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Add property for requesting AMD SEV measured kernel launch 

- The 'sev-guest' object gains a boolean 'kernel-hashes' property
    which must be enabled to request a measured kernel launch.
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Merge tag 'sev-hashes-pull-request' of https://gitlab.com/berrange/qemu into staging

Add property for requesting AMD SEV measured kernel launch

 - The 'sev-guest' object gains a boolean 'kernel-hashes' property
   which must be enabled to request a measured kernel launch.

# gpg: Signature made Thu 18 Nov 2021 02:33:25 PM CET
# gpg:                using RSA key DAF3A6FDB26B62912D0E8E3FBE86EBB415104FDF
# gpg: Good signature from "Daniel P. Berrange <dan@berrange.com>" [full]
# gpg:                 aka "Daniel P. Berrange <berrange@redhat.com>" [full]

* tag 'sev-hashes-pull-request' of https://gitlab.com/berrange/qemu:
  target/i386/sev: Replace qemu_map_ram_ptr with address_space_map
  target/i386/sev: Perform padding calculations at compile-time
  target/i386/sev: Fail when invalid hashes table area detected
  target/i386/sev: Rephrase error message when no hashes table in guest firmware
  target/i386/sev: Add kernel hashes only if sev-guest.kernel-hashes=on
  qapi/qom,target/i386: sev-guest: Introduce kernel-hashes=on|off option

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2021-11-18 15:06:05 +01:00
parent 0055ecca84 58603ba268
commit 44a3aa0608
3 changed files with 77 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
qapi/qom.json
View File

@ -769,6 +769,10 @@
# @reduced-phys-bits: number of bits in physical addresses that become
# unavailable when SEV is enabled
#
# @kernel-hashes: if true, add hashes of kernel/initrd/cmdline to a
# designated guest firmware page for measured boot
# with -kernel (default: false) (since 6.2)
#
# Since: 2.12
##
{ 'struct': 'SevGuestProperties',
@ -778,7 +782,8 @@
'*policy': 'uint32',
'*handle': 'uint32',
'*cbitpos': 'uint32',
'reduced-phys-bits': 'uint32' } }
'reduced-phys-bits': 'uint32',
'*kernel-hashes': 'bool' } }
##
# @ObjectType:

6
qemu-options.hx
View File

@ -5189,7 +5189,7 @@ SRST
-object secret,id=sec0,keyid=secmaster0,format=base64,\\
data=$SECRET,iv=$(<iv.b64)
``-object sev-guest,id=id,cbitpos=cbitpos,reduced-phys-bits=val,[sev-device=string,policy=policy,handle=handle,dh-cert-file=file,session-file=file]``
``-object sev-guest,id=id,cbitpos=cbitpos,reduced-phys-bits=val,[sev-device=string,policy=policy,handle=handle,dh-cert-file=file,session-file=file,kernel-hashes=on|off]``
Create a Secure Encrypted Virtualization (SEV) guest object,
which can be used to provide the guest memory encryption support
on AMD processors.
@ -5229,6 +5229,10 @@ SRST
session with the guest owner to negotiate keys used for
attestation. The file must be encoded in base64.
The ``kernel-hashes`` adds the hashes of given kernel/initrd/
cmdline to a designated guest firmware page for measured Linux
boot with -kernel. The default is off. (Since 6.2)
e.g to launch a SEV guest
.. parsed-literal::

