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postgres_fdw: SCRAM authentication pass-through

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This enables SCRAM authentication for postgres_fdw when connecting to
a foreign server without having to store a plain-text password on user
mapping options.

This is done by saving the SCRAM ClientKey and ServeryKey from the
client authentication and using those instead of the plain-text
password for the server-side SCRAM exchange.  The new foreign-server
or user-mapping option "use_scram_passthrough" enables this.

Co-authored-by: Matheus Alcantara <mths.dev@pm.me>
Co-authored-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://www.postgresql.org/message-id/flat/27b29a35-9b96-46a9-bc1a-914140869dac@gmail.com
This commit is contained in:
Peter Eisentraut
2025-01-15 17:55:18 +01:00
parent b6463ea6ef
commit 761c79508e
14 changed files with 450 additions and 42 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
contrib/postgres_fdw/Makefile
View File

@ -17,6 +17,7 @@ EXTENSION = postgres_fdw
DATA = postgres_fdw--1.0.sql postgres_fdw--1.0--1.1.sql postgres_fdw--1.1--1.2.sql
REGRESS = postgres_fdw query_cancel
TAP_TESTS = 1
ifdef USE_PGXS
PG_CONFIG = pg_config

69
contrib/postgres_fdw/connection.c
View File

@ -19,6 +19,7 @@
#include "access/xact.h"
#include "catalog/pg_user_mapping.h"
#include "commands/defrem.h"
#include "common/base64.h"
#include "funcapi.h"
#include "libpq/libpq-be.h"
#include "libpq/libpq-be-fe-helpers.h"
@ -177,6 +178,7 @@ static void pgfdw_finish_abort_cleanup(List *pending_entries,
static void pgfdw_security_check(const char **keywords, const char **values,
UserMapping *user, PGconn *conn);
static bool UserMappingPasswordRequired(UserMapping *user);
static bool UseScramPassthrough(ForeignServer *server, UserMapping *user);
static bool disconnect_cached_connections(Oid serverid);
static void postgres_fdw_get_connections_internal(FunctionCallInfo fcinfo,
enum pgfdwVersion api_version);
@ -485,7 +487,7 @@ connect_pg_server(ForeignServer *server, UserMapping *user)
* for application_name, fallback_application_name, client_encoding,
* end marker.
*/
n = list_length(server->options) + list_length(user->options) + 4;
n = list_length(server->options) + list_length(user->options) + 4 + 2;
keywords = (const char **) palloc(n * sizeof(char *));
values = (const char **) palloc(n * sizeof(char *));
@ -554,10 +556,37 @@ connect_pg_server(ForeignServer *server, UserMapping *user)
values[n] = GetDatabaseEncodingName();
n++;
if (MyProcPort->has_scram_keys && UseScramPassthrough(server, user))
{
int len;
keywords[n] = "scram_client_key";
len = pg_b64_enc_len(sizeof(MyProcPort->scram_ClientKey));
/* don't forget the zero-terminator */
values[n] = palloc0(len + 1);
pg_b64_encode((const char *) MyProcPort->scram_ClientKey,
sizeof(MyProcPort->scram_ClientKey),
(char *) values[n], len);
n++;
keywords[n] = "scram_server_key";
len = pg_b64_enc_len(sizeof(MyProcPort->scram_ServerKey));
/* don't forget the zero-terminator */
values[n] = palloc0(len + 1);
pg_b64_encode((const char *) MyProcPort->scram_ServerKey,
sizeof(MyProcPort->scram_ServerKey),
(char *) values[n], len);
n++;
}
keywords[n] = values[n] = NULL;
/* verify the set of connection parameters */
check_conn_params(keywords, values, user);
/*
* Verify the set of connection parameters only if scram pass-through
* is not being used because the password is not necessary.
*/
if (!(MyProcPort->has_scram_keys && UseScramPassthrough(server, user)))
check_conn_params(keywords, values, user);
/* first time, allocate or get the custom wait event */
if (pgfdw_we_connect == 0)
@ -575,8 +604,12 @@ connect_pg_server(ForeignServer *server, UserMapping *user)
server->servername),
errdetail_internal("%s", pchomp(PQerrorMessage(conn)))));
/* Perform post-connection security checks */
pgfdw_security_check(keywords, values, user, conn);
/*
* Perform post-connection security checks only if scram pass-through
* is not being used because the password is not necessary.
*/
if (!(MyProcPort->has_scram_keys && UseScramPassthrough(server, user)))
pgfdw_security_check(keywords, values, user, conn);
/* Prepare new session for use */
configure_remote_session(conn);
@ -629,6 +662,30 @@ UserMappingPasswordRequired(UserMapping *user)
return true;
}
static bool
UseScramPassthrough(ForeignServer *server, UserMapping *user)
{
ListCell *cell;
foreach(cell, server->options)
{
DefElem *def = (DefElem *) lfirst(cell);
if (strcmp(def->defname, "use_scram_passthrough") == 0)
return defGetBoolean(def);
}
foreach(cell, user->options)
{
DefElem *def = (DefElem *) lfirst(cell);
if (strcmp(def->defname, "use_scram_passthrough") == 0)
return defGetBoolean(def);
}
return false;
}
/*
* For non-superusers, insist that the connstr specify a password or that the
* user provided their own GSSAPI delegated credentials. This
@ -666,7 +723,7 @@ check_conn_params(const char **keywords, const char **values, UserMapping *user)
ereport(ERROR,
(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
errmsg("password or GSSAPI delegated credentials required"),
errdetail("Non-superusers must delegate GSSAPI credentials or provide a password in the user mapping.")));
errdetail("Non-superusers must delegate GSSAPI credentials, provide a password, or enable SCRAM pass-through in user mapping.")));
}
/*

