subject to restrictions on output
plugin paths, so they were able to bypass LOAD-time protections during
logical decoding. Unfortunately, adding the standard LOAD restrictions
now would retroactively require all third-party output plugins to be
installed under the $libdir/plugins directory. This would prevent the
use of dynamic_library_path, introduce a wire incompatibility for
clients, and require all plugin authors to check that their libraries
are safe for use by any unprivileged user; we want to avoid that.
Instead, introduce an output_plugin_libraries GUC so that DBAs can
specify the output plugins that are trusted for use in logical decoding.
For simplicity, superusers are subject to the restriction as well
(though they're free to modify the GUC at will during a session, so no
power is actually lost).
The default setting is 'pgoutput, test_decoding'. If other third-party
plugins are in use, DBAs will need to modify this parameter after they
update. Some pointers have been added to the documentation to assist
with this.
Author: Jacob Champion <jacob.champion@enterprisedb.com>
Reported-by: Vladimir Tokarev <vladimirelitokarev@gmail.com>
Reported-by: Yu Kunpeng <yu443940816@live.com>
Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de>
Reviewed-by: Noah Misch <noah@leadboat.com>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Backpatch-through: 14
Security: CVE-2026-6471
contrib/test_decoding/expected/permissions.out | 11 ++++
contrib/test_decoding/expected/slot.out | 3 +
contrib/test_decoding/sql/permissions.sql | 8 +++
contrib/test_decoding/sql/slot.sql | 3 +
doc/src/sgml/config.sgml | 57 +++++++++++++++++++
doc/src/sgml/logical-replication.sgml | 9 +++
src/backend/replication/logical/logical.c | 76 +++++++++++++++++++++++++-
src/backend/utils/misc/guc.c | 12 ++++
src/backend/utils/misc/postgresql.conf.sample | 1 +
src/bin/pg_dump/dumputils.c | 1 +
src/include/replication/logical.h | 3 +
src/test/subscription/t/100_bugs.pl | 28 +++++++++-
12 files changed, 209 insertions(+), 3 deletions(-)
diff --git a/contrib/test_decoding/expected/permissions.out b/contrib/test_decoding/expected/permissions.out
index ed97f81dda5..9b0670268ee 100644
--- a/contrib/test_decoding/expected/permissions.out
+++ b/contrib/test_decoding/expected/permissions.out
@@ -29,6 +29,17 @@ SELECT pg_drop_replication_slot('regression_slot');
(1 row)
RESET ROLE;
+-- no users can load an untrusted plugin
+SET output_plugin_libraries = pgoutput;
+SET ROLE regress_lr_replication;
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+ERROR: library "test_decoding" may not be used as an output plugin
+HINT: If it is safe for all REPLICATION users to use this library as an output plugin, add it to "output_plugin_libraries" and reload the server configuration.
+RESET ROLE;
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+ERROR: library "test_decoding" may not be used as an output plugin
+HINT: If it is safe for all REPLICATION users to use this library as an output plugin, add it to "output_plugin_libraries" and reload the server configuration.
+RESET output_plugin_libraries;
-- replication user can control replication
SET ROLE regress_lr_replication;
SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
diff --git a/contrib/test_decoding/expected/slot.out b/contrib/test_decoding/expected/slot.out
index 63a9940f73a..6faeebfd8ab 100644
--- a/contrib/test_decoding/expected/slot.out
+++ b/contrib/test_decoding/expected/slot.out
@@ -30,8 +30,11 @@ SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot_t2', 'tes
init
(1 row)
+BEGIN;
+SET LOCAL output_plugin_libraries = nonexistent;
SELECT pg_create_logical_replication_slot('foo', 'nonexistent');
ERROR: could not access file "nonexistent": No such file or directory
+ROLLBACK;
-- here we want to start a new session and wait till old one is gone
select pg_backend_pid() as oldpid \gset
\c -
diff --git a/contrib/test_decoding/sql/permissions.sql b/contrib/test_decoding/sql/permissions.sql
index 312b5145937..fee36f5a096 100644
--- a/contrib/test_decoding/sql/permissions.sql
+++ b/contrib/test_decoding/sql/permissions.sql
@@ -15,6 +15,14 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'inc
SELECT pg_drop_replication_slot('regression_slot');
RESET ROLE;
+-- no users can load an untrusted plugin
+SET output_plugin_libraries = pgoutput;
+SET ROLE regress_lr_replication;
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+RESET ROLE;
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+RESET output_plugin_libraries;
+
