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_VBMETA_IMAGE_H_ 30 #define AVB_VBMETA_IMAGE_H_ 31 32 #include "avb_sysdeps.h" 33 34 #ifdef __cplusplus 35 extern "C" { 36 #endif 37 38 #include "avb_crypto.h" 39 #include "avb_descriptor.h" 40 41 /* Size of the vbmeta image header. */ 42 #define AVB_VBMETA_IMAGE_HEADER_SIZE 256 43 44 /* Magic for the vbmeta image header. */ 45 #define AVB_MAGIC "AVB0" 46 #define AVB_MAGIC_LEN 4 47 48 /* Maximum size of the release string including the terminating NUL byte. */ 49 #define AVB_RELEASE_STRING_SIZE 48 50 51 /* Flags for the vbmeta image. 52 * 53 * AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED: If this flag is set, 54 * hashtree image verification will be disabled. 55 */ 56 typedef enum { 57 AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED = (1 << 0) 58 } AvbVBMetaImageFlags; 59 60 /* Binary format for header of the vbmeta image. 61 * 62 * The vbmeta image consists of three blocks: 63 * 64 * +-----------------------------------------+ 65 * | Header data - fixed size | 66 * +-----------------------------------------+ 67 * | Authentication data - variable size | 68 * +-----------------------------------------+ 69 * | Auxiliary data - variable size | 70 * +-----------------------------------------+ 71 * 72 * The "Header data" block is described by this struct and is always 73 * |AVB_VBMETA_IMAGE_HEADER_SIZE| bytes long. 74 * 75 * The "Authentication data" block is |authentication_data_block_size| 76 * bytes long and contains the hash and signature used to authenticate 77 * the vbmeta image. The type of the hash and signature is defined by 78 * the |algorithm_type| field. 79 * 80 * The "Auxiliary data" is |auxiliary_data_block_size| bytes long and 81 * contains the auxiliary data including the public key used to make 82 * the signature and descriptors. 83 * 84 * The public key is at offset |public_key_offset| with size 85 * |public_key_size| in this block. The size of the public key data is 86 * defined by the |algorithm_type| field. The format of the public key 87 * data is described in the |AvbRSAPublicKeyHeader| struct. 88 * 89 * The descriptors starts at |descriptors_offset| from the beginning 90 * of the "Auxiliary Data" block and take up |descriptors_size| 91 * bytes. Each descriptor is stored as a |AvbDescriptor| with tag and 92 * number of bytes following. The number of descriptors can be 93 * determined by walking this data until |descriptors_size| is 94 * exhausted. 95 * 96 * The size of each of the "Authentication data" and "Auxiliary data" 97 * blocks must be divisible by 64. This is to ensure proper alignment. 98 * 99 * Descriptors are free-form blocks stored in a part of the vbmeta 100 * image subject to the same integrity checks as the rest of the 101 * image. See the documentation for |AvbDescriptor| for well-known 102 * descriptors. See avb_descriptor_foreach() for a convenience 103 * function to iterate over descriptors. 104 * 105 * This struct is versioned, see the |required_libavb_version_major| 106 * and |required_libavb_version_minor| fields. This represents the 107 * minimum version of libavb required to verify the header and depends 108 * on the features (e.g. algorithms, descriptors) used. Note that this 109 * may be 1.0 even if generated by an avbtool from 1.4 but where no 110 * features introduced after 1.0 has been used. See the "Versioning 111 * and compatibility" section in the README.md file for more details. 112 * 113 * All fields are stored in network byte order when serialized. To 114 * generate a copy with fields swapped to native byte order, use the 115 * function avb_vbmeta_image_header_to_host_byte_order(). 