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