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      1 /*
      2  * Copyright (C) 2016 The Android Open Source Project
      3  *
      4  * Permission is hereby granted, free of charge, to any person
      5  * obtaining a copy of this software and associated documentation
      6  * files (the "Software"), to deal in the Software without
      7  * restriction, including without limitation the rights to use, copy,
      8  * modify, merge, publish, distribute, sublicense, and/or sell copies
      9  * of the Software, and to permit persons to whom the Software is
     10  * furnished to do so, subject to the following conditions:
     11  *
     12  * The above copyright notice and this permission notice shall be
     13  * included in all copies or substantial portions of the Software.
     14  *
     15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
     16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
     17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
     18  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
     19  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
     20  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
     21  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
     22  * SOFTWARE.
     23  */
     24 
     25 #if !defined(AVB_INSIDE_LIBAVB_H) && !defined(AVB_COMPILATION)
     26 #error "Never include this file directly, include libavb.h instead."
     27 #endif
     28 
     29 #ifndef AVB_CRYPTO_H_
     30 #define AVB_CRYPTO_H_
     31 
     32 #include "avb_sysdeps.h"
     33 
     34 #ifdef __cplusplus
     35 extern "C" {
     36 #endif
     37 
     38 /* Size of a RSA-2048 signature. */
     39 #define AVB_RSA2048_NUM_BYTES 256
     40 
     41 /* Size of a RSA-4096 signature. */
     42 #define AVB_RSA4096_NUM_BYTES 512
     43 
     44 /* Size of a RSA-8192 signature. */
     45 #define AVB_RSA8192_NUM_BYTES 1024
     46 
     47 /* Size in bytes of a SHA-256 digest. */
     48 #define AVB_SHA256_DIGEST_SIZE 32
     49 
     50 /* Size in bytes of a SHA-512 digest. */
     51 #define AVB_SHA512_DIGEST_SIZE 64
     52 
     53 /* Algorithms that can be used in the vbmeta image for
     54  * verification. An algorithm consists of a hash type and a signature
     55  * type.
     56  *
     57  * The data used to calculate the hash is the three blocks mentioned
     58  * in the documentation for |AvbVBMetaImageHeader| except for the data
     59  * in the "Authentication data" block.
     60  *
     61  * For signatures with RSA keys, PKCS v1.5 padding is used. The public
     62  * key data is stored in the auxiliary data block, see
     63  * |AvbRSAPublicKeyHeader| for the serialization format.
     64  *
     65  * Each algorithm type is described below:
     66  *
     67  * AVB_ALGORITHM_TYPE_NONE: There is no hash, no signature of the
     68  * data, and no public key. The data cannot be verified. The fields
     69  * |hash_size|, |signature_size|, and |public_key_size| must be zero.
     70  *
     71  * AVB_ALGORITHM_TYPE_SHA256_RSA2048: The hash function used is
     72  * SHA-256, resulting in 32 bytes of hash digest data. This hash is
     73  * signed with a 2048-bit RSA key. The field |hash_size| must be 32,
     74  * |signature_size| must be 256, and the public key data must have
     75  * |key_num_bits| set to 2048.
     76  *
     77  * AVB_ALGORITHM_TYPE_SHA256_RSA4096: Like above, but only with
     78  * a 4096-bit RSA key and |signature_size| set to 512.
     79  *
     80  * AVB_ALGORITHM_TYPE_SHA256_RSA8192: Like above, but only with
     81  * a 8192-bit RSA key and |signature_size| set to 1024.
     82  *
     83  * AVB_ALGORITHM_TYPE_SHA512_RSA2048: The hash function used is
     84  * SHA-512, resulting in 64 bytes of hash digest data. This hash is
     85  * signed with a 2048-bit RSA key. The field |hash_size| must be 64,
     86  * |signature_size| must be 256, and the public key data must have
     87  * |key_num_bits| set to 2048.
