dblink: Give user mapping precedence for use_scram_passthrough

Commit 97f6fc10fff changed postgres_fdw so that user-mapping settings
override foreign server settings for use_scram_passthrough. This commit
applies the same behavior to dblink.

Backpatch to v18, where use_scram_passthrough was introduced.

Author: Matheus Alcantara <matheusssilv97@gmail.com>
Reviewed-by: Fujii Masao <masao.fujii@gmail.com>
Discussion: https://postgr.es/m/CAHGQGwEJ8rZjmbOvCicyr4vbuLio082bNTde0WNoSWaWr9wVcg@mail.gmail.com
Backpatch-through: 18

diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
index 3ac47ce3e0e2bd7689b88b4d19b38a49b29cc9ab..c631c1aefcc0fcc93ef02e4e1b3ee105165b4550 100644 (file)
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -3231,12 +3231,18 @@ appendSCRAMKeysInfo(StringInfo buf)
 }
 
 
+/*
+ * Return whether SCRAM pass-through is enabled.
+ *
+ * If use_scram_passthrough is specified in both the foreign server
+ * and the user mapping, the user mapping setting takes precedence.
+ */
 static bool
 UseScramPassthrough(ForeignServer *foreign_server, UserMapping *user)
 {
        ListCell   *cell;
 
-       foreach(cell, foreign_server->options)
+       foreach(cell, user->options)
        {
                DefElem    *def = lfirst(cell);
 
@@ -3244,7 +3250,7 @@ UseScramPassthrough(ForeignServer *foreign_server, UserMapping *user)
                        return defGetBoolean(def);
        }
 
-       foreach(cell, user->options)
+       foreach(cell, foreign_server->options)
        {
                DefElem    *def = (DefElem *) lfirst(cell);
 

diff --git a/contrib/dblink/t/001_auth_scram.pl b/contrib/dblink/t/001_auth_scram.pl
index 9558ca83b7cc0913d23cc62cb31105c5970da9c5..b087b38e5a58a56b8d55d17f066a171b540b58ba 100644 (file)
--- a/contrib/dblink/t/001_auth_scram.pl
+++ b/contrib/dblink/t/001_auth_scram.pl
@@ -24,6 +24,7 @@ my $db1 = "db1";                               # For node1
 my $db2 = "db2";                               # For node2
 my $fdw_server = "db1_fdw";
 my $fdw_server2 = "db2_fdw";
+my $fdw_server3 = "db1_fdw_override";
 my $fdw_invalid_server = "db2_fdw_invalid";    # For invalid fdw options
 my $fdw_invalid_server2 =
   "db2_fdw_invalid2";    # For invalid scram keys fdw options
@@ -55,10 +56,12 @@ setup_fdw_server($node1, $db0, $fdw_server, $node1, $db1);
 setup_fdw_server($node1, $db0, $fdw_server2, $node2, $db2);
 setup_invalid_fdw_server($node1, $db0, $fdw_invalid_server, $node2, $db2);
 setup_fdw_server($node1, $db0, $fdw_invalid_server2, $node2, $db2);
+setup_fdw_server($node1, $db0, $fdw_server3, $node1, $db1);
 
 setup_user_mapping($node1, $db0, $fdw_server);
 setup_user_mapping($node1, $db0, $fdw_server2);
 setup_user_mapping($node1, $db0, $fdw_invalid_server);
+setup_user_mapping($node1, $db0, $fdw_server3);
 
 # Make the user have the same SCRAM key on both servers. Forcing to have the
 # same iteration and salt.
@@ -96,6 +99,27 @@ test_fdw_auth($node1, $db0, "t2", $fdw_server2,
 
 test_fdw_auth_with_invalid_overwritten_require_auth($fdw_invalid_server);
 
+# Test that use_scram_passthrough=false on user mapping overrides server setting
+{
+       my $connstr = $node1->connstr($db0) . qq' user=$user';
+
+       $node1->safe_psql($db0,
+               qq'ALTER USER MAPPING FOR $user SERVER $fdw_server3 OPTIONS(add use_scram_passthrough \'false\')',
+               connstr => $connstr
+       );
+
+       my ($ret, $stdout, $stderr) = $node1->psql(
+               $db0,
+               "select * from dblink('$fdw_server3', 'select * from t') as t(a int, b int)",
+               connstr => $connstr);
+
+       is($ret, 3, 'SCRAM passthrough disabled on user mapping should fail');
+       like(
+               $stderr,
+               qr/password/i,
+               'expected password-related error when scram passthrough disabled on user mapping');
+}
+
 # Ensure that trust connections fail without superuser opt-in.
 unlink($node1->data_dir . '/pg_hba.conf');
 unlink($node2->data_dir . '/pg_hba.conf');

diff --git a/doc/src/sgml/dblink.sgml b/doc/src/sgml/dblink.sgml
index dd6778d22a84af4dccedb89bb1b67f95ef4d3d69..fc496b74288db2df6172c6c1df0f1a2b25b1e8a6 100644 (file)
--- a/doc/src/sgml/dblink.sgml
+++ b/doc/src/sgml/dblink.sgml
@@ -154,10 +154,12 @@ dblink_connect(text connname, text connstr) returns text
     The foreign-data wrapper <filename>dblink_fdw</filename> has an additional
     Boolean option <literal>use_scram_passthrough</literal> that controls
     whether <filename>dblink</filename> will use the SCRAM pass-through
-    authentication to connect to the remote database.  With SCRAM pass-through
-    authentication, <filename>dblink</filename> uses SCRAM-hashed secrets
-    instead of plain-text user passwords to connect to the remote server. This
-    avoids storing plain-text user passwords in PostgreSQL system catalogs.
+    authentication to connect to the remote database.  It can be specified
+    for a foreign server or a user mapping.  A user mapping setting overrides
+    the foreign server setting.  With SCRAM pass-through authentication,
+    <filename>dblink</filename> uses SCRAM-hashed secrets instead of plain-text
+    user passwords to connect to the remote server. This avoids storing
+    plain-text user passwords in PostgreSQL system catalogs.
     See the documentation of the equivalent <link
     linkend="postgres-fdw-option-use-scram-passthrough"><literal>use_scram_passthrough</literal></link>
     option of postgres_fdw for further details and restrictions.