116 * 117 * Before reading and/or using any of this data, you MUST verify it 118 * using avb_vbmeta_image_verify() and reject it unless it's signed by 119 * a known good public key. 120 */ 121 typedef struct AvbVBMetaImageHeader { 122 /* 0: Four bytes equal to "AVB0" (AVB_MAGIC). */ 123 uint8_t magic[AVB_MAGIC_LEN]; 124 125 /* 4: The major version of libavb required for this header. */ 126 uint32_t required_libavb_version_major; 127 /* 8: The minor version of libavb required for this header. */ 128 uint32_t required_libavb_version_minor; 129 130 /* 12: The size of the signature block. */ 131 uint64_t authentication_data_block_size; 132 /* 20: The size of the auxiliary data block. */ 133 uint64_t auxiliary_data_block_size; 134 135 /* 28: The verification algorithm used, see |AvbAlgorithmType| enum. */ 136 uint32_t algorithm_type; 137 138 /* 32: Offset into the "Authentication data" block of hash data. */ 139 uint64_t hash_offset; 140 /* 40: Length of the hash data. */ 141 uint64_t hash_size; 142 143 /* 48: Offset into the "Authentication data" block of signature data. */ 144 uint64_t signature_offset; 145 /* 56: Length of the signature data. */ 146 uint64_t signature_size; 147 148 /* 64: Offset into the "Auxiliary data" block of public key data. */ 149 uint64_t public_key_offset; 150 /* 72: Length of the public key data. */ 151 uint64_t public_key_size; 152 153 /* 80: Offset into the "Auxiliary data" block of public key metadata. */ 154 uint64_t public_key_metadata_offset; 155 /* 88: Length of the public key metadata. Must be set to zero if there 156 * is no public key metadata. 157 */ 158 uint64_t public_key_metadata_size; 159 160 /* 96: Offset into the "Auxiliary data" block of descriptor data. */ 161 uint64_t descriptors_offset; 162 /* 104: Length of descriptor data. */ 163 uint64_t descriptors_size; 164 165 /* 112: The rollback index which can be used to prevent rollback to 166 * older versions. 167 */ 168 uint64_t rollback_index; 169 170 /* 120: Flags from the AvbVBMetaImageFlags enumeration. This must be 171 * set to zero if the vbmeta image is not a top-level image. 172 */ 173 uint32_t flags; 174 175 /* 124: Reserved to ensure |release_string| start on a 16-byte 176 * boundary. Must be set to zeroes. 177 */ 178 uint8_t reserved0[4]; 179 180 /* 128: The release string from avbtool, e.g. "avbtool 1.0.0" or 181 * "avbtool 1.0.0 xyz_board Git-234abde89". Is guaranteed to be NUL 182 * terminated. Applications must not make assumptions about how this 183 * string is formatted. 184 */ 185 uint8_t release_string[AVB_RELEASE_STRING_SIZE]; 186 187 /* 176: Padding to ensure struct is size AVB_VBMETA_IMAGE_HEADER_SIZE 188 * bytes. This must be set to zeroes. 189 */ 190 uint8_t reserved[80]; 191 } AVB_ATTR_PACKED AvbVBMetaImageHeader; 192 193 /* Copies |src| to |dest|, byte-swapping fields in the process. 194 * 195 * Make sure you've verified |src| using avb_vbmeta_image_verify() 196 * before accessing the data and/or using this function. 197 */ 198 void avb_vbmeta_image_header_to_host_byte_order(const AvbVBMetaImageHeader* src, 199 AvbVBMetaImageHeader* dest); 200 201 /* Return codes used in avb_vbmeta_image_verify(). 202 * 203 * AVB_VBMETA_VERIFY_RESULT_OK is returned if the vbmeta image header 204 * is valid, the hash is correct and the signature is correct. Keep in 205 * mind that you still need to check that you know the public key used 206 * to sign the image, see avb_vbmeta_image_verify() for details. 