blob: 809e1b663da8960312276bde4b58fac3008c6d50 [file] [log] [blame]
/* Copyright 2015 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*
* Kernel verified boot functions
*/
#include "2sysincludes.h"
#include "2misc.h"
#include "2nvstorage.h"
#include "2rsa.h"
#include "2secdata.h"
#include "2sha.h"
#include "vb2_common.h"
static const uint8_t *vb2_signature_data_const(const struct vb2_signature *sig)
{
return (uint8_t *)sig + sig->sig_offset;
}
/**
* Returns non-zero if the kernel needs to have a valid signature, instead of
* just a valid hash.
*/
static int vb2_need_signed_kernel(struct vb2_context *ctx)
{
/* Recovery kernels are always signed */
if (ctx->flags & VB2_CONTEXT_RECOVERY_MODE)
return 1;
/* Normal mode kernels are always signed */
if (!(ctx->flags & VB2_CONTEXT_DEVELOPER_MODE))
return 1;
/* Developers may require signed kernels */
if (vb2_nv_get(ctx, VB2_NV_DEV_BOOT_SIGNED_ONLY))
return 1;
return 0;
}
int vb2_verify_keyblock_hash(const struct vb2_keyblock *block,
uint32_t size,
const struct vb2_workbuf *wb)
{
const struct vb2_signature *sig = &block->keyblock_hash;
struct vb2_workbuf wblocal = *wb;
struct vb2_digest_context *dc;
uint8_t *digest;
uint32_t digest_size;
int rv;
/* Sanity check keyblock before attempting hash check of data */
rv = vb2_check_keyblock(block, size, sig);
if (rv)
return rv;
VB2_DEBUG("Checking key block hash...\n");
/* Digest goes at start of work buffer */
digest_size = vb2_digest_size(VB2_HASH_SHA512);
digest = vb2_workbuf_alloc(&wblocal, digest_size);
if (!digest)
return VB2_ERROR_VDATA_WORKBUF_DIGEST;
/* Hashing requires temp space for the context */
dc = vb2_workbuf_alloc(&wblocal, sizeof(*dc));
if (!dc)
return VB2_ERROR_VDATA_WORKBUF_HASHING;
rv = vb2_digest_init(dc, VB2_HASH_SHA512);
if (rv)
return rv;
rv = vb2_digest_extend(dc, (const uint8_t *)block, sig->data_size);
if (rv)
return rv;
rv = vb2_digest_finalize(dc, digest, digest_size);
if (rv)
return rv;
if (vb2_safe_memcmp(vb2_signature_data_const(sig), digest,
digest_size) != 0) {
VB2_DEBUG("Invalid key block hash.\n");
return VB2_ERROR_KEYBLOCK_SIG_INVALID;
}
/* Success */
return VB2_SUCCESS;
}
int vb2_load_kernel_keyblock(struct vb2_context *ctx)
{
struct vb2_shared_data *sd = vb2_get_sd(ctx);
struct vb2_workbuf wb;
uint8_t *key_data;
uint32_t key_size;
struct vb2_packed_key *packed_key;
struct vb2_public_key kernel_key;
struct vb2_keyblock *kb;
uint32_t block_size;
int rec_switch = (ctx->flags & VB2_CONTEXT_RECOVERY_MODE) != 0;
int dev_switch = (ctx->flags & VB2_CONTEXT_DEVELOPER_MODE) != 0;
int need_keyblock_valid = vb2_need_signed_kernel(ctx);
int keyblock_is_valid = 1;
int rv;
vb2_workbuf_from_ctx(ctx, &wb);
/*
* Clear any previous keyblock-valid flag (for example, from a previous
* kernel where the keyblock was signed but the preamble failed
* verification).
*/
sd->flags &= ~VB2_SD_FLAG_KERNEL_SIGNED;
/* Unpack the kernel key */
key_data = ctx->workbuf + sd->workbuf_kernel_key_offset;
key_size = sd->workbuf_kernel_key_size;
rv = vb2_unpack_key(&kernel_key, key_data, key_size);
if (rv)
return rv;
/* Load the kernel keyblock header after the root key */
kb = vb2_workbuf_alloc(&wb, sizeof(*kb));
if (!kb)
return VB2_ERROR_KERNEL_KEYBLOCK_WORKBUF_HEADER;
rv = vb2ex_read_resource(ctx, VB2_RES_KERNEL_VBLOCK, 0, kb,
sizeof(*kb));
if (rv)
return rv;
block_size = kb->keyblock_size;
/*
* Load the entire keyblock, now that we know how big it is. Note that
* we're loading the entire keyblock instead of just the piece after
* the header. That means we re-read the header. But that's a tiny
* amount of data, and it makes the code much more straightforward.
