| Message ID | 20220105135009.1584676-22-alex.bennee@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | testing/next and other misc fixes | expand |
On Wed, Jan 05, 2022 at 01:49:56PM +0000, Alex Bennée wrote: > Generally a guest needs an external source of randomness to properly > enable things like address space randomisation. However in a trusted > boot environment where the firmware will cryptographically verify > components having random data in the DTB will cause verification to > fail. Add a control knob so we can prevent this being added to the > system DTB. > > Signed-off-by: Alex Bennée <alex.bennee@linaro.org> > Tested-by: Heinrich Schuchardt <xypron.glpk@gmx.de> > Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org> > Acked-by: Jerome Forissier <jerome@forissier.org> > Message-Id: <20211215120926.1696302-1-alex.bennee@linaro.org> > --- > docs/system/arm/virt.rst | 7 +++++++ > include/hw/arm/virt.h | 1 + > hw/arm/virt.c | 32 ++++++++++++++++++++++++++++++-- > 3 files changed, 38 insertions(+), 2 deletions(-) > > diff --git a/docs/system/arm/virt.rst b/docs/system/arm/virt.rst > index 850787495b..c86a4808df 100644 > --- a/docs/system/arm/virt.rst > +++ b/docs/system/arm/virt.rst > @@ -121,6 +121,13 @@ ras > Set ``on``/``off`` to enable/disable reporting host memory errors to a guest > using ACPI and guest external abort exceptions. The default is off. > > +kaslr-dtb-seed > + Set ``on``/``off`` to pass a random seed via the guest dtb to use for features > + like address space randomisation. The default is ``on``. You will want > + to disable it if your trusted boot chain will verify the DTB it is > + passed. It would be the responsibility of the firmware to come up > + with a seed and pass it on if it wants to. > + > Linux guest kernel configuration > """""""""""""""""""""""""""""""" > > diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h > index dc6b66ffc8..acd0665fe7 100644 > --- a/include/hw/arm/virt.h > +++ b/include/hw/arm/virt.h > @@ -148,6 +148,7 @@ struct VirtMachineState { > bool virt; > bool ras; > bool mte; > + bool kaslr_dtb_seed; > OnOffAuto acpi; > VirtGICType gic_version; > VirtIOMMUType iommu; > diff --git a/hw/arm/virt.c b/hw/arm/virt.c > index 6bce595aba..1781e47c76 100644 > --- a/hw/arm/virt.c > +++ b/hw/arm/virt.c > @@ -247,11 +247,15 @@ static void create_fdt(VirtMachineState *vms) > > /* /chosen must exist for load_dtb to fill in necessary properties later */ > qemu_fdt_add_subnode(fdt, "/chosen"); > - create_kaslr_seed(ms, "/chosen"); > + if (vms->kaslr_dtb_seed) { > + create_kaslr_seed(ms, "/chosen"); > + } > > if (vms->secure) { > qemu_fdt_add_subnode(fdt, "/secure-chosen"); > - create_kaslr_seed(ms, "/secure-chosen"); > + if (vms->kaslr_dtb_seed) { > + create_kaslr_seed(ms, "/secure-chosen"); > + } > } > > /* Clock node, for the benefit of the UART. The kernel device tree > @@ -2235,6 +2239,20 @@ static void virt_set_its(Object *obj, bool value, Error **errp) > vms->its = value; > } > > +static bool virt_get_kaslr_dtb_seed(Object *obj, Error **errp) > +{ > + VirtMachineState *vms = VIRT_MACHINE(obj); > + > + return vms->kaslr_dtb_seed; > +} > + > +static void virt_set_kaslr_dtb_seed(Object *obj, bool value, Error **errp) > +{ > + VirtMachineState *vms = VIRT_MACHINE(obj); > + > + vms->kaslr_dtb_seed = value; > +} > + > static char *virt_get_oem_id(Object *obj, Error **errp) > { > VirtMachineState *vms = VIRT_MACHINE(obj); > @@ -2764,6 +2782,13 @@ static void virt_machine_class_init(ObjectClass *oc, void *data) > "Set on/off to enable/disable " > "ITS instantiation"); > > + object_class_property_add_bool(oc, "kaslr-dtb-seed", > + virt_get_kaslr_dtb_seed, > + virt_set_kaslr_dtb_seed); > + object_class_property_set_description(oc, "kaslr-dtb-seed", > + "Set off to disable passing of kaslr " > + "dtb node to guest"); > + > object_class_property_add_str(oc, "x-oem-id", > virt_get_oem_id, > virt_set_oem_id); > @@ -2828,6 +2853,9 @@ static void virt_instance_init(Object *obj) > /* MTE is disabled by default. */ > vms->mte = false; > > + /* Supply a kaslr-seed by default */ > + vms->kaslr_dtb_seed = true; > + > vms->irqmap = a15irqmap; > > virt_flash_create(vms); > -- > 2.30.2 > > Reviewed-by: Andrew Jones <drjones@redhat.com>