     88  *
     89  * AVB_ALGORITHM_TYPE_SHA512_RSA4096: Like above, but only with
     90  * a 4096-bit RSA key and |signature_size| set to 512.
     91  *
     92  * AVB_ALGORITHM_TYPE_SHA512_RSA8192: Like above, but only with
     93  * a 8192-bit RSA key and |signature_size| set to 1024.
     94  */
     95 typedef enum {
     96   AVB_ALGORITHM_TYPE_NONE,
     97   AVB_ALGORITHM_TYPE_SHA256_RSA2048,
     98   AVB_ALGORITHM_TYPE_SHA256_RSA4096,
     99   AVB_ALGORITHM_TYPE_SHA256_RSA8192,
    100   AVB_ALGORITHM_TYPE_SHA512_RSA2048,
    101   AVB_ALGORITHM_TYPE_SHA512_RSA4096,
    102   AVB_ALGORITHM_TYPE_SHA512_RSA8192,
    103   _AVB_ALGORITHM_NUM_TYPES
    104 } AvbAlgorithmType;
    105 
    106 /* Holds algorithm-specific data. The |padding| is needed by avb_rsa_verify. */
    107 typedef struct {
    108   const uint8_t* padding;
    109   size_t padding_len;
    110   size_t hash_len;
    111 } AvbAlgorithmData;
    112 
    113 /* Provides algorithm-specific data for a given |algorithm|. Returns NULL if
    114  * |algorithm| is invalid.
    115  */
    116 const AvbAlgorithmData* avb_get_algorithm_data(AvbAlgorithmType algorithm)
    117     AVB_ATTR_WARN_UNUSED_RESULT;
    118 
    119 /* The header for a serialized RSA public key.
    120  *
    121  * The size of the key is given by |key_num_bits|, for example 2048
    122  * for a RSA-2048 key. By definition, a RSA public key is the pair (n,
    123  * e) where |n| is the modulus (which can be represented in
    124  * |key_num_bits| bits) and |e| is the public exponent. The exponent
    125  * is not stored since it's assumed to always be 65537.
    126  *
    127  * To optimize verification, the key block includes two precomputed
    128  * values, |n0inv| (fits in 32 bits) and |rr| and can always be
    129  * represented in |key_num_bits|.
    130 
    131  * The value |n0inv| is the value -1/n[0] (mod 2^32). The value |rr|
    132  * is (2^key_num_bits)^2 (mod n).
    133  *
    134  * Following this header is |key_num_bits| bits of |n|, then
    135  * |key_num_bits| bits of |rr|. Both values are stored with most
    136  * significant bit first. Each serialized number takes up
    137  * |key_num_bits|/8 bytes.
    138  *
    139  * All fields in this struct are stored in network byte order when
    140  * serialized.  To generate a copy with fields swapped to native byte
    141  * order, use the function avb_rsa_public_key_header_validate_and_byteswap().
    142  *
    143  * The avb_rsa_verify() function expects a key in this serialized
    144  * format.
    145  *
    146  * The 'avbtool extract_public_key' command can be used to generate a
    147  * serialized RSA public key.
    148  */
    149 typedef struct AvbRSAPublicKeyHeader {
    150   uint32_t key_num_bits;
    151   uint32_t n0inv;
    152 } AVB_ATTR_PACKED AvbRSAPublicKeyHeader;
    153 
    154 /* Copies |src| to |dest| and validates, byte-swapping fields in the
    155  * process if needed. Returns true if valid, false if invalid.
    156  */
    157 bool avb_rsa_public_key_header_validate_and_byteswap(
    158     const AvbRSAPublicKeyHeader* src,
    159     AvbRSAPublicKeyHeader* dest) AVB_ATTR_WARN_UNUSED_RESULT;
    160 
    161 #ifdef __cplusplus
    162 }
    163 #endif
    164 
    165 #endif /* AVB_CRYPTO_H_ */
    166