*/
kb = vb2_workbuf_realloc(&wb, sizeof(*kb), block_size);
if (!kb)
return VB2_ERROR_KERNEL_KEYBLOCK_WORKBUF;
rv = vb2ex_read_resource(ctx, VB2_RES_KERNEL_VBLOCK, 0, kb, block_size);
if (rv)
return rv;
/* Verify the keyblock */
rv = vb2_verify_keyblock(kb, block_size, &kernel_key, &wb);
if (rv) {
keyblock_is_valid = 0;
if (need_keyblock_valid)
return rv;
/* Signature is invalid, but hash may be fine */
rv = vb2_verify_keyblock_hash(kb, block_size, &wb);
if (rv)
return rv;
}
/* Check the key block flags against the current boot mode */
if (!(kb->keyblock_flags &
(dev_switch ? VB2_KEY_BLOCK_FLAG_DEVELOPER_1 :
VB2_KEY_BLOCK_FLAG_DEVELOPER_0))) {
VB2_DEBUG("Key block developer flag mismatch.\n");
keyblock_is_valid = 0;
if (need_keyblock_valid)
return VB2_ERROR_KERNEL_KEYBLOCK_DEV_FLAG;
}
if (!(kb->keyblock_flags &
(rec_switch ? VB2_KEY_BLOCK_FLAG_RECOVERY_1 :
VB2_KEY_BLOCK_FLAG_RECOVERY_0))) {
VB2_DEBUG("Key block recovery flag mismatch.\n");
keyblock_is_valid = 0;
if (need_keyblock_valid)
return VB2_ERROR_KERNEL_KEYBLOCK_REC_FLAG;
}
/* Check for keyblock rollback if not in recovery mode */
/* Key version is the upper 16 bits of the composite version */
if (!rec_switch && kb->data_key.key_version > VB2_MAX_KEY_VERSION) {
keyblock_is_valid = 0;
if (need_keyblock_valid)
return VB2_ERROR_KERNEL_KEYBLOCK_VERSION_RANGE;
}
if (!rec_switch && kb->data_key.key_version <
(sd->kernel_version_secdatak >> 16)) {
keyblock_is_valid = 0;
if (need_keyblock_valid)
return VB2_ERROR_KERNEL_KEYBLOCK_VERSION_ROLLBACK;
}
sd->kernel_version = kb->data_key.key_version << 16;
/*
* At this point, we've checked everything. The kernel keyblock is at
* least self-consistent, and has either a valid signature or a valid
* hash. Track if it had a valid signature (that is, would we have
* been willing to boot it even if developer mode was off).
*/
if (keyblock_is_valid)
sd->flags |= VB2_SD_FLAG_KERNEL_SIGNED;
/* Preamble follows the keyblock in the vblock */
sd->vblock_preamble_offset = kb->keyblock_size;
/*
* Keep just the data key from the vblock. This follows the kernel key
* (which we might still need to verify the next kernel, if the
* assoiciated kernel preamble and data don't verify).
*/
sd->workbuf_data_key_offset = ctx->workbuf_used;
key_data = ctx->workbuf + sd->workbuf_data_key_offset;
packed_key = (struct vb2_packed_key *)key_data;
memmove(packed_key, &kb->data_key, sizeof(*packed_key));
packed_key->key_offset = sizeof(*packed_key);
memmove(key_data + packed_key->key_offset,
(uint8_t*)&kb->data_key + kb->data_key.key_offset,
packed_key->key_size);
/* Save the packed key size */
sd->workbuf_data_key_size =
packed_key->key_offset + packed_key->key_size;
/*
* Data key will persist in the workbuf after we return.
