From 0701529b55d1f831c179aa2dd5bf0588d6983953 Mon Sep 17 00:00:00 2001
From: Demi Marie Obenour <demi@invisiblethingslab.com>
Date: Tue, 21 May 2024 21:38:58 -0400
Subject: [PATCH] Send EOF whenever closing stdout

This is expected by the protocol.
---
 libqrexec/process_io.c       |  5 +++++
 qrexec/tests/socket/agent.py | 37 ++++++++++++++++++++++++++++++++++--
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/libqrexec/process_io.c b/libqrexec/process_io.c
index f100fc72..79df8bbf 100644
--- a/libqrexec/process_io.c
+++ b/libqrexec/process_io.c
@@ -333,6 +333,11 @@ int qrexec_process_io(const struct process_io_request *req,
                  * local FDs. However, don't exit yet, because there might
                  * still be some data in stdin_buf waiting to be flushed.
                  */
+                if (stdout_fd != -1) {
+                    /* Send EOF */
+                    struct msg_header hdr = { .type = stdout_msg_type, .len = 0, };
+                    libvchan_send(vchan, &hdr, (int)sizeof(hdr));
+                }
                 close_stdout();
                 close_stderr(stderr_fd);
                 stderr_fd = -1;
diff --git a/qrexec/tests/socket/agent.py b/qrexec/tests/socket/agent.py
index 32260a05..af9c15d7 100644
--- a/qrexec/tests/socket/agent.py
+++ b/qrexec/tests/socket/agent.py
@@ -1413,6 +1413,37 @@ def test_run_client_bidirectional_shutdown(self):
             remote.close()
             local.close()
 
+    def test_run_client_bidirectional_shutdown_early_exit(self):
+        try:
+            remote, local = socket.socketpair()
+            target_client = self.run_service(stdio=remote)
+            initial_data = b"stdout data\n"
+            target_client.send_message(qrexec.MSG_DATA_STDOUT, initial_data)
+            # FIXME: data can be received in multiple messages
+            self.assertEqual(local.recv(len(initial_data)), initial_data)
+            initial_data = b"stdin data\n"
+            local.sendall(initial_data)
+            self.assertStdoutMessages(target_client, initial_data, qrexec.MSG_DATA_STDIN)
+            target_client.send_message(qrexec.MSG_DATA_STDOUT, b"")
+            # Check that EOF got propagated on this side too, even though
+            # we still have a reference to the socket.  This indicates that
+            # qrexec-client-vm shut down the socket for writing.
+            self.assertEqual(local.recv(1), b"")
+            with self.assertRaises(BrokenPipeError):
+                remote.send(b"a")
+            target_client.send_message(
+                qrexec.MSG_DATA_EXIT_CODE, struct.pack("<L", 42)
+            )
+            local.shutdown(socket.SHUT_WR)
+            # Check that EOF received
+            self.assertEqual(target_client.recv_message(), (qrexec.MSG_DATA_STDIN, b""))
+            self.client.wait()
+            self.assertEqual(self.client.returncode, 42)
+        finally:
+            remote.close()
+            local.close()
+
+
     def test_run_client_replace_chars(self):
         target_client = self.run_service(options=["-t"])
         target_client.send_message(
@@ -1448,7 +1479,8 @@ def test_run_client_failed(self):
         )
         # there should be no MSG_DATA_EXIT_CODE from qrexec-client-vm
         # and also no MSG_DATA_STDIN after receiving MSG_DATA_EXIT_CODE
-        self.assertListEqual(target_client.recv_all_messages(), [])
+        self.assertListEqual(target_client.recv_all_messages(),
+                             [(qrexec.MSG_DATA_STDIN, b"")])
         self.assertEqual(self.client.stdout.read(), b"")
         self.client.wait()
         self.assertEqual(self.client.returncode, qrexec.QREXEC_EXIT_PROBLEM)
@@ -1538,7 +1570,8 @@ def test_run_client_with_local_proc_service_failed(self):
             qrexec.MSG_DATA_EXIT_CODE, struct.pack("<L", qrexec.QREXEC_EXIT_PROBLEM)
         )
         # there should be no MSG_DATA_EXIT_CODE from qrexec-client-vm
-        self.assertListEqual(target_client.recv_all_messages(), [])
+        self.assertListEqual(target_client.recv_all_messages(),
+                             [(qrexec.MSG_DATA_STDIN, b"")])
         target_client.close()
         self.assertEqual(self.client.stdout.read(), b"")
         self.client.wait()