4
contrib/postgres_fdw/expected/postgres_fdw.out
View File

@ -10301,7 +10301,7 @@ CREATE FOREIGN TABLE pg_temp.ft1_nopw (
) SERVER loopback_nopw OPTIONS (schema_name 'public', table_name 'ft1');
SELECT 1 FROM ft1_nopw LIMIT 1;
ERROR: password or GSSAPI delegated credentials required
DETAIL: Non-superusers must delegate GSSAPI credentials or provide a password in the user mapping.
DETAIL: Non-superusers must delegate GSSAPI credentials, provide a password, or enable SCRAM pass-through in user mapping.
-- If we add a password to the connstr it'll fail, because we don't allow passwords
-- in connstrs only in user mappings.
ALTER SERVER loopback_nopw OPTIONS (ADD password 'dummypw');
@ -10351,7 +10351,7 @@ DROP USER MAPPING FOR CURRENT_USER SERVER loopback_nopw;
-- lacks password_required=false
SELECT 1 FROM ft1_nopw LIMIT 1;
ERROR: password or GSSAPI delegated credentials required
DETAIL: Non-superusers must delegate GSSAPI credentials or provide a password in the user mapping.
DETAIL: Non-superusers must delegate GSSAPI credentials, provide a password, or enable SCRAM pass-through in user mapping.
RESET ROLE;
-- The user mapping for public is passwordless and lacks the password_required=false
-- mapping option, but will work because the current user is a superuser.

5
contrib/postgres_fdw/meson.build
View File

@ -41,4 +41,9 @@ tests += {
],
'regress_args': ['--dlpath', meson.build_root() / 'src/test/regress'],
},
'tap': {
'tests': [
't/001_auth_scram.pl',
],
},
}

3
contrib/postgres_fdw/option.c
View File

@ -279,6 +279,9 @@ InitPgFdwOptions(void)
{"analyze_sampling", ForeignServerRelationId, false},
{"analyze_sampling", ForeignTableRelationId, false},
{"use_scram_passthrough", ForeignServerRelationId, false},
{"use_scram_passthrough", UserMappingRelationId, false},
/*
* sslcert and sslkey are in fact libpq options, but we repeat them
* here to allow them to appear in both foreign server context (when

