David Zeuthen | 3a58015 | 2017-04-12 15:50:47 -0400 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2017 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 | #include "avb_user_verity.h" |
| 26 | |
| 27 | /* Maximum allow length (in bytes) of a partition name, including |
| 28 | * ab_suffix. |
| 29 | */ |
| 30 | #define AVB_PART_NAME_MAX_SIZE 32 |
| 31 | |
| 32 | /* Loads the toplevel AvbVBMetaImageHeader from the slot denoted by |
| 33 | * |ab_suffix| into |vbmeta_image|. No validation, verification, or |
| 34 | * byteswapping is performed. |
| 35 | * |
| 36 | * If successful, |true| is returned and the partition it was loaded |
| 37 | * from is returned in |out_partition_name| and the offset on said |
| 38 | * partition is returned in |out_vbmeta_offset|. |
| 39 | */ |
| 40 | bool load_top_level_vbmeta_header( |
| 41 | AvbOps* ops, |
| 42 | const char* ab_suffix, |
| 43 | uint8_t vbmeta_image[AVB_VBMETA_IMAGE_HEADER_SIZE], |
| 44 | char out_partition_name[AVB_PART_NAME_MAX_SIZE], |
| 45 | uint64_t* out_vbmeta_offset) { |
| 46 | uint64_t vbmeta_offset = 0; |
| 47 | size_t num_read; |
| 48 | bool ret = false; |
| 49 | AvbIOResult io_res; |
| 50 | |
| 51 | /* Construct full partition name. */ |
| 52 | if (!avb_str_concat(out_partition_name, |
| 53 | AVB_PART_NAME_MAX_SIZE, |
| 54 | "vbmeta", |
| 55 | 6, |
| 56 | ab_suffix, |
| 57 | avb_strlen(ab_suffix))) { |
| 58 | avb_error("Partition name and suffix does not fit.\n"); |
| 59 | goto out; |
| 60 | } |
| 61 | |
| 62 | /* Only read the header, not the entire struct. */ |
| 63 | io_res = ops->read_from_partition(ops, |
| 64 | out_partition_name, |
| 65 | vbmeta_offset, |
| 66 | AVB_VBMETA_IMAGE_HEADER_SIZE, |
| 67 | vbmeta_image, |
| 68 | &num_read); |
| 69 | if (io_res == AVB_IO_RESULT_ERROR_NO_SUCH_PARTITION) { |
| 70 | AvbFooter footer; |
| 71 | |
| 72 | /* Try looking for the vbmeta struct in 'boot' via the footer. */ |
| 73 | if (!avb_str_concat(out_partition_name, |
| 74 | AVB_PART_NAME_MAX_SIZE, |
| 75 | "boot", |
| 76 | 4, |
| 77 | ab_suffix, |
| 78 | avb_strlen(ab_suffix))) { |
| 79 | avb_error("Partition name and suffix does not fit.\n"); |
| 80 | goto out; |
| 81 | } |
| 82 | io_res = ops->read_from_partition(ops, |
| 83 | out_partition_name, |
| 84 | -AVB_FOOTER_SIZE, |
| 85 | AVB_FOOTER_SIZE, |
| 86 | &footer, |
| 87 | &num_read); |
| 88 | if (io_res != AVB_IO_RESULT_OK) { |
| 89 | avb_errorv("Error loading footer from partition '", |
| 90 | out_partition_name, |
| 91 | "'\n", |
| 92 | NULL); |
| 93 | goto out; |
| 94 | } |
| 95 | |
| 96 | if (avb_memcmp(footer.magic, AVB_FOOTER_MAGIC, AVB_FOOTER_MAGIC_LEN) != 0) { |
| 97 | avb_errorv("Data from '", |
| 98 | out_partition_name, |
| 99 | "' does not look like a vbmeta footer.\n", |
| 100 | NULL); |
| 101 | goto out; |
| 102 | } |
| 103 | |
| 104 | vbmeta_offset = avb_be64toh(footer.vbmeta_offset); |
| 105 | io_res = ops->read_from_partition(ops, |
| 106 | out_partition_name, |
| 107 | vbmeta_offset, |
| 108 | AVB_VBMETA_IMAGE_HEADER_SIZE, |
| 109 | vbmeta_image, |
| 110 | &num_read); |
| 111 | } |
| 112 | |
| 113 | if (io_res != AVB_IO_RESULT_OK) { |
| 114 | avb_errorv( |
| 115 | "Error loading from partition '", out_partition_name, "'\n", NULL); |
