avb_crypto.h
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/* SPDX-License-Identifier: MIT */
/*
* Copyright (C) 2016 The Android Open Source Project
*/
#if !defined(AVB_INSIDE_LIBAVB_H) && !defined(AVB_COMPILATION)
#error "Never include this file directly, include libavb.h instead."
#endif
#ifndef AVB_CRYPTO_H_
#define AVB_CRYPTO_H_
#include "avb_sysdeps.h"
#ifdef __cplusplus
extern "C" {
#endif
/* Size of a RSA-2048 signature. */
#define AVB_RSA2048_NUM_BYTES 256
/* Size of a RSA-4096 signature. */
#define AVB_RSA4096_NUM_BYTES 512
/* Size of a RSA-8192 signature. */
#define AVB_RSA8192_NUM_BYTES 1024
/* Size in bytes of a SHA-1 digest. */
#define AVB_SHA1_DIGEST_SIZE 20
/* Size in bytes of a SHA-256 digest. */
#define AVB_SHA256_DIGEST_SIZE 32
/* Size in bytes of a SHA-512 digest. */
#define AVB_SHA512_DIGEST_SIZE 64
/* Possible digest types supported by libavb routines. */
typedef enum {
AVB_DIGEST_TYPE_SHA256,
AVB_DIGEST_TYPE_SHA512,
} AvbDigestType;
/* Algorithms that can be used in the vbmeta image for
* verification. An algorithm consists of a hash type and a signature
* type.
*
* The data used to calculate the hash is the three blocks mentioned
* in the documentation for |AvbVBMetaImageHeader| except for the data
* in the "Authentication data" block.
*
* For signatures with RSA keys, PKCS v1.5 padding is used. The public
* key data is stored in the auxiliary data block, see
* |AvbRSAPublicKeyHeader| for the serialization format.
*
* Each algorithm type is described below:
*
* AVB_ALGORITHM_TYPE_NONE: There is no hash, no signature of the
* data, and no public key. The data cannot be verified. The fields
* |hash_size|, |signature_size|, and |public_key_size| must be zero.
*
* AVB_ALGORITHM_TYPE_SHA256_RSA2048: The hash function used is
* SHA-256, resulting in 32 bytes of hash digest data. This hash is
* signed with a 2048-bit RSA key. The field |hash_size| must be 32,
* |signature_size| must be 256, and the public key data must have
* |key_num_bits| set to 2048.
*
* AVB_ALGORITHM_TYPE_SHA256_RSA4096: Like above, but only with
* a 4096-bit RSA key and |signature_size| set to 512.
*
* AVB_ALGORITHM_TYPE_SHA256_RSA8192: Like above, but only with
* a 8192-bit RSA key and |signature_size| set to 1024.
*
* AVB_ALGORITHM_TYPE_SHA512_RSA2048: The hash function used is
* SHA-512, resulting in 64 bytes of hash digest data. This hash is
* signed with a 2048-bit RSA key. The field |hash_size| must be 64,
* |signature_size| must be 256, and the public key data must have
* |key_num_bits| set to 2048.
*
* AVB_ALGORITHM_TYPE_SHA512_RSA4096: Like above, but only with
* a 4096-bit RSA key and |signature_size| set to 512.
*
* AVB_ALGORITHM_TYPE_SHA512_RSA8192: Like above, but only with
* a 8192-bit RSA key and |signature_size| set to 1024.
*/
typedef enum {
AVB_ALGORITHM_TYPE_NONE,
AVB_ALGORITHM_TYPE_SHA256_RSA2048,
AVB_ALGORITHM_TYPE_SHA256_RSA4096,
AVB_ALGORITHM_TYPE_SHA256_RSA8192,
AVB_ALGORITHM_TYPE_SHA512_RSA2048,
AVB_ALGORITHM_TYPE_SHA512_RSA4096,
AVB_ALGORITHM_TYPE_SHA512_RSA8192,
_AVB_ALGORITHM_NUM_TYPES
} AvbAlgorithmType;
/* Holds algorithm-specific data. The |padding| is needed by avb_rsa_verify. */
typedef struct {
const uint8_t* padding;
size_t padding_len;
size_t hash_len;
} AvbAlgorithmData;
/* Provides algorithm-specific data for a given |algorithm|. Returns NULL if
* |algorithm| is invalid.
*/
const AvbAlgorithmData* avb_get_algorithm_data(AvbAlgorithmType algorithm)
AVB_ATTR_WARN_UNUSED_RESULT;
/* The header for a serialized RSA public key.
*
* The size of the key is given by |key_num_bits|, for example 2048
* for a RSA-2048 key. By definition, a RSA public key is the pair (n,
* e) where |n| is the modulus (which can be represented in
* |key_num_bits| bits) and |e| is the public exponent. The exponent
* is not stored since it's assumed to always be 65537.
*
* To optimize verification, the key block includes two precomputed
* values, |n0inv| (fits in 32 bits) and |rr| and can always be
* represented in |key_num_bits|.
* The value |n0inv| is the value -1/n[0] (mod 2^32). The value |rr|
* is (2^key_num_bits)^2 (mod n).
*
* Following this header is |key_num_bits| bits of |n|, then
* |key_num_bits| bits of |rr|. Both values are stored with most
* significant bit first. Each serialized number takes up
* |key_num_bits|/8 bytes.
*
* All fields in this struct are stored in network byte order when
* serialized. To generate a copy with fields swapped to native byte
* order, use the function avb_rsa_public_key_header_validate_and_byteswap().
*
* The avb_rsa_verify() function expects a key in this serialized
* format.
*
* The 'avbtool extract_public_key' command can be used to generate a
* serialized RSA public key.
*/
typedef struct AvbRSAPublicKeyHeader {
uint32_t key_num_bits;
uint32_t n0inv;
} AVB_ATTR_PACKED AvbRSAPublicKeyHeader;
/* Copies |src| to |dest| and validates, byte-swapping fields in the
* process if needed. Returns true if valid, false if invalid.
*/
bool avb_rsa_public_key_header_validate_and_byteswap(
const AvbRSAPublicKeyHeader* src,
AvbRSAPublicKeyHeader* dest) AVB_ATTR_WARN_UNUSED_RESULT;
#ifdef __cplusplus
}
#endif
#endif /* AVB_CRYPTO_H_ */