On Wed, 5 Jan 2022 at 14:00, Alex Bennée <alex.bennee@linaro.org> wrote: > > Generally a guest needs an external source of randomness to properly > enable things like address space randomisation. However in a trusted > boot environment where the firmware will cryptographically verify > components having random data in the DTB will cause verification to > fail. Add a control knob so we can prevent this being added to the > system DTB. > > Signed-off-by: Alex Bennée <alex.bennee@linaro.org> > Tested-by: Heinrich Schuchardt <xypron.glpk@gmx.de> > Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org> > Acked-by: Jerome Forissier <jerome@forissier.org> > Message-Id: <20211215120926.1696302-1-alex.bennee@linaro.org> > --- > docs/system/arm/virt.rst | 7 +++++++ > include/hw/arm/virt.h | 1 + > hw/arm/virt.c | 32 ++++++++++++++++++++++++++++++-- > 3 files changed, 38 insertions(+), 2 deletions(-) > > diff --git a/docs/system/arm/virt.rst b/docs/system/arm/virt.rst > index 850787495b..c86a4808df 100644 > --- a/docs/system/arm/virt.rst > +++ b/docs/system/arm/virt.rst > @@ -121,6 +121,13 @@ ras > Set ``on``/``off`` to enable/disable reporting host memory errors to a guest > using ACPI and guest external abort exceptions. The default is off. > > +kaslr-dtb-seed > + Set ``on``/``off`` to pass a random seed via the guest dtb to use for features > + like address space randomisation. The default is ``on``. You will want > + to disable it if your trusted boot chain will verify the DTB it is > + passed. It would be the responsibility of the firmware to come up > + with a seed and pass it on if it wants to. We should say what the name of the DTB node is here: it is "kaslr-seed" (in the "/chosen" and /secure-chosen nodes, if we want to get that specific). Side note: it's odd that in naming this proporty we've inserted "dtb" into the middle of the node name we're controlling the creation of. Maybe use "dtb-kaslr-seed" ? > + > Linux guest kernel configuration > """""""""""""""""""""""""""""""" > > diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h > index dc6b66ffc8..acd0665fe7 100644 > --- a/include/hw/arm/virt.h > +++ b/include/hw/arm/virt.h > @@ -148,6 +148,7 @@ struct VirtMachineState { > bool virt; > bool ras; > bool mte; > + bool kaslr_dtb_seed; > OnOffAuto acpi; > VirtGICType gic_version; > VirtIOMMUType iommu; > diff --git a/hw/arm/virt.c b/hw/arm/virt.c > index 6bce595aba..1781e47c76 100644 > --- a/hw/arm/virt.c > +++ b/hw/arm/virt.c > @@ -247,11 +247,15 @@ static void create_fdt(VirtMachineState *vms) > > /* /chosen must exist for load_dtb to fill in necessary properties later */ > qemu_fdt_add_subnode(fdt, "/chosen"); > - create_kaslr_seed(ms, "/chosen"); > + if (vms->kaslr_dtb_seed) { > + create_kaslr_seed(ms, "/chosen"); > + } > > if (vms->secure) { > qemu_fdt_add_subnode(fdt, "/secure-chosen"); > - create_kaslr_seed(ms, "/secure-chosen"); > + if (vms->kaslr_dtb_seed) { > + create_kaslr_seed(ms, "/secure-chosen"); > + } > } > > /* Clock node, for the benefit of the UART. The kernel device tree > @@ -2235,6 +2239,20 @@ static void virt_set_its(Object *obj, bool value, Error **errp) > vms->its = value; > } > > +static bool virt_get_kaslr_dtb_seed(Object *obj, Error **errp) > +{ > + VirtMachineState *vms = VIRT_MACHINE(obj); > + > + return vms->kaslr_dtb_seed; > +} > + > +static void