postgres.git / summary / log / commit / refs
commit 32a4ce55ccabe4c1e9b1e45d4efc1e62e69fc754
Author: Michael Paquier <michael@paquier.xyz>
Commit: Noah Misch <noah@leadboat.com>
Date: Mon May 11 12:13:48 2026 +0000
First released in: 14.23, 15.18, 16.14, 17.10, 18.4
Fix unbounded recursive handling of SSL/GSS in ProcessStartupPacket()
The handling of SSL and GSS negotiation messages in
ProcessStartupPacket() could cause a recursion of the backend,
ultimately crashing the server as the negotiation attempts were not
tracked across multiple calls processing startup packets.
A malicious client could therefore alternate rejected SSL and GSS
requests indefinitely, each adding a stack frame, until the backend
crashed with a stack overflow, taking down a server.
This commit addresses this issue by modifying ProcessStartupPacket() so
as processed negotiation attempts are tracked, preventing infinite
recursive attempts. A TAP test is added to check this problem, where
multiple SSL and GSS negotiated attempts are stacked.
Reported-by: Calif.io in collaboration with Claude and Anthropic
Research
Author: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Security: CVE-2026-6479
Backpatch-through: 14
src/backend/tcop/backend_startup.c | 23 +++++++++-
src/test/Makefile | 2 +-
src/test/meson.build | 1 +
src/test/postmaster/.gitignore | 2 +
src/test/postmaster/Makefile | 23 ++++++++++
src/test/postmaster/README | 27 +++++++++++
src/test/postmaster/meson.build | 12 +++++
src/test/postmaster/t/004_negotiate.pl | 82 ++++++++++++++++++++++++++++++++++
8 files changed, 169 insertions(+), 3 deletions(-)
diff --git a/src/backend/tcop/backend_startup.c b/src/backend/tcop/backend_startup.c
index ce1275bccfe..2fe67015e3b 100644
--- a/src/backend/tcop/backend_startup.c
+++ b/src/backend/tcop/backend_startup.c
@@ -457,6 +457,7 @@ ProcessStartupPacket(Port *port, bool ssl_done, bool gss_done)
ProtocolVersion proto;
MemoryContext oldcontext;
+retry:
pq_startmsgread();
/*
@@ -608,7 +609,16 @@ ProcessStartupPacket(Port *port, bool ssl_done, bool gss_done)
* another SSL negotiation request, and a GSS request should only
* follow if SSL was rejected (client may negotiate in either order)
*/
- return ProcessStartupPacket(port, true, SSLok == 'S');
+ ssl_done = true;
+ if (SSLok == 'S')
+ {
+ /*
+ * We are done with SSL and negotiated correctly, so consider the
+ * same for GSS.
+ */
+ gss_done = true;
+ }
+ goto retry;
}
else if (proto == NEGOTIATE_GSS_CODE && !gss_done)
{
@@ -662,7 +672,16 @@ ProcessStartupPacket(Port *port, bool ssl_done, bool gss_done)
* another GSS negotiation request, and an SSL request should only
* follow if GSS was rejected (client may negotiate in either order)
*/
- return ProcessStartupPacket(port, GSSok == 'G', true);
+ gss_done = true;
+ if (GSSok == 'G')
+ {
+ /*
+ * We are done with GSS and negotiated correctly, so consider the
+ * same for SSL.
+ */
+ ssl_done = true;
+ }
+ goto retry;
}
/* Could add additional special packet types here */
diff --git a/src/test/Makefile b/src/test/Makefile
index dbd3192874d..abdd6e5a985 100644
--- a/src/test/Makefile
+++ b/src/test/Makefile
@@ -12,7 +12,7 @@ subdir = src/test
top_builddir = ../..
include $(top_builddir)/src/Makefile.global
-SUBDIRS = perl regress isolation modules authentication recovery subscription
+SUBDIRS = perl postmaster regress isolation modules authentication recovery subscription
ifeq ($(with_icu),yes)
SUBDIRS += icu
diff --git a/src/test/meson.build b/src/test/meson.build
index c3d0dfedf1c..67376e4b7fd 100644
--- a/src/test/meson.build
+++ b/src/test/meson.build
@@ -4,6 +4,7 @@ subdir('regress')
subdir('isolation')
subdir('authentication')
+subdir('postmaster')
subdir('recovery')
subdir('subscription')
subdir('modules')
diff --git a/src/test/postmaster/.gitignore b/src/test/postmaster/.gitignore
new file mode 100644
index 00000000000..871e943d50e
--- /dev/null
+++ b/src/test/postmaster/.gitignore
@@ -0,0 +1,2 @@
+# Generated by test suite
+/tmp_check/
diff --git a/src/test/postmaster/Makefile b/src/test/postmaster/Makefile
new file mode 100644
index 00000000000..e06b81f8c47
--- /dev/null
+++ b/src/test/postmaster/Makefile
@@ -0,0 +1,23 @@
+#-------------------------------------------------------------------------
+#
+# Makefile for src/test/postmaster
+#
+# Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
+# Portions Copyright (c) 1994, Regents of the University of California
+#
+# src/test/postmaster/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/test/postmaster
+top_builddir = ../../..
