blob: 7e8d7e21ca4805465373baaa1b37c960898ef020
| 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 |