virt_set_kaslr_dtb_seed(Object *obj, bool value, Error **errp) > +{ > + VirtMachineState *vms = VIRT_MACHINE(obj); > + > + vms->kaslr_dtb_seed = value; > +} > + > static char *virt_get_oem_id(Object *obj, Error **errp) > { > VirtMachineState *vms = VIRT_MACHINE(obj); > @@ -2764,6 +2782,13 @@ static void virt_machine_class_init(ObjectClass *oc, void *data) > "Set on/off to enable/disable " > "ITS instantiation"); > > + object_class_property_add_bool(oc, "kaslr-dtb-seed", > + virt_get_kaslr_dtb_seed, > + virt_set_kaslr_dtb_seed); > + object_class_property_set_description(oc, "kaslr-dtb-seed", > + "Set off to disable passing of kaslr " "kaslr-seed", not just "kaslr". > + "dtb node to guest"); > + > object_class_property_add_str(oc, "x-oem-id", > virt_get_oem_id, > virt_set_oem_id); > @@ -2828,6 +2853,9 @@ static void virt_instance_init(Object *obj) -- PMM
diff --git a/docs/system/arm/virt.rst b/docs/system/arm/virt.rst index 850787495b..c86a4808df 100644 --- a/docs/system/arm/virt.rst +++ b/docs/system/arm/virt.rst @@ -121,6 +121,13 @@ ras Set ``on``/``off`` to enable/disable reporting host memory errors to a guest using ACPI and guest external abort exceptions. The default is off. +kaslr-dtb-seed + Set ``on``/``off`` to pass a random seed via the guest dtb to use for features + like address space randomisation. The default is ``on``. You will want + to disable it if your trusted boot chain will verify the DTB it is + passed. It would be the responsibility of the firmware to come up + with a seed and pass it on if it wants to. + Linux guest kernel configuration """""""""""""""""""""""""""""""" diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h index dc6b66ffc8..acd0665fe7 100644 --- a/include/hw/arm/virt.h +++ b/include/hw/arm/virt.h @@ -148,6 +148,7 @@ struct VirtMachineState { bool virt; bool ras; bool mte; + bool kaslr_dtb_seed; OnOffAuto acpi; VirtGICType gic_version; VirtIOMMUType iommu; diff --git a/hw/arm/virt.c b/hw/arm/virt.c index 6bce595aba..1781e47c76 100644 --- a/hw/arm/virt.c +++ b/hw/arm/virt.c @@ -247,11 +247,15 @@ static void create_fdt(VirtMachineState *vms) /* /chosen must exist for load_dtb to fill in necessary properties later */ qemu_fdt_add_subnode(fdt, "/chosen"); - create_kaslr_seed(ms, "/chosen"); + if (vms->kaslr_dtb_seed) { + create_kaslr_seed(ms, "/chosen"); + } if (vms->secure) { qemu_fdt_add_subnode(fdt, "/secure-chosen"); - create_kaslr_seed(ms, "/secure-chosen"); + if (vms->kaslr_dtb_seed) { + create_kaslr_seed(ms, "/secure-chosen"); + } } /* Clock node, for the benefit of the UART. The kernel device tree @@ -2235,6 +2239,20 @@ static void virt_set_its(Object *obj, bool value, Error **errp) vms->its = value; } +static bool virt_get_kaslr_dtb_seed(Object *obj, Error **errp) +{ + VirtMachineState *vms = VIRT_MACHINE(obj); + + return vms->kaslr_dtb_seed; +} + +static void virt_set_kaslr_dtb_seed(Object *obj, bool value, Error **errp) +{ + VirtMachineState *vms = VIRT_MACHINE(obj); + + vms->kaslr_dtb_seed = value; +} + static char *virt_get_oem_id(Object *obj, Error **errp) { VirtMachineState *vms = VIRT_MACHINE(obj); @@ -2764,6 +2782,13 @@ static void virt_machine_class_init(ObjectClass *oc, void *data) "Set on/off to enable/disable " "ITS instantiation"); + object_class_property_add_bool(oc, "kaslr-dtb-seed", + virt_get_kaslr_dtb_seed, + virt_set_kaslr_dtb_seed); + object_class_property_set_description(oc, "kaslr-dtb-seed", + "Set off to disable passing of kaslr " + "dtb node to guest"); + object_class_property_add_str(oc, "x-oem-id", virt_get_oem_id, virt_set_oem_id); @@ -2828,6 +2853,9 @@ static void virt_instance_init(Object *obj) /* MTE is disabled by default. */ vms->mte = false; + /* Supply a kaslr-seed by default */ + vms->kaslr_dtb_seed = true; + vms->irqmap = a15irqmap; virt_flash_create(vms);