+include $(top_builddir)/src/Makefile.global
+
+check:
+ $(prove_check)
+
+installcheck:
+ $(prove_installcheck)
+
+clean distclean:
+ rm -rf tmp_check
diff --git a/src/test/postmaster/README b/src/test/postmaster/README
new file mode 100644
index 00000000000..7e47bf5cff0
--- /dev/null
+++ b/src/test/postmaster/README
@@ -0,0 +1,27 @@
+src/test/postmaster/README
+
+Regression tests for postmaster
+===============================
+
+This directory contains a test suite for postmaster's handling of
+connections, connection limits, and startup/shutdown sequence.
+
+
+Running the tests
+=================
+
+NOTE: You must have given the --enable-tap-tests argument to configure.
+
+Run
+ make check
+or
+ make installcheck
+You can use "make installcheck" if you previously did "make install".
+In that case, the code in the installation tree is tested. With
+"make check", a temporary installation tree is built from the current
+sources and then tested.
+
+Either way, this test initializes, starts, and stops a test Postgres
+cluster.
+
+See src/test/perl/README for more info about running these tests.
diff --git a/src/test/postmaster/meson.build b/src/test/postmaster/meson.build
new file mode 100644
index 00000000000..6666ced8f31
--- /dev/null
+++ b/src/test/postmaster/meson.build
@@ -0,0 +1,12 @@
+# Copyright (c) 2022-2025, PostgreSQL Global Development Group
+
+tests += {
+ 'name': 'postmaster',
+ 'sd': meson.current_source_dir(),
+ 'bd': meson.current_build_dir(),
+ 'tap': {
+ 'tests': [
+ 't/004_negotiate.pl',
+ ],
+ },
+}
diff --git a/src/test/postmaster/t/004_negotiate.pl b/src/test/postmaster/t/004_negotiate.pl
new file mode 100644
index 00000000000..836b197aa8e
--- /dev/null
+++ b/src/test/postmaster/t/004_negotiate.pl
@@ -0,0 +1,82 @@
+# Copyright (c) 2026, PostgreSQL Global Development Group
+
+# Test the negotiation of combined SSL and GSS requests. This test
+# relies on both SSL and GSS requests to be rejected first, followed
+# by more requests.
+
+use strict;
+use warnings FATAL => 'all';
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+use Time::HiRes qw(usleep);
+
+my $node = PostgreSQL::Test::Cluster->new('main');
+$node->init;
+$node->append_conf('postgresql.conf', "log_min_messages = debug2");
+$node->append_conf('postgresql.conf',
+ "log_connections = 'on'");
+$node->append_conf('postgresql.conf', 'trace_connection_negotiation=on');
+$node->start;
+
+if (!$node->raw_connect_works())
+{
+ plan skip_all => "this test requires working raw_connect()";
+}
+
+my $sock = $node->raw_connect();
+
+# SSLRequest: packet length followed by NEGOTIATE_SSL_CODE.
+my $ssl_request = pack("Nnn", 8, 1234, 5679);
+
+# GSSENCRequest: packet length followed by NEGOTIATE_GSS_CODE.
+my $gss_request = pack("Nnn", 8, 1234, 5680);
+
+# Send SSLRequest, reject or bypass.
+$sock->send($ssl_request);
+my $reply = "";
+$sock->recv($reply, 1);
+if ($reply ne 'N')
+{
+ $sock->close();
+ plan skip_all =>
+ "server accepted SSL; test requires SSL to be rejected";
+}
+
+# Send GSSENCRequest, reject or bypass test.
+$sock->send($gss_request);
+$reply = "";
+$sock->recv($reply, 1);
+if ($reply ne 'N')
+{
+ $sock->close();
+ plan skip_all =>
+ "server accepted GSS; test requires GSS to be rejected";
+}
+
+my $log_offset = -s $node->logfile;
+
+# Send a second SSLRequest, now that we know that both SSL and GSS have
+# been rejected for this connection. We are done with both requests, so
+# extra requests will be rejected and fail with an invalid protocol
+# version, and the connection should be closed by the server.
+$sock->send($ssl_request);
+
+# Try to read a response, there should be nothing, and certainly not an
+# extra 'N' message indicating a rejection.
+$reply = "";
+my $bytes = $sock->recv($reply, 1024);
+isnt($reply, 'N',
+ "server does not re-enter SSL negotiation after SSL+GSS were both tried");
+
+$sock->close();
+$node->wait_for_log(qr/FATAL: .* unsupported frontend protocol 1234.5679/,
+ $log_offset);
+
+# Check extra connection with a simple query.
+my $result = $node->safe_psql('postgres', 'select 1;');
+is($result, '1', 'server able to accept connection');
+
+$node->stop;
+
+done_testing();
[parent: 6dffaeb8e54c]