-- replication user can control replication
SET ROLE regress_lr_replication;
SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
diff --git a/contrib/test_decoding/sql/slot.sql b/contrib/test_decoding/sql/slot.sql
index 1aa27c56674..f4d2b0cd557 100644
--- a/contrib/test_decoding/sql/slot.sql
+++ b/contrib/test_decoding/sql/slot.sql
@@ -9,7 +9,10 @@ SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot_p', 'test
SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot_t2', 'test_decoding', true);
+BEGIN;
+SET LOCAL output_plugin_libraries = nonexistent;
SELECT pg_create_logical_replication_slot('foo', 'nonexistent');
+ROLLBACK;
-- here we want to start a new session and wait till old one is gone
select pg_backend_pid() as oldpid \gset
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 16a9355cc86..46ad873442a 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4247,6 +4247,63 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows
</listitem>
</varlistentry>
+ <varlistentry id="guc-output-plugin-libraries" xreflabel="output_plugin_libraries">
+ <term><varname>output_plugin_libraries</varname> (<type>string</type>)
+ <indexterm>
+ <primary><varname>output_plugin_libraries</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Lists the libraries installed in <xref linkend="guc-dynamic-library-path"/>
+ that are also trusted for use as logical output plugins by replication
+ clients. Any <link linkend="logicaldecoding-example">logical decoding</link>
+ or <link linkend="protocol-replication">replication</link> requests for
+ other libraries will be refused. All users are subject to this
+ restriction. The default is <literal>'pgoutput, test_decoding'</literal>,
+ which are the two logical output plugins included in the standard
+ <productname>PostgreSQL</productname> distribution.
+ </para>
+ <para>
+ The format is a comma-separated list of library names, where each name
+ is interpreted as for the <link linkend="sql-load"><command>LOAD</command></link>
+ command (but logical decoding clients must specify a plugin name that
+ <emphasis>exactly</emphasis> matches an entry in the list, without
+ variations in case or path structure). Whitespace between entries is
+ ignored; surround a library name with double quotes if you need to
+ include whitespace or commas in the name.
+ </para>
+ <para>
+ It is the responsibility of the server administrator to ensure that
+ libraries added to this list do not unintentionally give additional
+ privileges to non-superusers when they are loaded into the server.
+ </para>
+ <note>
+ <para>
+ When updating the server from a version that does not have the
+ <literal>output_plugin_libraries</literal> parameter, the following
+ query can help construct the list of plugins that are required by all
+ persistent logical replication slots:
+<programlisting>
+SELECT DISTINCT plugin FROM pg_replication_slots WHERE plugin IS NOT NULL;
+</programlisting>
+ Review the list carefully for safety before adjusting
+ <literal>output_plugin_libraries</literal>.
+ </para>
+ <para>
+ The above query can only display plugins which were successfully
+ added to replication slots at some point in the past. Newly refused
+ requests will appear in the logs with a message similar to
+<programlisting>
+ERROR: library "..." may not be used as an output plugin
+DETAIL: The configuration parameter "output_plugin_libraries" (currently 'pgoutput, test_decoding') does not name this library as a trusted output plugin.
+HINT: If it is safe for all REPLICATION users to use this library as an output plugin, add it to "output_plugin_libraries" and reload the server configuration.
+</programlisting>
+ </para>
+ </note>
+ </listitem>
+ </varlistentry>
+
<varlistentry id="guc-wal-keep-size" xreflabel="wal_keep_size">
<term><varname>wal_keep_size</varname> (<type>integer</type>)
<indexterm>
diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index d44eeca779a..55d7a849674 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1561,6 +1561,15 @@ CONTEXT: processing remote data for replication origin "pg_16395" during "INSER
and it must have the <literal>LOGIN</literal> attribute.
</para>
+ <para>
+ The name of the output plugin used by the replication connection must be
+ included in the server's <xref linkend="guc-output-plugin-libraries"/>. (For
+ subscriptions, the plugin name that is used is <literal>pgoutput</literal>.)
+ Superusers may modify the trusted list per-connection, by including
+ <literal>options=-coutput_plugin_libraries=...</literal> in the connection
+ string.
