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-1 digest. */ 48 #define AVB_SHA1_DIGEST_SIZE 20 49 50 /* Size in bytes of a SHA-256 digest. */ 51 #define AVB_SHA256_DIGEST_SIZE 32 52 53 /* Size in bytes of a SHA-512 digest. */ 54 #define AVB_SHA512_DIGEST_SIZE 64 55 56 /* Possible digest types supported by libavb routines. */ 57 typedef enum { 58 AVB_DIGEST_TYPE_SHA256, 59 AVB_DIGEST_TYPE_SHA512, 60 } AvbDigestType; 61 62 /* Algorithms that can be used in the vbmeta image for 63 * verification. An algorithm consists of a hash type and a signature 64 * type. 65 * 66 * The data used to calculate the hash is the three blocks mentioned 67 * in the documentation for |AvbVBMetaImageHeader| except for the data 68 * in the "Authentication data" block. 69 * 70 * For signatures with RSA keys, PKCS v1.5 padding is used. The public 71 * key data is stored in the auxiliary data block, see 72 * |AvbRSAPublicKeyHeader| for the serialization format. 73 * 74 * Each algorithm type is described below: 75 * 76 * AVB_ALGORITHM_TYPE_NONE: There is no hash, no signature of the 77 * data, and no public key. The data cannot be verified. The fields 78 * |hash_size|, |signature_size|, and |public_key_size| must be zero. 79 * 80 * AVB_ALGORITHM_TYPE_SHA256_RSA2048: The hash function used is 81 * SHA-256, resulting in 32 bytes of hash digest data. This hash is 82 * signed with a 2048-bit RSA key. The field |hash_size| must be 32, 83 * |signature_size| must be 256, and the public key data must have 84 * |key_num_bits| set to 2048. 85 * 86 * AVB_ALGORITHM_TYPE_SHA256_RSA4096: Like above, but only with 87 * a 4096-bit RSA key and |signature_size| set to 512. 88 * 89 * AVB_ALGORITHM_TYPE_SHA256_RSA8192: Like above, but only with 90 * a 8192-bit RSA key and |signature_size| set to 1024. 91 * 92 * AVB_ALGORITHM_TYPE_SHA512_RSA2048: The hash function used is 93 * SHA-512, resulting in 64 bytes of hash digest data. This hash is 94 * signed with a 2048-bit RSA key. The field |hash_size| must be 64, 95 * |signature_size| must be 256, and the public key data must have 96 * |key_num_bits| set to 2048. 97 * 98 * AVB_ALGORITHM_TYPE_SHA512_RSA4096: Like above, but only with 99 * a 4096-bit RSA key and |signature_size| set to 512. 100 * 101 * AVB_ALGORITHM_TYPE_SHA512_RSA8192: Like above, but only with 102 * a 8192-bit RSA key and |signature_size| set to 1024. 103 */ 104 typedef enum { 105 AVB_ALGORITHM_TYPE_NONE, 106 AVB_ALGORITHM_TYPE_SHA256_RSA2048, 107 AVB_ALGORITHM_TYPE_SHA256_RSA4096, 108 AVB_ALGORITHM_TYPE_SHA256_RSA8192, 109 AVB_ALGORITHM_TYPE_SHA512_RSA2048, 110 AVB_ALGORITHM_TYPE_SHA512_RSA4096, 111 AVB_ALGORITHM_TYPE_SHA512_RSA8192, 112 _AVB_ALGORITHM_NUM_TYPES 113 } AvbAlgorithmType; 114 115 /* Holds algorithm-specific data. The |padding| is needed by avb_rsa_verify. */ 116 typedef struct { 117 const uint8_t* padding; 118 size_t padding_len; 119 size_t hash_len; 120 } AvbAlgorithmData; 121 122 /* Provides algorithm-specific data for a given |algorithm|. Returns NULL if 123 * |algorithm| is invalid. 124 */ 125 const AvbAlgorithmData* avb_get_algorithm_data(AvbAlgorithmType algorithm) 126 AVB_ATTR_WARN_UNUSED_RESULT; 127 128 /* The header for a serialized RSA public key. 129 * 130 * The size of the key is given by |key_num_bits|, for example 2048 131 * for a RSA-2048 key. By definition, a RSA public key is the pair (n, 132 * e) where |n| is the modulus (which can be represented in 133 * |key_num_bits| bits) and |e| is the public exponent. The exponent 134 * is not stored since it's assumed to always be 65537. 135 * 136 * To optimize verification, the key block includes two precomputed 137 * values, |n0inv| (fits in 32 bits) and |rr| and can always be 138 * represented in |key_num_bits|. 139 140 * The value |n0inv| is the value -1/n[0] (mod 2^32). The value |rr| 141 * is (2^key_num_bits)^2 (mod n). 142 * 143 * Following this header is |key_num_bits| bits of |n|, then 144 * |key_num_bits| bits of |rr|. Both values are stored with most 145 * significant bit first. Each serialized number takes up 146 * |key_num_bits|/8 bytes. 147 * 148 * All fields in this struct are stored in network byte order when 149 * serialized. To generate a copy with fields swapped to native byte 150 * order, use the function avb_rsa_public_key_header_validate_and_byteswap(). 151 * 152 * The avb_rsa_verify() function expects a key in this serialized 153 * format. 154 * 155 * The 'avbtool extract_public_key' command can be used to generate a 156 * serialized RSA public key. 157 */ 158 typedef struct AvbRSAPublicKeyHeader { 159 uint32_t key_num_bits; 160 uint32_t n0inv; 161 } AVB_ATTR_PACKED AvbRSAPublicKeyHeader; 162 163 /* Copies |src| to |dest| and validates, byte-swapping fields in the 164 * process if needed. Returns true if valid, false if invalid. 165 */ 166 bool avb_rsa_public_key_header_validate_and_byteswap( 167 const AvbRSAPublicKeyHeader* src, 168 AvbRSAPublicKeyHeader* dest) AVB_ATTR_WARN_UNUSED_RESULT; 169 170 #ifdef __cplusplus 171 } 172 #endif 173 174 #endif /* AVB_CRYPTO_H_ */ 175