1 <html devsite><head> 2 <title> SELinux </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 <p>Android (AOSP) Android AOSP 90-95% 5-10% </p> 24 25 <h2 id="device_bringup"></h2> 26 27 <p></p> 28 29 <h3 id="run_in_permissive_mode"></h3> 30 31 <p><a href="index.html#background"></a></p> 32 33 <ol> 34 <li> 35 </li><li> 36 </li></ol> 37 38 <p><a href="validate.html#switching_to_permissive"></a> BoardConfig.mk <code>platform/device/<vendor>/<target>/BoardConfig.mk</code> <code>make clean</code> <code>make bootimage</code></p> 39 40 <p></p> 41 42 <p><code>adb getenforce</code></p> 43 44 <p></p> 45 46 <h3 id="enforce_early"></h3> 47 48 <p> <a href="https://en.wikipedia.org/wiki/Eating_your_own_dog_food">dogfooding</a></p> 49 50 <h3 id="remove_or_delete_existing_policy"></h3> 51 52 <p></p> 53 54 <ul> 55 <li></li><li> <a href="#overuse_of_negation"></a> 56 </li><li> <a href="#policy_size_explosion"></a> 57 </li><li>Dead </li></ul> 58 59 <h3 id="address_denials_of_core_services"></h3> 60 61 <p></p> 62 63 <pre class="no-pretty-print"> 64 avc: denied { open } for pid=1003 comm=mediaserver path="/dev/kgsl-3d0 65 dev="tmpfs" scontext=u:r:mediaserver:s0 tcontext=u:object_r:device:s0 66 tclass=chr_file permissive=1 67 avc: denied { read write } for pid=1003 name="kgsl-3d0" dev="tmpfs" 68 scontext=u:r:mediaserver:s0 69 tcontext=u:object_r:device:s0 tclass=chr_file permissive=1 70 </pre> 71 72 <p> <code>/dev/kgsl-3d0</code> <code>tcontext</code> <code>device</code><code>/dev</code> <a href="https://android.googlesource.com/platform/external/sepolicy/+/marshmallow-dev/file_contexts#31">device</a> <a href="validate.html#using_audit2allow">audit2allow</a> </p> 73 74 <p> <a href="https://android.googlesource.com/device/lge/hammerhead/+/marshmallow-dev/sepolicy/file_contexts#1">gpu_device</a> <a href="https://android.googlesource.com/platform/external/sepolicy/+/marshmallow-dev/mediaserver.te#24">mediaserver gpu_device </a></p> 75 76 <p></p> 77 78 <ol> 79 <li> <a href="https://android.googlesource.com/device/lge/hammerhead/+/marshmallow-dev/sepolicy/file_contexts#31"></a> 80 </li><li> <a href="https://android.googlesource.com/device/lge/hammerhead/+/marshmallow-dev/sepolicy/file_contexts#80"></a> 81 </li><li> <a href="https://android.googlesource.com/device/lge/hammerhead/+/marshmallow-dev/sepolicy/file_contexts#21"></a> 82 </li><li> <a href="https://android.googlesource.com/device/lge/hammerhead/+/marshmallow-dev/sepolicy/file_contexts#89"></a> 83 </li><li> <a href="https://android.googlesource.com/device/lge/hammerhead/+/marshmallow-dev/sepolicy/file_contexts#8">nfc</a> 84 </li><li>gps_device</li><li> <a href="https://android.googlesource.com/device/lge/hammerhead/+/marshmallow-dev/sepolicy/file_contexts#139">/sys </a> 85 </li><li>/proc </li></ol> 86 87 <p> <a href="customize.html#neverallow">neverallow</a> </p> 88 89 <h3 id="label_new_services_and_address_denials"></h3> 90 91 <p> init SELinux foo SELinux </p> 92 93 <p> <code>init.<target>.rc</code> </p> 94 95 <pre class="no-pretty-print"> 96 service foo /system/bin/foo 97 class core 98 </pre> 99 100 <ol> 101 <li>foo<br /> 102 103 <p> <code>device/<oem>/<target>/sepolicy/foo.te</code></p> 104 105 <pre class="no-pretty-print"> 106 # foo service 107 type foo, domain; 108 type foo_exec, exec_type, file_type; 109 110 init_daemon_domain(foo) 111 </pre> 112 113 <p> foo SELinux </p> 114 </li> 115 116 <li> <code>/system/bin/foo</code> <br /> 117 118 <p> <code>device/<oem>/<target>/sepolicy/ 119 file_contexts</code></p> 120 121 <pre class="no-pretty-print"> 122 /system/bin/foo u:object_r:foo_exec:s0 123 </pre> 124 125 <p> SELinux </p> 126 </li> 127 128 <li></li> 129 130 <li> SELinux <br /> 131 132 <p><a href="validate.html#using_audit2allow">audit2allow</a> </p> 133 </li> 134 </ol> 135 136 <h3 id="enforcing_mode"></h3> 137 138 <p></p> 139 140 <h2 id="common_mistakes"></h2> 141 142 <p></p> 143 144 <h3 id="overuse_of_negation"></h3> 145 146 <p></p> 147 148 <p><code>allow { domain -untrusted_app } scary_debug_device:chr_file rw_file_perms</code></p> 149 150 <p></p> 151 152 <p> <code>untrusted_app</code> <code>isolated_app</code> AOSP <code>scary_debug_device</code></p> 153 154 <h3 id="debugging_features_in_production"></h3> 155 156 <p></p> 157 158 <p> eng/userdebug SELinux <code>adb root</code> <code>adb setenforce 0</code></p> 159 160 <p> <a href="https://android.googlesource.com/device/lge/hammerhead/+/marshmallow-dev/sepolicy/platform_app.te#3">userdebug_or_eng</a> </p> 161 162 <h3 id="policy_size_explosion"></h3> 163 164 <p><a href="http://arxiv.org/abs/1510.05497"> Wild SEAndroid </a> 5-10% 20% Dead </p> 165 166 <p></p> 167 168 <ul> 169 <li> ramdisk 170 </li><li> 171 </li><li> 172 </li></ul> 173 174 <p> 50% 40% AOSP Shamu Flounder </p> 175 176 <p><img alt=" 1" src="images/selinux_device_policy_reduction.png"/></p> 177 <p class="img-caption"><strong> 1</strong>. </p> 178 179 <p> audit2allow Dead </p> 180 181 <h3 id="granting_the_dac_override_capability"> dac_override </h3> 182 183 <p><code> dac_override</code> unix user/group/world <code>dac_override</code> <a href="https://android-review.googlesource.com/#/c/174530/5/update_engine.te@11"> unix </a> initvold installd unix <a href="http://danwalsh.livejournal.com/69478.html">Dan Walsh </a></p> 184 185 <h2 id="additional_resources"></h2> 186 187 <p><a href="http://seandroid.bitbucket.org/ForMoreInformation.html">SEAndroid </a></p> 188 189 <p>AOSP <a href="index.html">Android SELinux</a> </p> 190 191 <p><a href="http://seandroid.bitbucket.org/"></a></p> 192 193 </body></html>