+ </para>
+
<para>
In order to be able to copy the initial table data, the role used for the
replication connection must have the <literal>SELECT</literal> privilege on
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index 12371d379e9..d796abbde78 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -41,7 +41,9 @@
#include "storage/proc.h"
#include "storage/procarray.h"
#include "utils/builtins.h"
+#include "utils/guc.h"
#include "utils/memutils.h"
+#include "utils/varlena.h"
/* data for errcontext callback */
typedef struct LogicalErrorCallbackState
@@ -51,6 +53,9 @@ typedef struct LogicalErrorCallbackState
XLogRecPtr report_location;
} LogicalErrorCallbackState;
+/* GUC variables */
+char *output_plugin_libraries_string;
+
/* wrappers around output plugin callbacks */
static void output_plugin_error_callback(void *arg);
static void startup_cb_wrapper(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
@@ -175,7 +180,72 @@ StartupDecodingContext(List *output_plugin_options,
* now.
*/
if (!fast_forward)
- LoadOutputPlugin(&ctx->callbacks, NameStr(slot->data.plugin));
+ {
+ /*
+ * Before loading this library, make sure it's been blessed for
+ * logical decoding.
+ */
+ const char *plugin = NameStr(slot->data.plugin);
+ bool plugin_allowed = false;
+
+ if (output_plugin_libraries_string && output_plugin_libraries_string[0])
+ {
+ /* Check this plugin against output_plugin_libraries. */
+ char *rawstring;
+ List *elemlist = NIL;
+ ListCell *lc;
+
+ /* Need a modifiable copy */
+ rawstring = pstrdup(output_plugin_libraries_string);
+
+ if (!SplitGUCList(rawstring, ',', &elemlist))
+ {
+ /* syntax error in list */
+ ereport(LOG,
+ (errcode(ERRCODE_SYNTAX_ERROR),
+ errmsg("invalid list syntax in parameter \"%s\"",
+ "output_plugin_libraries")));
+
+ list_free(elemlist);
+ elemlist = NIL;
+ }
+
+ foreach(lc, elemlist)
+ {
+ char *allowed = lfirst(lc);
+
+ if (strcmp(allowed, plugin) == 0)
+ {
+ plugin_allowed = true;
+ break;
+ }
+ }
+
+ list_free(elemlist);
+ pfree(rawstring);
+ }
+
+ if (!plugin_allowed)
+ {
+ /*
+ * Use the same error message as check_restricted_library_name(),
+ * but provide additional context for the DBA in the logs. (The
+ * HINT will be sent to the client, but that's not a secret.)
+ */
+ ereport(ERROR,
+ errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+ errmsg("library \"%s\" may not be used as an output plugin",
+ plugin),
+ /*- translator: The second %s is the value of the output_plugin_libraries GUC, which may contain whitespace, commas, and double-quotes (") */
+ errdetail_log("The configuration parameter \"%s\" (currently '%s') does not name this library as a trusted output plugin.",
+ "output_plugin_libraries",
+ output_plugin_libraries_string),
+ errhint("If it is safe for all REPLICATION users to use this library as an output plugin, add it to \"%s\" and reload the server configuration.",
+ "output_plugin_libraries"));
+ }
+
+ LoadOutputPlugin(&ctx->callbacks, plugin);
+ }
/*
* Now that the slot's xmin has been set, we can announce ourselves as a
@@ -691,7 +761,9 @@ OutputPluginUpdateProgress(struct LogicalDecodingContext *ctx,
/*
* Load the output plugin, lookup its output plugin init function, and check
- * that it provides the required callbacks.
+ * that it provides the required callbacks. The caller must have checked that
+ * the current user has the necessary privileges to load the given plugin;
+ * standard LOAD restrictions are not applied here.