207 * 208 * AVB_VBMETA_VERIFY_RESULT_OK_NOT_SIGNED is returned if the vbmeta 209 * image header is valid but there is no signature or hash. 210 * 211 * AVB_VBMETA_VERIFY_RESULT_INVALID_VBMETA_HEADER is returned if the 212 * header of the vbmeta image is invalid, for example, invalid magic 213 * or inconsistent data. 214 * 215 * AVB_VBMETA_VERIFY_RESULT_UNSUPPORTED_VERSION is returned if a) the 216 * vbmeta image requires a minimum version of libavb which exceeds the 217 * version of libavb used; or b) the vbmeta image major version 218 * differs from the major version of libavb in use. 219 * 220 * AVB_VBMETA_VERIFY_RESULT_HASH_MISMATCH is returned if the hash 221 * stored in the "Authentication data" block does not match the 222 * calculated hash. 223 * 224 * AVB_VBMETA_VERIFY_RESULT_SIGNATURE_MISMATCH is returned if the 225 * signature stored in the "Authentication data" block is invalid or 226 * doesn't match the public key stored in the vbmeta image. 227 */ 228 typedef enum { 229 AVB_VBMETA_VERIFY_RESULT_OK, 230 AVB_VBMETA_VERIFY_RESULT_OK_NOT_SIGNED, 231 AVB_VBMETA_VERIFY_RESULT_INVALID_VBMETA_HEADER, 232 AVB_VBMETA_VERIFY_RESULT_UNSUPPORTED_VERSION, 233 AVB_VBMETA_VERIFY_RESULT_HASH_MISMATCH, 234 AVB_VBMETA_VERIFY_RESULT_SIGNATURE_MISMATCH, 235 } AvbVBMetaVerifyResult; 236 237 /* Get a textual representation of |result|. */ 238 const char* avb_vbmeta_verify_result_to_string(AvbVBMetaVerifyResult result); 239 240 /* Checks that vbmeta image at |data| of size |length| is a valid 241 * vbmeta image. The complete contents of the vbmeta image must be 242 * passed in. It's fine if |length| is bigger than the actual image, 243 * typically callers of this function will load the entire contents of 244 * the 'vbmeta_a' or 'vbmeta_b' partition and pass in its length (for 245 * example, 1 MiB). 246 * 247 * See the |AvbVBMetaImageHeader| struct for information about the 248 * three blocks (header, authentication, auxiliary) that make up a 249 * vbmeta image. 250 * 251 * If the function returns |AVB_VBMETA_VERIFY_RESULT_OK| and 252 * |out_public_key_data| is non-NULL, it will be set to point inside 253 * |data| for where the serialized public key data is stored and 254 * |out_public_key_length|, if non-NULL, will be set to the length of 255 * the public key data. If there is no public key in the metadata then 256 * |out_public_key_data| is set to NULL. 257 * 258 * See the |AvbVBMetaVerifyResult| enum for possible return values. 259 * 260 * VERY IMPORTANT: 261 * 262 * 1. Even if |AVB_VBMETA_VERIFY_RESULT_OK| is returned, you still 263 * need to check that the public key embedded in the image 264 * matches a known key! You can use 'avbtool extract_public_key' 265 * to extract the key (at build time, then store it along your 266 * code) and compare it to what is returned in 267 * |out_public_key_data|. 268 * 269 * 2. You need to check the |rollback_index| field against a stored 270 * value in NVRAM and reject the vbmeta image if the value in 271 * NVRAM is bigger than |rollback_index|. You must also update 272 * the value stored in NVRAM to the smallest value of 273 * |rollback_index| field from boot images in all bootable and 274 * authentic slots marked as GOOD. 275 * 276 * This is a low-level function to only verify the vbmeta data - you 277 * are likely looking for avb_slot_verify() instead for verifying 278 * integrity data for a whole set of partitions. 279 */ 280 AvbVBMetaVerifyResult avb_vbmeta_image_verify( 281 const uint8_t* data, 282 size_t length, 283 const uint8_t** out_public_key_data, 284 size_t* out_public_key_length) AVB_ATTR_WARN_UNUSED_RESULT; 285 286 #ifdef __cplusplus 287 } 288 #endif 289 290 #endif /* AVB_VBMETA_IMAGE_H_ */ 291
