/*
* Copyright (C) 2016 The Android Open Source Project
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy,
* modify, merge, publish, distribute, sublicense, and/or sell copies
* of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include "avb_vbmeta_image.h"
#include "avb_crypto.h"
#include "avb_rsa.h"
#include "avb_sha.h"
#include "avb_util.h"
#include "avb_version.h"
AvbVBMetaVerifyResult avb_vbmeta_image_verify(
const uint8_t* data,
size_t length,
const uint8_t** out_public_key_data,
size_t* out_public_key_length) {
AvbVBMetaVerifyResult ret;
AvbVBMetaImageHeader h;
uint8_t* computed_hash;
const AvbAlgorithmData* algorithm;
AvbSHA256Ctx sha256_ctx;
AvbSHA512Ctx sha512_ctx;
const uint8_t* header_block;
const uint8_t* authentication_block;
const uint8_t* auxiliary_block;
int verification_result;
ret = AVB_VBMETA_VERIFY_RESULT_INVALID_VBMETA_HEADER;
if (out_public_key_data != NULL) {
*out_public_key_data = NULL;
}
if (out_public_key_length != NULL) {
*out_public_key_length = 0;
}
/* Ensure magic is correct. */
if (avb_safe_memcmp(data, AVB_MAGIC, AVB_MAGIC_LEN) != 0) {
avb_error("Magic is incorrect.\n");
goto out;
}
/* Before we byteswap, ensure length is long enough. */
if (length < sizeof(AvbVBMetaImageHeader)) {
avb_error("Length is smaller than header.\n");
goto out;
}
avb_vbmeta_image_header_to_host_byte_order((const AvbVBMetaImageHeader*)data,
&h);
/* Ensure we don't attempt to access any fields if we do not meet
* the specified minimum version of libavb.
*/
if ((h.required_libavb_version_major != AVB_VERSION_MAJOR) ||
(h.required_libavb_version_minor > AVB_VERSION_MINOR)) {
avb_error("Mismatch between image version and libavb version.\n");
ret = AVB_VBMETA_VERIFY_RESULT_UNSUPPORTED_VERSION;
goto out;
}
/* Ensure |release_string| ends with a NUL byte. */
if (h.release_string[AVB_RELEASE_STRING_SIZE - 1] != '\0') {
avb_error("Release string does not end with a NUL byte.\n");
goto out;
}
/* Ensure inner block sizes are multiple of 64. */
if ((h.authentication_data_block_size & 0x3f) != 0 ||
(h.auxiliary_data_block_size & 0x3f) != 0) {
avb_error("Block size is not a multiple of 64.\n");
goto out;
}
/* Ensure block sizes all add up to at most |length|. */
uint64_t block_total = sizeof(AvbVBMetaImageHeader);
if (!avb_safe_add_to(&block_total, h.authentication_data_block_size) ||
!avb_safe_add_to(&block_total, h.auxiliary_data_block_size)) {
avb_error("Overflow while computing size of boot image.\n");
goto out;
}
if (block_total > length) {
avb_error("Block sizes add up to more than given length.\n");
goto out;
}
uintptr_t data_ptr = (uintptr_t)data;
/* Ensure passed in memory doesn't wrap. */
if (!avb_safe_add(NULL, (uint64_t)data_ptr, length)) {
avb_error("Boot image location and length mismatch.\n");
goto out;
}
/* Ensure hash and signature are entirely in the Authentication data block. */
uint64_t hash_end;
if (!avb_safe_add(&hash_end, h.hash_offset, h.hash_size) ||
hash_end > h.authentication_data_block_size) {
avb_error("Hash is not entirely in its block.\n");
goto out;
}
uint64_t signature_end;
if (!avb_safe_add(&signature_end, h.signature_offset, h.signature_size) ||
signature_end > h.authentication_data_block_size) {
avb_error("Signature is not entirely in its block.\n");
goto out;
}
/* Ensure public key is entirely in the Auxiliary data block. */
uint64_t pubkey_end;
if (!avb_safe_add(&pubkey_end, h.public_key_offset, h.public_key_size) ||
pubkey_end > h.auxiliary_data_block_size) {
avb_error("Public key is not entirely in its block.\n");
goto out;
}
/* Ensure public key metadata (if set) is entirely in the Auxiliary
* data block. */
if (h.public_key_metadata_size > 0) {
uint64_t pubkey_md_end;
if (!avb_safe_add(&pubkey_md_end,
h.public_key_metadata_offset,
h.public_key_metadata_size) ||
pubkey_md_end > h.auxiliary_data_block_size) {
avb_error("Public key metadata is not entirely in its block.\n");
goto out;
}
}
/* Bail early if there's no hash or signature. */
if (h.algorithm_type == AVB_ALGORITHM_TYPE_NONE) {
ret = AVB_VBMETA_VERIFY_RESULT_OK_NOT_SIGNED;
goto out;
}
/* Ensure algorithm field is supported. */
algorithm = avb_get_algorithm_data(h.algorithm_type);
if (!algorithm) {
avb_error("Invalid or unknown algorithm.\n");
goto out;
}
/* Bail if the embedded hash size doesn't match the chosen algorithm. */
if (h.hash_size != algorithm->hash_len) {
avb_error("Embedded hash has wrong size.\n");
goto out;
}
/* No overflow checks needed from here-on after since all block
* sizes and offsets have been verified above.
