From cff03145ed3cec5c7bd542ea2e6b4458439e0bb0 Mon Sep 17 00:00:00 2001 From: Dov Murik Date: Thu, 30 Sep 2021 08:49:14 +0300 Subject: [PATCH] sev/i386: Introduce sev_add_kernel_loader_hashes for measured linux boot MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add the sev_add_kernel_loader_hashes function to calculate the hashes of the kernel/initrd/cmdline and fill a designated OVMF encrypted hash table area. For this to work, OVMF must support an encrypted area to place the data which is advertised via a special GUID in the OVMF reset table. The hashes of each of the files is calculated (or the string in the case of the cmdline with trailing '\0' included). Each entry in the hashes table is GUID identified and since they're passed through the sev_encrypt_flash interface, the hashes will be accumulated by the AMD PSP measurement (SEV_LAUNCH_MEASURE). Co-developed-by: James Bottomley Signed-off-by: James Bottomley Signed-off-by: Dov Murik Reviewed-by: Daniel P. Berrangé Message-Id: <20210930054915.13252-2-dovmurik@linux.ibm.com> Signed-off-by: Paolo Bonzini --- target/i386/sev-stub.c | 5 ++ target/i386/sev.c | 137 +++++++++++++++++++++++++++++++++++++++++ target/i386/sev_i386.h | 12 ++++ 3 files changed, 154 insertions(+) diff --git a/target/i386/sev-stub.c b/target/i386/sev-stub.c index 0227cb5177..d8e6583171 100644 --- a/target/i386/sev-stub.c +++ b/target/i386/sev-stub.c @@ -81,3 +81,8 @@ sev_get_attestation_report(const char *mnonce, Error **errp) error_setg(errp, "SEV is not available in this QEMU"); return NULL; } + +bool sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp) +{ + g_assert_not_reached(); +} diff --git a/target/i386/sev.c b/target/i386/sev.c index fa7210473a..bcd9260fa4 100644 --- a/target/i386/sev.c +++ b/target/i386/sev.c @@ -23,6 +23,7 @@ #include "qemu/base64.h" #include "qemu/module.h" #include "qemu/uuid.h" +#include "crypto/hash.h" #include "sysemu/kvm.h" #include "sev_i386.h" #include "sysemu/sysemu.h" @@ -83,6 +84,32 @@ typedef struct __attribute__((__packed__)) SevInfoBlock { uint32_t reset_addr; } SevInfoBlock; +#define SEV_HASH_TABLE_RV_GUID "7255371f-3a3b-4b04-927b-1da6efa8d454" +typedef struct QEMU_PACKED SevHashTableDescriptor { + /* SEV hash table area guest address */ + uint32_t base; + /* SEV hash table area size (in bytes) */ + uint32_t size; +} SevHashTableDescriptor; + +/* hard code sha256 digest size */ +#define HASH_SIZE 32 + +typedef struct QEMU_PACKED SevHashTableEntry { + QemuUUID guid; + uint16_t len; + uint8_t hash[HASH_SIZE]; +} SevHashTableEntry; + +typedef struct QEMU_PACKED SevHashTable { + QemuUUID guid; + uint16_t len; + SevHashTableEntry cmdline; + SevHashTableEntry initrd; + SevHashTableEntry kernel; + uint8_t padding[]; +} SevHashTable; + static SevGuestState *sev_guest; static Error *sev_mig_blocker; @@ -1071,6 +1098,116 @@ int sev_es_save_reset_vector(void *flash_ptr, uint64_t flash_size) return 0; } +static const QemuUUID sev_hash_table_header_guid = { + .data = UUID_LE(0x9438d606, 0x4f22, 0x4cc9, 0xb4, 0x79, 0xa7, 0x93, + 0xd4, 0x11, 0xfd, 0x21) +}; + +static const QemuUUID sev_kernel_entry_guid = { + .data = UUID_LE(0x4de79437, 0xabd2, 0x427f, 0xb8, 0x35, 0xd5, 0xb1, + 0x72, 0xd2, 0x04, 0x5b) +}; +static const QemuUUID sev_initrd_entry_guid = { + .data = UUID_LE(0x44baf731, 0x3a2f, 0x4bd7, 0x9a, 