79
target/i386/sev.c
View File

@ -37,6 +37,7 @@
#include "qapi/qmp/qerror.h"
#include "exec/confidential-guest-support.h"
#include "hw/i386/pc.h"
#include "exec/address-spaces.h"
#define TYPE_SEV_GUEST "sev-guest"
OBJECT_DECLARE_SIMPLE_TYPE(SevGuestState, SEV_GUEST)
@ -62,6 +63,7 @@ struct SevGuestState {
char *session_file;
uint32_t cbitpos;
uint32_t reduced_phys_bits;
bool kernel_hashes;
/* runtime state */
uint32_t handle;
@ -109,9 +111,19 @@ typedef struct QEMU_PACKED SevHashTable {
SevHashTableEntry cmdline;
SevHashTableEntry initrd;
SevHashTableEntry kernel;
uint8_t padding[];
} SevHashTable;
/*
* Data encrypted by sev_encrypt_flash() must be padded to a multiple of
* 16 bytes.
*/
typedef struct QEMU_PACKED PaddedSevHashTable {
SevHashTable ht;
uint8_t padding[ROUND_UP(sizeof(SevHashTable), 16) - sizeof(SevHashTable)];
} PaddedSevHashTable;
QEMU_BUILD_BUG_ON(sizeof(PaddedSevHashTable) % 16 != 0);
static SevGuestState *sev_guest;
static Error *sev_mig_blocker;
@ -327,6 +339,20 @@ sev_guest_set_sev_device(Object *obj, const char *value, Error **errp)
sev->sev_device = g_strdup(value);
}
static bool sev_guest_get_kernel_hashes(Object *obj, Error **errp)
{
SevGuestState *sev = SEV_GUEST(obj);
return sev->kernel_hashes;
}
static void sev_guest_set_kernel_hashes(Object *obj, bool value, Error **errp)
{
SevGuestState *sev = SEV_GUEST(obj);
sev->kernel_hashes = value;
}
static void
sev_guest_class_init(ObjectClass *oc, void *data)
{
@ -345,6 +371,11 @@ sev_guest_class_init(ObjectClass *oc, void *data)
sev_guest_set_session_file);
object_class_property_set_description(oc, "session-file",
"guest owners session parameters (encoded with base64)");
object_class_property_add_bool(oc, "kernel-hashes",
sev_guest_get_kernel_hashes,
sev_guest_set_kernel_hashes);
object_class_property_set_description(oc, "kernel-hashes",
"add kernel hashes to guest firmware for measured Linux boot");
}
static void
@ -1196,18 +1227,35 @@ bool sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp)
uint8_t *data;
SevHashTableDescriptor *area;
SevHashTable *ht;
PaddedSevHashTable *padded_ht;
uint8_t cmdline_hash[HASH_SIZE];
uint8_t initrd_hash[HASH_SIZE];
uint8_t kernel_hash[HASH_SIZE];
uint8_t *hashp;
size_t hash_len = HASH_SIZE;
int aligned_len;
hwaddr mapped_len = sizeof(*padded_ht);
MemTxAttrs attrs = { 0 };
bool ret = true;
/*
* Only add the kernel hashes if the sev-guest configuration explicitly
* stated kernel-hashes=on.
*/
if (!sev_guest->kernel_hashes) {
return false;
}
if (!pc_system_ovmf_table_find(SEV_HASH_TABLE_RV_GUID, &data, NULL)) {
error_setg(errp, "SEV: kernel specified but OVMF has no hash table guid");
error_setg(errp, "SEV: kernel specified but guest firmware "
"has no hashes table GUID");
return false;
}
area = (SevHashTableDescriptor *)data;
if (!area->base || area->size < sizeof(PaddedSevHashTable)) {
error_setg(errp, "SEV: guest firmware hashes table area is invalid "
"(base=0x%x size=0x%x)", area->base, area->size);
return false;
}
/*
* Calculate hash of kernel command-line with the terminating null byte. If
@ -1248,7 +1296,13 @@ bool sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp)
* Populate the hashes table in the guest's memory at the OVMF-designated
* area for the SEV hashes table
*/
ht = qemu_map_ram_ptr(NULL, area->base);
padded_ht = address_space_map(&address_space_memory, area->base,
&mapped_len, true, attrs);
if (!padded_ht || mapped_len != sizeof(*padded_ht)) {
error_setg(errp, "SEV: cannot map hashes table guest memory area");
return false;
}
ht = &padded_ht->ht;
ht->guid = sev_hash_table_header_guid;
ht->len = sizeof(*ht);
@ -1265,18 +1319,17 @@ bool sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp)
ht->kernel.len = sizeof(ht->kernel);
memcpy(ht->kernel.hash, kernel_hash, sizeof(ht->kernel.hash));
/* When calling sev_encrypt_flash, the length has to be 16 byte aligned */
aligned_len = ROUND_UP(ht->len, 16);
if (aligned_len != ht->len) {
/* zero the excess data so the measurement can be reliably calculated */
memset(ht->padding, 0, aligned_len - ht->len);
/* zero the excess data so the measurement can be reliably calculated */
memset(padded_ht->padding, 0, sizeof(padded_ht->padding));
if (sev_encrypt_flash((uint8_t *)padded_ht, sizeof(*padded_ht), errp) < 0) {
ret = false;
}
if (sev_encrypt_flash((uint8_t *)ht, aligned_len, errp) < 0) {
return false;
}
address_space_unmap(&address_space_memory, padded_ht,
mapped_len, true, mapped_len);
return true;
return ret;
}
static void