*/
static void
LoadOutputPlugin(OutputPluginCallbacks *callbacks, const char *plugin)
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index ccaa99e9089..6225fe78a20 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -79,6 +79,7 @@
#include "postmaster/startup.h"
#include "postmaster/syslogger.h"
#include "postmaster/walwriter.h"
+#include "replication/logical.h"
#include "replication/logicallauncher.h"
#include "replication/reorderbuffer.h"
#include "replication/slot.h"
@@ -4723,6 +4724,17 @@ static struct config_string ConfigureNamesString[] =
check_restrict_nonsystem_relation_kind, assign_restrict_nonsystem_relation_kind, NULL
},
+ {
+ {"output_plugin_libraries", PGC_SUSET, REPLICATION_SENDING,
+ gettext_noop("Lists libraries that may be named as logical decoding output plugins."),
+ gettext_noop("Users with REPLICATION privileges may only use plugins in this list when creating logical replication slots."),
+ GUC_LIST_INPUT | GUC_LIST_QUOTE | GUC_SUPERUSER_ONLY
+ },
+ &output_plugin_libraries_string,
+ "pgoutput, test_decoding",
+ NULL, NULL, NULL
+ },
+
/* End-of-list marker */
{
{NULL, 0, 0, NULL, NULL}, NULL, NULL, NULL, NULL, NULL
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 7705dbc181e..d1e763e9794 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -744,6 +744,7 @@
#dynamic_library_path = '$libdir'
#gin_fuzzy_search_limit = 0
+#output_plugin_libraries = 'pgoutput, test_decoding' # approved plugins for logical decoding
#------------------------------------------------------------------------------
diff --git a/src/bin/pg_dump/dumputils.c b/src/bin/pg_dump/dumputils.c
index 9dd406b9c11..c98675864dc 100644
--- a/src/bin/pg_dump/dumputils.c
+++ b/src/bin/pg_dump/dumputils.c
@@ -727,6 +727,7 @@ bool
variable_is_guc_list_quote(const char *name)
{
if (pg_strcasecmp(name, "local_preload_libraries") == 0 ||
+ pg_strcasecmp(name, "output_plugin_libraries") == 0 ||
pg_strcasecmp(name, "search_path") == 0 ||
pg_strcasecmp(name, "session_preload_libraries") == 0 ||
pg_strcasecmp(name, "shared_preload_libraries") == 0 ||
diff --git a/src/include/replication/logical.h b/src/include/replication/logical.h
index 030ce1eef5b..4ad828da110 100644
--- a/src/include/replication/logical.h
+++ b/src/include/replication/logical.h
@@ -150,4 +150,7 @@ extern bool filter_by_origin_cb_wrapper(LogicalDecodingContext *ctx, RepOriginId
extern void ResetLogicalStreamingState(void);
extern void UpdateDecodingStats(LogicalDecodingContext *ctx);
+/* GUCs */
+extern PGDLLIMPORT char *output_plugin_libraries_string;
+
#endif
diff --git a/src/test/subscription/t/100_bugs.pl b/src/test/subscription/t/100_bugs.pl
index eee297efa2b..9ffc0059aa5 100644
--- a/src/test/subscription/t/100_bugs.pl
+++ b/src/test/subscription/t/100_bugs.pl
@@ -415,6 +415,32 @@ $result = $node_subscriber->safe_psql('postgres',
is($result, qq(2|f
3|t), 'check replicated update on subscriber');
+my $publisher_host = $node_publisher->host;
+my $publisher_port = $node_publisher->port;
+my $connstr_db =
+ "host=$publisher_host port=$publisher_port replication=database dbname=postgres";
+
+# REPLICATION users should not be able to bypass LOAD restrictions.
+$node_publisher->safe_psql(
+ 'postgres', qq(
+ CREATE USER repluser REPLICATION;
+));
+
+my ($ret, $stdout, $stderr) = $node_publisher->psql(
+ 'postgres',
+ qq[
+ SET ROLE repluser;
+ CREATE_REPLICATION_SLOT fail_slot LOGICAL regress;',
+ ],
+ timeout => $PostgreSQL::Test::Utils::timeout_default,
+ extra_params => [ '-d', $connstr_db ]);
+
+is($ret, 3, 'loading unblessed output plugin fails');
+like(
+ $stderr,
+ qr/ERROR: library "regress" may not be used as an output plugin/,
+ 'loading unblessed output plugin fails: stderr');
+
$node_publisher->stop('fast');
$node_subscriber->stop('fast');
@@ -435,7 +461,7 @@ $node_publisher->safe_psql(
CREATE SUBSCRIPTION regress_sub1 CONNECTION '$publisher_connstr' PUBLICATION regress_pub WITH (connect=false);
));
-my ($ret, $stdout, $stderr) =
+($ret, $stdout, $stderr) =
$node_publisher->psql('postgres', q{DROP SUBSCRIPTION regress_sub1});
isnt($ret, 0, "replication slot does not exist: exit code not 0");
[parent: e43e74756b4c]