0xf1, 0x41, 0xe2, + 0x91, 0x69, 0x78, 0x1d) +}; +static const QemuUUID sev_cmdline_entry_guid = { + .data = UUID_LE(0x97d02dd8, 0xbd20, 0x4c94, 0xaa, 0x78, 0xe7, 0x71, + 0x4d, 0x36, 0xab, 0x2a) +}; + +/* + * Add the hashes of the linux kernel/initrd/cmdline to an encrypted guest page + * which is included in SEV's initial memory measurement. + */ +bool sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp) +{ + uint8_t *data; + SevHashTableDescriptor *area; + SevHashTable *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; + + 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"); + return false; + } + area = (SevHashTableDescriptor *)data; + + /* + * Calculate hash of kernel command-line with the terminating null byte. If + * the user doesn't supply a command-line via -append, the 1-byte "\0" will + * be used. + */ + hashp = cmdline_hash; + if (qcrypto_hash_bytes(QCRYPTO_HASH_ALG_SHA256, ctx->cmdline_data, + ctx->cmdline_size, &hashp, &hash_len, errp) < 0) { + return false; + } + assert(hash_len == HASH_SIZE); + + /* + * Calculate hash of initrd. If the user doesn't supply an initrd via + * -initrd, an empty buffer will be used (ctx->initrd_size == 0). + */ + hashp = initrd_hash; + if (qcrypto_hash_bytes(QCRYPTO_HASH_ALG_SHA256, ctx->initrd_data, + ctx->initrd_size, &hashp, &hash_len, errp) < 0) { + return false; + } + assert(hash_len == HASH_SIZE); + + /* Calculate hash of the kernel */ + hashp = kernel_hash; + struct iovec iov[2] = { + { .iov_base = ctx->setup_data, .iov_len = ctx->setup_size }, + { .iov_base = ctx->kernel_data, .iov_len = ctx->kernel_size } + }; + if (qcrypto_hash_bytesv(QCRYPTO_HASH_ALG_SHA256, iov, ARRAY_SIZE(iov), + &hashp, &hash_len, errp) < 0) { + return false; + } + assert(hash_len == HASH_SIZE); + + /* + * 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); + + ht->guid = sev_hash_table_header_guid; + ht->len = sizeof(*ht); + + ht->cmdline.guid = sev_cmdline_entry_guid; + ht->cmdline.len = sizeof(ht->cmdline); + memcpy(ht->cmdline.hash, cmdline_hash, sizeof(ht->cmdline.hash)); + + ht->initrd.guid = sev_initrd_entry_guid; + ht->initrd.len = sizeof(ht->initrd); + memcpy(ht->initrd.hash, initrd_hash, sizeof(ht->initrd.hash)); + + ht->kernel.guid = sev_kernel_entry_guid; + 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); + } + + if (sev_encrypt_flash((uint8_t *)ht, aligned_len, errp) < 0) { + return false; + } + + return true; +} + static void sev_register_types(void) { diff --git a/target/i386/sev_i386.h b/target/i386/sev_i386.h index ae6d840478..2afe108069 100644 --- a/target/i386/sev_i386.h +++ b/target/i386/sev_i386.h @@ -28,6 +28,17 @@ #define SEV_POLICY_DOMAIN 0x10 #define SEV_POLICY_SEV 0x20 +typedef struct SevKernelLoaderContext { + char *setup_data; + size_t setup_size; + char *kernel_data; + size_t kernel_size; + char *initrd_data; + size_t initrd_size; + char *cmdline_data; + size_t cmdline_size; +} SevKernelLoaderContext; + extern bool sev_es_enabled(void); extern uint64_t sev_get_me_mask(void); extern SevInfo *sev_get_info(void); @@ -37,5 +48,6 @@ extern char *sev_get_launch_measurement(void); extern SevCapability *sev_get_capabilities(Error **errp); extern SevAttestationReport * sev_get_attestation_report(const char *mnonce, Error **errp); +extern bool sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp); #endif