| 116 | goto out; |
| 117 | } |
| 118 | |
| 119 | if (out_vbmeta_offset != NULL) { |
| 120 | *out_vbmeta_offset = vbmeta_offset; |
| 121 | } |
| 122 | |
| 123 | ret = true; |
| 124 | |
| 125 | out: |
| 126 | return ret; |
| 127 | } |
| 128 | |
| 129 | bool avb_user_verity_get(AvbOps* ops, |
| 130 | const char* ab_suffix, |
| 131 | bool* out_verity_enabled) { |
| 132 | uint8_t vbmeta_image[AVB_VBMETA_IMAGE_HEADER_SIZE]; /* 256 bytes. */ |
| 133 | char partition_name[AVB_PART_NAME_MAX_SIZE]; /* 32 bytes. */ |
| 134 | AvbVBMetaImageHeader* header; |
| 135 | uint32_t flags; |
| 136 | bool ret = false; |
| 137 | |
| 138 | if (!load_top_level_vbmeta_header( |
| 139 | ops, ab_suffix, vbmeta_image, partition_name, NULL)) { |
| 140 | goto out; |
| 141 | } |
| 142 | |
| 143 | if (avb_memcmp(vbmeta_image, AVB_MAGIC, AVB_MAGIC_LEN) != 0) { |
| 144 | avb_errorv("Data from '", |
| 145 | partition_name, |
| 146 | "' does not look like a vbmeta header.\n", |
| 147 | NULL); |
| 148 | goto out; |
| 149 | } |
| 150 | |
| 151 | /* Set/clear the HASHTREE_DISABLED bit, as requested. */ |
| 152 | header = (AvbVBMetaImageHeader*)vbmeta_image; |
| 153 | flags = avb_be32toh(header->flags); |
| 154 | |
| 155 | if (out_verity_enabled != NULL) { |
| 156 | *out_verity_enabled = !(flags & AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED); |
| 157 | } |
| 158 | |
| 159 | ret = true; |
| 160 | |
| 161 | out: |
| 162 | return ret; |
| 163 | } |
| 164 | |
| 165 | bool avb_user_verity_set(AvbOps* ops, |
| 166 | const char* ab_suffix, |
| 167 | bool enable_verity) { |
| 168 | uint8_t vbmeta_image[AVB_VBMETA_IMAGE_HEADER_SIZE]; /* 256 bytes. */ |
| 169 | char partition_name[AVB_PART_NAME_MAX_SIZE]; /* 32 bytes. */ |
| 170 | uint64_t vbmeta_offset; |
| 171 | AvbIOResult io_res; |
| 172 | AvbVBMetaImageHeader* header; |
| 173 | uint32_t flags; |
| 174 | bool ret = false; |
| 175 | |
| 176 | if (!load_top_level_vbmeta_header( |
| 177 | ops, ab_suffix, vbmeta_image, partition_name, &vbmeta_offset)) { |
| 178 | goto out; |
| 179 | } |
| 180 | |
| 181 | if (avb_memcmp(vbmeta_image, AVB_MAGIC, AVB_MAGIC_LEN) != 0) { |
| 182 | avb_errorv("Data from '", |
| 183 | partition_name, |
| 184 | "' does not look like a vbmeta header.\n", |
| 185 | NULL); |
| 186 | goto out; |
| 187 | } |
| 188 | |
| 189 | /* Set/clear the HASHTREE_DISABLED bit, as requested. */ |
| 190 | header = (AvbVBMetaImageHeader*)vbmeta_image; |
| 191 | flags = avb_be32toh(header->flags); |
| 192 | flags &= ~AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED; |
| 193 | if (!enable_verity) { |
| 194 | flags |= AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED; |
| 195 | } |
| 196 | header->flags = avb_htobe32(flags); |
| 197 | |
| 198 | /* Write the header. */ |
| 199 | io_res = ops->write_to_partition(ops, |
| 200 | partition_name, |
| 201 | vbmeta_offset, |
| 202 | AVB_VBMETA_IMAGE_HEADER_SIZE, |
| 203 | vbmeta_image); |
| 204 | if (io_res != AVB_IO_RESULT_OK) { |
| 205 | avb_errorv("Error writing to partition '", partition_name, "'\n", NULL); |
| 206 | goto out; |
| 207 | } |
| 208 | |
| 209 | ret = true; |
| 210 | |
| 211 | out: |
| 212 | return ret; |
| 213 | } |