v8-0001-Add-password_expire_warning-GUC-to-warn-clients.patch

From 9b4fe1f5fa7d55799f95be356625fee0400cb77e Mon Sep 17 00:00:00 2001
From: Gilles Darold <gilles@darold.net>
Date: Thu, 8 Jan 2026 13:23:10 +0100
Subject: [PATCH v8] Add password_expire_warning GUC to warn clients

Introduce a new server configuration parameter, password_expire_warning,
which controls how many days before a role's password expiration a
warning message is sent to the client upon successful connection.

Author: Gilles Darold <gilles@darold.net>
---
 doc/src/sgml/config.sgml                      | 16 ++++++++
 src/backend/libpq/crypt.c                     | 39 +++++++++++++++----
 src/backend/utils/init/miscinit.c             |  1 +
 src/backend/utils/init/postinit.c             |  7 ++++
 src/backend/utils/misc/guc_parameters.dat     |  9 +++++
 src/backend/utils/misc/postgresql.conf.sample |  1 +
 src/include/libpq/crypt.h                     |  3 ++
 src/include/libpq/libpq-be.h                  |  9 +++++
 8 files changed, 78 insertions(+), 7 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 0fad34da6eb..9d1361dfad3 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1106,6 +1106,22 @@ include_dir 'conf.d'
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-password-expire-warning" xreflabel="password_expire_warning">
+      <term><varname>password_expire_warning</varname> (<type>integer</type>)
+      <indexterm>
+       <primary><varname>password_expire_warning</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        Controls how many time before a role's password expiration a <literal>WARNING</literal>
+        message is sent to the client upon successful connection. It requires that
+        a <command>VALID UNTIL</command> date is set for the user. A value of <literal>0d</literal>
+        disable this behavior. The default value is <literal>7d</literal> and the max value <literal>30d</literal>.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-password-encryption" xreflabel="password_encryption">
       <term><varname>password_encryption</varname> (<type>enum</type>)
       <indexterm>
diff --git a/src/backend/libpq/crypt.c b/src/backend/libpq/crypt.c
index 4c1052b3d42..147c8834380 100644
--- a/src/backend/libpq/crypt.c
+++ b/src/backend/libpq/crypt.c
@@ -20,6 +20,7 @@
 #include "common/scram-common.h"
 #include "libpq/crypt.h"
 #include "libpq/scram.h"
+#include "postmaster/postmaster.h"
 #include "utils/builtins.h"
 #include "utils/syscache.h"
 #include "utils/timestamp.h"
@@ -27,6 +28,12 @@
 /* Enables deprecation warnings for MD5 passwords. */
 bool		md5_password_warnings = true;
 
+/*
+ * Threshold (in seconds) before password expiration to emit a warning
+ * at login (0 = disabled; default 7 days)
+ */
+int		password_expire_warning = 604800;
+
 /*
  * Fetch stored password for a user, for authentication.
  *
@@ -70,14 +77,32 @@ get_role_password(const char *role, const char **logdetail)
 
 	ReleaseSysCache(roleTup);
 
-	/*
-	 * Password OK, but check to be sure we are not past rolvaliduntil
-	 */
-	if (!isnull && vuntil < GetCurrentTimestamp())
+	if (!isnull)
 	{
-		*logdetail = psprintf(_("User \"%s\" has an expired password."),
-							  role);
-		return NULL;
+		TimestampTz	now = GetCurrentTimestamp();
+
+		/*
+		 * Password OK, but check to be sure we are not past rolvaliduntil
+		 */
+		if (vuntil < now)
+		{
+			*logdetail = psprintf(_("User \"%s\" has an expired password."),
+								  role);
+			return NULL;
+		}
+
+		/*
+		 * Password OK, but check if rolvaliduntil is less than GUC
+		 * password_expire_warning days to send a warning to the client
+		 */
+		if (password_expire_warning > 0 && vuntil < PG_INT64_MAX)
+		{
+			TimestampTz result = (vuntil - now) / USECS_PER_SEC; /* in seconds */
+
+			if (result <= (TimestampTz) password_expire_warning)
+				MyClientConnectionInfo.warning_message =
+						psprintf("your password will expire in %d day(s)", (int) (result / 86400));
+		}
 	}
 
 	return shadow_pass;
diff --git a/src/backend/utils/init/miscinit.c b/src/backend/utils/init/miscinit.c
index 563f20374ff..24737c95c28 100644
--- a/src/backend/utils/init/miscinit.c
+++ b/src/backend/utils/init/miscinit.c
@@ -1089,6 +1089,7 @@ RestoreClientConnectionInfo(char *conninfo)
 