*
* Work buffer now contains:
* - vb2_shared_data
* - kernel key
* - packed kernel data key
*/
ctx->workbuf_used = sd->workbuf_data_key_offset +
sd->workbuf_data_key_size;
return VB2_SUCCESS;
}
int vb2_verify_kernel_preamble(struct vb2_kernel_preamble *preamble,
uint32_t size,
const struct vb2_public_key *key,
const struct vb2_workbuf *wb)
{
struct vb2_signature *sig = &preamble->preamble_signature;
uint32_t min_size = EXPECTED_VB2_KERNEL_PREAMBLE_2_0_SIZE;
VB2_DEBUG("Verifying kernel preamble.\n");
/* Make sure it's even safe to look at the struct */
if(size < min_size) {
VB2_DEBUG("Not enough data for preamble header.\n");
return VB2_ERROR_PREAMBLE_TOO_SMALL_FOR_HEADER;
}
if (preamble->header_version_major !=
KERNEL_PREAMBLE_HEADER_VERSION_MAJOR) {
VB2_DEBUG("Incompatible kernel preamble header version.\n");
return VB2_ERROR_PREAMBLE_HEADER_VERSION;
}
if (preamble->header_version_minor >= 2)
min_size = EXPECTED_VB2_KERNEL_PREAMBLE_2_2_SIZE;
else if (preamble->header_version_minor == 1)
min_size = EXPECTED_VB2_KERNEL_PREAMBLE_2_1_SIZE;
if(preamble->preamble_size < min_size) {
VB2_DEBUG("Preamble size too small for header.\n");
return VB2_ERROR_PREAMBLE_TOO_SMALL_FOR_HEADER;
}
if (size < preamble->preamble_size) {
VB2_DEBUG("Not enough data for preamble.\n");
return VB2_ERROR_PREAMBLE_SIZE;
}
/* Check signature */
if (vb2_verify_signature_inside(preamble, preamble->preamble_size,
sig)) {
VB2_DEBUG("Preamble signature off end of preamble\n");
return VB2_ERROR_PREAMBLE_SIG_OUTSIDE;
}
/* Make sure advertised signature data sizes are sane. */
if (preamble->preamble_size < sig->data_size) {
VB2_DEBUG("Signature calculated past end of the block\n");
return VB2_ERROR_PREAMBLE_SIGNED_TOO_MUCH;
}
if (vb2_verify_data((const uint8_t *)preamble, size, sig, key, wb)) {
VB2_DEBUG("Preamble signature validation failed\n");
return VB2_ERROR_PREAMBLE_SIG_INVALID;
}
/* Verify we signed enough data */
if (sig->data_size < sizeof(struct vb2_fw_preamble)) {
VB2_DEBUG("Didn't sign enough data\n");
return VB2_ERROR_PREAMBLE_SIGNED_TOO_LITTLE;
}
/* Verify body signature is inside the signed data */
if (vb2_verify_signature_inside(preamble, sig->data_size,
&preamble->body_signature)) {
VB2_DEBUG("Body signature off end of preamble\n");
return VB2_ERROR_PREAMBLE_BODY_SIG_OUTSIDE;
}
/*
* If bootloader is present, verify it's covered by the body
* signature.
*/
if (preamble->bootloader_size) {
const void *body_ptr =
(const void *)(uintptr_t)preamble->body_load_address;
const void *bootloader_ptr =
(const void *)(uintptr_t)preamble->bootloader_address;
if (vb2_verify_member_inside(body_ptr,
preamble->body_signature.data_size,
bootloader_ptr,
preamble->bootloader_size,
0, 0)) {
VB2_DEBUG("Bootloader off end of signed data\n");
return VB2_ERROR_PREAMBLE_BOOTLOADER_OUTSIDE;
}
}
/*
* If vmlinuz header is present, verify it's covered by the body
* signature.
