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From 1b9845dcf959421db3a071a6bc0aa9d8edbffb50 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= <roger.pau@citrix.com>
Date: Wed, 3 Aug 2022 12:41:18 +0200
Subject: [PATCH 031/126] tools/libxl: env variable to signal whether disk/nic
backend is trusted
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Introduce support in libxl for fetching the default backend trusted
option for disk and nic devices.
Users can set LIBXL_{DISK,NIC}_BACKEND_UNTRUSTED environment variable
to notify libxl of whether the backends for disk and nic devices
should be trusted. Such information is passed into the frontend so it
can take the appropriate measures.
This is part of XSA-403.
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
---
docs/man/xl.1.pod.in | 18 ++++++++++++++++++
tools/libs/light/libxl_disk.c | 5 +++++
tools/libs/light/libxl_nic.c | 7 +++++++
3 files changed, 30 insertions(+)
diff --git a/docs/man/xl.1.pod.in b/docs/man/xl.1.pod.in
index e2176bd696cb..45e1430aeb74 100644
--- a/docs/man/xl.1.pod.in
+++ b/docs/man/xl.1.pod.in
@@ -1946,6 +1946,24 @@ shows the decimal value. For non-linear mode, it shows hexadecimal value.
=back
+=head1 ENVIRONMENT
+
+=over 4
+
+=item B<LIBXL_DISK_BACKEND_UNTRUSTED>
+
+Set this environment variable to "1" to suggest to the guest that the disk
+backend shouldn't be trusted. If the variable is absent or set to "0", the
+backend will be trusted.
+
+=item B<LIBXL_NIC_BACKEND_UNTRUSTED>
+
+Set this environment variable to "1" to suggest to the guest that the network
+backend shouldn't be trusted. If the variable is absent or set to "0", the
+backend will be trusted.
+
+=back
+
=head1 IGNORED FOR COMPATIBILITY WITH XM
xl is mostly command-line compatible with the old xm utility used with
diff --git a/tools/libs/light/libxl_disk.c b/tools/libs/light/libxl_disk.c
index 93936d0dd0f8..67d1cc18578f 100644
--- a/tools/libs/light/libxl_disk.c
+++ b/tools/libs/light/libxl_disk.c
@@ -246,6 +246,7 @@ static void device_disk_add(libxl__egc *egc, uint32_t domid,
libxl_domain_config d_config;
libxl_device_disk disk_saved;
libxl__flock *lock = NULL;
+ const char *envvar;
libxl_domain_config_init(&d_config);
libxl_device_disk_init(&disk_saved);
@@ -395,6 +396,10 @@ static void device_disk_add(libxl__egc *egc, uint32_t domid,
flexarray_append(front, GCSPRINTF("%d", device->devid));
flexarray_append(front, "device-type");
flexarray_append(front, disk->is_cdrom ? "cdrom" : "disk");
+ flexarray_append(front, "trusted");
+ envvar = getenv("LIBXL_DISK_BACKEND_UNTRUSTED");
+ /* Set "trusted=1" if envvar missing or is "0". */
+ flexarray_append(front, !envvar || !strcmp("0", envvar) ? "1" : "0");
/*
* Old PV kernel disk frontends before 2.6.26 rely on tool stack to
diff --git a/tools/libs/light/libxl_nic.c b/tools/libs/light/libxl_nic.c
index 0b9e70c9d13d..f87890d1d65f 100644
--- a/tools/libs/light/libxl_nic.c
+++ b/tools/libs/light/libxl_nic.c
@@ -132,6 +132,8 @@ static int libxl__set_xenstore_nic(libxl__gc *gc, uint32_t domid,
flexarray_t *back, flexarray_t *front,
flexarray_t *ro_front)
{
+ const char *envvar;
+
flexarray_grow(back, 2);
if (nic->script)
@@ -255,6 +257,11 @@ static int libxl__set_xenstore_nic(libxl__gc *gc, uint32_t domid,
flexarray_append(back, "hotplug-status");
flexarray_append(back, "");
+ flexarray_append(front, "trusted");
+ envvar = getenv("LIBXL_NIC_BACKEND_UNTRUSTED");
+ /* Set "trusted=1" if envvar missing or is "0". */
+ flexarray_append(front, !envvar || !strcmp("0", envvar) ? "1" : "0");
+
return 0;
}
--
2.37.4
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