 	/* Copy the fields back into place */
 	MyClientConnectionInfo.authn_id = NULL;
+	MyClientConnectionInfo.warning_message = NULL;
 	MyClientConnectionInfo.auth_method = serialized.auth_method;
 
 	if (serialized.authn_id_len >= 0)
diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index 52c05a9d1d5..d0d5c87d4ea 100644
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -1229,6 +1229,13 @@ InitPostgres(const char *in_dbname, Oid dboid,
 	if (!bootstrap)
 		pgstat_bestart_final();
 
+	/*
+	 * Emit a warning message to the client when set, for example
+	 * to warn the user that the password will expire.
+	 */
+	if (MyClientConnectionInfo.warning_message)
+		ereport(WARNING, (errmsg("%s", MyClientConnectionInfo.warning_message)));
+
 	/* close the transaction we started above */
 	if (!bootstrap)
 		CommitTransactionCommand();
diff --git a/src/backend/utils/misc/guc_parameters.dat b/src/backend/utils/misc/guc_parameters.dat
index 7c60b125564..15e0d10e162 100644
--- a/src/backend/utils/misc/guc_parameters.dat
+++ b/src/backend/utils/misc/guc_parameters.dat
@@ -2248,6 +2248,15 @@
   options => 'password_encryption_options',
 },
 
+{ name => 'password_expire_warning', type => 'int', context => 'PGC_SIGHUP', group => 'CONN_AUTH_AUTH',
+  short_desc => 'Sets how many time before password expire to emit a warning at client connection. Default is 7 days, 0 means no warning.',
+  flags => 'GUC_UNIT_S',
+  variable => 'password_expire_warning',
+  boot_val => '604800',
+  min => '0',
+  max => '2592000',
+},
+
 { name => 'plan_cache_mode', type => 'enum', context => 'PGC_USERSET', group => 'QUERY_TUNING_OTHER',
   short_desc => 'Controls the planner\'s selection of custom or generic plan.',
   long_desc => 'Prepared statements can have custom and generic plans, and the planner will attempt to choose which is better.  This can be set to override the default behavior.',
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index dc9e2255f8a..ca59b7cc1f6 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -98,6 +98,7 @@
 #scram_iterations = 4096
 #md5_password_warnings = on             # display md5 deprecation warnings?
 #oauth_validator_libraries = '' # comma-separated list of trusted validator modules
+#password_expire_warning = '7d'         # 0-30d time before password expiration to emit a warning
 
 # GSSAPI using Kerberos
 #krb_server_keyfile = 'FILE:${sysconfdir}/krb5.keytab'
diff --git a/src/include/libpq/crypt.h b/src/include/libpq/crypt.h
index f01886e1098..420f8053255 100644
--- a/src/include/libpq/crypt.h
+++ b/src/include/libpq/crypt.h
@@ -28,6 +28,9 @@
 /* Enables deprecation warnings for MD5 passwords. */
 extern PGDLLIMPORT bool md5_password_warnings;
 
+/* number of seconds before emitting a warning for password expiration */
+extern PGDLLIMPORT int password_expire_warning;
+
 /*
  * Types of password hashes or secrets.
  *
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index 921b2daa4ff..4dac9f98089 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -103,6 +103,15 @@ typedef struct ClientConnectionInfo
 	 * meaning if authn_id is not NULL; otherwise it's undefined.
 	 */
 	UserAuth	auth_method;
+
+	/*
+	 * Message to send to the client in case of connection success.
+	 * When not NULL a WARNING message is sent to the client after a
+	 * successful connection in src/backend/utils/init/postinit.c at
+	 * enf of InitPostgres(), currently only used to show the password
+	 * expiration warning.
+	 */
+	const char *warning_message;
 } ClientConnectionInfo;
 
 /*
-- 
2.43.0