1 <html devsite><head> 2 <title> dm-verity</title> 3 <meta name="project_path" value="/_project.yaml"/> 4 <meta name="book_path" value="/_book.yaml"/> 5 </head> 6 <body> 7 <!-- 8 Copyright 2017 The Android Open Source Project 9 10 Licensed under the Apache License, Version 2.0 (the "License"); 11 you may not use this file except in compliance with the License. 12 You may obtain a copy of the License at 13 14 http://www.apache.org/licenses/LICENSE-2.0 15 16 Unless required by applicable law or agreed to in writing, software 17 distributed under the License is distributed on an "AS IS" BASIS, 18 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 19 See the License for the specific language governing permissions and 20 limitations under the License. 21 --> 22 23 <h2 id="operation"></h2> 24 25 <p>dm-verity Root </p> 26 27 <p><a href="verified-boot.html"></a></p> 28 29 <p></p> 30 31 <p> dm-verity </p> 32 33 <p> I/O </p> 34 35 <p></p> 36 37 <h2 id="implementation"></h2> 38 39 <h3 id="summary"></h3> 40 41 <ol> 42 <li> EXT4 </li> 43 <li><a href="#hash-tree"></a></li> 44 <li><a href="#mapping-table"> dm-verity </a></li> 45 <li><a href="#signing"> dm-verity </a></li> 46 <li> dm-verity <a href="#metadata"></a> Verity </li> 47 <li>Verity </li> 48 </ol> 49 50 <p> dm-verity <a href="http://www.chromium.org/chromium-os/chromiumos-design-docs/verified-boot">Chromium - </a></p> 51 52 <h3 id="hash-tree"></h3> 53 54 <p><a href="#introduction"></a> dm-verity <a href="https://gitlab.com/cryptsetup/cryptsetup/wikis/DMVerity">cryptsetup</a> </p> 55 56 <pre> 57 <your block device name> <your block device name> <block size> <block size> <image size in blocks> <image size in blocks + 8> <root hash> <salt> 58 </pre> 59 60 <p> 0 4k SHA256 SHA256 4k 1 1 SHA256 2 </p> 61 62 <p> SHA256 SHA256 </p> 63 64 <p> 30 MB</p> 65 66 <p> 0 4k </p> 67 68 <p> 2 1 3 2 0 </p> 69 70 <p></p> 71 72 <ol> 73 <li></li> 74 <li> 4k </li> 75 <li> SHA256 </li> 76 <li></li> 77 <li> 0 4k </li> 78 <li></li> 79 <li> 2-6 </li> 80 </ol> 81 82 <p> dm-verity </p> 83 84 <h3 id="mapping-table"> dm-verity </h3> 85 86 <p> dm-verity <code>fstab</code> hash_start 0 </p> 87 88 <p> Verity <a href="https://code.google.com/p/cryptsetup/wiki/DMVerity">cryptsetup</a></p> 89 90 <h3 id="signing"> dm-verity </h3> 91 92 <p> dm-verity </p> 93 94 <p></p> 95 96 <ol> 97 <li> libmincrypt RSA-2048 /boot /verity_key </li> 98 <li> fstab verify fs_mgr </li> 99 </ol> 100 101 <h3 id="metadata"></h3> 102 103 <p> dm-verity Verity </p> 104 105 <p> EXT4 </p> 106 107 <p><br />0xb001b001</p> 108 109 <p></p> 110 111 <ul> 112 <li> = b0</li> 113 <li> = 01</li> 114 <li> = b0</li> 115 <li> = 01</li> 116 </ul> 117 118 <p> Verity </p> 119 120 <pre><magic number>|<version>|<signature>|<table length>|<table>|<padding> 121 \-------------------------------------------------------------------/ 122 \----------------------------------------------------------/ | 123 | | 124 | 32K 125 block content 126 </pre> 127 128 <p></p> 129 130 <p class="table-caption" id="table1"> 131 <strong> 1.</strong> Verity </p> 132 133 <table> 134 <tbody><tr> 135 <th></th> 136 <th></th> 137 <th></th> 138 <th></th> 139 </tr> 140 <tr> 141 <td></td> 142 <td> fs_mgr </td> 143 <td>4 </td> 144 <td>0xb001b001</td> 145 </tr> 146 <tr> 147 <td></td> 148 <td></td> 149 <td>4 </td> 150 <td> 0</td> 151 </tr> 152 <tr> 153 <td></td> 154 <td>PKCS1.5 </td> 155 <td>256 </td> 156 <td></td> 157 </tr> 158 <tr> 159 <td></td> 160 <td>dm-verity </td> 161 <td>4 </td> 162 <td></td> 163 </tr> 164 <tr> 165 <td></td> 166 <td> dm-verity </td> 167 <td></td> 168 <td></td> 169 </tr> 170 <tr> 171 <td></td> 172 <td> 0 32k </td> 173 <td></td> 174 <td>0</td> 175 </tr> 176 </tbody></table> 177 178 <h3 id="optimize"> dm-verity</h3> 179 180 <p> dm-verity </p> 181 <ul> 182 <li> NEON SHA-2 ARMv7 SHA-2 ARMv8 183 </li><li> prefetch_cluster 184 </li></ul> 185 186 </body></html>
