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 /* 26 #if !defined(AVB_INSIDE_LIBAVB_H) && !defined(AVB_COMPILATION) 27 #error "Never include this file directly, include libavb.h instead." 28 #endif 29 */ 30 31 #ifndef AVB_CRYPTO_H_ 32 #define AVB_CRYPTO_H_ 33 34 #include <android_avb/avb_sysdeps.h> 35 36 #ifdef __cplusplus 37 extern "C" { 38 #endif 39 40 /* Size of a RSA-2048 signature. */ 41 #define AVB_RSA2048_NUM_BYTES 256 42 43 /* Size of a RSA-4096 signature. */ 44 #define AVB_RSA4096_NUM_BYTES 512 45 46 /* Size of a RSA-8192 signature. */ 47 #define AVB_RSA8192_NUM_BYTES 1024 48 49 /* Size in bytes of a SHA-256 digest. */ 50 #define AVB_SHA256_DIGEST_SIZE 32 51 52 /* Size in bytes of a SHA-512 digest. */ 53 #define AVB_SHA512_DIGEST_SIZE 64 54 55 /* Algorithms that can be used in the vbmeta image for 56 * verification. An algorithm consists of a hash type and a signature 57 * type. 58 * 59 * The data used to calculate the hash is the three blocks mentioned 60 * in the documentation for |AvbVBMetaImageHeader| except for the data 61 * in the "Authentication data" block. 62 * 63 * For signatures with RSA keys, PKCS v1.5 padding is used. The public 64 * key data is stored in the auxiliary data block, see 65 * |AvbRSAPublicKeyHeader| for the serialization format. 66 * 67 * Each algorithm type is described below: 68 * 69 * AVB_ALGORITHM_TYPE_NONE: There is no hash, no signature of the 70 * data, and no public key. The data cannot be verified. The fields 71 * |hash_size|, |signature_size|, and |public_key_size| must be zero. 72 * 73 * AVB_ALGORITHM_TYPE_SHA256_RSA2048: The hash function used is 74 * SHA-256, resulting in 32 bytes of hash digest data. This hash is 75 * signed with a 2048-bit RSA key. The field |hash_size| must be 32, 76 * |signature_size| must be 256, and the public key data must have 77 * |key_num_bits| set to 2048. 78 * 79 * AVB_ALGORITHM_TYPE_SHA256_RSA4096: Like above, but only with 80 * a 4096-bit RSA key and |signature_size| set to 512. 81 * 82 * AVB_ALGORITHM_TYPE_SHA256_RSA8192: Like above, but only with 83 * a 8192-bit RSA key and |signature_size| set to 1024. 84 * 85 * AVB_ALGORITHM_TYPE_SHA512_RSA2048: The hash function used is 86 * SHA-512, resulting in 64 bytes of hash digest data. This hash is 87 * signed with a 2048-bit RSA key. The field |hash_size| must be 64, 88 * |signature_size| must be 256, and the public key data must have 89 * |key_num_bits| set to 2048. 90 * 91 * AVB_ALGORITHM_TYPE_SHA512_RSA4096: Like above, but only with 92 * a 4096-bit RSA key and |signature_size| set to 512. 93 * 94 * AVB_ALGORITHM_TYPE_SHA512_RSA8192: Like above, but only with 95 * a 8192-bit RSA key and |signature_size| set to 1024. 96 */ 97 typedef enum { 98 AVB_ALGORITHM_TYPE_NONE, 99 AVB_ALGORITHM_TYPE_SHA256_RSA2048, 100 AVB_ALGORITHM_TYPE_SHA256_RSA4096, 101 AVB_ALGORITHM_TYPE_SHA256_RSA8192, 102 AVB_ALGORITHM_TYPE_SHA512_RSA2048, 103 AVB_ALGORITHM_TYPE_SHA512_RSA4096, 104 AVB_ALGORITHM_TYPE_SHA512_RSA8192, 105 _AVB_ALGORITHM_NUM_TYPES 106 } AvbAlgorithmType; 107 108 /* Holds algorithm-specific data. The |padding| is needed by avb_rsa_verify. */ 109 typedef struct { 110 const uint8_t* padding; 111 size_t padding_len; 112 size_t hash_len; 113 } AvbAlgorithmData; 114 115 /* Provides algorithm-specific data for a given |algorithm|. Returns NULL if 116 * |algorithm| is invalid. 117 */ 118 const AvbAlgorithmData* avb_get_algorithm_data(AvbAlgorithmType algorithm) 119 AVB_ATTR_WARN_UNUSED_RESULT; 120 121 /* The header for a serialized RSA public key. 122 * 123 * The size of the key is given by |key_num_bits|, for example 2048 124 * for a RSA-2048 key. By definition, a RSA public key is the pair (n, 125 * e) where |n| is the modulus (which can be represented in 126 * |key_num_bits| bits) and |e| is the public exponent. The exponent 127 * is not stored since it's assumed to always be 65537. 128 * 129 * To optimize verification, the key block includes two precomputed 130 * values, |n0inv| (fits in 32 bits) and |rr| and can always be 131 * represented in |key_num_bits|. 132 133 * The value |n0inv| is the value -1/n[0] (mod 2^32). The value |rr| 134 * is (2^key_num_bits)^2 (mod n). 135 * 136 * Following this header is |key_num_bits| bits of |n|, then 137 * |key_num_bits| bits of |rr|. Both values are stored with most 138 * significant bit first. Each serialized number takes up 139 * |key_num_bits|/8 bytes. 140 * 141 * All fields in this struct are stored in network byte order when 142 * serialized. To generate a copy with fields swapped to native byte 143 * order, use the function avb_rsa_public_key_header_validate_and_byteswap(). 144 * 145 * The avb_rsa_verify() function expects a key in this serialized 146 * format. 147 * 148 * The 'avbtool extract_public_key' command can be used to generate a 149 * serialized RSA public key. 150 */ 151 typedef struct AvbRSAPublicKeyHeader { 152 uint32_t key_num_bits; 153 uint32_t n0inv; 154 } AVB_ATTR_PACKED AvbRSAPublicKeyHeader; 155 156 /* Copies |src| to |dest| and validates, byte-swapping fields in the 157 * process if needed. Returns true if valid, false if invalid. 158 */ 159 bool avb_rsa_public_key_header_validate_and_byteswap( 160 const AvbRSAPublicKeyHeader* src, 161 AvbRSAPublicKeyHeader* dest) AVB_ATTR_WARN_UNUSED_RESULT; 162 163 #ifdef __cplusplus 164 } 165 #endif 166 167 #endif /* AVB_CRYPTO_H_ */ 168