151
contrib/postgres_fdw/t/001_auth_scram.pl Normal file
View File

@ -0,0 +1,151 @@
# Copyright (c) 2024-2025, PostgreSQL Global Development Group
# Test SCRAM authentication when opening a new connection with a foreign
# server.
#
# The test is executed by testing the SCRAM authentifcation on a looplback
# connection on the same server and with different servers.
use strict;
use warnings FATAL => 'all';
use PostgreSQL::Test::Utils;
use PostgreSQL::Test::Cluster;
use Test::More;
my $hostaddr = '127.0.0.1';
my $user = "user01";
my $db0 = "db0"; # For node1
my $db1 = "db1"; # For node1
my $db2 = "db2"; # For node2
my $fdw_server = "db1_fdw";
my $fdw_server2 = "db2_fdw";
my $node1 = PostgreSQL::Test::Cluster->new('node1');
my $node2 = PostgreSQL::Test::Cluster->new('node2');
$node1->init;
$node2->init;
$node1->start;
$node2->start;
# Test setup
$node1->safe_psql('postgres', qq'CREATE USER $user WITH password \'pass\'');
$node2->safe_psql('postgres', qq'CREATE USER $user WITH password \'pass\'');
$ENV{PGPASSWORD} = "pass";
$node1->safe_psql('postgres', qq'CREATE DATABASE $db0');
$node1->safe_psql('postgres', qq'CREATE DATABASE $db1');
$node2->safe_psql('postgres', qq'CREATE DATABASE $db2');
setup_table($node1, $db1, "t");
setup_table($node2, $db2, "t2");
$node1->safe_psql($db0, 'CREATE EXTENSION IF NOT EXISTS postgres_fdw');
setup_fdw_server($node1, $db0, $fdw_server, $node1, $db1);
setup_fdw_server($node1, $db0, $fdw_server2, $node2, $db2);
setup_user_mapping($node1, $db0, $fdw_server);
setup_user_mapping($node1, $db0, $fdw_server2);
# Make the user have the same SCRAM key on both servers. Forcing to have the
# same iteration and salt.
my $rolpassword = $node1->safe_psql('postgres',
qq"SELECT rolpassword FROM pg_authid WHERE rolname = '$user';");
$node2->safe_psql('postgres', qq"ALTER ROLE $user PASSWORD '$rolpassword'");
setup_pghba($node1);
setup_pghba($node2);
# End of test setup
test_fdw_auth($node1, $db0, "t", $fdw_server,
"SCRAM auth on the same database cluster must succeed");
test_fdw_auth($node1, $db0, "t2", $fdw_server2,
"SCRAM auth on a different database cluster must succeed");
test_auth($node2, $db2, "t2",
"SCRAM auth directly on foreign server should still succeed");
# Helper functions
sub test_auth
{
local $Test::Builder::Level = $Test::Builder::Level + 1;
my ($node, $db, $tbl, $testname) = @_;
my $connstr = $node->connstr($db) . qq' user=$user';
my $ret = $node->safe_psql(
$db,
qq'SELECT count(1) FROM $tbl',
connstr => $connstr);
is($ret, '10', $testname);
}
sub test_fdw_auth
{
local $Test::Builder::Level = $Test::Builder::Level + 1;
my ($node, $db, $tbl, $fdw, $testname) = @_;
my $connstr = $node->connstr($db) . qq' user=$user';
$node->safe_psql(
$db,
qq'IMPORT FOREIGN SCHEMA public LIMIT TO ($tbl) FROM SERVER $fdw INTO public;',
connstr => $connstr);
test_auth($node, $db, $tbl, $testname);
}
sub setup_pghba
{
my ($node) = @_;
unlink($node->data_dir . '/pg_hba.conf');
$node->append_conf(
'pg_hba.conf', qq{
local all all scram-sha-256
host all all $hostaddr/32 scram-sha-256
});
$node->restart;
}
sub setup_user_mapping
{
my ($node, $db, $fdw) = @_;
$node->safe_psql($db,
qq'CREATE USER MAPPING FOR $user SERVER $fdw OPTIONS (user \'$user\');'
);
$node->safe_psql($db, qq'GRANT USAGE ON FOREIGN SERVER $fdw TO $user;');
$node->safe_psql($db, qq'GRANT ALL ON SCHEMA public TO $user');
}
sub setup_fdw_server
{
my ($node, $db, $fdw, $fdw_node, $dbname) = @_;
my $host = $fdw_node->host;
my $port = $fdw_node->port;
$node->safe_psql(
$db, qq'CREATE SERVER $fdw FOREIGN DATA WRAPPER postgres_fdw options (
host \'$host\', port \'$port\', dbname \'$dbname\', use_scram_passthrough \'true\') '
);
}
sub setup_table
{
my ($node, $db, $tbl) = @_;
$node->safe_psql($db,
qq'CREATE TABLE $tbl AS SELECT g, g + 1 FROM generate_series(1,10) g(g)'
);
$node->safe_psql($db, qq'GRANT USAGE ON SCHEMA public TO $user');
$node->safe_psql($db, qq'GRANT SELECT ON $tbl TO $user');
}
done_testing();