*/
header_block = data;
authentication_block = header_block + sizeof(AvbVBMetaImageHeader);
auxiliary_block = authentication_block + h.authentication_data_block_size;
switch (h.algorithm_type) {
/* Explicit fall-through: */
case AVB_ALGORITHM_TYPE_SHA256_RSA2048:
case AVB_ALGORITHM_TYPE_SHA256_RSA4096:
case AVB_ALGORITHM_TYPE_SHA256_RSA8192:
avb_sha256_init(&sha256_ctx);
avb_sha256_update(
&sha256_ctx, header_block, sizeof(AvbVBMetaImageHeader));
avb_sha256_update(
&sha256_ctx, auxiliary_block, h.auxiliary_data_block_size);
computed_hash = avb_sha256_final(&sha256_ctx);
break;
/* Explicit fall-through: */
case AVB_ALGORITHM_TYPE_SHA512_RSA2048:
case AVB_ALGORITHM_TYPE_SHA512_RSA4096:
case AVB_ALGORITHM_TYPE_SHA512_RSA8192:
avb_sha512_init(&sha512_ctx);
avb_sha512_update(
&sha512_ctx, header_block, sizeof(AvbVBMetaImageHeader));
avb_sha512_update(
&sha512_ctx, auxiliary_block, h.auxiliary_data_block_size);
computed_hash = avb_sha512_final(&sha512_ctx);
break;
default:
avb_error("Unknown algorithm.\n");
goto out;
}
if (avb_safe_memcmp(authentication_block + h.hash_offset,
computed_hash,
h.hash_size) != 0) {
avb_error("Hash does not match!\n");
ret = AVB_VBMETA_VERIFY_RESULT_HASH_MISMATCH;
goto out;
}
verification_result =
avb_rsa_verify(auxiliary_block + h.public_key_offset,
h.public_key_size,
authentication_block + h.signature_offset,
h.signature_size,
authentication_block + h.hash_offset,
h.hash_size,
algorithm->padding,
algorithm->padding_len);
if (verification_result == 0) {
ret = AVB_VBMETA_VERIFY_RESULT_SIGNATURE_MISMATCH;
goto out;
}
if (h.public_key_size > 0) {
if (out_public_key_data != NULL) {
*out_public_key_data = auxiliary_block + h.public_key_offset;
}
if (out_public_key_length != NULL) {
*out_public_key_length = h.public_key_size;
}
}
ret = AVB_VBMETA_VERIFY_RESULT_OK;
out:
return ret;
}
void avb_vbmeta_image_header_to_host_byte_order(const AvbVBMetaImageHeader* src,
AvbVBMetaImageHeader* dest) {
avb_memcpy(dest, src, sizeof(AvbVBMetaImageHeader));
dest->required_libavb_version_major =
avb_be32toh(dest->required_libavb_version_major);
dest->required_libavb_version_minor =
avb_be32toh(dest->required_libavb_version_minor);
dest->authentication_data_block_size =
avb_be64toh(dest->authentication_data_block_size);
dest->auxiliary_data_block_size =
avb_be64toh(dest->auxiliary_data_block_size);
dest->algorithm_type = avb_be32toh(dest->algorithm_type);
dest->hash_offset = avb_be64toh(dest->hash_offset);
dest->hash_size = avb_be64toh(dest->hash_size);
dest->signature_offset = avb_be64toh(dest->signature_offset);
dest->signature_size = avb_be64toh(dest->signature_size);
dest->public_key_offset = avb_be64toh(dest->public_key_offset);
dest->public_key_size = avb_be64toh(dest->public_key_size);
dest->public_key_metadata_offset =
avb_be64toh(dest->public_key_metadata_offset);
dest->public_key_metadata_size = avb_be64toh(dest->public_key_metadata_size);
dest->descriptors_offset = avb_be64toh(dest->descriptors_offset);
dest->descriptors_size = avb_be64toh(dest->descriptors_size);
dest->rollback_index = avb_be64toh(dest->rollback_index);
dest->flags = avb_be32toh(dest->flags);
}
const char* avb_vbmeta_verify_result_to_string(AvbVBMetaVerifyResult result) {
const char* ret = NULL;
switch (result) {
case AVB_VBMETA_VERIFY_RESULT_OK:
ret = "OK";
break;
case AVB_VBMETA_VERIFY_RESULT_OK_NOT_SIGNED:
ret = "OK_NOT_SIGNED";
break;
case AVB_VBMETA_VERIFY_RESULT_INVALID_VBMETA_HEADER:
ret = "INVALID_VBMETA_HEADER";
break;
case AVB_VBMETA_VERIFY_RESULT_UNSUPPORTED_VERSION:
ret = "UNSUPPORTED_VERSION";
break;
case AVB_VBMETA_VERIFY_RESULT_HASH_MISMATCH:
ret = "HASH_MISMATCH";
break;
case AVB_VBMETA_VERIFY_RESULT_SIGNATURE_MISMATCH:
ret = "SIGNATURE_MISMATCH";
break;
/* Do not add a 'default:' case here because of -Wswitch. */
}
if (ret == NULL) {
avb_error("Unknown AvbVBMetaVerifyResult value.\n");
ret = "(unknown)";
}
return ret;
}