*/
if (preamble->header_version_minor >= 1 &&
preamble->vmlinuz_header_size) {
const void *body_ptr =
(const void *)(uintptr_t)preamble->body_load_address;
const void *vmlinuz_header_ptr = (const void *)
(uintptr_t)preamble->vmlinuz_header_address;
if (vb2_verify_member_inside(body_ptr,
preamble->body_signature.data_size,
vmlinuz_header_ptr,
preamble->vmlinuz_header_size,
0, 0)) {
VB2_DEBUG("Vmlinuz header off end of signed data\n");
return VB2_ERROR_PREAMBLE_VMLINUZ_HEADER_OUTSIDE;
}
}
/* Success */
return VB2_SUCCESS;
}
int vb2_load_kernel_preamble(struct vb2_context *ctx)
{
struct vb2_shared_data *sd = vb2_get_sd(ctx);
struct vb2_workbuf wb;
uint8_t *key_data = ctx->workbuf + sd->workbuf_data_key_offset;
uint32_t key_size = sd->workbuf_data_key_size;
struct vb2_public_key data_key;
/* Preamble goes in the next unused chunk of work buffer */
/* TODO: what's the minimum workbuf size? Kernel preamble is usually
* padded to around 64KB. */
struct vb2_kernel_preamble *pre;
uint32_t pre_size;
int rv;
vb2_workbuf_from_ctx(ctx, &wb);
/* Unpack the kernel data key */
if (!sd->workbuf_data_key_size)
return VB2_ERROR_KERNEL_PREAMBLE2_DATA_KEY;
rv = vb2_unpack_key(&data_key, key_data, key_size);
if (rv)
return rv;
/* Load the kernel preamble header */
pre = vb2_workbuf_alloc(&wb, sizeof(*pre));
if (!pre)
return VB2_ERROR_KERNEL_PREAMBLE2_WORKBUF_HEADER;
rv = vb2ex_read_resource(ctx, VB2_RES_KERNEL_VBLOCK,
sd->vblock_preamble_offset,
pre, sizeof(*pre));
if (rv)
return rv;
pre_size = pre->preamble_size;
/* Load the entire preamble, now that we know how big it is */
pre = vb2_workbuf_realloc(&wb, sizeof(*pre), pre_size);
if (!pre)
return VB2_ERROR_KERNEL_PREAMBLE2_WORKBUF;
rv = vb2ex_read_resource(ctx, VB2_RES_KERNEL_VBLOCK,
sd->vblock_preamble_offset,
pre, pre_size);
if (rv)
return rv;
/*
* Work buffer now contains:
* - vb2_shared_data
* - kernel key
* - packed kernel data key
* - kernel preamble
*/
/* Verify the preamble */
rv = vb2_verify_kernel_preamble(pre, pre_size, &data_key, &wb);
if (rv)
return rv;
/*
* Kernel preamble version is the lower 16 bits of the composite kernel
* version.
*/
if (pre->kernel_version > VB2_MAX_PREAMBLE_VERSION)
return VB2_ERROR_KERNEL_PREAMBLE_VERSION_RANGE;
/* Combine with the key version from vb2_load_kernel_keyblock() */
sd->kernel_version |= pre->kernel_version;
if (vb2_need_signed_kernel(ctx) &&
sd->kernel_version < sd->kernel_version_secdatak)
return VB2_ERROR_KERNEL_PREAMBLE_VERSION_ROLLBACK;
/* Keep track of where we put the preamble */
sd->workbuf_preamble_offset = vb2_offset_of(ctx->workbuf, pre);
sd->workbuf_preamble_size = pre_size;
/*
* Preamble will persist in work buffer after we return.
*
* Work buffer now contains:
* - vb2_shared_data
* - kernel key
* - packed kernel data key
* - kernel preamble
*
* TODO: we could move the preamble down over the kernel data key
* since we don't need it anymore.
*/
ctx->workbuf_used = sd->workbuf_preamble_offset + pre_size;
return VB2_SUCCESS;
}
void vb2_kernel_get_vmlinuz_header(const struct vb2_kernel_preamble *preamble,
uint64_t *vmlinuz_header_address,
uint32_t *vmlinuz_header_size)
{
if (preamble->header_version_minor < 1) {
*vmlinuz_header_address = 0;
*vmlinuz_header_size = 0;
} else {
/*
* Set header and size only if the preamble header version is >
* 2.1 as they don't exist in version 2.0 (Note that we don't
* need to check header_version_major; if that's not 2 then
* vb2_verify_kernel_preamble() would have already failed.
*/
*vmlinuz_header_address = preamble->vmlinuz_header_address;
*vmlinuz_header_size = preamble->vmlinuz_header_size;
}
}
uint32_t vb2_kernel_get_flags(const struct vb2_kernel_preamble *preamble)
{
if (preamble->header_version_minor < 2)
return 0;
return preamble->flags;
}