diff --git a/qapi/qom.json b/qapi/qom.json index ccd1167808..eeb5395ff3 100644 --- a/qapi/qom.json +++ b/qapi/qom.json @@ -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: diff --git a/qemu-options.hx b/qemu-options.hx index 7749f59300..ae2c6dbbfc 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -5189,7 +5189,7 @@ SRST -object secret,id=sec0,keyid=secmaster0,format=base64,\\ data=$SECRET,iv=$(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